ESE's works engine tuner

[Buckets4Me]

where is the heat coming from at the bottom of the barrel

whould have thought that most or all the heat was near the head

is it that the heat is dissapated faster up top but not down below ????

see you sunday both bikes are back together but havent started either yet

couldn't find what i did with the kick start
and it's to hot to go out side :drool: now to get an ice cream

[TZ350]

.

I thought most of the heat would be all up top too.

As it was just a little ride up the drive and back I was not expecting any heat in the under barrel fins at all.

I think the heat is coming from the exhaust tract.
Whether the under fins remain unexpectedly hotter than the head fins after every thing gets a good heat soaking during a race I don't know.

It could be the under fins get up to temperature quickest. Hopefully know more tomorrow.

I have the Red bike running and will take it for you to use tomorrow.

Will get you to run my bike around for a bit in practice while I take temperatures and play with the jets if thats OK with you.

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[craisin]

So i had an idea that since the crankcase is part of the intake tract and on the side is a hot sweaty gearbox with no provision to let the hot air expand and cool because the gearbox is not vented . My idea was to make a ram-air arrngement with a filter and it would have forced cool air into the gearbox and then make an outlet for the hot air to come out with a suitable heat-resistant hose and going up high to prevent hot oil being siphoned out. The back-up plan was using a cheap 12 volt compressor to force cool air in :niceone::weird:

[TZ350]

.

Thanks for your interest, cooling the gearbox oil and inlet air stream is the next part of the project.

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[Buckets4Me]

what a beast but I think the clutches are the next thing to worry about :eek5:

[craisin]

hi Buckets4Me i went to the track today but found it hard to socialise with all the push-starting going on i didnt want to get in the way or alter anybodies schedule

[Buckets4Me]

didn't notice you sorry

where where you etc

I think the heat got to a few people
I was stuffed and couldn't ride anymore lol

did you see the undie race :jerry:

[TZ350]

Copper head results.

Using one of those laser point and read digital heat guns I took readings from some CB125T’s

The head temp., front, flat area between the cylinders, ranged 125 to 135 degrees C. Bottom fin on the barrel 95 degrees and crankcase 71 degrees.

The head temp., of a Suzuki GP125 ridden by Rick56 and without any copper finning. Head 139, bottom fin of barrel 129 and crank case 71 degrees C. Best lap 32 sec.

The head temp., of a Suzuki GP125 ridden by Cully and without any copper finning. Head 127, bottom fin of barrel 101 and crank case 98 degrees C. Best lap 34 sec.

Speedpros MB100 which was sounding really, really good. From memory head 101, barrel bottom
fin 90 and case 70.

I had been over generous with the copper coat during assembly of the copper fins and it was fouling the plugs. Who would have thought copper coat would be a problem for plugs!!!!...:Oops:

Only getting one lap or so before the plug would quit. So one lap warm-up readings were typically Head 55, copper head fin 42, CPU cooler 39, bottom barrel fin 60, copper under barrel fins 60 to 45 and crank case 43.

Tried to clear the copper coat by swapping in “good” old plugs until it cleared but after about 6 plugs I gave up and pulled the head and barrel of and washed the excess copper coat out.

After this we warmed it up, changed the plug again and managed 5 good laps. Best time 36 sec Head 76, copper head fin 45, CPU cooler 31, bottom barrel fin 97, copper under barrel fins 90 to 58 and crank case 53.

It was a really hot day and I didn’t do very well at collecting the data. Will have to think about what the numbers might mean.

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[craisin]

didn't notice you sorry

where where you etc

I think the heat got to a few people
I was stuffed and couldn't ride anymore lol

did you see the undie race :jerry: I should have asked shelracing where you were I was on a little blue bike with chrome side panels on the tank I went to get a drink and parked on the hill when I came back. I was wearing a blue ski-mask when I first turned up I am just over 6 feet my hair is grey there ia still some black in my hair though. Yes it looked too tough for me as i had a parachute accident 22 years ago and i need to set up a hand gearchange for my moped. Sorry for the threadjack TZ350

[TZ350]

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Sorry for the threadjack TZ350

A "PM" works well for personal messages!! :rolleyes:

.

[craisin]

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A "PM" works well for personal messages!! :rolleyes:

.well TZ350 I PMed you and you didnt answer. If you guys had 2 engines it would be easier as you could do back to back comparisons. Anyway I hope your luck changes

[TZ350]

.

Temp’s of Suzuki GP125’s without any copper finning.

Rick56,.Head 139..………………………………............…..bottom barrel fin 129………………............………case 71. 32 sec.

Cully,…Head 127..…………………………………...............bottom barrel fin 101…...........…………………...case 98. 34 sec.

Temp’s of Suzuki GP125 with copper finning.

Carl,….Head 76, copper head fin 45, CPU cooler 31, bottom barrel fin 97, copper fins 90-70-58, case 53. 36 sec

It’s apparent that when every thing has reached full operating temperature the head runs marginally hotter than the top of the barrel and 20-30 degrees hotter than the bottom fin of the barrel.

Also the barrel gets up to temperature much quicker than the head and runs much hotter than I expected. Ceramic coating of the exhaust tract has got to be the go.

Also the cases below the barrel run much hotter than I expected them to.

Because Carls best lap of 36 sec is significantly different to Rick’s 32 sec laps, the full head temps can’t really be compared.

What can be seen though is that the relative temperature difference between the bottom barrel fin and case is significantly better on Carl’s bike which has the extra copper fins under the barrel. This in itself would seem a worth while modification.

During the day, taking temperatures, it became apparent how fast the heat moved through the copper head fin compared to the alloy of the head.

I can’t yet say that ceramic coating the combustion chamber is wrong and I can’t yet say that my copper combustion chamber is better but it is looking good so far.

I have become convinced that making the cylinder spacer out of copper and larger so it forms an under barrel fin and making the head gasket oversized and out of copper so it becomes a fin too has got to be worth while.

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[TZ350]

.

I need to stay open minded but I feel I am on the money, with the copper and if I can get some better reading next time out we will know one way or the other.

At some point I will ceramic coat the piston and exhaust port tract. With the exhaust ceramic it will be interesting to see if the barrel temperature is reduced.

Next move is to use ice water to chill the incoming air charge and water injection to control detonation.

Thomas is following up F5's suggestion and is thinking about a faster burning fuel so we can retard the ignition to reduce the negative work done on the piston BTDC.

.

[craisin]

dual ignition

[TZ350]

dual ignition

I wonder if this could work? A plug each end combinded with a bath tub head, might be possible. Could a bath tub head shaped properly be a better shape for the scavinging transfer streams. Something to think about.

[F5 Dave]

With crasin who knows if that was what he was implying?, perhaps he was to suggest a dual curve CNG conversion?:laugh:

Twin plug heads work well i understand on bikes prone to detonation like 500cc mx bikes set up for desert race. - big bore, high revs, open throtttle & often high drag conditions.

Smaller cc less & less likely to do much, but i have read of people experimenting on 125s set up for higher revs cleaner running.

[TZ350]

With crasin who knows if that was what he was implying?, perhaps he was to suggest a dual curve CNG conversion?:laugh:

A wright up from the 2004 Natural Gas Vehicles World Congress (NGV2004), held in Buenos Aires.

Next march, Buenos Aires will be the first city to have motorcycles running with Compressed Natural Gas (CNG). This fuel is the cleanest of the fossil fuels available, as it's composed of methane. When combusted, it transforms into very small amounts of sulfur dioxide and nitrogen oxides, virtually no ash or particles, and lower levels of carbon dioxide, carbon monoxide, and other reactive hydrocarbons. Coal and oil, on the other hand, result in higher carbon emissions, nitrogen oxide, sulfur dioxide, and the release of ash particles, which don't burn and are carried to the atmosphere, contributing to pollution.

The prototype was presented in the last Natural Gas Vehicles World Congress (NGV2004), held in Buenos Aires, and two companies just announced the launch of models for sale for next march. The special gas tanks (smaller than the cars') have to be approved by the government, but the approvals are in their final stages. The brands responsible are Zanella (Argentinean, site seems to be having problems) and Honda, in association with gas equipment firms. Also, these special tanks will enable current motorcycles to make the switch for $1000 (around US $300).

And he lower picture is a Chinese CNG motorcycle DUAL FUEL 125CC MOTORCYCLE , 12 L of gasoline , 8 L of gas...

This is not such a bad idea as CNG has a very high octane rating of 120 and runs 18:1 in small four strokes.

At work we are familiar with the technology involved with running vehicles on CNG. A bus would run at 14:1 and get long engine life.

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[craisin]

With crasin who knows if that was what he was implying?, perhaps he was to suggest a dual curve CNG conversion?:laugh:

Twin plug heads work well i understand on bikes prone to detonation like 500cc mx bikes set up for desert race. - big bore, high revs, open throtttle & often high drag conditions.

Smaller cc less & less likely to do much, but i have read of people experimenting on 125s set up for higher revs cleaner running.your full of crap F5 can you understand that

[koba]

your full of crap F5 can you understand that

With your comments im never sure if I should laugh or, well laugh in a different way!

[F5 Dave]

Well, I get the gist of your poorly formed sentence. It is at least more detailed than your last two-random-word communiqué.

If you paid any attention at school you would have picked up some simple rules of English; ‘You’re’ is short for ‘You are’. ‘Your’ implies the person owns it. My ‘something’ (bucket?) is full of crap perhaps? Try throwing in a full stop or some capitals, I'm making an effort while typing only with my left hand.

Or maybe I just don’t know what I’m talking about. Well I’ve got 4 national titles on bikes I built. How many have you got buddy?<_<

People take the piss when you leave yourself open for it.

[saxet]

your full of crap F5 can you understand that
:baby:Well can you explain what you mean please.:buggerd:

[Sully60]

your full of crap F5 can you understand that

Dude, I think you need to check that attitude at the door. TeeZeeThreeFiddy has a wicked thread going here with some very usefull discussion going on, are you trying to detract from that? If so tell us now so we can get your posts moved somewhere else.

If you don't have a good grasp of what's being discussed that's fine. I have some understanding of the concepts being dicussed in this thread but being a dirty diesel (that means 4-stroke BTW) tuner I don't have the practical knowledge to contribute to the technical aspects of this thread. If I'm unsure about the details of the discussion I will pose a considered question.

You need to be aware that guys like F5Dave and Speedpro have been at this caper for years, this stuff is running in their blood, so their replies to a less considered technical posts may seem somewhat condescending, don't take it personally!

The bucket forum on KB is usually free of the shit slinging that goes on in the wider forum, yes we have some fairly pointed banter going on at times but we leave it alone when the day is done, just like on track rivalry.
Please don't bring things down to the level of the general forums, I'd like to think that we're better than that.

[gav]

Well said Sully60, I'll leave my moderators hat at the door for now. :Police:
Maybe Craisin, you can start your own thread, so we can try and keep this thread pretty much on track. Congrats to TZ350, sounds like you might be onto something!

[Buddha#81]

Dude, I think you need to check that attitude at the door.


Stink one Sully, I was looking forward to where that was going.........TZ350 lost me with the two smoker mumbo jumbo in the first page and was fooling myself reading on. Craisin was giving 2 smoker witchcraft some spark......... Fair nuff, rack off craisin!:2guns:

[TZ350]

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A couple of interesting lines I copied from an automotive engineering book.

"Engine cylinders must be cooled to maintain a lubricant film on the cylinder walls and other sliding surfaces. The cylinders, heads, pistons and exhaust valves are cooled to prevent combustion knock or destruction of these parts due to over heating.

The heat removed from the engine by the cooling system is 25% to 35% on full load and may run as high as 40% on one third load.
An increase in speed reduces the heat lost to the cooling system.

60% of the cooling flow is directed to the cylinder and 40% to the head. The permissible compression ratio and output of air cooled aero engines depends on the efficiency of cooling of the cylinder head and have long fins 25mm to 50mm closely spaced 2.5mm to 5mm."

Interesting especially the close spacing of the fins. I could possibly make a head from a block of alloy with copper fins pressed into it.

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[Yow Ling]

aircraft cylinder heads are close spaced, heads on the old radial engines were cut using a slitting saw on a mill, Ill go look for a picture

[Sully60]

aircraft cylinder heads are close spaced, heads on the old radial engines were cut using a slitting saw on a mill, Ill go look for a picture

Holy cow, I didn't realise that.

That would mean a lot of swarf from one of these! (http://www.vectorsite.net/Yeccb_2m.jpg)

[Yow Ling]

Here is said picture, its not an average milling machine but you should be able to get the idea

[koba]

Wow thats very interesting,
Quick search and...

BMW801 (http://en.wikipedia.org/wiki/BMW_801) had a cooling fan too.

Prat and Whitney R1830 (http://en.wikipedia.org/wiki/Pratt_%26_Whitney_R-1830)

Nakajima Sakae (http://en.wikipedia.org/wiki/Nakajima_Sakae)

Shvetsov ASh-82 (http://en.wikipedia.org/wiki/Shvetsov_ASh-82)

Wright R-2600 (http://en.wikipedia.org/wiki/Wright_R-2600)

Bristol Hercules (http://en.wikipedia.org/wiki/Bristol_Hercules)

Fiat A.74 (http://en.wikipedia.org/wiki/Fiat_A.74)

I see this close finning especially on the BMW.
All very interesting reading too.

[TZ350]

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Koba. Great Pictures of air cooled finning. That BMW is a work of art. It gets one thinking about the possibilities of making a close finned head with a thermostatically controlled cooling fan and possibly inserting more copper cooling fins between the alloy barrel fins.
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[Fooman]

Wow thats very interesting,
Quick search and...

BMW801 (http://en.wikipedia.org/wiki/BMW_801) had a cooling fan too.

...



Erm, most air cooled radial piston aircraft engines had a cooling fan in front. They also used it to generate forward thrust...

Having said that, towards the end of the war, the (liquid cooled) Merlin/Griffon engines in the Spitfire used radiators so cleverly designed (in terms of flow through the heat exchanger and the exhaust diffuser) that the underwing radiators generated something like 150 lb's of thrust by themselves.

Cheers,
FM

[bucketracer]

Erm, most air cooled radial piston aircraft engines had a cooling fan in front. They also used it to generate forward thrust...


Good Point FM



Having said that, towards the end of the war, the (liquid cooled) Merlin/Griffon engines in the Spitfire used radiators so cleverly designed (in terms of flow through the heat exchanger and the exhaust diffuser) that the underwing radiators generated something like 150 lb's of thrust by themselves.

Cheers,
FM

The heat from the radiator had a jet propulsion effect.

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[koba]

Thats really smart shit.

[TZ350]

The heat from the radiator had a jet propulsion effect.

.

A bit of info I scraped from an air cooled aero engine page that mentions the jet effect.

" First off, the interior shape of the cowl is just as important, if not more so, than the exterior. So it would be a good idea to design a convergent/divergent shape into the front half of the cowl. Next, cooling air that enters the cowl should all be put to good use doing what it's supposed to do; carry away heat rejected through the cooling fins.

And once the air has picked up the rejected heat, the exit duct should, again, be given a lot of thought. This includes the shape and the exit area. It may be possible to design an augmenter system whereby the exhaust pulses are used to 'pump' cooling air through the cowl. Convair designed a twin engined commuter aircraft powered by a pair of Pratt & Whitney R-2800s in the late 1940s. The eighteen exhaust stacks were utilized to pump cooling air through the cowl.

Exhaust and cooling air were mixed and dumped overboard over the trailing edge of the wing. It was claimed that 500 pounds of thrust and 20mph resulted from this innovation."


I once heard/saw a Sea-Fury doing a flat run across the water and when it was real close it pulled up into a maximum rate climb. The sound was the most beautiful thing, the big radial engine climbing out at full power, truly awesome.
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[TZ350]

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Another page scrape, that talks about a ram air scoop.

"Another aspect that hasn't been touched upon is that of induction ram recovery. With a front induction engine, a carefully designed ram duct for the induction system could gain 1 to 2 in.Hg. at 150mph. This is a significant amount. Again, look at a high performance WWII fighter for good ram air induction systems. The opening, which should be normal to the air flow, must be sized correctly; too large and air spills out of the ram air duct and creates drag. Too little and full ram recovery is not possible. If, for arguments sake, the induction venturi is at 45 degrees, a duct that 'bends' the air from horizontal to 45 degrees is required. And it may even need a flow splitter within the duct to further assist the ram effect. For a rear induction engine a similar duct can be used and again, the duct should discharge into the venturi, preferably well sealed. Only with this system the air needs to bend through 180 degrees."

Picture below is of a Sea Furys ram air duct on the top of the cowl and the anular gap (about 1.5" to 2") engines cooling air.

1.5" annular gap on Sea Fury This is Nelson Ezell's Sea Fury powered by a Wright R-3350-26W. The annular gap is 1-1/2 inches and it cools just fine. Unfortunately, I couldn't get a picture of the after body but many of the 3350 powered Sea Furys' use a 1-1/2' or 2' gap. Of course, a lot of heat is rejected through the oil coolers which have spray bar assist.

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[TZ350]

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Looking at aero engines, Kobas BMW radial engine above and the cooling cowls on air cooled engines.

Gives me ideas for making a close finned head and ducting to improve the head and barrel cooling to get more sustained power from the GP125.

I have also seen a lot of ideas amoungst the aero engines that the FXR boys could use.

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[speedpro]

One of the ideas I would like to see (from a distance) you try is putting a really big propeller on the end of the crankshaft.

[TZ350]

One of the ideas I would like to see (from a distance) you try is putting a really big propeller on the end of the crankshaft.


Ok! I'v got it done. Don't say you didn't ask! :rofl: and yes they are F4 complient and when I catch you the propeller is going to chew your arse! ...:nya:

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[TZ350]

A page scrape that talks about stopping detonation.

Note the bit where it says that the latest Yamaha road racer uses a copper head insert.
Was Thomas right or was Thomas right! :woohoo: whats more he thought of it first. Who's your daddy now. :wari:

Or at least we thought of it and implemented it before reading about Yamaha doing it. You can bet they used a dyno and explored all the options. There is some satisfaction in taking a thought out approach that goes against conventional wisdom and finding your were right.

Now we know! ceramic coating the combustion chamber is defiantly "not" the go! and as we came to suspect, only a sales gimmick like the "Port and Polish" for 4-strokes became. If you want high flow in a 4-stroke port, shape it and then sand blast the port walls. There is a reason why golf balls have a dimpled surface.

Coating the piston and exhaust port still has possibilities though.

The rest of the article can be read here:- http://www.factorypipe.com/t_deto.php


"Therefore the following will work; (to combat detonation)

(1) Lower intake temperature

(2) Lower throttle position, lower volumetric efficiency, or reduced turbo boost the less mixture that enters the cylinder, the less it is heated by compression.

(3) Lower intake pipe, crankcase, and/or cylinder, piston, or head temperatures. This year's Yamaha 250cc road race engine, for instance, has a copper cylinder head insert to conduct combustion heat away faster, resulting in a lower combustion chamber surface temperature.

(the operative words are "lower combustion chamber surface temperature" which is the thing you don't get with a ceramic coating)

(4) Lower compression ratio. The less you squeeze it, the less it is heated.

(5) A more breakdown resistant fuel, such as toluene or isooctane. If straight chain molecules are not present, the fuel will not be broken down so rapidly by preflame reactions.

(6) A negative catalyst something that will either pin down active radicals or convert them into something harmless. Tetraethyl lead, MMT, or other antiknock compounds are the medicine.

(7) Retarded timing shortens the time during which proknock reactions can take place.

(8) Incylinder turbulence or anything else that will speed up combustion (faster burning fuel such as benzene). This works by completing combustion before the time bomb of preflame reactions cooks long enough to cause autoignition.

(9) Higher engine rpm This simply shortens the time during which the mixture is held at high temp. In Honda experiments in the 1960's, they found that an engine's octane requirements began to decrease steadily over 12,000 rpm, and were under 60 octane up near 20,000. In a more accessible example, note that engines knock when they are "lugged" run at low rpm, wide open throttle and stop knocking promptly when you shift down a gear and let the engine rev up more. This stops deto by not allowing enough time for the reactions that cause it.

(10) Redesigning troublesome exhaust pipes. Some pipes give great numbers on the dyno, but can't be used because they cause seizures. They either simply overcharge the engine in some narrow rpm band (pushing it into detonation just as too much turbo boost would do), or back pump mixture from the header pipe that has picked up too much heat (this is why nobody heat wraps header pipes anymore).

(11) Avoiding excessive backpressure. Exhaust pipes always create back pressure, but the more there is, the higher the fraction of hot exhaust gas that will be unable to leave the cylinder during exhaust. Its heat, added to the fresh charge that next enters the cylinder, may push the engine over the line into detonation. Sometimes a one or two millimeter reduction in tailpipe ID will get you a couple of extra horsepower, but it may also push enough extra heat into the charge to make the engine detonate after a few seconds.

The number of ways of playing footsie with detonation is endless, but nothing works every time. This guarantees that we will never be bored, and will never run out of seized pistons."

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[Buckets4Me]

Those of us who began racing before water cooling arrived tend to think that engines get hotter the more we jet them down. With air cooling, this seems to be true, but isn't. The engine runs cool when it's rich because the extra fuel reduces peak flame temperature, and as we jet down towards chemically correct mixture, the engine runs hotter and hotter.

you run you engine leaner than mine :eek5: just a thought

[TZ350]

Those of us who began racing before water cooling arrived tend to think that engines get hotter the more we jet them down. With air cooling, this seems to be true, but isn't. The engine runs cool when it's rich because the extra fuel reduces peak flame temperature, and as we jet down towards chemically correct mixture, the engine runs hotter and hotter.

you run you engine leaner than mine :eek5: just a thought

More from the same article

Now we know, from our experiences with water-cooled engines, that power, engine temperature, and exhaust gas temperature all rise as we jet down until we go beyond chemically correct mixture. When we do, power, engine temperature, and exhaust gas temperature all begin to fall again. We couldn't see this before, with air-cooling, because the power we were making was overwhelming the engine's cooling ability. But it makes perfect sense because heat release in combustion depends upon finding enough oxygen so that each and every hydrogen and carbon in the fuel is completely reacted to form water and carbon dioxide. Any fuel left over is potential chemical energy unreleased which is why running lean makes less power. On a well cooled engine that is not detonating, you can jet down until it starts to slow down.

http://www.factorypipe.com/t_deto.php

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[Rick 52]

Great work fellas you must be pleased to hear that Yamaha used the copper gaskets it shows you are on the same thinking scale .

[Buckets4Me]

Great work fellas you must be pleased to hear that Yamaha used the copper gaskets it shows you are on the same thinking scale .

Yamaha TZ350 where did it all start I wonder
i remember a t250 suzuki with yahama barrels on it lol
and the biggest drilled disks a 5 yearold had ever seen

[bucketracer]

So you and F5 Dave were right, Ceramic Coating the combustion chamber is counter productive.

Interesting to see that a 2-stroke can be tuned up with porting etc and then need to be de-tuned with a rich mixture so that the waste heat from the extra power does not overwhelm the cooling system.

Not much point in porting/chamber for extra power in an air cooled engine, better to go for wider power band.

[F5 Dave]

not sure that cellar dweller articles have been written for many years, suspect the article is say 10 yrs old, but no mind.

Does reiterate the bit about wrapping pipes & appears the belief that head inserts (that people had been using since the late 80s, but probably before) were actually helping rather than just reducing the damage from detonation. Would be proof i suppose if set up with a det counter & fitted same head with a ring insert & see if det count reduces or stops. (tricky electronic racing setups mean you can jet your RS or whatever so that it is just on borderline of detonating where it produces most power, but not go too far. Shorter sparkplugs are fitted with a piezoelectric det counter underneath).

[F5 Dave]

. . .

Not much point in porting/chamber for extra power in an air cooled engine, better to go for wider power band.
not messy celery.
You can still drastically improve the BMEP of a roadbike/farmbike engine Buckets are generally made from, but yes there is a tradeoff that; high revs, high compression, peaky power, are all counter productive after a point of compromise. But that is why the rules allow an extra 25% capacity which is quite generous. Hence the carb size i guess.

[bucketracer]

not sure that cellar dweller articles have been written for many years, suspect the article is say 10 yrs old, but no mind.

Does reiterate the bit about wrapping pipes & appears the belief that head inserts (that people had been using since the late 80s, but probably before) were actually helping rather than just reducing the damage from detonation. Would be proof i suppose if set up with a det counter & fitted same head with a ring insert & see if det count reduces or stops. (tricky electronic racing setups mean you can jet your RS or whatever so that it is just on borderline of detonating where it produces most power, but not go too far. Shorter sparkplugs are fitted with a piezoelectric det counter underneath).

Not sure they are talking about detonation ring which is usualy made from brase, it specificaly talks about the copper chamber inserts job is to reduce combustion chamber surface temperature.

[F5 Dave]

yes it's not hugely specific, the squish area is in the chamber. nice to see pic

[bucketracer]

yes it's not hugely specific, the squish area is in the chamber. nice to see pic

These are brass detonation rings. Brass has a low thermal conductivity compared to copper or alloy but has a high wear resistance to the erosive effect of detonation. I am not sure the copper insert that TZ's artical talks about is a brass detonation ring but something more to do with improved combustion chamber surface cooling using a copper insert for the combustion chamber itself.

All the detonation rings I have seen were made of brass not copper, never seen a copper one.

As F5 says, a pic would be good.

[Kickaha]

Detontation rings I have seen fitted to TZs were machined in the top of the barrel like pic 1 but that wasn't a factory Yamaha thing, the later unleaded TZ the whole chamber seemed to be done like that one in the picture

[TZ350]

yes it's not hugely specific, the squish area is in the chamber. nice to see pic

These are homemade copper cylinder head inserts for an Aprilia.

This is what I would call " a copper cylinder head insert to conduct combustion heat away faster "as apposed to a detonation insert which is more of a ring around the squish band area.

I have not been able to find a Honda or Aprilia RS125 head thats been ceramic coated.

Would like to confirm if the Yamaha ones actualy exist, and a pic would be nice.

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[F5 Dave]

That will be probably a vhm head with replaceable inserts & perhaps as you say they have made own inserts. Not sure why you would bother on a water cooled bike, you can over-cool them quite easily.

[bucketracer]

That will be probably a vhm head with replaceable inserts & perhaps as you say they have made own inserts. Not sure why you would bother on a water cooled bike, you can over-cool them quite easily.

Over-Cool them quite easily, good point when you think about it.

I think a combustion chamber cut into a slug of copper and then pressed into an alloy muff may have possibilities for an air cooled motor.

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[F5 Dave]

Yeah [thinks] you still have that thermal barrier that the heat has to pass into the ally cooling fins, even as 'cast over it' like the japs do their barrels over steel liners, not sure you would be better off. as 'pressed in' you may well be quite a bit worse off. Be hard to measure if it was working better or worse. Hmmm...

[bucketracer]

Yeah [thinks] you still have that thermal barrier that the heat has to pass into the ally cooling fins, even as 'cast over it' like the japs do their barrels over steel liners, not sure you would be better off. as 'pressed in' you may well be quite a bit worse off. Be hard to measure if it was working better or worse. Hmmm...

My thinking on my own GP100 was to use a copper insert to quickly remove thermal energy from the smallish surface of the combustion chamber (copper does this faster than aluminum) which the copper transmits quickly (twice as fast as alloy) to the larger outside surface area of the copper plug to be transmitted by conduction across the copper/alloy interface and onto the alloy fins.

I was hoping because of its much greater surface area the conduction across the copper/alloy interface would happen quicker than the thermal uptake at the relatively smaller combustion chamber surface.

My thinking is if this happens then the combustion chamber surface should run cooler with the copper insert than it would have with the ordanary alloy combustion chamber.

Its a fine thery but measuring/proving it, thats a bit harder.
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[Sully60]

This thread needs a musical interlude...
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[TZ350]

not sure that cellar dweller articles have been written for many years, suspect the article is say 10 yrs old, but no mind.

Does reiterate the bit about wrapping pipes & appears the belief that head inserts (that people had been using since the late 80s, but probably before) were actually helping rather than just reducing the damage from detonation. Would be proof i suppose if set up with a det counter & fitted same head with a ring insert & see if det count reduces or stops. (tricky electronic racing setups mean you can jet your RS or whatever so that it is just on borderline of detonating where it produces most power, but not go too far. Shorter sparkplugs are fitted with a piezoelectric det counter underneath).

F5 your right, I emailed the source, that article was writen in the 90's by Kevin Cameron an engine tuner, I had not heard of him before. I Googled him and he has written several books and many articles. He's worth a Google. I am trying to find a contact so I can ask about the TZ copper inserted heads.

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[F5 Dave]

He wrote for Cycle which merged with Cycle world, he took over as technical writer from Gorden Jennings. Has been very prolific. Seek out a copy of his Sport bike performance handbook, is very worthwhile.

[TZ350]

Going to Tech Books Saturday to see what I can find.

[TZ350]

An Abstract from a Uni paper that looked into combustion chamber temperature. Although this was done using a 4-stroke it makes interesting reading and gives some insight into the combustion heat processes in a 2-stroke.


Combustion Chamber Temperature and Instantaneous Local Heat Flux Measurements in a Spark Ignition Engine

Document Number: 930217
Date Published: March 1993

Abstract:
Cylinder head combustion chamber and piston temperatures and heat fluxes were measured in a 2.2 L 4 cylinder spark ignition engine. Measurements for the combustion chamber were made at wide open throttle conditions, 1400 rpm to 5000 rpm at 600 rpm increments, additional measurements were made on the combustion chamber at part throttle conditions at 3200 rpm. Piston temperature and heat flux measurements were made at WOT conditions from 1400 to 3200 rpm in 600 rpm increments. Average combustion chamber surface temperatures ranged from 130 degrees C to 248 degrees C, while peak combustion chamber surface temperatures ranged from 142 degrees C to 258 degrees C for WOT conditions. Peak heat flux at the surface for WOT conditions in the combustion chamber ranged from 1.2 MW/m\u2 to 5.0 MW/m\u2. Central region heat fluxes were 2.3 to 2.8 times greater than those in the end gas regions of the combustion chamber. Piston temperatures were 10 to 25 degrees centigrade hotter than corresponding combustion chamber surfaces at WOT conditions. Peak heat flux values in the end gas region of the piston were 2 to 4 times greater than corresponding locations on the combustion chamber at WOT conditions. The Woschni heat transfer model correlated well with the experimental instantaneous local heat flux data. Long term heat flux data indicates that deposit formation greatly modifies surface heat transfer.


I found it interesting that:-

Average combustion chamber surface temperatures ranged from 130 degrees C to 248 degrees C and peak combustion chamber surface temperatures ranged from 142 degrees C to 258 degrees C.

Central region heat fluxes were 2.3 to 2.8 times greater than those in the end gas regions (squish area) of the combustion chamber.

Piston temperatures were 10 to 25 degrees Centigrade hotter than the corresponding combustion chamber surface.

Peak heat flux values in the end gas region (squish area) of the piston were 2 to 4 times greater than corresponding locations on the combustion chamber (squish area).

As the heat load goes up and drives the combustion chamber surface temperature up you can see how the thermal conductivity through the combustion chamber wall becomes important in avoiding localized overheating.
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[F5 Dave]

Going to Tech Books Saturday to see what I can find.

yeah they can order anything in, or try online book shop, fishpond, real groovey, or Amazon that def do have it, useful to see what looks like.

[bucketracer]

This thread needs a musical interlude...


Sully60, did you make this video? it's very good, very clever!

[TZ350]

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I loved Sully's video clip. I wish I could think of arty stuff like that. :doobey:

I have been looking at this pile of bits and been thinking about the possibilites of using ice water for making an induction air chiller.

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[Sully60]

Sully60, did you make this video? it's very good, very clever!

No I ain't that clever, If I was I'd be building an H100 motor and applying some of the things I've learned in this thread, oh wait :whistle:


I loved Sully's video clip. I wish I could think of arty stuff like that. :doobey:

Don't worry, you seem clever enough without being arty just stay off the. :doobey:

You know I posted that as a compliment eh?

[TZ350]

You know I posted that as a compliment eh?

Yes, yes I really enjoyed it. It added some much needed colour.

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[Buckets4Me]

Some rotary valve covers from vintage go-karts. The valves are 95 or 108mm and some have 34mm carbs.

I think the port area is no bigger than the carb.

Gives some idea of the port shape the fast rotary valve karts were using back in the day.

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[speedpro]

Gives a good idea of the port shape fast AC50s used as well

[TZ350]

Suzuki GP100/125 Covers and Rotary Valves.

Std. Suzuki GP100 Inlet Opens 135 BTDC Closes 45 ATDC
Ex Opens 94 ATDC Transfers Open 123, 125, 126 ATDC.

Std. Suzuki GP125 Inlet Opens 145 BTDC Closes 55 ATDC
Ex Opens 91 ATDC Transfers Open 122, 122.5, 123 ATDC.

The round Suzuki port is the same size as the carb.

I did try to make the port more square’ish like the cart’s do and the books say too, but I found I wound up with a port much larger than the carb and it did not work well for me.

If I could run a bigger carb (Bigger than 24mm) then I could square the port up and match the port area to the carb.

For now I just clean and match the port without changing its shape.

The early Suzuki racers had round ports but there are later Suzukis with the square ports like TS90's and RG500's and my Kawasaki F81M racer also has the square port shape. They all seem to have the port area the same as the carb.

.

[F5 Dave]

Well you could make a 100 & use any size carb, but if stuck with a 24 then no point making something pass through a venture & then open it up again only to have it pass through another restriction & a round tube flows best all things being equal.

However as with dirty nasty 4 strokes the entry to the valves is not simple, however they stuck a dirty great wedge poppet in the way so it serves them right. But what I am saying is look at how best to curve the gas after the valve so it flows over the crank. Perhaps it is best to transition the carb side from round to square at the top on the valve side, but only 2/3 height, ie: fill the bottom. So would that match the other side better is the question?

[TZ350]

.

As its a 125 air cooled 2-stroke we are restricted to a 24mm carb.

F5 I like your idea of squaring up the top portion of the inlet port and raising the floor so the area of the port remains the same and the incoming charge has an easier time flowing over the crank and into the crankcase.

We have been putting a 45 degree chamfer on the inlet side crank wheel to help the incoming charge flow up and over the crank on its way into the crankcase.

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[Buckets4Me]

.

Part 1

The Art of Squishing Things Till They Give (Power), Part 1

An excerp. By Dale Alexander. Its worth a read.

"My own experience with road racing was just beginning to develop. I was soon to observe that the RD would run pretty strong in 6th gear out of one corner, only to be reduced to 5th gear and finally 4th gear by the end of the race. The engine was consistently losing power as the race progressed. Something was overheating, BUT WHAT? Suzuki had Ram-Air heads on their 380 and 550 triples, after-market water-cooled heads were available but even the factory water pumpers were having a like problem so what was the point?

To make matters really confusing, all manner of porting ideas were being tried, but everyone was going pretty much the same speed or slower. So it would seem the whatever the problem was, it was related to heat, the development of power and the amount of time that the power was being used."

........................So, What IS Going On ? :scratch:

The rest can be read here:- http://www.aircooled-rd.com/default.asp?txtPage=squish1.htm
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[Buckets4Me]

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Part2

The Art of Squishing Things Till They Give (Power), Part 2

By Dale Alexander. More good reading.

Now the head is centered. Use a 1/8" "gun drill" which is simply a very long drill bit and drill down between the fins through the head and into the barrel. Don't go more than about 5-7mm, you just need enough to hold a dowel pin.

The rest is here:- http://www.aircooled-rd.com/default.asp?txtPage=squish2.htm

.

[Buckets4Me]

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Part3

The Art of Squishing Things Till They Give (Power), Part 3

By Dale Alexander

"Well, we've got a motor now that runs better than most others out there and all that we have done is close up the squish clearances to a proper value and eliminate a bothersome head gasket leak. Is there anything else that can be done? Yes, there is an even easier method of sealing the head."

And also the part "A Better Way To Cook " talks about ceramic coating the piston.

It all can be read here:- http://www.aircooled-rd.com/default.asp?txtPage=squish3.htm

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[Buckets4Me]

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Rotary valve 50cc Suzuki triple racer with the round inlet port shape.

I think the GP100/125 was based on the racers from this era., Late 60's.

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[TZ350]

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By Dale Alexander "A Better Way To Cook " talks about ceramic coating the piston.

It can be read here:- http://www.aircooled-rd.com/default.asp?txtPage=squish3.htm

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Thanks Buckets4Me they are great pictures, its been great to see how the inlet port has been arranged by factory racers and carts. The artical by Dale Alexander and especialy the bit on ceramic coating the piston crown, thats very interesting, gets me thinking again!

We are also looking at the exhaust port tract and the heat uptake in this area and have a few ideas.

There is a niggling thought in the back of my mind, :weird: that if copper is so good why has'nt the factory racers used it before?

Are we going somewhere new or is it a dead end that the factory has explored and pulled out of? Could it be possible that they got in their own rut and over looked it? <_< it;s a bit sus.

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[Chambers]

Where can I get a 14 speed gearbox for my bucket:eek:
The thermal issue is the secret where the power is (or not) and it will be interesting if the copper helps. Have you got a dyna?

[Yow Ling]

Where can I get a 14 speed gearbox for my bucket:eek:
The thermal issue is the secret where the power is (or not) and it will be interesting if the copper helps. Have you got a dyna?

roadranger will have one for you , might only be a 12 speed though

[Buddha#81]

roadranger will have one for you , might only be a 12 speed though

Two speed diff would take care of that.

[Buckets4Me]

As cooling for the air cooled 125's is the power limiting issue.

An excerpt, from an aero modler artical that talks about ducted cooling and aero engine cooling.

"It goes like this. Blowing cold air at high speed over an engine is a lousy way to cool it. Never mind that that is standard practise, it is still lousy. The heat transfer is poor, and the drag is very high.The correct way to cool is to blow low speed, high pressure air over the fins."

That chamber formed by the upper cowling is called a plenum chamber: it has a wonderful property. Being of large volume, the air that rushes in through the intake holes is permitted to expand to fill the volume of the plenum chamber. Now the magic part is that when air expands in the fashion, its speed falls and its pressure increases! Wonderful, just what we wanted, low speed air at high pressure.

how this is done can be read here:- http://www.supercoolprops.com/articles/ducted_cooling.php


More on cooling airplane engines:- http://www.supercoolprops.com/articles/gwhite.php

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[TZ350]

Thanks Buckets4Me for all your very interesting input.

We have a problem with the copper combustion chamber.

Heat from combustion reaches the combustion chamber surface in two ways, radiation and conduction. The boundry layer reduces conduction and heat take up from radiation can be minimised by having a polished surface with a low emissivity value.

Well we have discovered one of the problems with using polished copper in the combustion chamber. That is, it discolours when heated and goes a very dark brown/black where as polished aluminium retains its polish and reflective properties after normal heating.

Looking at the emissivity charts we can see that coloured copper has a high emissivity and will take up radiated heat in much larger quantities than polished aluminium.

Now we have a problem, there is not much point in having a copper combustion chamber that sheds heat twice as fast as aluminium if it takes up heat five times faster.

We think this could be a real problem and we are looking at gold plating the copper combustion chamber to try and retain its reflective properties.
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[Bren_chch]

We think this could be a real problem and we are looking at gold plating the copper combustion chamber to try and retain its reflective properties.
.

farken hard out!!! u coming to the BOB this year, i wanna see/hear this mad machine!

[koba]

We think this could be a real problem and we are looking at gold plating the copper combustion chamber to try and retain its reflective properties.
.

On old fella I know who knows alot about these things said look at silver too.

[TZ350]

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Thomas points out that ceramic coating the exhaust port tract has the same sort of problems as wraping the header pipe. It allows over heating of the fresh charge drawn into the pipe then this overheated mixture is pushed back into the cylinder by the returning pressure wave in the pipe. The over heated mixture in the combustion chamber then limits performance..

We have been looking at making a copper insert that fits in the exhaust port which draws the heat out to its own set of fins thereby reducing the cooling load on the barrel and heat transfer into the head. But converting the idea into a practical solution is proving difficult.

All I want is to be able to improve the (air) cooling so I can lean the mixture a little and recover some power, is that to much to ask from the :sunny: God of Speed?
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[TZ350]

farken hard out!!! u coming to the BOB this year, i wanna see/hear this mad machine!

We would love too! I have to get work to find an excuse for me to be in the South Island then. So I can tow the bikes down and the others can fly. When is the BoB this year?

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[TZ350]

On old fella I know who knows alot about these things said look at silver too.

Silver might be more pratical from a cost point of view, but wouldn't it tarnish with the heat?

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[TZ350]

On old fella I know who knows alot about these things said look at silver too.

Silver might be more pratical from a cost point of view, but wouldn't it tarnish with the heat?

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[speedpro]

What about aluminium. It polishes nicely and doesn't seem to tarnish in a 2-stroke chamber and it should be a pretty good price.

[TZ350]

What about aluminium. It polishes nicely and doesn't seem to tarnish in a 2-stroke chamber and it should be a pretty good price.

Could this be why the factory uses aluminium? :doh: :crybaby: this hotting up business is real hard to do! :angry2:

[SS90]

hmmmmmmmmm

[SS90]

Sorry to pull back on the topic a bit, but I was looking at the photo's of the seizure marks on your piston, and would like to suggest that there is a good chance that the cam grind is not too far wrong for your air cooled engine. True, a Piston designed for a Liquid cooled engine, has less Cam grind (less of an egg shape), due to the fact that the thrust face of the piston is subject to less heat expansion, but, in my experience, you only have to pay particular attention to the piston to bore clearance.

What is the clearance you use when honing the new cylinder to size?

What is interesting to note, is that (from what you describe, and what is evident in the picture), there are 4 even seizure marks that would correspond with the pressure points on the side of the cylinder, where the studs run.

I believe they are 8mm studs.

Due to the fact that the engine is in a high state of tune, as you have clearly established, extreme amounts of heat are thereby generated...... The original expansion amount of the cylinder (particularly in regards to height) is well and truly exceeded.

Therefore, the 8mm bolts, in my opinion, are causing the cylinder to "squash", as the studs, do not expand the same amount as the cylinder.

Basically, when hot, the cylinder goes "hour glass shape".

This, coupled with, possibly, incorrect piston clearance would cause this problem.

One solution would be to use thinner studs (7mm are hard to come by, but are available), or, as the Japanese did in some bigger 4 stroke engines, use "waisted studs", where the studs tapers in in the middle, allowing for more elastisity of the studs..........

If I am right, then this (more clearance, thinner studs) would decrease the temperature of the engine somewhat.

There are literally hundreds of thousands of modified high powered air cooled two stroke engines in use today using pistons designed for liquid cooled engines that have no seizure problems.

Also, a piston that seizes because of the incorrect cam grind, does not seize on all 4 stud points, it seizes on the thrust face (because if the cam grind was too small to suit the heat of the air cooled cylinder, the first part to touch would be the thrust face, not the stud pressure points.......... (think about it)...... That's because of heat... the very thing you are battling!)

Remember that a cast iron lined cylinder is 30% more efficient at displacing heat than a cast iron one, and a Nigusil (or similar) coated cast aluminum cylinder is 30% more again than that (approximately), and there are plenty of examples of cast iron cylinders 125-133cc that can be modified to put out more than 22HP (marginally though), for example Mallossi Small frame Vespa Cylinders (although they are force fed air via a fan and shroud) Can be modified (alot) to put out 23 HP or so, but they do not suffer from excessive heat related power fading, due to the fact that the guys doing this have VERY carefully designed exhaust systems, that maintain a more constant combustion chamber temperature, (and yes, the fan), also a big consideration is again, compression ratio..... TO FINISH FIRST, FIRST YOU MUST FINISH, and with an air cooled motor, there is always going to be a compromise in relation to cooling vs power.

Also, what is your primary compression ratio?

I see you are familiar with Gordon Jennings writings.... he points out (and you have touched on this subject much earlier on) that the suggested (and this is backed up by the Japanese engineer Fujio Nagao) that primary compression ratio's over 1.5:1 give "little to no advantage", and also, the pumping losses are increased!

I realise that you have lowered the ratio with things like the chamfering of the intake side of the crank web, but have you measured the ratio at any time? It could be worthwhile at some stage.

Maybe it is actually lower that 1.5:1

If this is that case, increasing it would improve overall efficiency, and therefore lower overall temperature.

A more efficient engine is simply a cooler engine.

Although, it should also be noted that Gordon Jennings points out.....

" deficiency in air delivery due to a crankcase volume too great for a given engine speed is fairly well compensated by properly tuned intake and exhaust pipes"


I seriously would look at the design of the exhaust as another option to lower overall engine temperature as well.

[koba]

Not sure on the logic behind the silver, but the guy who said it tends to be right on weird shit I don't understand.

Onthe stud subject Volkswagen switched from 8mm studs to 7 or maybe even 6mm studs when they upped the flow of the heads and they stopped the cases cracking from un-even expansion.

[F5 Dave]

Well i think irrespective of the plating on the inside you should definitely gold plate the outside of the head.

YoYo, boys in the hood check out my bling bling [& so on & so forth] A few medallions worn outside your leathers, well, you could be the badest Ho talkin Homie at the track. Word.

:shifty:

[Bren_chch]

Sorry to pull back on the topic a bit,....

man... just as i thought i was getting to grips with all this you come along and confuse me again! :clap: :niceone:

Good explination of things, i like the idea of tapered studs.

[speedpro]

Could this be why the factory uses aluminium? :doh: :crybaby: this hotting up business is real hard to do! :angry2:

You noticed the irony in my suggestion??

[Sully60]

You noticed the irony in my suggestion??

What's irony about aluminium?

[Buckets4Me]

What's irony about aluminium?

:eek5: starts with ally head
goes to copper as it trasmitts more heat faster
then goes back to ally :crazy:

round and round he goes
nobody knows where he will stop

(with a stock engine again) :bash:

[TZ350]

Well i think irrespective of the plating on the inside you should definitely gold plate the outside of the head.

YoYo, boys in the hood check out my bling bling [& so on & so forth] A few medallions worn outside your leathers, well, you could be the badest Ho talkin Homie at the track. Word.

:shifty:


Your just making fun of my good looks :eek: and charm.
Yes I know looks like I have excitedly run down another blind alley scattering $$$$ behind me.


I haven't given up on the copper yet.

Koba and SS90 make some good suggestions. They are worth looking at but it will take some time to digest them.

Same piston set up, 0.002" clearance, with a new piston but same type, make size Etc., as previous season. I have measured the crankcase volume before using a measuring cylinder but there are differing ideas about what constitutes the crankcase volume, Does it include the transfer ducts?

The stud idea sounds promising.The GP has a composite head gasket standard but I don't use one as I have "O" ringed the barrel. Could be the composite gasket took up some of the cylinder expansion before.

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[koba]

Didn't some old bikes use bronze heads?
Excelsior (UK) Maybe?
I wonder if there is anything to that...

Edit:
Rudge!
Four valves too!

Edit again:
Cut and paste -
The first machine to bear the Ulster name emanating from the Rudge factory was announced during 1928 in celebration of their success in that years Ulster Grand Prix. The Ulster became a fixture at head of the company's catalogue until production ceased in 1940, early versions featuring a pent roof four valve head which was replaced for the 1932 season with a radial four valve head with the option of a foot operated gear change becoming available in the same year. The valve gear remained exposed to the elements until 1937 when a simple cast alloy cover was adopted although the bronze cylinder head remained finally being replaced with a light alloy example in 1939.

Image provided by www.classic-auctions.com.



Thats some high tech shit for its day!

[TZ350]

A 250cc four valve two exhaust ports bronze head Rudge.

[Buckets4Me]

A 250cc four valve two exhaust ports bronze head Rudge.

Looks like a bucket to me

[SS90]

Bronze Cylinder head?

The last time I heard that I fell off my Dinosaur!

Come on people, if Bronze cylinder heads where any good, don't you think that they would have been used later that the 1920's

Seriously, an ally head is completely feasable in this situation, with-out the need for heat sinks (as good an idea as that was), or cylinder heads made out of "unobtainium" or any other precious metal!

Can any one here show me a japanese (or european) (air cooled) 125 GP bike that had anything other than an Aluminium head?

Personally I don't know of one.

The way that the "founding fathers" of tuned air cooled two strokes dealt with this problem, was to treat the cause, not the problem........

Now, I know that you are limited to a piddly little 24mm carb (booooo!), And this in itself will cause a hotter engine (anyone who doesn't know why needs to read a little about two strokes........)
....and, as such, you cannot increase the carb size, but there are alot of other ways to decrease your overall engine temp, (and, in particular,your combustion chamber temp,and therefore your cylinder head temp)

Tee zeee tree fiddee, from what you write, I can see you have read some of Gordon Jennings writings.......take a look and see what he has to say in regards to exhaust port duration, and cylinder head temperature......perhaps it could be considered an option to drop a few degrees (a simple task really, even though that will also lower your transfer timing if you simply use the spacer method)

Lowering your exhaust timing will also increase your torque at lower RPM's, giving you more drive out of the corners.....who knows, that might lower your lap times too!:clap:

Who many P.S does the engine currently have, and more importantly, how many NM...... (and at what RPM).... this is THE REAL TEST of an engine (afterall, you cannot measure P.S (or HORSEPOWER), you can only measure torque, then divide it by the RPM and multiply it by 5252 to get P.S (or horse power)

Correction factors not withstanding.

I digress....

Basically, it seems that you have exceeded the thermetric efficency of the materials of your engine (perhaps because of the fact that you are using calculations (port timing and exhaust designs) that where developed for modern (read liquid cooled) engines.

That's how it seems to me.

personally, I would never exceed 191 (MAXIMUM) degrees exhaust, and 131 transfer on an air cooled engine

I would opt for something like 188 and 131..............

I'm not trying to knock all your hard work Teee Zeee, just trying to encourage you too see it through to the end!

[TZ350]

Certainly a lot to think about here.

I have come to understand that tuners often spend much effort tuning their motors up with ports and pipes etc., then have to reduce the power output by tuning their engines down with a rich mixture so that the engines waste heat from that extra power does not overwhelm the (air) cooling system.

From this I understand that by leaning out the over rich mixture I will be able to use more of the power my motor can make from the modified ports and pipe if I can improve the cooling system.

To improve the air cooling system on my motor I need to think about the total distance from the combustion chamber surface to the fins. Ie the total mean thermal path and how to shorten it.

Port timings I have been using.

Short Track Ex opens 86 ATDC 188 Duration.
............Trans opens 116ATDC 128 Duration.
or.........Trans opens 114ATDC 132 Duration. to widen the power band.

Short Track Ex opens 83 ATDC 194 Duration.
............Trans opens 115ATDC 130 Duration.

Taupo Track Ex opens 81 ATDC 198 Duration.
.............Trans opens 114ATDC 132 Duration.

Started with a pipe from a RG250 then modified it to the RM125 specs found in Gordon Jennings book. (A list of books that can be down loaded from the net appear earlier in this thread).

Interestingly the port specs below are much like what you sugest.

Suzuki RM 125 Ex opens 86 ATDC 188 Duration.
...............Trans opens 114ATDC 132 Duration.

Honda RS 125 Ex opens 86 ATDC 188 Duration.
................Trans opens 115ATDC 130 Duration.

It might be Gordon Jennings et.,all and the approch I have followed from them is a bit old school.

I see current trends like The Wobbly port/pipe specs are for shorter durations. ie., Ex opens 87.5 ATDC Trans 116.5

Speedpro has just finished a Wobbly spec port/pipe setup and his bike runs realy fast.

I don't know why a smaller carb would cause a two stroke to run hotter, will have to find out.

This is buckets, having a go, finding out, and trying it out is all part of the fun, with my old TZ I could never have afforded to experiment like this.

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[F5 Dave]

I don't think one can just throw around port timing numbers with much sense. Ok here's some; I used to run 202deg ex. Worked well on that particular engine.

Taken out of context it means nothing. No talk of where peak power is or spread, or other constraints of the engine, rings etc.

TZ I would be careful about going down the lower transfer path. MBs for example have quite okish transfer ports. GPs are a little less cool.

2thou clearance is quite loose, but entirely appropriate for this engine I'd say & what I ran on the aircooled H100 with no drama & no seizing, wear or excessive overheating. But that was a lowly stressed low revving midrangey 18hp aircooled 100cc.

[F5 Dave]

........ Now, I know that you are limited to a piddly little 24mm carb (booooo!), And this in itself will cause a hotter engine (anyone who doesn't know why needs to read a little about two strokes...........
Well it will greatly increase the intake velocity as the revs go up, but I can't see why it would increase engine temperature, one could easily make it as rich as you wanted & in fact with less charge being burnt there is less energy to dissipate. They of course came with 24mm as std.

I'd consider myself well read in this area, but that's not something I have come across.

[Bren_chch]

:corn::drinkup:

[Skunk]

:corn::drinkup:
Me too... :corn:

[SS90]

Well it will greatly increase the intake velocity as the revs go up, but I can't see why it would increase engine temperature, one could easily make it as rich as you wanted & in fact with less charge being burnt there is less energy to dissipate. They of course came with 24mm as std.

I'd consider myself well read in this area, but that's not something I have come across.

Quite right on the fact that they came with a 24mm carb..... and this is a perfect example.

I am going to assume that the original engine, due to the fact that it did not have a) an expansion chamber
b) "squish band head"
c) high compression
d) a "gas flowed", or "chamfered" intake web
would only rev to say....5000 RPM (or thereabouts)

a 24mm carb would be adequate, given the fact that the engine does not require large amounts of air, and it would run as designed.

Quite nicely actually.

Now, the engine is really spinning (11,000 RPM?) particularly at high RPM, the pumping losses (horsepower absorbed by the action of operating the crankcase "pump") go up exponentially (regardless of the fact that the chamber is "helping" scavenge, and decreasing this loss a little)

This is really unevoidable, but, in this case is compounded by the fact that the carb is simply too small for a 125cc engine spinning at 11,000 RPM

Think of it like this.

If you are cycling (possibly to the pub), and you are breathing only through your nose (not getting enough air), you will overheat, as your "pumping losses" are increased.

O.K, the human body is not a pump, but I think it's a nice example, as we can all relate......

If you where then to start breathing through your mouth, and allowing your body to get more air, you then become more energy efficient, and you will in turn run cooler.

An engine (particularly a two stroke, as you all know is just a pump), if you restrict the amount of intake ( to a point that is too far below optimum), efficiency will go down, and temperature will increase.

I think you would all agree that a good size would actually be something closer to 29mm - 32mm (max), and, as you pointed out a smaller carb would increase velocity as revs go up, but as velocity increases, so to does the temperature of the air fuel mixture....not always a good thing.....

I believe if he did away with the whole disc valve set up, and adapted a reedblock to the intake port, then this would also help as the negative pressure under the piston will control the intake as and when the engine needs it.......but, my god, I don't want to kill the guy with trying out theories that may only slightly alleviate the problem, or not even make a difference

The little GP125 has Asthma..........

And, this is unevoidable, because it's in a semi "controlled" class.

I agree also with the notion that it is aimless to talk about port timings "willy nilly", as, in reality, as you pointed out, every single design is different (reed valve, crankcase induction engines (Mb100 for example) are quite different in what they run "best" at in regards to port time areas.



I did, however, ask where is peak torque was, as that is quite important..........

The only reason I mentioned it was to point out that larger exhaust port time areas increase cylinder and cylinder head temperatures, and I want to suggest that if the engine was a little "down tuned" ( A little less peak power, and more torque in the lower RPM), ( But can you consider that "Downtuning", or is it really UP tuning...... it's all about perspective I guess) then the engine will run cooler, and be alot easier to ride.

[bucketracer]

.

SS90 I see some very confident statements being made and it would be a mistake I think, for any one to judge TZ's understanding to harshly. :nono: I suspect, just because he listens to you and considers what you say, doesn’t mean he is without any clues himself.

.

[TZ350]

A preview of Kevin Camerons book “Sportbike Performance Handbook” can be found here:-

http://books.google.co.nz/books?id=LswdRd2Zm8YC&pg=PA85&lpg=PA85&dq=tz250+detonation+repair&source=bl&ots=zYYDz0MEyv&sig=pRPBbN00SOAg-wfME3O1YZCk9KU&hl=en&ei=Ve2tSb6iBYT06QO585zgBQ&sa=X&oi=book_result&resnum=1&ct=result#PPA81,M1

It's worth a look.
.

[TZ350]

The little GP125 has Asthma..........

And, this is unevoidable, because it's in a semi "controlled" class.

I did, however, ask where is peak torque was, as that is quite important..........



Quite right about the Asthma.

The Std GP125 from memory is 13HP or 15HP (depending on who you listen too), at 8,500 Rpm and peak torque at 7500.

With the limitation of a 24mm carb I am looking at a peak Rpm of 10,000/10,500 and peak torque around the 9,000 mark and have tried to adjust the time area values of the ports to suit these constraints.

.

[TZ350]

The only reason I mentioned it was to point out that larger exhaust port time areas increase cylinder and cylinder head temperatures, and I want to suggest that if the engine was a little "down tuned" ( A little less peak power, and more torque in the lower RPM), ( But can you consider that "Downtuning", or is it really UP tuning...... it's all about perspective I guess) then the engine will run cooler, and be alot easier to ride.

I think your right, this could be a case of "a little less is more".

.

[F5 Dave]

. . .
Think of it like this.

If you are cycling (possibly to the pub), and you are breathing only through your nose (not getting enough air), you will overheat, as your "pumping losses" are increased.

O.K, the human body is not a pump, but I think it's a nice example, as we can all relate......

If you where then to start breathing through your mouth, and allowing your body to get more air, you then become more energy efficient, and you will in turn run cooler.

An engine (particularly a two stroke, as you all know is just a pump), if you restrict the amount of intake ( to a point that is too far below optimum), efficiency will go down, and temperature will increase.
. . .
Um. . .actually I don't think that is a good analogy. Yes I see the 24mm carb as a restriction, but I still don't see it as a source of extra heat. The heatsource is reliant on the calorific value of the petrol being burnt at a particular efficiency, & then the efficiency of how that heat is dissipated determines how hot the engine remains after doing set work. I do however agree about the height & size of exhaust port as that falls into both columns.

Are you saying that a smaller carb increases the efficiency that gas burns? . . . or how it is dissipated? :Pokey:

ok so just to be a nit picker 'cause I'm a bit of a krunt, I don't think of an engine as just a pump, particularly not a 2 stroke with an expansion chamber. For 2 reasons. Let's see if we can all name them (and that's is disregarding the whole thermodynamic side of an engine).

[speedpro]

Interesting statements being made here. I have to side with F5 in questioning the "smaller carb making things hotter" idea though.

Port timing, welllll . . . . . where to start? I've run a piston port TS100 with 200deg of exhaust port and 200deg of intake and a 32mm carb. Somehow or other it was a tractor but still made 19.9rwhp at about 10,000rpm. The dyno curve was big and fat.

I've run 200deg ex on a MB100 with a 28mm keihin and it made 19.9rwhp with a big fat powerband as well with over 14hp between 9000rpm and 13500rpm.

I've run RG 50s, piston port and full reed valve, with in excess of 200deg ex port timing and they both made a nice 10+hp.

My best MB had about 190+ ex timing, 4 petal reed and the same 32mm carb and it made a real good 22.5rwhp with a huge wide powerband.

I haven't dyno'd the latest MB but it is VERY good and has I think even less port timing than a standard MB. There has been a bit of careful porting done though.

[Buckets4Me]

who is a nip pikking krunchy bar then :confused:

hay how about this
why dont you coat the copper inside the head with ceramic (the old ceramic coating creats HP)

but not a very thick coat just thick enough to protect the copper from discolouring and changing it's heat absorbing properties but not thick enough to stop the heat getting to it :jerry:

now that may stop you having to take the head off and polishing it between races :eek:

round and round we go ????
just a thought

also what about the 4 studs could they be the problem at Taupo with the siezures ????? ( seems like a valid point how to test how to test. without spending any money or time making new thinner studs)

:jerry: back to it then keep making my next engine better :eek:

[speedpro]

The studs question. I assembled the new MB with a bit less than .002" and carefully ran it in. It has usage marks front and rear and that's it. I presume the suggestion to use thinner studs is to deliberately weaken them and therefore allow the motor to expand with heat. What would be interesting would be to clamp a barrel to something real solid with the head on top and slowly up the torque on the studs while measuring the bore. Then you would see if the bore distorting due to increased clamping force was the culprit for the piston damage. I personally don't think so.

[TZ350]

.

In one of the many articles I’ve read recently it talked about pistons seizing from to much clearance as they have reduced thermal contact with the bore.

.

[Yow Ling]

I have an old Gordon Jennings article where he belives most seizires are caused by worn rings, His thoery is worn rings give rise to blow by or gas leakage which interferes with the integrity of the oil film on the piston and bore making an engine with worn rings more likley to seize. He also recomends running as much oil as your ignition can stand.

Running fresh rings makes sense in that they are the means for the piston to transfer heat to the cylinder walls. If you are interested I can scan the atricle and post it up

[speedpro]

Years ago Bob Haldane did an experiment with some Yamaha 2 stroke. On the dyno it made more and more horsepower the more oil they had in the mixture. Makes sense. Oil is a lubricant and as we all know you can't go wrong with more lubrication. The other purpose of oil is to help seal the piston/rings to the bore

[TZ350]

I have an old Gordon Jennings article where he belives most seizires are caused by worn rings, His thoery is worn rings give rise to blow by or gas leakage which interferes with the integrity of the oil film on the piston and bore making an engine with worn rings more likley to seize. He also recomends running as much oil as your ignition can stand.

Running fresh rings makes sense in that they are the means for the piston to transfer heat to the cylinder walls. If you are interested I can scan the atricle and post it up


Yes please, that would be interesting to read.

[TZ350]

.

How strong is a cast iron liner? When I was reconditioning engines and needed to fit a sleeve we would bore the cylinder to size and sit the sleeve on top. Then place a round thick (2") steel block on top of the sleeve. Then use a sledgehammer to drive the sleeve down into the block. Some times when the interferance was a bit tight the buggers were realy hard to drive down, cracked a few blocks, never broke a sleeve.

When I was running an RD350 I made up a jig from two heavy plates with studs that a cylinder could be clamped between. With the assembly all correctly torqued up the cylinder could be honed or rebored. The cylinder would then be perfectly round and parallel when fitted to the engine. Possibly its something I should do again for the GP.

.

[SS90]

.

How strong is a cast iron liner? When I was reconditioning engines and needed to fit a sleeve we would bore the cylinder to size and sit the sleeve on top. Then place a round thick (2") steel block on top of the sleeve. Then use a sledgehammer to drive the sleeve down into the block. Some times when the interferance was a bit tight the buggers were realy hard to drive down, cracked a few blocks, never broke a sleeve.

When I was running an RD350 I made up a jig from two heavy plates with studs that a cylinder could be clamped between. With the assembly all correctly torqued up the cylinder could be honed or rebored. The cylinder would then be perfectly round and parallel when fitted to the engine. Possibly its something I should do again for the GP.

.

What you refer to here teezee, are called "Torque plates".....

Big, heavy, air cooled, steel lined, notoriously hot running engines (Mr Harley davidson, I'm looking at you.......) can only be bored and honed using torque plates, as, when the engine gets hot, the cylinder goes out of round (due to the fact that these have very long studs, (which, incidently are wasted, as I described....), and when the engine goes from hot to cold (a height difference of some 20thou in terms of height), the cylinder gets "squashed", and goes out of round, leading to more heat related problems (much like TeeZee is experiencing)

F5, questions my belief that the size of the carb is causing more heat problems, and, rightly so..

Perhaps if you think of it this way.

There is a point where the carb is just too small (as there is a point where a carb is just too big (opposed to being 1 or 2 mm bigger than the opitimum, and having no advantage/disadvantage (other than a larger induction "roar")

I suggest that the carb is on the side of "too small",and, as such, is restricting more than just the power of the engine.

What f5 points out in regards to calorific values is clearly correct, however, this engine is at a stage of "increasing returns" in regards to improved cooling of the entire engine plant, and every little thing would help.

Mind you, he can't change the carb size... so talking about it is purely academic.

I will however, alter by my statement to say, that a carb that is on the side of "too small" (opposed to just "smaller") will make engine run hotter.

But, to get to where I was heading with this concept.

My thought is this.

I have referred to the idea that (possibly) the primary compression is too low, and I have quoted "losses made by too bigger crankcase volumes (exceeding ratios over 1.5:1) at given RPM can be more than compensated by correctly tuned ex and intakes"

Now, I know that the modern tuning methods use 1.5:1 as a constant (because, well, this rule is correct)

But, maybe the engine is (due to the fact that material has been removed from the intake side crankweb ( incresing the volume of the crankcase, possibly making it lower than 1.5:1, and losing efficiency)

Or, more to the point, due to the fact that the intake system is not "properly tuned" (because, due to the rules, it is too small), maybe a ratio of OVER 1.5:1 is applicable for this situation.

Now, I know that this "increase the primary compression" is a very old concept, and may well be treated with some disdain, but, in my opinion, you need to come up with a way of compensating for your intake size deficit.

[SS90]

I have an old Gordon Jennings article where he belives most seizires are caused by worn rings, His thoery is worn rings give rise to blow by or gas leakage which interferes with the integrity of the oil film on the piston and bore making an engine with worn rings more likley to seize. He also recomends running as much oil as your ignition can stand.

Running fresh rings makes sense in that they are the means for the piston to transfer heat to the cylinder walls. If you are interested I can scan the atricle and post it up

OK, now that someone has brought up this, I would like to bring up another idea...(sorry Tee Zee, but.....)

What are the gains (in your opinion) that you are getting from having a single ring piston?

As Yowling correctly points out, the rings are a means of the piston transferring heat to the cylinder wall,

.......and you only have one....

Now, using a modern "high silicone" piston, is a great idea, but, the only real advantage of having one ring, is the fact that you gain more RPM (and not much else)

There are alot of myths around single ring pistons, and alot of these start in bar rooms and pit lane.

I would like to suggest that having one ring on a piston in an engine that only revs to 10,000 or so, may well be a deficit, particularly in terms of heat dissipation.

Infact, I believe that you would only get tangible gains if the engine was revving to say......12,000 and up!

But again, if I am right, this would only be part of the solution, as it is a contributing fact, rather than a primary cause.

[SS90]

Certainly a lot to think about here.

I have come to understand that tuners often spend much effort tuning their motors up with ports and pipes etc., then have to reduce the power output by tuning their engines down with a rich mixture so that the engines waste heat from that extra power does not overwhelm the (air) cooling system.

From this I understand that by leaning out the over rich mixture I will be able to use more of the power my motor can make from the modified ports and pipe if I can improve the cooling system.

To improve the air cooling system on my motor I need to think about the total distance from the combustion chamber surface to the fins. Ie the total mean thermal path and how to shorten it.

Port timings I have been using.

Short Track Ex opens 86 ATDC 188 Duration.
............Trans opens 116ATDC 128 Duration.
or.........Trans opens 114ATDC 132 Duration. to widen the power band.

Short Track Ex opens 83 ATDC 194 Duration.
............Trans opens 115ATDC 130 Duration.

Taupo Track Ex opens 81 ATDC 198 Duration.
.............Trans opens 114ATDC 132 Duration.

Started with a pipe from a RG250 then modified it to the RM125 specs found in Gordon Jennings book. (A list of books that can be down loaded from the net appear earlier in this thread).

Interestingly the port specs below are much like what you sugest.

Suzuki RM 125 Ex opens 86 ATDC 188 Duration.
...............Trans opens 114ATDC 132 Duration.

Honda RS 125 Ex opens 86 ATDC 188 Duration.
................Trans opens 115ATDC 130 Duration.

It might be Gordon Jennings et.,all and the approch I have followed from them is a bit old school.

I see current trends like The Wobbly port/pipe specs are for shorter durations. ie., Ex opens 87.5 ATDC Trans 116.5

Speedpro has just finished a Wobbly spec port/pipe setup and his bike runs realy fast.

I don't know why a smaller carb would cause a two stroke to run hotter, will have to find out.

This is buckets, having a go, finding out, and trying it out is all part of the fun, with my old TZ I could never have afforded to experiment like this.

.

Ok,

Taupo, 198 ex 132 transfer........

Hmmmm, and Taupo was where you had your heat seizure related damage......and these are the highest timings you have run....

Lets put that simply......

The same track that you experienced the most heat related problems, is the same track you ran the highest ex port time areas.......

I'm seeing a pattern here, anyone else?

Can I also point out that I question the wisdom of changing the port timings for an individual track.

Wouldn't it be more advisable to lower or raise the squish too suit (allowing more over-rev for longer, faster tracks)

This in itself will cool the combustion chamber.

[Buddha#81]

If anyone hear me talking of running a 2 stroke please slap me. Go the Deisels!

[Sully60]

If anyone hear me talking of running a 2 stroke please slap me. Go the Deisels!
^^^^:yes:
Suck, squeeze, bang, blow, none of this doing two things at once shit 4TFTW!:Punk:

Just don't mention two stroke diesels:whistle:

[F5 Dave]

If anyone hear me talking of running a 2 stroke please slap me. Go the Deisels!

Oh I think what you need down in Chch is another fast 2 stroke to give you all the learn. I'll put a man on it.:msn-wink:

[Buckets4Me]

If anyone hear me talking of running a 2 stroke please slap me. Go the Deisels!

at least this bike runs and dosent stop unlike the trusty FXR which brake conrods :shit:

[TZ350]

.
Crankcase Compression Ratio
Let V1 be the swept volume of the cylinder.
V2 be the crankcase clearance volume, that is, the volume below the piston crown at BDC excluding the volume of the transfer duct(s).
Crankcase Compression Ratio = (V1 + V2)/V2

The Data:-

.................................................. . = 250cc CR = 1.50

Std GP125 crankcase clearance volume = 275cc CR = 1.46

Chamfered Crank Inlet Side ............... = 280cc CR = 1.45

Long Rod 14mm Spacer under the Barrel= 375cc CR = 1.33

I understand from Graham Bells book (1) to increase torque and reduce engine peekeness, I need increased crankcase volume to lower the velocity of the transfer streams and increased transfer period. And from John Dixons book (2) that a ratio of 1.5 is good which is what SS90 also said.

These results look wrong to me :scratch: I used Bells formula (1) and got similar results. It looks like I need to reduce the crankcase volume to get a CR of 1.5. I thought I would be close or have to increase the volume on the GP. Even the STD GP125 engine is a bit low.

Totaly opposite to what I expected.

(1) Two-Stroke Performance Tuning. A. Graham Bell. First Edition. Pages 41-45
(2) The High-Performance Two-Stroke Engine Dr John C. Dixon First Edition page 67


Graham Bell http://www.kreidler.nl/artikelen/per...raham-bell.pdf

Gordon Jennings http://www.edj.net/2stroke/jennings/

.

[speedpro]

The crankcase volume has very little to do with getting the mixture from under the piston to on top of the piston. The pressure differential across the transfer ports at the moment they open at operating speeds is mostly due to tuning specs - pipe/ex port. Gas velocity, and therefore inertia, in the ports also contributes and what is trapped/returned to the cylinder after the transfers close is due to the pipe design again and the port. The crankcases are more or less just somewhere to store air/fuel mix until it's sucked up the transfers.

I'm sure studs are waisted for a different reason than what is being suggested here.

[Yow Ling]

I'm sure studs are waisted for a different reason than what is being suggested here.
I thought it was to stop the barrels seizing on to the studs, I had a H1 triple that I nearly wrecked because the buildup of corrosion had mede the fit close to interference

[Yow Ling]

Heres the Gordon Jennings article , its from the 70's when TZs were new and just the shit

[Yow Ling]

I tried reading one of the pages but it seems to have lost some readibility, I can email them to some brainiac who knows how to fix such things, if needed

[TZ350]

Heres the Gordon Jennings article , its from the 70's when TZs were new and just the shit

Its readable, Great stuff Yow Ling. Page 3 center column midway down talks about piston seizure.

.

[TZ350]

.

Great info on crankcase delivery ratios and inlet timing for rotary disk motors. The end of page one talks about a wide low inlet port being better than a tall narrow one of the same area.

"Case of Rotary Disc-Valve Inlet Port Engine"

http://www.edj.net/2stroke/jennings/delivery_ratio.pdf

By Kazunari Komotori and Eiichin Watanabe. Keio University. :mellow:

.

[SS90]

The crankcase volume has very little to do with getting the mixture from under the piston to on top of the piston. The pressure differential across the transfer ports at the moment they open at operating speeds is mostly due to tuning specs - pipe/ex port. Gas velocity, and therefore inertia, in the ports also contributes and what is trapped/returned to the cylinder after the transfers close is due to the pipe design again and the port. The crankcases are more or less just somewhere to store air/fuel mix until it's sucked up the transfers.

I'm sure studs are waisted for a different reason than what is being suggested here.

Speedpro, I think you are mistaken here.

The crankcase is more than "just a place to store the air/fuel mixture till it's sucked up into the transfers."

CRANKCASE PRESSURE IS RESPONSIBLE FOT THE FACT THAT THE AIR FUEL MIXTURE FINDS IT'S WAY THROUGH THE TRANSFERS INTO THE CYLINDER IN THE FIRST PLACE..............

I'll elaborate.....
The very fact that the Air/fuel mixture even finds it's way into the transfers (actually, it's not "sucked", but more on that later....)
is because of the fact that there is a pressure differential between the cylinder (which is somewhere near atmospheric), and the crankcase is approx. 1.5 atmospheres (22p.s.i)

Now, this principal is not a secret, it's how any carbed internal combustion engine gets it's air fuel mixture into the combustion chamber.....

Think of it like this.....

When you watch the weather report on telly, if there is a big LOW pressure sitting around NZ, that means there will be what????

Wind (and rain, booo!)

The reason that there is wind, is because physics dictates that a high pressure will "rush" to a low pressure to equalise it.....

The same is true in 4 strokes, or 2 strokes.....



(this scenario is not including the fact that you also have the benifit of the extractor like effect from an expansion chamber, so for this purpose, we will ignore that, just for BASIC information on how an engine works, ignoring all the facts and figures that confuse everyone.....)

If there was 3 p.s.i in the cylinder, and 3 p.s.i in the crankcase...... nothing would happen, simply, the engine would never run, it never could......

Try this....

"THE AIR/FUEL MIXTURE GETS INTO THE CYLINDER/COMBUSTION AREA AS A RESULT OF A PRESSURE DIFFERENTIAL BETWEEN THE CRANKCASE (IN THE CASE OF A TWO STROKE, OR INLET MANIFOLD IN THE CASE OF A 4 STROKE)

The air/fuel mixture sitting in the crankcase is in a higher pressure state, it travels through the transfers, to the combustion area, because the combustion area is at a LOWER pressure than the crankcase

There is a DEPRESSION created in the combustion chamber, (caused by the fact that the piston is going down, creating that depression)

Underneath the piston, a positive pressure is being created, because the area under the piston (the crankcase) is being compressed by the piston.

Herein lies our Primary compression ratio.

Primary compression ratio= case volume at TDC
case volume at BDC

THE CRANKCASE BEING A HIGHER PRESSURE (APPROX. 1.5 ATMOSPHERE) THAN THE CYLINDER/COMBUSTION CHAMBER (APPROX 1 ATMOSPHERE)

Or, if we now take into account the extractor effect of the expansion chamber, more like NEGATIVE .5 atmosphere....

As such, I argue that cranckase pressure is VITAL in regards to how a 2 stroke runs, infact, that it runs at all..... and as such, careful attention to its ratio is paramount to it's overall efficiency!

No mate, the crankcase is more than "Just a place to store the air/fuel mixture"

Remember, that the important thing about this process is that we are trying to make this engine more efficient, and this is an important part.

If you have too low primary compression, then the pressure differential (the pressure difference between the crankcase and the cylinder/combustion chamber) is not high enough to efficiently "extract" the air/fuel mixture into the cylinder/combustion chamber (and keep it sufficiently atomised, which is critical for efficient combustion)

If you have too much primary compression, then the gains you make by having "more" are used up in the "pumping losses" (the energy (horse power" it takes to compress the air/fuel at that higher rate)

AS such, I will clarify my reasons for suggesting that this may be a way to improve power, AND run cooler....

Once again....


Fujio Nagao (one of the men responsible for the early Yamaha 125cc rockets back in the day researched this very subject extensively), and I quote..

"That any deficiency in air delivery due to a crankcase volume too great for an engine speed id fairly well compensated by properly tuned intake and exhaust pipes"

This engine does not have "properly tunes intake and exhaust pipes", (particularly because 1 the carb is too small, and, because they are constantly changing the port timing for an individual track, and not the pipe)

But, mainly the carb (due to the rules) is too small.

I believe that as such, determinating the current ratio correctly is prudent, (primary tests indicate that it's much below the 1.5 that is the "standard", as it is indicated that it may be more like 1.33 or so.......

So, I say, if you cannot "compensate for the advantages of a high primary compression ratio" by tuning the intake (bigger carb), then consider raising the primary compression........

I know it sounds old school, but in this case, I believe it has merit.

At least determine what it is to start with!

Remember, it is considerably LOWER than an original GP125, due to the fact that it has a spacer under the cylinder, as well as the fact that the intake side web has been chamfered, all increasing the crankcase volume, and lowering the ratio.......

[SS90]

The crankcase volume has very little to do with getting the mixture from under the piston to on top of the piston. The pressure differential across the transfer ports at the moment they open at operating speeds is mostly due to tuning specs - pipe/ex port. Gas velocity, and therefore inertia, in the ports also contributes and what is trapped/returned to the cylinder after the transfers close is due to the pipe design again and the port. The crankcases are more or less just somewhere to store air/fuel mix until it's sucked up the transfers.

I'm sure studs are waisted for a different reason than what is being suggested here.

Some times pictures help.....

http://science.howstuffworks.com/two-stroke2.htm

[TZ350]

Speedpro once explained the benifits of a larger crankcase volume to me.

He told me that it was easier to quickly scoop up a full cup of water from a larger bucket than a smaller one. Or fill a cylinder from a larger crankcase than a smaller one.

It made sense. especialy when you relate it to the gas law P1V1= P2V2

.

[F5 Dave]

The crankcase volume has very little to do with getting the mixture from under the piston to on top of the piston. The pressure differential across the transfer ports at the moment they open at operating speeds is mostly due to tuning specs - pipe/ex port. Gas velocity, and therefore inertia, in the ports also contributes and what is trapped/returned to the cylinder after the transfers close is due to the pipe design again and the port. The crankcases are more or less just somewhere to store air/fuel mix until it's sucked up the transfers.

I'm sure studs are waisted for a different reason than what is being suggested here.

Mike has now answered my question from the page before. That is why I don't think of 2 stroke as just a pump. Pipe extraction & gas inertia.

As far as primary compression is concerned Honda & Yamaha have often gone in different directions on this. It will be a compromise, but the more modern approach is that as pipes have gotten more effective, lower primary ratios have been beneficial. I don't shoot for high primary ratios.

However that isn't to say that it is possible to go this way all the time. Running super effective pipes on engines with transfers that are not curved enough produces bad results over scavenging.

In this case :scooter:man may have a point. Within class rules a good compromise leaves no one happy.

[SS90]

Yea, I have to admit I felt silly even suggesting "raise the primary compression", as it is the battle cry of the "I can tune a two stroke, but don't know jack squat" guys,


How many times has some guy asked you...

"That's fast mate....did you polish the ports and raise the primary compression?"

"ermmmm..... no"

"oh, you should do that, it would really go then!"

But by what I see from your results so far, there needs to be an alternative solution to this problem, and possibly, in this case it would help.

I was thinking as well, whenever someone has tuned these sorts of engines normally any mod is open bar fuel type....but in this case, your two restricting factors are air cooled and carb size....... I suggest that VERY little research and testing,has been done.

Because in reality, you would have STARTED with a bigger carb, day one!

I also believe that when you get it sorted, you will perhaps be in a field of your own, (as far as undercarbed 125cc aircoold disc valve two strokes go that is!):headbang:

And yes, F5 is quite right, current trends are towards lower Primary compression......and to some VERY big carb sizes as well....... I wonder if there is a pattern there....... Maybe not, but... HE CAN'T CHANGE THE CARB SIZE (dammmmmmmm Ittttttt!):cry:

[TZ350]

Sorry SS90, there has been so much to look at that I have not been able to keep up.

I am pleased that the primary compression is so low on my long rod GP as now I can fill in the area above the crank wheels and improve the flow at the entry to the transfer ports next time I have the motor apart.

Why did I use a long rod. Becouse it was all the go with TZ's back in the day and I had a box of RD400 rod kits, same with the pistons, had a box of them at the back of the shed. This is buckets, do the work your self make use of what you can and learn as you go.

What have you done with your SS90?
.

[SS90]

Ermmm,

Would you believe polished the ports and raised the primary compression?

Lets forget about my "scoota" tho, your problem is more interesting....!!!!

[TZ350]

Yea, I have to admit I felt silly even suggesting "raise the primary compression", as it is the battle cry of the "I can tune a two stroke, but don't know jack squat" guys,


How many times has some guy asked you...

"That's fast mate....did you polish the ports and raise the primary compression?"

"ermmmm..... no"

"oh, you should do that, it would really go then!"

But by what I see from your results so far, there needs to be an alternative solution to this problem, and possibly, in this case it would help.



Yes I think so too, thanks. Will put it on my to do list. I had wanted to improve the internal air flow, now I know I can without over compressing the crankcase.



What have you done with your SS90?


Ermmm,

Would you believe polished the ports and raised the primary compression?


Ooooo the irony, that's pretty funny. :D

I see you have your scooter with a good looking pipe up on a dyno, how did that work out?

We have tried an on-bike dyno system that used the change in spark frequency to calculate the rate of acceleration and graph HP and Torque from the mass/acceleration relationship.

The idea was to use a tape recorder to pickup the ignition noise. Then down load it to a computer through the sound card. Clean it up, enter some basic data like gear ratio's weight etc., then the software graphed it all.

It worked with the car but just could not get it to work on the bike. It just would not pickup a clean signal that the software could recognise.

I think the problem was that the amplitude of the bikes ignition varied so much with the applied load. The peak to peak levels were much more consistent with the cars ignition.

.

[speedpro]

I'm well familiar with gas flow and why it does. I own a home made turbo Z1 that makes a bit of power, I've crewed on a top door slammer blown drag race car that also made a bit of power, my buckets have all been reasonably competitive.

The critical factor with crankcase volumes in a 2-stroke is that there is enough volume to not stifle flow before the transfers close when the motor is operating at maximum. Obviously having excessively large volumes beyond that which is "required" will be detrimental at all other times. Hence a typical 2-stroke compromise is required. I do agree that the primary compression "aids" transfer, but, once the motor is operating at max the volume becomes the critical parameter and it may be greater than what is ideal off-peak. We are discussing a race motor so aren't particularly worried about off-peak, except in the usual 2-stroke tuning way - it has to be rideable.
I've spent a few hours pissing round on dynos testing this sort of thing plus more recently i spent a few $$ getting the Wobbly treatment and words of wisdom. He's pretty hard to disagree with I reckon. Results talk as well and I'm happy to do comparisons on a dyno.

[bucketracer]

I don't think of an engine as just a pump, particularly not a 2 stroke with an expansion chamber. For 2 reasons. Let's see if we can all name them (and that's is disregarding the whole thermodynamic side of an engine).

Ill chance my arm here.

Resonance in the inlet tract/crankcase.

Resonance in the expansion chamber.

Either of which and especialy if they are working together achieve more mass flow than the pumping action of the motor could by itself.

Do I get a Chocolate Fish?

.

[Buckets4Me]

no choclate fish for you
it's a 2 stroke so as well as pumping air
the engine


makes NOISE
and SMOKE
:2thumbsup:whistle::hug:

[bucketracer]

The crankcase volume has very little to do with getting the mixture from under the piston to on top of the piston. The pressure differential across the transfer ports at the moment they open at operating speeds is mostly due to tuning specs - pipe/ex port. Gas velocity, and therefore inertia, in the ports also contributes and what is trapped/returned to the cylinder after the transfers close is due to the pipe design again and the port. The crankcases are more or less just somewhere to store air/fuel mix until it's sucked up the transfers.

I can see what is going on here. The pumping effect gets the motor going but when its up on the pipe. The mass flow through the motor has a lot more to do with the resonant effect of the inlet-tract/crankcase and expansion chamber and the pumping effect just calls time like the cox does in a rowing six.

Those waves are tough little sods, shifting all that air/fuel mass.

And they can get a lot done when they work in unison. :mega::brick::brick::brick::brick::brick::brick:

[Buckets4Me]

:hug::wacko::hug:

:weird: :blah:

:weird:

:stoogie: :apint:

[Ned Kelly]

.

Good on you SS90. Great to see someone giving Speedpro and F5 Dave the learn. What would TeeZeethreefiddy know he's just a grey haired geriatric old fart, only finshed third in the last Bucket GP at Taupo, how pathetic is that, third!! I ask you.

Can't be to hard on him I suppose, He did finish, others didn't. Some of them were good guns too. Can't blame them 45min or so full tit around Taupo might be a bit hard on a buckets reliability.

.

[speedpro]

The Air Force GP tracks were bigger and faster. My bucket has been round Pukekohe at a couple of meetings with no problems which is probably one of the bigger tests available now for a bucket. I've won the odd meeting and championship all on buckets I built and tuned. F5 even more, even if I had taken him out earlier in the day. As for the "learn", I think TZ could probably run rings round all of us but as is usual with learned(lur ned) ones he sometimes gets distracted by a good theory.
Oh yeah - a bucket of mine completed the 6-hour still going strong and in good condition, unlike the owner.

[TZ350]

.

Taupo....Fortune smiled for me on the day.

.

[xwhatsit]

Coolest thread on KB!

Keep going with the 2T lessons!

[TZ350]

As for the "learn", I think TZ could probably run rings round all of us but as is usual with learned(lur ned) ones he sometimes gets distracted by a good theory.


Don't you just love a good theory :hug: I do.

Yep. I have found that the problem with a good theory is that, its Ohoo so easy to also believe its true.

And then reality, pays a visit :buggerd: ..... :crybaby: goodby theory!!

.

[SS90]

Don't you just love a good theory :hug: I do.

Yep. I have found that the problem with a good theory is that, its Ohoo so easy to also believe its true.

And then reality, pays a visit :buggerd: ..... :crybaby: goodby theory!!

.

Guys, Prepare to learn that 1) Nz is a cool place, and I love it but .....A) NZ IS NOT THE CENTRE OF TWO STROKE DEVELOPMENT..... AND B).....

I don't want to turn this into a BLOG, but I am a Kiwi, (born in the North, raised in the South...Son of an Ohakea Air force guy (and girl)....)) I now live in Germany (Baveria to be precise), And earn my living from developing .......................

AIR COOLED, TWO STROKE 125 (AND 140) CC CYLINDERS......................




See the pics attached..

If you don't believe me, does your keyboard have these characters.............


ä......ö......ü......, or the best one (the give away...ß )...........
Anyway....... I am not trying to be a "know all", but I have ALOT of experience with this subject matter, and am willing to pass it on to.....

"the boys back home"

Two years ago, I developed a cylinder (air cooled, cast iron lined, aluminium skinned cylinder for small fame Vespa's)

....When I say "developed", I mean I was given a plagerised pieced of scrap, that was just that.....scrap.....

However..this piece of scrap managed 15 P.S , and 15 N.M on the Dyno....

And, the port timing was A) stolen from another cylinder designed to fit tuned small frame Vespa's, and B) 10 years old.


So, 2 years ago, I set about making it better


Developing it.......

I started with 15 P.S, and, when I started (with only the exhaust port timing which was much too low, as was the transfer.... THEN I LEARNED THAT EVERYTHING WAS WRONG.....)

.... And, also the transfer design had a problem, (PARTICULARLY THE TRNSFER SCAVENGING) as it was stolen from another company, who specialises in Vespa scooters....... It's called C.V.F.... (DESIGNED BY MALLOSSI)......and if you don't know what C.V.F is, and...... consider yourself an "EXPERT" .......(x being a factor of Y, and spurt being something that comes out the end of your man servent)

Then you are 10 years behind Two stroke development.........


I digress......

This Cylinder is an Aluminiun skinned cast iron lined cylider, with piston wíndow induction (via reed valve....much like an RZ250/350)


I started with 15 P.S, and after the first "attack" with the Dremel (die grinder, along with a degree wheel and a Dial test indicator)... I ended up with 19 Ps and 15 odd NM..... but it was too peaky......

The Pipe I was using was called "Franz", and develped by a guy called Mataus Shierer, who started with a pipe developed by Norrie Kerr (an English guy, who wrote a book called "TUNING VESPA'S THE NORRIE KERR WAY"..... I suggest you all read it..... It's still relevent.....especially when you consider a small frame Vespa is.......

" AN AIR COOLED DISC VALVED 125 (OR 50,OR 90) CC TWO STROKE"

Anyway, the "Franz" was (and is) a really good pipe....(by the way, it's named after the designers son, Franz...(pronounced Frantz).... the problem was (is) if you subject it to full throttle for prolonged periods, it has too lower volume in the chamber, and after sustained periods, it causes the combustion chamber to overheat....which in turn passes the heat on to the cylinder, which then expands at a rate that the materials cannot handle, which means that it expands too much....which means that the studs compress the cylinder too much......

So, yea, I know what I am talking about when it comes to cylinder studs compressing the cylinder............

The studs that a vespa uses are origonally 7 mm all the way through the shank........, and if you make them 8 mm , (like I did)... then the cylinder runs hotter, because it's "squashed"...going back to 7mm studs fixed this problem............

There is heaps of information of the "wasted" stud theory......

BY THE WAY, THE ORIGONAL AIR COOLED ENGINE FOR THE BRITTEN ENGINE (THE ONE BUILT AND DESIGNED BY BRIAN DENSON OF DENCO ENGINEERING ENDED UP HAVING WASTEN STUDS BECAUSE OF EXACTLY THE SAME PROBLEM...)

If you don't believe me, then read the book......

"John Britten, one man and his Dream", By Tim Hanna.....

So, back to my job.....

I played around all year with this thing (two years ago), and ended up trashing the whole C.V.F theory, as, because A) the cylinder skirt was too short to have an effect (in this situation)

and B) the application of FOREFRONT TWO STROKE DESIGN THEORY negated the nessesary weakening of the piston (and cylinder) that was required for the C.V.F system

Man, you guys are way behind....


And it is also copywrited....... "DOH"........

But, it didn't matter....because with a short short spiggot, the C.V.F system is (in my opinion...and over 250 runs on this cylinder 2 years ago has proved) is of little (actually none whatsoever) effect......

Can any one tell me A) Why, and B) how you can achieve a better result that C.V.F...with out weakening the piston (or cylinder wall ))


The pictures I have shown include the C.V.F system.......... (Which, as I say, is stolen...but the pictures of the Cylinder are the same ones that make Over 20 P.S (as are the Dyno graph pics).....

Oh, yea, the Pic that shows 28 P.S (WHICH DOES NOT HAVE THE C.V.S SYSTEM...AS I FOUND AN ALTERNATIVE TO THE C.V.F METHOD OF IMPROVING THE UNDER PISTON SCAVENGING AT B.D.C........is the most I have ever seen out of an............

AIR COOLED, DISC VALVED 125cc TWO STROKE....


Also, I know alot about "DISC VALVED, 130CC TWO STROKES RUNNNING 24MM CARBS.."

As, that is the day to day business of any Small Frame Vespa Tuning shop in Europe....Because Polini make the most reliable "Jeden Tag Roller " (Every Day Scooter) tuning cylinder available....


Now, This is (The Polini Cylinder, not the one I have developed, which is an ally skinned cylinder with a cast iron liner......like a GP 125, aye...Although, We now have either a 125, or 140cc option....) a CAST IRON cylinder, and, it needs a VERY long inlet manifold(because of the design of the small frame Vespa requiring it to be that long) (which is included in the kit, to which ONLY A DELLORTO PHBH24 (That's right.... a 24mm carb........) will fit.... (other than extensive mods....which are expensive to say the least)

Oh, the 28 P.S is with my own exhaust as well.....

And.... the cylinder head HAS NO SQUISH BAND............ Does that blow ya mind..........

The reason I did that was to keep "THINGS COOL".....

And..... The Primary compression ratio is 1.49:1

I have loads of dyno runs experimenting with primary compression ratios......

1.5:1 is always the best curve (long and fat)....

Oh Yea baby........

LONG AND THING MIGHT GO STRAIGHT IN,:wari:

BUT LONG AND FAT IS WHERE IT'S AT!....:scooter:



I just finished designing an ignition system too.........

It was easier than the Cylinder.........

It only took from November last year untill the 20th of Fen this year.....

It retards 10 DEG from idle (at 9000 RPM), which test have shown is ideal for

AN AIR COOLED DISC VALVED...


YOU GET THE IDEA......



I Know what I am talking about.....

Oh, yea, If anyone tries to tell me that the transfers are too small (from the pictures), then they are right, they are only 10% bigger than the pics to give the results in the graph.....makes you think about transfer port area .....AYE
Boys..........

Happy Hunting.....

Try not to hit the key board when you aim for the screen.................. aye guys!!!!!!!!!!!!!!!!

[bucketracer]

:)

Honestly SS90 you look like you could contribute some interesting/usefull info that we would all like to read and benifit from but your attitude is getting in the way. Lose the imature "Need to be Right" chip on your shoulder and then we can be friends :D otherwise bugger off :girlfight: and be an "EXPERT" (as you define it) some where else.

So whats it to be :niceone:

.

[TZ350]

Hi SS90

Impressive stats. I have Googled "TUNING VESPA'S THE NORRIE KERR WAY" looks an interesting source.

I have been looking at your barrel pic. I need your help in understanding it.

This is what I see:- inlet looks like it has two boost ports above it, the exhaust port width looks in the low 65% of bore diameter, not much port time area there, a bridge port is said to flow less than a single port of the same area and I don't understand the extra ports below the transfers.

I need your help in understanding how this barrel makes 28Ps. please could you enlighten me with a few pic's and diagrams (hand drawn's ok).

Your work place sounds interesting, how about a few pics of the man himself at work.

There are pics of us at work on the GP at the begining of this thread.

.

[Buckets4Me]

cool whats this C.V.F you speek about

28 hp sounds scary

pitty you when't up this way show us all how it's all done

[Yow Ling]

:)

Honestly SS90 you look like you could contribute some interesting/usefull info that we would all like to read and benifit from but your attitude is getting in the way. Lose the imature "Need to be Right" chip on your shoulder and then we can be friends :D otherwise bugger off :girlfight: and be an "EXPERT" (as you define it) some where else.

So whats it to be :niceone:

.

Dont be so harsh on him, read this thread and understand something about Germany http://www.kiwibiker.co.nz/forums/showthread.php?t=87923&highlight=german+jokes

[TZ350]

CVF

Screen Scrape:-

Malossi 166cc Kit for P125X-PX150-Stella
Part Number: M314093
Price: $346.00
On Sale: $269.00

Malossi 61mm, 166cc kit, fits Sprint, Super, GTR 125, TS 125, P125E, PX125E, P150X, PX150E, Stella and COSA 125 (can also be modified to fit on some old 125 and 150's). Extra 2 stroke power, larger transfer ports, and a larger exhaust port. Includes BIG bore cylinder, high compression head, CVF flow piston, rings, wrist pin, pin clips, gasket set, carb jets, Malossi stickers, and instructions. This will bump up your old Vespa in horsepower, and with a pipe and carb you can increase it much more. (This kit needs the ports chamfered. We can do this for you)

Related Items:
Ports Chamfered

I had not thought of looking at Scooters for tuning ideas before.

SS90 I don't understand how this works, can you explain it to me??

[Yow Ling]

http://cgi.ebay.com.my/ws/eBayISAPI.dll?ViewItem&item=110302584066&ssPageName=MERC_VI_RCRX_Pr4_PcY_BIN_Stores_IT&refitem=120324799782&itemcount=4&refwidgetloc=active_view_item&usedrule1=CrossSell_LogicX&refwidgettype=cross_promot_widget&_trksid=p284.m184&_trkparms=algo%3DCRX%26its%3DS%252BI%252BSS%26itu% 3DISS%252BUCI%252BSI%26otn%3D4
http://galerie.competition50cc.info/thumbnails.php?album=16&page=1

Ive been looking at this too, looks like the transfers are duplicated below the rings when the piston is at bdc as well as your normal transfer flow up the transfer poert the lower "duplicate transfers" are opened up to the inside of the piston crown which shortcut to the main transfer channels, I guess this provides better piston cooling and a less torturous path for the last of the crankcase contents . pretty clever really. have a look at the piston in the ebay link

[TZ350]

Some more Scotter stuff here

http://images.google.co.nz/imgres?imgurl=http://www.sip-scootershop.com/wwimages/9fe1988c-3114-46f7-bb8b-2aead43e7a08.jpg&imgrefurl=http://www.sip-scootershop.com/Products/11000000/Racing%2Bcylinder%2BMALOSSI%2B210cc.aspx&usg=__O8Sf3bcPEkjlRxHnqRSpYNWqLhM=&h=480&w=465&sz=38&hl=en&start=75&um=1&tbnid=fGRfJj9TA4MekM:&tbnh=129&tbnw=125&prev=/images%3Fq%3Dcvf%2B125%26ndsp%3D20%26hl%3Den%26cli ent%3Dfirefox-a%26channel%3Ds%26rls%3Dorg.mozilla:en-GB:official%26sa%3DN%26start%3D60%26um%3D1

Looks pretty trick.

[Buckets4Me]

http://galerie.competition50cc.info/thumbnails.php?album=16&page=1

:shutup::blink::shit:

[TZ350]

The rear port on this cylinder looks like a gully port just like the GP125 has, flanked by ordinary transfer ports.

The main side transfer ports have extra mixture entry windows. I would not have thought the short transfer ducts would produce enough inertia in the transfer streams to work well.

Looking at the piston I can see how the mixture traped under the piston crown is suposed to be ejected into the main transfers through the extra side ports.

All very interesting stuff. Does it work? Could it be adapted to the GP125???

IF SS90 wants to put some ideas and sketches on paper I would be happy to see if they can be implimented on the GP125.

:yes:

[TZ350]

A MALLOSSI Kit:-

The data:
Compression: 14,8:1
Max power: 31,15 CV @ 8250
Max torque: 2,4 kgm @ 7250

Besides mounting the new Cylinder you have to work on the APTS Power Valve wich is to be made a bit bigger, change 2 clutch springs with the enforced ones in the kit and adjust the Power Valve, your Carburetor set-up and timing.

[koba]

Max power: 31,15 CV @ 8250
Max torque: 2,4 kgm @ 7250


CV?
kgm?

crazy euro speak...?

[SS90]

:)

Honestly SS90 you look like you could contribute some interesting/usefull info that we would all like to read and benifit from but your attitude is getting in the way. Lose the imature "Need to be Right" chip on your shoulder and then we can be friends :D otherwise bugger off :girlfight: and be an "EXPERT" (as you define it) some where else.

So whats it to be :niceone:

.

For the record, I NEVER referred to myself as an expert, and never will, I said

"If you consider yourself an expert, and you don't know what C.V.F is....."

I'm sorry if I am coming of condesending, it's not intentional!
:calm:

[SS90]

The rear port on this cylinder looks like a gully port just like the GP125 has, flanked by ordinary transfer ports.

The main side transfer ports have extra mixture entry windows. I would not have thought the short transfer ducts would produce enough inertia in the transfer streams to work well.

Looking at the piston I can see how the mixture traped under the piston crown is suposed to be ejected into the main transfers through the extra side ports.

All very interesting stuff. Does it work? Could it be adapted to the GP125???

IF SS90 wants to put some ideas and sketches on paper I would be happy to see if they can be implimented on the GP125.

:yes:

O.K, I will try to answer everything in one post...to make it easier to read.

First..... before I explain C.V.F, a little information on "CYLINDER SCAVENGING", because this is what it is about

ONE (there are quite a few) of the problems with a two stroke engine is that they are VERY inefficient in achieving "a pure charge" when it comes to the power/exhaust stroke.

(some of you MAY know this, but I suspect that you havn't fully explored it to the fullest extent....as if you did, you would have some more powerfull engines)

Again, please don't think I am being a "know all", I'm just stating the facts as I see them, and trying to help.

Now, I believe I have clearly explained the BASICS of how fuel gets from the crankcase to the cylinder, (and as such, the importance of carful attention to primary compression, and it's ratio)

Mistakingly, it was said (not by me, by another poster)

"that the only reason the fuel gets into the combustion chamber is that it is sucked into the cylinder when the transfers are opened"

I believe I have broken that myth (a very common one it seems)

What is important to note though, is, (along with a correctly designed expansion chamber), the transfers, if they are designed well (here in lies some clues of where the REAL power is......) actually "extract" more fuel from the Crankcase than the primary compression differential (the difference between the crankcase pressure and the cylinder pressure), which on it's own, makes the engine function, but VERY inefficiently, much like a 1923 Villiers, or an old two stroke lawn mower.

At this point, I am saying that the transfers are vital in regards to "SCAVENGING" the crankcases, and achieving a "more complete" evacuation of the crankcases.

The method used in pretty much every two stroke you will see in your life is called "Schneurle Loop", (ironically, a German.....), which is sometimes called "Loop scavenge"

This system was patented by Dr Schnurle in 1925, which meant, for quite some time Germany was at the front of Two stroke development, because, with the patent, no-one could use the system.

Then, when the patents ran out (end of 2nd War I am guessing), anyone could use it, and, it rapidly was used by every manufacturer.

Now, of course, the original "Loop Scavenge" system was quite basic, and it wasn't long before it was improved (but, it is, pretty much the same as it was, just with some clever development as time progressed)

All the engines you guys are running are "loop scavenge"

ONE of the main focuses today for modern two stroke engine tuners is this this area, and improving aspects of it........

I'm not going to give all my secrets away...what I will say, what is done here, is considered to be your "signature" when it comes to porting work and design.......

Now, C.V.F

Which is copyrighted by Mallossi.

Sorry, no cylinders sitting at home just now to take photo's, but I'll see what I can find if enough people don't understand what I am saying.

When the piston is at the bottom of it's stroke (basically, with out using too much "tech words") this is the time that a two stroke has to empty the burned gasses, and fill it with fresh charge (from the crankcases), and, as we know, while an expansion chamber has the effect of "pulling back" some of the good charge that consequently goes out the open exhaust (unevoidable), still, alot just goes to waste.

Now, there is still some "good" air/fuel trapped under the piston (on every stroke), that normally, (with a basic set up), never gets put to good use, and is as such "wasted"

What C.V.F does is, when the piston is at B.D.C, holes in the piston (above the gudgeon pin) see pic, align with corresponding holes in the cylinder, so, that this "good fuel" get used by going up the transfers

What I learned (not discovered), high tech Japanese two stroke teams found this out years ago, but only now people are starting to pay attention....... There is a way of designing the transfers that will effectively "scavenge" the crankcase as much (I believe possibly more...that's up for debate)

I'm not going to hand feed you on that one tho.....

At this point I am going to dissapoint evey one, and not show detailed pictures of my cylinders.......

If I did, it would just give away this information (possibly, maybe you would still miss it), and where is the fun in that :devil2:

Also, TeeZeeeTreeFidddy asked for some pics of me "at work" (I have heaps...but at this stage I would prefer to remain anonymous (just for the fun of it all), but all in good time......

But, a few answers to his questions
By the way, they are good ones!

The pics I showed are indeed 2 years old, and that particular cylinder (used in the pics) is still in use (modified in port height, width etc), and has (I think the best spread of power of any engine I have made (altho not the most peak)

TeeZeee....... You are right about the bridge (with a port that small, the bridge was not needed), but as you know, if you have a bridge (and you are developing an engine) you can go REALLY wide.

Basically, the prototype was designed as a "base" and I was able to see results from incremental widening of the port (to eventually exceed 70%, and I am only limited by the studs in the latest incarnation)

Also, "For the same port area", "an unbridged port will only flow 4% more than a bridged one"

I believe that

"4% more exhaust flow can be offset by advantages of having an exhaust port area wider than 70%, (up to as much as your piston (or in this case, workable area) will allow"))
This has been verified by some clever people (in Austria), who have the gear to do such testing....

Also, in regards to the boost port system I have, there is HUGE power gains there as well (The gully thing you refer to TeeZee, was actually designed by Kääden (the man himself,granfather of two stroke tech) as a way too cool the underside of the piston, but, after testing, it had an unexpected power gain........ when it has relivence, we can develop that idea too!!


I am not trying to highjack this thread either, just trying to help.

Let's not forget, that this post is about TeeZeeTreeFiddy and his GP125 Bucket..... That runs too hot.....and loses power.ö

On a personal note.....

No will not start my own thread, (or Blog), while I respect that many people would have a real intertest in this "Kiwi guy in Germany" at this stage I am not willing to do that.

Maybe some stage in the future.

However, I will "help the boys back home"

I appreciate your respecting this.

I have some good working pics too, but, I want to stay "annon." (for now)

Thanks

[SS90]

As a little extra, here is an excerpt from a very clever guy (one of the best), in regards to C.V.F..... (translated from German)

I am only posting this as a way of "stirring up debate", and hopefully encourage everyone to find "the better alternate" to C.V.F......Which incidently, does actually work, but only if the cylinder has an excessively long spiggot (therfore obscuring better evacuation of the crankcase....)



"i personally believe the cvf thing was more of a marketing measure than a true performance must. i can't remember seing a single other two-stroke piston which has it, and unless i'm mistaken, even malossi has dumped it on anything but their oldest designs, that's their vespa stuff. no idea why one would want to spend time and effort on that. as far as i remember it has been proven that a polini is good for 24 brake or so (at comparatively low rpm), which, in my book, equals a pretty high bmep, hence i guess that even more power would be possible at slightly higher rpm "

Like I say, it does work, but only has a big effect on cylinders with long spiggots.......

There is a better way............. And it's not as hard as you might think...........

Note it's mentioned that a "Polini is good for 24 brake or so......."

Now, that's really "worked", but it is a cast iron Cylinder, with 130cc's.........

GULP!

:scooter::rockon::Punk::yes::woohoo::gob::wari:

If did it all over, knowing what I know now..... I would look at HONDA engines (racing ones that is)......

there is a good clue in that.

Some people in Europe have 30 P.S...........:bye:

But they use a Nickasil cylinder......

Which is very special.

[SS90]

Found this on wikipedia for all you guys interested.....

READ IT CAREFULLY, THE ANSWER IS HERE, YOU JUST HAVE TO LOOK FOR IT!
:eek:

Loop-scavenged
Main article: Schneurle porting
This method of scavenging uses carefully shaped and positioned transfer ports to direct the flow of fresh mixture toward the combustion chamber as it enters the cylinder. The fuel air mixture strikes the cylinder head then follows the curvature of the combustion chamber then is deflected downward. This not only prevents the fuel/air mixture travelling directly out the exhaust port but creates a swirling turbulence which improves combustion efficiency, power and economy. Usually a piston deflector is not required, so this approach has a distinct advantage over the cross flow scheme (above). Often referred to as "Schnuerle" (or "Schnürl") loop scavenging after the German inventor of an early form in the mid 1920s, it became widely adopted in that country during the 1930s and spread further afield after World War II. Loop scavenging is the most common type of fuel/air mixture transfer used on modern two stroke engines. Suzuki was one of the first manufacturers outside of Europe to adopt loop scavenged two stroke engines. This operational feature was used in conjunction with the expansion chamber exhaust developed by German motorcycle manufacturer, MZ and Walter Kaaden. Loop scavenging, disc valves and expansion chambers worked in a highly coordinated way that saw a significant increase in the power output of two-stroke engines, particularly from the Japanese manufacturers Suzuki, Yamaha and Kawasaki. Suzuki and Yamaha enjoyed success in grand Prix motorcycle racing in the 1960's due in no small way to the increased power afforded by loop scavenging. An additional benefit of loop scavenging was that the piston could be made nearly flat or slightly dome shaped. This enabled the piston to be appreciably lighter and stronger and consequently tolerated higher engine speeds. The "flat top" piston also has better thermal properties and is less prone to uneven heating, expansion, piston seizures, dimensional changes and compression losses.

No, this is not where I got my information, I read the book

"THE TWO STROKE TUNERS HANDBOOK", By Gordon Jennings (among others)

It's all in there..... (well it's old, but the physics of it all is the same)

[Yow Ling]

OK, ss90 reading your posts , I get the Idea that you think that nobody in NZ has made a 2 stroke capable of much more than powering a lawnmower. 20hp from a 100cc engine seems common 23hp less common but still done.
Your style of "I know it but arent going to tell you" isnt going to win you any admirers.
If CVF is the answer , what was the question? Overheating? If cvf was the true path to power GP teams would use it, and motocross would have adopted it. It seems like a solution looking for a problem, mask the transfer tunnels so the cvf will work, getting tha last bit of good mix from under the piston at the expense of the good mix in the bottom of the crankcase.

My understanding of "scavenging" seems to differ from yours, scavenging is the process of sweeping the exhaust gasses from the cylinder after combustion, the better the scavenging the less the fresh charge is diluted/polluted by the spent gasses. The crankcase is not scavenged just pumped out or emptied into the cylinder , the depression caused by the pipe assists in this.

High crankcase compression and skinny pipes results in peaky engines , low crankcase compression and fat pipes wider power.

bucket racing isnt just about flash motors, you actually need to be able to ride to win, a 28ps motor isnt a ticket to win, plenty of guys kick my arse on bikes making less powerthan mine because they know the real secret, but I cant tell you what is is because that wouldnt be any fun:msn-wink:

[saxet]

Well I've been reading this thread as it progresses and it's gettin more and more interesting. I think SS90 may have surprised us all ( well me at least, but I'm no expert at all). It can be hard to accept someones claims when we can't see the evidence ourselves, that does'nt mean they're not true. Most of us are limited by time, money and access to resources( info and equipment).Also by not knowing where to look. Thanks for your tips SS90, I do understand you don't want to give away all your info but any more hints would be cool as I'm nowhere at the level of TZ350, F5 Dave and all the others who have commented.
Awesome thread and keep up the dialogue and , in particular the good work and hard effort by TZ350.

Looks like I should read Gordon Jennings book a few more times. I think I may have some clues as to what SS90 is on about but don't want to comment yet as I need to do some reading before I spout forth and look like a drip.

[saxet]

As a side note to all. It's not just about power, though it can mean lots. Don't underestimate handling. After changes to my handling I estimate I could take a second a lap off my Taupo times. Might get a cance to prove that at some stage.

[SS90]

OK, ss90 reading your posts , I get the Idea that you think that nobody in NZ has made a 2 stroke capable of much more than powering a lawnmower. 20hp from a 100cc engine seems common 23hp less common but still done.
Your style of "I know it but arent going to tell you" isnt going to win you any admirers.
If CVF is the answer , what was the question? Overheating? If cvf was the true path to power GP teams would use it, and motocross would have adopted it. It seems like a solution looking for a problem, mask the transfer tunnels so the cvf will work, getting tha last bit of good mix from under the piston at the expense of the good mix in the bottom of the crankcase.

My understanding of "scavenging" seems to differ from yours, scavenging is the process of sweeping the exhaust gasses from the cylinder after combustion, the better the scavenging the less the fresh charge is diluted/polluted by the spent gasses. The crankcase is not scavenged just pumped out or emptied into the cylinder , the depression caused by the pipe assists in this.

High crankcase compression and skinny pipes results in peaky engines , low crankcase compression and fat pipes wider power.

bucket racing isnt just about flash motors, you actually need to be able to ride to win, a 28ps motor isnt a ticket to win, plenty of guys kick my arse on bikes making less powerthan mine because they know the real secret, but I cant tell you what is is because that wouldnt be any fun:msn-wink:

Well, your making this a bit personal, and that's a bit rough!

Now, don't get upset, but did you read the quote from Wikipedia?

The whole system of this 2 stroke design is called "loop scavenging", I am saying, this does not only refer to the exhaust scavenging, (after which it was named) but also to the crankcase.

The original system of loop scavenging, I believe can be expanded on, to include "crankcase scavenging"

That's the point I am trying to make.

Also, I am certainly NOT advocating the use of C.V.F, my earlier posts have pointed out that I learned that it is less effective than people first believed.

But it does have an effect.....

The reason I point it out is to help TeeZee (and others who want to help, and remember, in doing this, I am also learning!)

Maybe something new can be found.

My references to C.V.F are to demonstrate the direction that the rest of the world has gone.

To go forward, you have to see where others have been.

The attachment you posted........

My god. It makes you look silly, not me.

However, this is all....."off topic"

That over, lets get back "on topic....."

TeeeZeeee's GP125, and keeping it cooler. I don't have all the answers (by any means), but , I have some ideas.



This all came about because I was prompted to explain the concept of the carb size (24mm, the maximum allowed by the rules) is contributing to the hotter hunning of the engine, and I stated that I believed that to make it more efficient, (in this case, not a general rule by any means), then the primary compression ratio needs to be increased, due to the fact that the mods (cylinder spacer, chamfered crank web) have lowered that ratio, and it needs to be raised to 1.5:1, in order to improve the pumping efficiency of the crankcase.

[SS90]

As a side note to all. It's not just about power, though it can mean lots. Don't underestimate handling. After changes to my handling I estimate I could take a second a lap off my Taupo times. Might get a cance to prove that at some stage.

Yup, 100% right on that one......We have all seen RS125R's kick bigger bikes arse all the way round the track!:Punk:

[bucketracer]

SS90 We are still waiting for an original idea.

.

[koba]

Awesome thread and keep up the dialogue and , in particular the good work and hard effort by TZ350.

Aye, This is awesomly interesting!

[TZ350]

.

I suspect the main players are already familiar with the material but I am pleased to see SS90 taking the trouble to write it up.

Better handling, I am desperate to get onto improving the handling and am in complete agreement, but its not what I am trying to do today. I want to get on top of the heat issue, I see it as a means to improve the driveability of the bike.

I reckon that if my bike was gently warmed up then run up on an inertia dyno it would feel Phat and score in the low 20's for HP. I think an inertia dyno run looks like the same sort of work out for the engine as pulling out of the pits and away from the first corner and maybe half way up the first hill at Taupo.

Then the second inertia dyno run equivalent is pulling out of the back sweeper uphill to the back straight (drag strip). So by the time I get to the start line the bike has done at least two solid inertia dyno run equivalents.

The Green Flag drops and by the time I have done the first lap the motor has done two more dyno runs.

12 minutes later the bike has done maybe 14 dyno run equivalents and is hot tired sagy and not lifting out of corners like it did and certainly not making 20+ HP.

I suspect the HP figures quoted for the Malossi and other barrels was not taken from the 14th dyno run, of 14 runs all in quick succession.

I suspect the Malossi HP figures were taken from the first run in most cases and for the more genuine tuner possibly the third run.

A real test would be twelve quick consecuitave hard runs, discarding the higest and lowest and then averaging the rest.

Heat is the issue for me today, so I can keep more of what Ive got.

Busting my guts to get onto the handling.

There is so much work to do.

Learning to ride, now that's just frightening!

.

[TZ350]

.

The more I read the more I suspected the CVF Malossi idea had become a marketing ploy like ceramic coating is, than a real performance improvement, but an interesting idea.

I have my own ideas on how to utilise the dead space under the piston.

My first thought was that its ok if the mixture stays there and gets a free ride up and down. Then the GP has the gully port at the back and the mixture flow through the piston cools it and thats good and "Not" so good as this means that hoter mixture is now entering the combustion chamber.

My idea was to use fuel injection and to inject some or all of the fuel in such away as the liquid fuel directly strikes the underside of the piston crown as the piston descends to BDC.

This has several effects, directly cools the piston crown, more completely vaporises the fuel and the pressure of the vaporised fuel helps in the transfer process by pushing mixture up the transfers.

There it is an "original idea" (for me anyway), what have you got for us SS90.

Does anyone know how fast a common car fuel injector can be run? I would like to know.

.

[bucketracer]

The original system of loop scavenging, I believe can be expanded on, to include "crankcase scavenging"

That's the point I am trying to make.


And expanded on again to include the "suck from the exhaust pipe and expanded once more to include the push from the inlet resonance and you have the picture that Speedpro was painting.

From what Speedpro says I can see Mass flow comes from an inter-dependent system made up of several parts of which crankcase pumping is one part.

.

[Yow Ling]

.


Does anyone know how fast a common car fuel injector can be run? I would like to know.

.

1 to 3mS to open , at 12000rpm you have 5mS between firings so you gunna need big injector(s) 4t stuff moves slower so you get longer dwell time to sort out the injections

[saxet]

O.k. i havn't read anything yet and despite what i said earlier about not spoutin forth I've a sneaking suspicion SS90 is on about shaping the transfer port inlet to creat a pressure pulse to aid crankcase scavenging rather than shaping them for least restriction. Comments,praise or scorn please.

[TZ350]

Current handling mods to the GP125:- 2.5X17 front 3.5X17 rear wire wheels, RS125 Rubber, braced frame, braced swingarm, GT185 forks and front brake, quality rear shock, rubber swing arm bushes replaced with bronse/steel inserts, rear sets, race seat, ballance 55% rear 45% front with rider aboard and everything tucked in so nothing scrapes the ground during hard cornering.

Planned mods (wish list):- bigger front brake (I get tired pulling the bike up every 33-34sec.) and would like something easier to use. Get the balance 50/50, Lower the stearing head 2", shorten the forks and fork travel. Improve the front compression damping. RPM triggered Air quick Shifter and Data logger.

.

[Sully60]

O.k. i havn't read anything yet and despite what i said earlier about not spoutin forth I've a sneaking suspicion SS90 is on about shaping the transfer port inlet to creat a pressure pulse to aid crankcase scavenging rather than shaping them for least restriction. Comments,praise or scorn please.

Have some scorn; go to bed old man!:laugh:

[saxet]

Have some scorn; go to bed old man!:laugh:

:Oops:Shoula seen that comin.

[TZ350]

O.k. i havn't read anything yet and despite what i said earlier about not spoutin forth I've a sneaking suspicion SS90 is on about shaping the transfer port inlet to creat a pressure pulse to aid crankcase scavenging rather than shaping them for least restriction. Comments,praise or scorn please.

I hope so, if the GP transfers need reshaping because of the thick cylinder spacer I use I have the room to do it.

As I need to reduce the crankcase volume, building up and reshaping the transfer inlets would be a good way to do it.

.

[saxet]

Like the handing plans TZ350

[SS90]

O.k. i havn't read anything yet and despite what i said earlier about not spoutin forth I've a sneaking suspicion SS90 is on about shaping the transfer port inlet to creat a pressure pulse to aid crankcase scavenging rather than shaping them for least restriction. Comments,praise or scorn please.

100% correct mate!

You on to it.

This system is referred to a "THE SCAVENGE PATTERN", and it currently is where huge amounts of research are still (even after all these years) being done, and I have been told (from the industry) that there is still more to come.

I also will point out that the "scavenge pattern" does, not only include the transfer design, but also the area at the bottom of the liner (again surprising amounts of power can be found, with just some basic applications of logic that most of us miss.)

I even think that there is a chance that TeeZee has (inadvertedly compounded this problem with his piston he uses.....which, by the way TeeZee, I did the same thing! (water cooled piston,poor "scavenge pattern" at the cylinder side)

This is what I meant when I was talking about "signature" of a 2 stroke tuner, while some basic rules in these areas remain constant, small changes have profound effects in not only power, but also characteristics of the power delivery, and every tuner has his own design, based in his (or her...there are a few) own experiences.

I was fully aware that someone here would be familure with this, and am trying to make the point that this is where a large amount of work is still being done.

It would be cool for TeeZee to develop his own scavenge pattern (in my opinion, then it would truly be his own "signature" of his tuning!

I believe that his "scavenge pattern" would be quite unique, because he has to run a carb that is too small for the engine.........

Thanks mate, it was all worth it!

[SS90]

And expanded on again to include the "suck from the exhaust pipe and expanded once more to include the push from the inlet resonance and you have the picture that Speedpro was painting.

From what Speedpro says I can see Mass flow comes from an inter-dependent system made up of several parts of which crankcase pumping is one part.

.

O.K, I am going to choose my words carefully, and please be aware that I mean no malice with what I write, and nothing personal.

Speedpro wrote

The crankcase volume has very little to do with getting the mixture from under the piston to on top of the piston. The pressure differential across the transfer ports at the moment they open at operating speeds is mostly due to tuning specs - pipe/ex port. Gas velocity, and therefore inertia, in the ports also contributes and what is trapped/returned to the cylinder after the transfers close is due to the pipe design again and the port. The crankcases are more or less just somewhere to store air/fuel mix until it's sucked up the transfers.

The Crankcase has every thing to do with getting the mixture from under the piston to the top of the piston.

I hope I have established this already.

The pressure differential (the same physics as the pressure differential between the crankcase, and the cylinder) ASSISTS with the "transfer of the gasses" (and as does the chamber, assist with this (among other operations, the chamber really is a busy piece of kit!)

I maintain the the pressure difference (crankcase/combustion chamber) is 70% of the reason the fuel gets into the combustion chamber in the first place (the other 30% is from the exhaust, the scavenge pattern, and intake resonance)

Remember, there was engines before the "schnürle loop" (like the "cross flow"), which obviously had no "scavenge pattern" whatsoever, but would still run.......... The way to make it run (and make at least some power) was to include a "kicker" on top of the piston (which incidently made huge scavenge flow, but had a big piston crown area, which restricted high specific output.

The transfer Shape, size and "spray" pattern, in a "schnürle loop", if properly developed (different for every application) can be developed to assist (quite alot) in the scavenging of the crankcase (as saxet has pointed out).

But, the use of an origonal GP125 "scavenge pattern" is 25-30 years behind the time......and if you have enlarged them....(maybe it is worse!)

I mean no disrespect. I just think it prudent to point that out, as it is relevant.

[SS90]

I hope so, if the GP transfers need reshaping because of the thick cylinder spacer I use I have the room to do it.

As I need to reduce the crankcase volume, building up and reshaping the transfer inlets would be a good way to do it.

.

Yes, but that's only one part of it......(like saxon has mentioned), The "scavenge pattern" also (and predominantly) includes the "spray pattern" of the transfers into the cylinder.

I know it seems unbelievable, but check out the graph that I have attached.....(this was early days in the work, and, as such, there have been much more improvements (exhaust design, ignition etc.....), but I assure you, this was ONLY "scavenge pattern work"

I'm serious.

[F5 Dave]

SS I assume your rambling post a few pages back was done on a Friday night after the effects of some mind altering drugs that bring out a Jekyll & Hyde personality.

I work in the electronics industry & it irks me that some characters talk in ever increasing TLAs (three letter acronyms, it is of course a PT to give it an acronym). Sometimes it simplifies conversation & documentation, but it spirals out of control & the purpose ends up becoming to hinder communication & make those ‘in the know’ of these meanings feel special about themselves. QA & wanky management use TLAs for the same purpose.

So no; I’ve never heard the TLA CVF. So therefore I must be behind the times. Well, - behind the times in scooter design marketing speak. Whoopie.

Since the dawn of time people have been adding more transfer ports, often fed by the piston with holes near the top. This does smack of a compromised transfer arrangement. To put them in the main transfers more so.

I suspect this is borne of your typical scooter having a very compromised crankcase design affecting where you can place & feed transfers. Sometimes you really have to work with a compromise & go in that direction.

For instance my 50 has a dumb arrangement where the intact is primarily a piston port, but has a reedvalve passage to the crankcase. Also due to this the transfers also feed the rear ‘boost ports’ that would otherwise be fed from the reedblock, (often directly). This is a compromise & was popular on RMs (& some very early KTMs I think). But ultimately it has been discarded by mainstream. However it can work acceptably. My 50 still retains this feature, although I do appreciate its compromise. The fact that this engine has spanked Aprilias & Derbis in the past attests to this. . . and the odd aircooled 125, well, all of them at Taupo.

I suspect you are next going to be introducing collide stream porting as the big secret (Kevin Cameron did an article on this using 91 TZ250 as example, but had been used to some extent well before this).

But I am getting a bit tired of the attitude that is coming with all this. Some very condescending tones are super evident. Why come with attitude?

I’d say there is only one person on KB who I’d call a 2 stroke expert. And he frequents the suspension forum & never talks about 2 strokes.

[TZ350]

Yes, but that's only one part of it......(like saxon has mentioned), The "scavenge pattern" also (and predominantly) includes the "spray pattern" of the transfers into the cylinder.


Jante Patterns do you know what they are SS90 if not, you can find examples of them on P182 The High-Performance Two-Stroke Engine. Dr John C. Dixon.

.

[TZ350]

Remember, there was engines before the "schnürle loop" (like the "cross flow"), which obviously had no "scavenge pattern" whatsoever, but would still run.......... The way to make it run (and make at least some power) was to include a "kicker" on top of the piston (which incidently made huge scavenge flow, but had a big piston crown area, which restricted high specific output.


As an apprentice I remember hearing about a two stroke (Diesel?) industrial engine with no crank case pumping at all and was "cross flow" I think. It ran at a constant speed and was charged and governed by the inlet resonance, it had a long inlet from memory. To start it you cranked it up as fast as you could then sent a puff of compressed air down the inlet and it chugged away happily.

.

[TZ350]

Originally Posted by saxet
O.k. i havn't read anything yet and despite what i said earlier about not spoutin forth I've a sneaking suspicion SS90 is on about shaping the transfer port inlet to creat a pressure pulse to aid crankcase scavenging rather than shaping them for least restriction. Comments,praise or scorn please.

Posted by SS90

100% correct mate!

You on to it.

This system is referred to a "THE SCAVENGE PATTERN", and it currently is where huge amounts of research are still (even after all these years) being done, and I have been told (from the industry) that there is still more to come.

I also will point out that the "scavenge pattern" does, not only include the transfer design, but also the area at the bottom of the liner (again surprising amounts of power can be found, with just some basic applications of logic that most of us miss.)

Posted by TZ350

A while back I read up about the work being done on Honda RS125 crankcases and the "Tuners" offering to work magic by reworking the flow inside the case/transfer-ports.

Then I read counter arguments about its worth and decided it was one of those small gain areas. I got the impresion that again it was driven more by the marketing people than anyone with a clue and I put it on the list of things to look at again when the motor was next apart.

Heat is my current problem, not making more power.

.

[F5 Dave]

As an apprentice I remember hearing about a two stroke (Diesel?) industrial engine with no crank case pumping at all and was "cross flow" I think. It ran at a constant speed and was charged and governed by the inlet resonance, it had a long inlet from memory. To start it you cranked it up as fast as you could then sent a puff of compressed air down the inlet and it chugged away happily.

.
Or supercharge it,

[TZ350]

I know it seems unbelievable, but check out the graph that I have attached.....(this was early days in the work, and, as such, there have been much more improvements (exhaust design, ignition etc.....), but I assure you, this was ONLY "scavenge pattern work"

I'm serious.


Its not so great! my bike already does that.

The trick is to quickly do 14 consecutive hard runs (to stress the engine like it was in a real race at Taupo) then see if it can still produce that graph. Or hold it on full load for 30's, the length of a straight (not that you can do that with an inertia dyno) then tell me what the power curve looks like. I expect it will have droped off like my bike currently does.

Inerta Dynos have their limitations, give me a good Dynamic Dyno Brake where you can vary/hold the applied load any day.

.

[TZ350]

Or supercharge it,

Yep, Cummings Diesel, overhalled a few of those. No heads and cranks were all roller mains and rockers connected the conrods to the cranks. Clever. The smart boys got the Roots Blowers of them for supercharging their cars.

.

[TZ350]

My 50 still retains this feature, although I do appreciate its compromise. The fact that this engine has spanked Aprilias & Derbis in the past attests to this. . . and the odd aircooled 125, well, all of them at Taupo.

Yep, rub it in, rub it in. :rofl: I did try but you beat me fair and square. :clap:

.

[speedpro]

You have to agree though that there is very little going on in this part of the world 2-stroke wise anyway. One little project I've noticed but not sure if it counts - http://www.twostrokeshop.com/Aprilia_RS500_2008.htm . Those engine enhancements were designed by a kiwi in Welcome Bay who just happens to have also done a bit of work on my current bike and LOTS on the next one. He did Nigel's motor design as well and anyone who has seen that will attest to the effectiveness. Designed for 31hp at the crank I've seen it make 27.5rwhp on a dynojet.

That transfer system looks to be a real compromise. I can see why they did it. With the big intake ports the bottom of the barrels could easily snap off. It isn't too dissimilar to certain highly modified MB100s I know. The answer is to do what they've done - make the base of the barrel full circle for support. The problem is that the transfer ports are then masked so you need to come up with an alternative transfer method. Piston port TS100s can get close to having the same problem if you are running 200deg intake timing.

I always dummy up the barrel to each case seperately and match the barrel to the transfers and make sure that the bottom of the barrel isn't masking the feed in to the transfers. Typically there is a major problem in standard form. By the time I finishing unmasking the transfers there isn't much metal to support the very bottom of the barrel below the intake port. There's ways around it and so far I haven't had a problem.

My current transfer flow pattern is due to the opposite port roof angles to my past engines but evidently is more modern thinking. It works. HP is unknown at the moment.

Regarding small carbs causing hot engines - fit a big carb and measure the temp. Just the sort of experiment that TZ would be into for sure.

[TZ350]

Regarding small carbs causing hot engines - fit a big carb and measure the temp. Just the sort of experiment that TZ would be into for sure.

Nope. :girlfight: easier for you to put a smaller carb on your bike! But I am happy to take measurements with the Lazer heat gun.

PS great link

.

[SS90]

You have to agree though that there is very little going on in this part of the world 2-stroke wise anyway. One little project I've noticed but not sure if it counts - http://www.twostrokeshop.com/Aprilia_RS500_2008.htm . Those engine enhancements were designed by a kiwi in Welcome Bay who just happens to have also done a bit of work on my current bike and LOTS on the next one. He did Nigel's motor design as well and anyone who has seen that will attest to the effectiveness. Designed for 31hp at the crank I've seen it make 27.5rwhp on a dynojet.

That transfer system looks to be a real compromise. I can see why they did it. With the big intake ports the bottom of the barrels could easily snap off. It isn't too dissimilar to certain highly modified MB100s I know. The answer is to do what they've done - make the base of the barrel full circle for support. The problem is that the transfer ports are then masked so you need to come up with an alternative transfer method. Piston port TS100s can get close to having the same problem if you are running 200deg intake timing.

I always dummy up the barrel to each case seperately and match the barrel to the transfers and make sure that the bottom of the barrel isn't masking the feed in to the transfers. Typically there is a major problem in standard form. By the time I finishing unmasking the transfers there isn't much metal to support the very bottom of the barrel below the intake port. There's ways around it and so far I haven't had a problem.

My current transfer flow pattern is due to the opposite port roof angles to my past engines but evidently is more modern thinking. It works. HP is unknown at the moment.

Regarding small carbs causing hot engines - fit a big carb and measure the temp. Just the sort of experiment that TZ would be into for sure.

Because of the fact that it is very rare to be limited by the size of your carb (and water cooling) only there is very little experience in tuning of the type that TeeZee has undertaken, and therefore little published.

If, in the near future, I can either find the time, or, a customer is willing to pay for the work, I will do just that.

Experience (and research) tells me what I will find already (smaller carb, hotter engine), but, I will attempt to obtain the data in a timely fashion.

What I have tried to point out is that his current set up is, by default, highly inneficient, and in particular in the area of crankcase pumping efficiency.....(and, therein began the "I know more that you" nonsense that a few of us all got involved in)

Human nature I expect.



TeeZee has problems with his engine running too hot (as has been the case since people starting trying to extract more power, which is why they went to liquid cooling in the first place)

Now, I have plenty of ideas (backed up by experience) that would enable him to make more power (as I am sure some people on here do as well), and ideas (backed up by experience) that would enable him to make possibly the same power (with a wider power band), for alot longer during the race.

TeeZee still has not shown us any Dyno graphs.

In my opinion (and as was my intention) I have concentrated peoples attention (and their subsequent research) on "things that matter", rather than "coated cumbustion chambers, bronze cylinder heads", and such unfruitful endeavours.

I have never seen a realistic alternative to the venerable alloy head personally.
Just look where everyone (still doing two stroke air cooled work) has been, and are now.....

Also, can I direct you to "the unmasking of the transfer area", I have learned (and proved, conclusively that unmasking is of large benefit (naturally), but more gains can be made in the shapes you use to unmask.......

[SS90]

Its not so great! my bike already does that.

The trick is to quickly do 14 consecutive hard runs (to stress the engine like it was in a real race at Taupo) then see if it can still produce that graph. Or hold it on full load for 30's, the length of a straight (not that you can do that with an inertia dyno) then tell me what the power curve looks like. I expect it will have droped off like my bike currently does.

Inerta Dynos have their limitations, give me a good Dynamic Dyno Brake where you can vary/hold the applied load any day.

.

Now, pleae, please don't be offended, tis really is not my intention.

Please forget all about this 14 consecutive runs nonsense.

Have you any dyno graphs to post?

The last one I posted was not for maxumum power ( you have already seen that one), it was to show the effect of careful attention to ONLY scavenge pattern.

I think that it is a very good graph. An excellent example.

Particularly if you take it in context.

Anyone here is aware that when you pass a temperature ideal, your engine will loose power.

The skill is to get it to run more efficiently (thereby making more power for longer)

Please, if you have not already done, get it on a dyno, do several runs, pay no attention to the numbers (for they are just that.....numbers), and look at the curve, where it starts making it's tourque, at what R.P.M.

That's what you should be concentrating on in my opinion.

More torque, in lower R.P.M's for a longer time is what to aim for!

[SS90]

SS I assume your rambling post a few pages back was done on a Friday night after the effects of some mind altering drugs that bring out a Jekyll & Hyde personality.

I work in the electronics industry & it irks me that some characters talk in ever increasing TLAs (three letter acronyms, it is of course a PT to give it an acronym). Sometimes it simplifies conversation & documentation, but it spirals out of control & the purpose ends up becoming to hinder communication & make those ‘in the know’ of these meanings feel special about themselves. QA & wanky management use TLAs for the same purpose.

So no; I’ve never heard the TLA CVF. So therefore I must be behind the times. Well, - behind the times in scooter design marketing speak. Whoopie.

Since the dawn of time people have been adding more transfer ports, often fed by the piston with holes near the top. This does smack of a compromised transfer arrangement. To put them in the main transfers more so.

I suspect this is borne of your typical scooter having a very compromised crankcase design affecting where you can place & feed transfers. Sometimes you really have to work with a compromise & go in that direction.

For instance my 50 has a dumb arrangement where the intact is primarily a piston port, but has a reedvalve passage to the crankcase. Also due to this the transfers also feed the rear ‘boost ports’ that would otherwise be fed from the reedblock, (often directly). This is a compromise & was popular on RMs (& some very early KTMs I think). But ultimately it has been discarded by mainstream. However it can work acceptably. My 50 still retains this feature, although I do appreciate its compromise. The fact that this engine has spanked Aprilias & Derbis in the past attests to this. . . and the odd aircooled 125, well, all of them at Taupo.

I suspect you are next going to be introducing collide stream porting as the big secret (Kevin Cameron did an article on this using 91 TZ250 as example, but had been used to some extent well before this).

But I am getting a bit tired of the attitude that is coming with all this. Some very condescending tones are super evident. Why come with attitude?

I’d say there is only one person on KB who I’d call a 2 stroke expert. And he frequents the suspension forum & never talks about 2 strokes.

I think I have already established alot of what you pointed out here F5....... My purpose was to, show that some guys where getting "lost in the woods", and where missing some fundementals.

Afterall, this isn't a "how a two stroke works" topic, but sometimes reverting back will remind us all that we don't know everything, and never will (even if it is unlikely that none of us will admit that this has made us all research topics, and become better off for it)....


Bronze heads indeed!<_<

(No offence intended.)

[Chambers]

Afterall, this isn't a "how a two stroke works" topic, but sometimes reverting back will remind us all that we don't know everything, and never will (even if it is unlikely that none of us will admit that this has made us all research topics, and become better off for it)....


Bronze heads indeed!<_<

(No offence intended.)

Like you say SS90 you don't know everything!

Bronze heads were a great idea in their day. Bronze is a better heat conductor than cast iron and the valve seats could be cut directly into the bronze. At the time aluminium alloy was not sufficiently developed for its hot strength to be able to reliable hold valve seat inserts. Later cast sculls for the valve seats and plug were used in alloy heads up to the 50's.

SS90 your well read but talk a lot without saying anything. and usually about things we have already been over in our own research.

A couple of quick sketches of where you think we are going wrong and a sketch or two on how we can improve it and your a hero otherwise your zero.

.

[SS90]

Granted,
But, that was a long time ago (like a cast iron head)
The point I am/was trying to make is that aluminum is far better than Bronze, and that I failed too see the logic in that discussion, especially as it was also heading towards coating the Cylinder head in Gold..........

I see the point in discussing the Bronze head/coating options, but the way the thread was progressing, it seemed like all this guys hard work was being compromised by some steps in the wrong direction.

I don't want to be a hero in this, or any other situation, I am trying to assist and encourage.

While I am unfamilure with posting in a forum, and as such lack the literary skills needed, I feel that I have written in such a way that many people who read this thread, and have not done research, can follow and learn, as you are aware, the people who contribute can all write in such a way that very few would understand, even though the subject matter is more simple than most realise.

I hope this is the end of personal attacks, and we can continue back to the thread, and I hope TeeZee can show us a few dyno runs as the engine is now (ignoring the 17 runs theory, and just see what it has (in so far as curve shape etc), and after some attention to some things we have discussed, put it back on the dyno and compare the curves.)

That would be a good way to continue (and advance) some interesting discussion.

In the direction of TeeZee's engine, (and to change the current line of subject) I am thinking (after re-reading his earlier posts, in particular a race report) there is a big low R.P.M torque deficit (I make this statement after reading how he has to slip the clutch "all the way round the track").

After our discussion about the likely Primary compression deficit, can anyone offer a solution for that? Or at least some theories (researched or otherwise)
.....I am thinking one (a solution) that would also lower the cylinder head temperature......

[F5 Dave]

There is a surprising amount of cooling provided by moving & thus attached to a dyno the fan provided is comparatively puny despite feeling like you are being blown around. Watercooled bikes will start to over heat after several runs on the trot. However it is important to ignore the first few runs or they may well end up being the best of the session. I like to do a few runs & then let the top end cool a bit & then test in earnest. This gives the crankcase time to heat up to operating temperature.

Which brings me to the ‘slipping the clutch’ bit. The GP has a 5 speed gearbox so there will always be more of a gap esp on a very tight kart track like mt wgtn. Presumably you have geared down as low as required for here?

[TZ350]

Which brings me to the ‘slipping the clutch’ bit. The GP has a 5 speed gearbox so there will always be more of a gap esp on a very tight kart track like mt wgtn. Presumably you have geared down as low as required for here?


The GP's 5 speed gearbox is all ways a problem especialy 3rd.

In hind site I realise I was a bit over geared at Taupo but still would not have been shy about using the clutch.

I find gearing, is always a compromise between acceleration in some corners or smooth drivability through other corners at Mt Wellington where I find its easy to be under geared and over revey.

If I can set it up to avoid a gear change between corners like the infield and pull strongly out of another corner or two I recon I've got it about right and compromise by using the clutch to enter/exit others.

In difficult corners I often flick it down a gear, buzz the motor up on the throttle and slip the clutch entering the corner as well, I find slipping the clutch in this way before the apex, steadies the bike other wise it bounces around on the over run.

When diving for a gap a dab on the clutch helps there too.

.

[saxet]

SS90 your well read but talk a lot without saying anything. and usually about things we have already been over in our own research.

A couple of quick sketches of where you think we are going wrong and a sketch or two on how we can improve it

.
Some more concise info would be very cool. I can see a few possibilties e.g. a tuned length tract to make use of preessure pulses but somehow I doubt it. Or maybe viewing the tranfer tract as the header of an expansion camber and shaping it accordingly to extract fuel/air from the crankcase into the combustion chamber.
I'm probably one of the least qualified,experienced posters on this thread so I've got little in the way of reputation to lose.But I'm really guessing in the dark cause like most people posting on this thread I've got little resources to put into any personal research.

[TZ350]

The GP has a 5 speed gearbox so there will always be more of a gap esp on a very tight kart track like mt wgtn.

I am looking at changing the primary gear ratio from the 3.2:1 (from memory) to something closer to 2.5:1 this should bring the ratios closer together.

.

[koba]

Experience (and research) tells me what I will find already (smaller carb, hotter engine), but, I will attempt to obtain the data in a timely fashion.


I dont get this bit.

I'm not trying to be personal or anything either but I just don't understand it.

Small hole = high airspeed = cool inlet charge right?

My Volkswagen has a 28mm carb on a 1500cc four-stroke engine, the small hole and long inlet manifold lead to manifold icing! yeah, none of this cold air induction shit, it needs to be heated in winter so it doesn't freeze up!

While this is a totally different example I would have thought the theory would carry over at least in part.

Could you give us an idea of why? even without data to support it yet.

[diesel pig]

I am looking at changing the primary gear ratio from the 3.2:1 (from memory) to something closer to 2.5:1 this should bring the ratios closer together.

.

Thats an interesting idea TZ, How do you think you will go about doing it?
Adapt the primary gear ratio off an other small motor, Suzuki small two strokes engines have very similar gearbox and crutch designs it might be possible. Or will you bite the bullet and get a set made? Kickaha had a look at doing this and got quotes along the lines of 5 to 4 hundred bucks.

[speedpro]

I've played with tuned length inlets on a disc valve 50. Very interesting results. When it was on resonance it was REAL good but an absolute pig everywhere else. The noise was pretty amazing as well. I tried the carb next to the disc valve and also at the end of the tuned length. Tried different diameters as well. End result was that you are better off without any resonance in the carb. From experimenting on a dyno the only resonance you need to worry about is reed valve petal resonance - it needs to be above the operating frequency or power tapers off. It's interesting watching the "stand-off" at the entry to the carb during dyno runs. Typically there is lots with the revs low down, then it disappears suddenly as the revs rise and then right at the top you can get a bit back again, probably due to reed valve issues. Though it did essentially the same thing on a piston port engine as well.

With another bike I built with a bit of bottom end power missing, I increased primary compression and definitely improved bottom end. That is the power off-pipe was better. No dyno runs back then so no actual numbers.

[speedpro]

I still think the copper head lining with some sort of shiny coating is worth trying. We all agree that heat is the killer in an air cooled 2-stroke and TZ350 has already explained the heat conduction properties of copper. Next time I'm making a copper head gasket its gonna be a biggy though won't be a part of the chamber.

[Yow Ling]

Going back a few hundred pages and after having tons of time to digest them, one idea that keeps me thinking was from the model aeroplane site. Making a diffuser to create high perssure low velocity cooling , as opposed to what we use low pressure High velocity, maybe this is the one scooter thing that is worth keeping, but try and do it without the fan, maybe it needs a full fairing and a couple of properly designed naca ductsand some shrouding around the engine. It sounds so wrong that it might be right

[TZ350]

I still think the copper head lining with some sort of shiny coating is worth trying. We all agree that heat is the killer in an air cooled 2-stroke and TZ350 has already explained the heat conduction properties of copper. Next time I'm making a copper head gasket its gonna be a biggy though won't be a part of the chamber.

I have my doubts about the durability of polishing the copper then using a modern car wax or gold or silver but we do know ceramic sticks and there might be a white reflective ceramic that can be appled thinly.

I haven’t given up on the copper head but until I can get it sorted. I am making another head and copper cooling fin. Following Speedpros suggestions it will be like a big head gasket and the combustion chamber itself will be alloy. It will be sealed both sides by "O" rings, one "O" ring groove in the head and the other in the barrel. Unlike Speedpro my copper fin will extend into the combustion chamber and form the squish land. I think these extra large copper head gaskets have potential.

.

[TZ350]

Going back a few hundred pages and after having tons of time to digest them, one idea that keeps me thinking was from the model aeroplane site. Making a diffuser to create high perssure low velocity cooling , as opposed to what we use low pressure High velocity, maybe this is the one scooter thing that is worth keeping, but try and do it without the fan, maybe it needs a full fairing and a couple of properly designed naca ductsand some shrouding around the engine. It sounds so wrong that it might be right

This has got to have potential but I just don't know how to go about it. Did you see how small the opening to the ducting on the model and the aircraft is? and what is low speed and high pressure to an aircraft? travelling at 500mph and 30,000 feet, I just don't know. But its got to be worth a look.

.

[TZ350]

I've played with tuned length inlets on a disc valve 50. Very interesting results. When it was on resonance it was REAL good but an absolute pig everywhere else. The noise was pretty amazing as well. I tried the carb next to the disc valve and also at the end of the tuned length. Tried different diameters as well. End result was that you are better off without any resonance in the carb.

Last year we had an Engineering student working with us who for his practical project at Uni had done a study on resonance in the inlet system and its effect on torque.

He and another student set up a motor with no tuned length effect in the exhaust so the point of peak torque would be at the point of inlet resonance only.

They made a device so they could adjust the inlet length. Then they ran the motor, changed the tuned length of the inlet and plotted the peak torque point. After step by step changes and plotting the results it was clear if you could have an automatically varying tuned length you could have a very long, Phat flat and high torque curve.

I can't help thinking about what could be done with an electric power valve actuator and a couple of pieces of pipe that slide inside each other.

.

[koba]

They made a device so they could adjust the inlet length. Then they ran the motor, changed the tuned length of the inlet and plotted the peak torque point. After step by step changes and plotting the results it was clear if you could have an automatically varying tuned length you could have a very long, Phat flat and high torque curve.

I can't help thinking about what could be done with an electric power valve actuator and a couple of pieces of pipe that slide inside each other.

.

I think the current R1s have somthing like that, I think its just a two stage job tho, essentially long trumpets and short.

[SS90]

There was heaps of research done by Fujio Nagao (of Kyoto Univerisity) on the subject of the resonance effect of the intake side of a two stroke.

Alot (most) two stroke tuners use his data in their books, and I have been lucky enough to read several portions.

Basically, It is quite simple to calculate the resonance frequency in an exhaust system as it's frequency is ALMOST exclusively a function of it's length.

But, the intake side is termed a "resonance flask" (as it consists of the crankcase, and the inlet tract.)

(Another example of how important the crankcase is, and how much modifications can effect the engine!)

And, there is a simple formula for determining the resonance frequency of a flask, but, when you look further into it, it starts to get complicated when you try to use it, as there are so many variables when it comes to a specific example.

One of many examples of a variable is Sonic speed, ( which is dependent on temperature, and how do you calculate the temperature of gasses when it is not only being cooled by evaporating petrol, AND heated at the same time by the metal of the engine when it is being).

there are many variables, but it is pointed out the biggest problem in calculating the correct length for a specific engine is that the volume of the intake in question (which includes the crankcase) changes constantly with the movement of the piston.

Couple this with the fact that the intake tract (as is the case of a GP125, is not just a simple tube)

Not only the shape, but the area varies all through this length, which is not only difficult to measure, but in being so, difficult to calculate, even if you could measure it accurately (as there are so many different formulas needed for such a complex shape)

You could waste an amazing amount of time on this calculation, and , even today it is considered acceptable (even with some of these very clever computer programmes (MOTA, coupled with a rendering programme like CATIA for example)) to simply experiment, but in a scientific way.....

One method involves isolating the effect of the inlet tract on the engine.

Which, in itself is a basic concept, you must of course, design and build a "stub" exhaust that will be too SHORT to operate effectively with-in your projected operating speeds, BUT be long enough to prevent the "Kadenacy effect" which will cause "back breathing" into the combustion chamber and also upset mixture strength.

Kadency effect , basically, is the name given for the reason a high pressure will balance out a low pressure, an example of which is the Crankcase/combustion chamber scenario...... So this effect is not always a bad thing!

There are a few more steps in this method, but, it is quite time consuming (and noisy).

It is well documented (and I suspect that some people may know), that the closer you mount the carb to the cylinder (in the case of piston porting), or, such as is the case of a GP125, the disc valve, that MAXIMUM air delivery (permitted by the carb size, and primary compression ratio that is) is delivered to the crankcase.

Great!

Not quite.

When you get that close, the wave activity at such a location creates MASSIVE pressure fluctuations, and the carb really has trouble doing it's job of metering the fuel.

Myself (and thousends and thousends of peoole before me) have found that using a reed block helps dramatically (and also the distance of the reed block from the disc (in a disc valve example) has profound effects when only increased/decreased by 3-4mm

My personal experience has been 5mm can be as much as 200RPM more effective range.

But that does vary from design to design, and cannot be considered a rule by any means.

With such a small carb, could it be an idea to go to the effort of adapting a reed block (a short one, so that it doesn't end up wider than a Benelli Sei') to the inlet (and, also increasing you inlet timing to maximum, as now the reed block will only allow fuel in as a result of the piston pressures).

It's just a thought (and perhaps inpractical), but with a little carb, maybe there are some tangible gains having the carb as close as possible to achieve MAXIMUM AIR DELIVERY (with your piddly little 24mm carb.)

Just a thought.

[F5 Dave]

I dont get this bit.

I'm not trying to be personal or anything either but I just don't understand it.

Small hole = high airspeed = cool inlet charge right?

My Volkswagen has a 28mm carb on a 1500cc four-stroke engine, the small hole and long inlet manifold lead to manifold icing! yeah, none of this cold air induction shit, it needs to be heated in winter so it doesn't freeze up!

While this is a totally different example I would have thought the theory would carry over at least in part.

Could you give us an idea of why? even without data to support it yet.Oh come on Mal, if you'd done any reading on 2 strokes this would be evident:Pokey:.

[SS90]

No, I don't take it personally.

What we are dealing with here is the "pumping efficiency" of the engine.

Having a smaller carb (in particular an excessively small carb, rather than just 1 or 2mm smaller than ideal) increases the pumping loss (the horsepower the action of "drawing the air in" through a smaller hole.

This " higher than normal pumping loss" in turn adds to the overall temperature of the engine.

A four stroke (like your Käfer, (beetle)) for example has less "pumping losses", particularly in the intake stroke, as the inlet valve opens after the piston has started its downward stroke, and there is alot more energy from one four stroke power stroke than one two stroke power stroke, and the crankcase is not pressurised on a four stroke (it's actually vented to atmosphere) making pumping losses more of a factor on the two stroke.

This may or may not include VW's!:laugh:

I think a good example would be if you had a syringe (with an opening of 1mm and extracted the plunger, and paid attention to how much energy was required to do so (perhaps using a spring scale), then, with the same syringe, decrease the opening to 0.4mm, and did the same test, you would require sigificantly more energy to perform the same task. (due to the fact that the opening has decreased it size, and there is more energy required to perform the same task. The air you draw through this smaller hole will also be quite a bit hotter than the air you draw through the larger hole.

This is a pumping loss.

[F5 Dave]

Ahh, So you are saying the frictional increase of pushing the same amount of air through a small orifice compared to a bigger orifice will mean an increase in heat.

. . . However this does ignore the latent cooling effect of the petrol in the gas mixture.

And, and more importantly I would argue is that you aren’t pumping the same amount of air through. You are sucking less in (aided by some extent by inertia I concede). You have a given amount of suck & there is a restriction so you can’t get that much in. That is why it is a restriction in the rules as it restricts power from the larger 125 engine (from the 100s which can run any size & be watercooled).

[speedpro]

Ahh, So you are saying the frictional increase of pushing the same amount of air through a small orifice compared to a bigger orifice will mean an increase in heat.

As mentioned by you a bit later in your post, the air is being sucked through the hole. There is therefore air at atmospheric pressure outside the hole and a reduced pressure area on the other side of the hole and the air moves through the hole accordingly.

The air outside the hole as it moves through the hole to the inside of the crankcase will reduce in pressure, it wouldn't move otherwise, and what happens to a gas as it's pressure is reduced , , , , hmmmmm?

And yet somehow or other the theory is that we end up with a hotter engine. Actually when you take all the friction and combustion going on I'd be very surprised if the temp change is anything other than academic.

[Buckets4Me]

Pushing pulling pocking and prodding
I would be hot uner the collar to :angry2:

[saxet]

One way to look at it could be that the motor has to work harder with a smaller dia. hole. Heat would be the natural outcome of the extra energy used ...I sound like a tech tutor.........maybe I was listening.

[TZ350]

Hopefully this leads to an animation of the complete 2-stroke process.

http://www.atvriders.com/articles/twostroke.html

And this page has a description of the various 2-Stroke types.

http://en.wikipedia.org/wiki/Two-stroke_cycle

* 1 Applications
* 2 Different two-stroke design types
o 2.1 Piston controlled inlet port
o 2.2 Reed inlet valve
o 2.3 Rotary inlet valve
o 2.4 Crossflow-scavenged
o 2.5 Loop-scavenged
o 2.6 Uniflow-scavenged
o 2.7 Stepped Piston Engine
* 3 Power valve systems
* 4 Direct Injection
* 5 Two-stroke Diesel engines
* 6 Lubrication
* 7 Reversibility
* 8 Sources
* 9 See also
* 10 External links
.

[koba]

No, I don't take it personally.

What we are dealing with here is the "pumping efficiency" of the engine.

Having a smaller carb (in particular an excessively small carb, rather than just 1 or 2mm smaller than ideal) increases the pumping loss (the horsepower the action of "drawing the air in" through a smaller hole.

This " higher than normal pumping loss" in turn adds to the overall temperature of the engine.

A four stroke (like your Käfer, (beetle)) for example has less "pumping losses", particularly in the intake stroke, as the inlet valve opens after the piston has started its downward stroke, and there is alot more energy from one four stroke power stroke than one two stroke power stroke, and the crankcase is not pressurised on a four stroke (it's actually vented to atmosphere) making pumping losses more of a factor on the two stroke.

This may or may not include VW's!:laugh:

I think a good example would be if you had a syringe (with an opening of 1mm and extracted the plunger, and paid attention to how much energy was required to do so (perhaps using a spring scale), then, with the same syringe, decrease the opening to 0.4mm, and did the same test, you would require sigificantly more energy to perform the same task. (due to the fact that the opening has decreased it size, and there is more energy required to perform the same task. The air you draw through this smaller hole will also be quite a bit hotter than the air you draw through the larger hole.

This is a pumping loss.

Hmm, I get the idea.


Ahh, So you are saying the frictional increase of pushing the same amount of air through a small orifice compared to a bigger orifice will mean an increase in heat.

. . . However this does ignore the latent cooling effect of the petrol in the gas mixture.

And, and more importantly I would argue is that you aren’t pumping the same amount of air through. You are sucking less in (aided by some extent by inertia I concede). You have a given amount of suck & there is a restriction so you can’t get that much in. That is why it is a restriction in the rules as it restricts power from the larger 125 engine (from the 100s which can run any size & be watercooled).

But I also see what you mean...


As mentioned by you a bit later in your post, the air is being sucked through the hole. There is therefore air at atmospheric pressure outside the hole and a reduced pressure area on the other side of the hole and the air moves through the hole accordingly.

The air outside the hole as it moves through the hole to the inside of the crankcase will reduce in pressure, it wouldn't move otherwise, and what happens to a gas as it's pressure is reduced , , , , hmmmmm?

And yet somehow or other the theory is that we end up with a hotter engine. Actually when you take all the friction and combustion going on I'd be very surprised if the temp change is anything other than academic.

And your angle...


Pushing pulling pocking and prodding
I would be hot uner the collar to :angry2:

I do know all about what you are talking about but thats another story...


One way to look at it could be that the motor has to work harder with a smaller dia. hole. Heat would be the natural outcome of the extra energy used ...I sound like a tech tutor.........maybe I was listening.


I think I'm confused :confused::blink::scratch:

Tee Zee, CAN you test this by whacking a bigger carb on and measuring heat and all that?
It would be interesting to see.

[Buckets4Me]

I'm sure he can test the theory but no one is to complain at the next gp ok :shifty:

[koba]

I'm sure he can test the theory but no one is to complain at the next gp ok :shifty:

Hmm, good point.

TeeZee, Maybe it would be a waste of time testing that theory :whistle:

[SS90]

Hmm, I get the idea.



But I also see what you mean...



And your angle...



I do know all about what you are talking about but thats another story...





I think I'm confused :confused::blink::scratch:

Tee Zee, CAN you test this by whacking a bigger carb on and measuring heat and all that?
It would be interesting to see.

This is all very interesting, however, I feel that some of the basic understandings are being compromised by irrelivent references to technical terms.

Speedpro...........

In the case of the intake stroke of an internal combustion engine.............the air is not "sucked through a hole"

....... It is "pushed".

(by the higher pressure air behind it)

A highschool science teacher will teach that.

Let's not get lost here!


I have written earlier (as discovered by air-cooled 125GP developing engineers) when you are calculating the required length of an inlet manifold, while it is easy to find a suitable formula to suit the occasion, as is subjected to too many variables (and therefore too many variables in the equation) to be a worthwhile exercise.

Four Strokes are somewhat different (an example of which has been offered.....ironically, a VW Beatle.

It would be a good idea to point out now, that the generalised standard for the calculating the length of a four stroke inlet manifiold, is from the back of the inlet valve to atmosphere (I am sure there are other variables, but this is considered a constant......, whereas the two stroke includes the Crankcase volume (.....which changes)

As such, every two stroke engine must undergo it's own developing procedure.

Lets us all remember that we can get "lost" using big words, and forget some basic principals.

This is one area in particular that the levels of gains to be made (compared to a four stroke) are quite significant, due to the in-nefficienty of a two stroke engine.

Pumping losses are considered critical on a Two stroke engine.

More pumping losses mean more heat.

An example of pumping losses being so important, is attention to the correct primary compression ratio.

(for a given engine, in a given situation)

[saxet]

Perhaps another thread needs to be started for this sort of discussion( two stroke tuning thread) so TZ350 can have his thread back???

[SS90]

That's a very good idea.

I would contribute to both, (to the best of my ability,and with-out any hidden agenda)

It would be very cool to contribute to the "resurrection" of New Zealand in the race bike scene.

We have been absent for a while...........:grouphug:

[Buckets4Me]

:eek5::eek5::gob::yes:

[speedpro]

Speedpro...........

In the case of the intake stroke of an internal combustion engine.............the air is not "sucked through a hole"

....... It is "pushed".

(by the higher pressure air behind it)

A highschool science teacher will teach that.

Let's not get lost here!

So of course it is incorrect to say that for instance I sucked Coca Cola through the straw and drank it. You would have me say that atmospheric pressure acting on the surface of the Coca Cola in the glass "pushed" the Coca Cola up the straw into my mouth. The point is there was a pressure differential and the gas or fluid was free to move from the area of high pressure to the area of low pressure. When gas moves from an area of high(er) pressure to an area of low(er) pressure there is a law, Boyles Law I think, that covers what happens to the gas.

It is common english language usage to use the term "suck" when referring to causing a reduction of pressure at one point to cause a fluid to move.

Definition: Suction, the creation of a partial vacuum, or region of low pressure.

This is what happens when a 2-stroke piston rises and logically if we have suction then there must be sucking happening.

Some people just own up to being wrong but not others . . . they start being really really picky over things we all know anyway

[speedpro]

and a bit more on the matter of sucking. I have noted the point about sucking or pushing.

"Suction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not innately attract matter. Dust being "sucked" into a vacuum cleaner is actually being pushed in by the higher pressure air on the outside of the cleaner.
The higher pressure of the surrounding fluid can push matter into a vacuum but a vacuum cannot attract matter."

[bucketracer]

Has any one else thought that SS90 is not what he says he is?

Granted He is well read, but so are we. SS90 has persisted in saying a lot without saying much. In his posts he is more like trying to string us along and his maturity and socialisation is well below what I would expect of someone entrusted with the gear to develop engines...... <_<.....To informed to be a school boy, but not much more I expect.

A lot of quoting and referances and telling us how it should be and seems totaly unable to accept we might have a clue ourselves. I don't see any hands on personal experiance of the :Oops: blood :sweatdrop sweat and :crybaby: tears kind that goes with tuning shining through, do you?.. :angry:

I think he is just blagging on and taking the piss. could be a :tugger: around NZ somewhere having fun winding us up and sending us off on wild goose chasses.

[bucketracer]

and a bit more on the matter of sucking. I have noted the point about sucking or pushing.

"Suction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not innately attract matter. Dust being "sucked" into a vacuum cleaner is actually being pushed in by the higher pressure air on the outside of the cleaner.
The higher pressure of the surrounding fluid can push matter into a vacuum but a vacuum cannot attract matter."

Sucked - Pushed it all depends on what initiated the change in state. In this case it was the engine and therefor its right to say "sucked the air in".

Another example of SS90 being unable to let someone else shine.

[gav]

So SS90, in your opinion, would TZ350 be far better off to avoid the restiction of the 24mm carb. He can simply do this by running a 100cc engine rather than a 125cc engine.

[Bren_chch]

So SS90, in your opinion, would TZ350 be far better off to avoid the restiction of the 24mm carb. He can simply do this by running a 100cc engine rather than a 125cc engine.


i think Gav, he should just give it to me and i'll ride it.

[SS90]

This is getting hilarious!

To some people (who are reading this thread from over here) It is starting to look like there are some Ego's getting bruised.

And some people really are looking silly......... It's a shame, as I have introduced people to people here to Kiwi hero's, like Kim Newcombe, and the B.S.L concept, and they thought that N.Z was full of free thinking individuals with a talent for two stroke tuning.

What has come up in this thread has made me have to explain

"THE TALL POPPY SYNDROME"

I surmise that there are efforts being made to fustrate me, in order to stop me posting here, so that a group of three or four can go back to continuing the ILLUSION of being "Clever bastards......."

It was just pointed out to me that, IF I do have a need to always be right, that need is only beaten by some peoples need to prove me wrong.

You win children........, go back to your gold coated cylinder heads..... :shifty:.....
.........the rest of us will continue on with real development.

In this case, when you win, you lose.

I am a little ashamed of a few of you guys, and I have never met you.

I have met f5 dave once, showed him a clean pair of heels all weekend at a black meeting in Blenhiem about 5 years ago.

He was just as bitter then!

[bucketracer]

I surmise that there are efforts being made to fustrate me, in order to stop me posting here, so that a group of three or four can go back to continuing the ILLUSION of being "Clever bastards......."

You win children........, go back to your gold coated cylinder heads..... :shifty:.....
.........the rest of us will continue on with real development.

In this case, when you win, you lose.


SS90 in 100's of words you've not said anything constructive yet.

PS In spite of basically hijacking TZ's thread and in your arrogance offering to take control of his engine development he has been very gracious yet you mock him. Sure, gold might be a bit over the top but he is thinking about it, doing it and genuine, you’re something else.

You do talk a lot and yet havent said anything of substance.......... I don't think were losing anything.

.

[bucketracer]

What has come up in this thread has made me have to explain

"THE TALL POPPY SYNDROME"




.

SS90 Don't flatter yourself. There are Tall Poppys and then there are Smothering Weeds.

.

[quallman1234]

SS90 Don't flatter yourself. There are Tall Poppys and then there are Smothering Weeds.

.

SS90 is offering, his opinion on things. What isn't necessarily right or wrong. Respect his opinion. He might actually have some very good information to share.

:blank:

[bucketracer]

SS90 is offering, his opinion on things. What isn't necessarily right or wrong. Respect his opinion. He might actually have some very good information to share.

:blank:

I dont think he wants to share, and he certainly hasn't respected anyone elses opinion. Take an interst and he wants to take controle. Smothering weed about covers it.

.

[Sideways Sam]

Dudes, pull your freakin' heads in.

TZ350 builds a fast consistent engine and he's always developing it further, beats mine every time........ Best thing is, he's always there and his bike always goes, more than I can say for mine.

Anyways, when he learns how to go 'round corners he could be a threat to someone a lot faster than me.........

Bottom line is, he's there every meet (plus the odd out of town event) and his bikes run........... And they go better than mine........ Bastard!

No further comment necesary!!!!!!!!

[saxet]

I was looking at fairings and it's occurred to me that the front of the lower fairing on a sport bike seems to share similarities to the design of the shroud in the link to aero engine cooling. Is this coincedence or by design.

[F5 Dave]

So of course it is incorrect to say that for instance I sucked Coca Cola through the straw and drank it. You would have me say that atmospheric pressure acting on the surface of the Coca Cola in the glass "pushed" the Coca Cola up the straw into my mouth. . . .

That is how the CocaCola company would prefer it, you just being a unwilling (but paying) participant.:laugh:

[F5 Dave]

. . .
I have met f5 dave once, showed him a clean pair of heels all weekend at a black meeting in Blenhiem about 5 years ago.

He was just as bitter then!
. . . So hands up who has ever seen me being bitter about being beaten racing? What an odd thing to say.

About the only time I get pissy is when people knock me off & it's not an honest racing incident.

[speedpro]

Tall Poppies??? At bucket racing??? What a joke. There is ALWAYS someone who knows more, or who is faster, or better looking. Me for example.

[speedpro]

maybe not, eh!

[speedpro]

Some of us have done 5-600 dyno runs and experimented with nearly every aspect of engine tuning. Me, I've done that, and I've decided that I can't go any faster without professional help, which has also helped my understanding a lot as well and completely turned a few ideas on their heads. My mates have also done hundreds of dyno runs testing things and we share all the info gleaned from those runs. If anyone is interested they can always have a look inside my engines and in fact I don't mind posting photos of port configurations etc. I just want to see development being done and learning from the results.
I also firmly believe that a lot of what is produced by the main manufacturers is marketing bullshit and that not enough questions are asked. Which is where the average bucket racer comes in, especially guys like TZ350. Everything is questioned. Sometimes the answer is already known, sometimes not. Like , , , , How would a copper head work? Who really knows?

[Skunk]

Tall Poppies??? At bucket racing??? What a joke. There is ALWAYS someone who knows more, or who is faster, or better looking. Me for example.
You're just old and tall...