ESE's works engine tuner

[SS90]

Thanks for the reply.

From SS90’s post :-

2) Compression Ratio, don't go too high. Gordon Jennings has an opening chapter called "Fundamentals", in there it talks of "flash horsepower engines", where the compression ratio is too high, so that for a few dyno runs (or laps) it goes like hell, but sharply drops off, and end up for the rest of the race having less horsepower than other competitors.

With respect, I think you engine falls into this category.

The high horswpower engines that I build run quite low cylinder compression, due to the fact that the first stage of devlopment showed me that what I gained when the engine was cold, I more than lost when it was
hot......

TZ350:- This is the Taupo experience.

From SS90’s post:- You will find that high tuned scooter engines run quite low cylinder compression, and primary compression in the vicinity of industry norms.

TZ350:- What corrected cylinder compression ratio would you expect to work in my GP? What works in tuned Scotters?

I built the motor and pipe modelled on Gordon Jennings description of what could be done with an early RM125 and the cooling improvements based on the known heat load in the cooling system and ideas from air cooled aero engines.

…………………………………...

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

"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.

.

Hmm, what compression ratio would I recommend?
That is a pretty good question, I have looked back to the beggining,and taken a look at your figures.........

Teezee's post-:
So the total dynamic ClearanceVolume is now 10cc’s at 10,000rpm
Dynamic Corrected Compresion Ratio = 6.8
Dynamic Uncorrected Compression Ratio = 13.5

Our aim was for a bit more than this.

So a couple of skims and re-measures later we had:-

The total dynamic ClearanceVolume is now 9.4cc’s
Dynamic Corrected Compresion Ratio = 7.3
Dynamic Uncorrected Compression Ratio = 14.3

My experience would suggest that the first volume was better in this situation, and perhaps even that could at times be a little high....... (I'm going to expect a bollocking here!)

[SS90]

I am interested in the transfer streams that SS90 talks about.

The picture and quote are from an earlier post,

"A picture of my combustion chamber after Taupo. The wash from the transfer streams can be clearly seen. If anyone can tell me anything about their shape, I would be interested to know if they look right or otherwise."

I have been looking at the way the transfers wash the piston and head to determin their flow pattern.

When I get back to work Monday I will see if I can scan the relevant pages about Janti (transfer stream) patterns and post them.

Pics to make it easy for SS90 to tell me if this is what he is talking about or maybe elaborate on them or the head with a few scketches of his own.

I feel comfortable with 2-stroke theory, practical implimentation is the chalange.

.

This is from a very early post by Teezee (number 9 actually)-:

Thomas is working on the ports. Rear port angles up 55 degrees, secondaries 45 and mains are angled flat across the bore. All the transfer ports were made to open at the same time, 114 degrees ATDC, duration 132.

The rear port at 55 degrees is pretty much on the money (in my opinion), but where it goes amiss is-:

"And the mains angled flat across the bores"

This is going to give you a pretty crap scavenge pattern really.....because you are losing so much fuel out the exhaust (as you are "short circuiting" the loop scavenge system, by having the mains "angled flat across the bore" )

My experience suggests that with a set up like this, you are not going to get a visible pattern on the piston at all. My work has shown that when I start to get the pattern correct, it becomes more visible on the piston crown (as opposed to the piston having a uniform colour)

But, I see you have found some interesting information on the net, and it I think if you followed the things there, with some experimenting (I really suggest a dyno run or 3 now, so you have some "hard data" to compare)

I can't remember ever seeing a pronounced pattern on the head since I started getting the scavenge pattern "more on Par (with-out copying)", and always read the piston. But plenty of other people are well ahead of me........

I said this in an earlier post ( as a broad hint....)

"I would would look at HONDA race engines when it comes to quality scavenge patterns"

Having said that, I was told a while back to take a look Kart Sport patterns as well.

But I have to admit I never did, but just because I was being lazy!

[SS90]

"will also dramatically increase cylinder efficiency" by improved scavenging effectiveness and thereby "make better power"

Am I reading this correctly? Wouldn't this mean more waste heat to the cooling system or am I missing something? Please explain.

Sure, logic dictates that more power will generate more heat......
But (in this context), By better power, I don't mean more "peak power", I mean "better power" (more torque in lower R.P.M is an example of this)

I have attached a picture from Gordon Jennings, this particular picture is an image used to show the effects of the different power curve achieved from a difference of "misaligned" transfers, compared to "correctly" aligned transfers.... Granted, in this context, it is "vertical" misalignment, but the gains (in terms of comparative curve shapes) are somewhat the same as the gains you will see when you have effective scavenge patterns, compared to transfers that "short circuit".

By having effective scavenge patterns, you essentially have more "cool swirling air fuel mixure" staying in the combustion chamber (and of course, less hot burned gasses sitting there, as the effective scavenge pattern has not only kept more fuel in the cylinder, it has "scavenged" the cylinder more that before. (it has helped push more hot burned gasses out)

Granted, there is a power increase, (and, as such a heat increase) but it is offset by the increased cooling of the combustion chamber.

The engines efficiency is increased.... it wastes less energy.

[SS90]

I'm gonna have to work on my "piss taking" I see. Obviously a bit too subtle for most.
It's only the percentages that change as far as heat dissipation. At full throttle we may have say 1000BTU being dissipated in the cooling system assuming for simplicity that 3000BTU is being generated when the fuel is burnt & a 33% split. At part throttle the fuel burnt may only provide 2000BTU total but the % split changes so that maybe 40% is dissipated in the cooling system. 40% of 2000BTU is 800BTU so the cooling system is dissipating less energy than before. I've simplified this example and I don't know how the %s change but hopefully you get the idea. By reducing the throttle opening my engine does not get hotter, unless the %s are changed WAY more than I would expect.

A good point has been raised about compression ratios. Through vast combined experience of many fast bucket racers we think that depending on the actual air-cooled engine involved that 14.7-15:1 (swept+trapped/trapped) is about the max for good sustained power. My current MB is running at 15.2:1 and holds good power all day on any track. My new motor supposedly will be more efficient at trapping mixture in the cylinder and because of that, even with the water-cooled head, the compression ratio has been set at a lower value. I haven't relied on experience for the new motor as I think I got to where I could using that and went for "professional" help and advice. Time will tell if it was money well spent. Supposedly I should be able to dust Nigel good and proper as the same guy designed both our motors at the same time and we had our pipes laser cut at the same time, etc etc.

I particularly agree with speedpro's statement that "depending on the different two stroke engine....."

Every engine is different (depending on it design) (e.g, Crankcase (reed) induction, compared to disk valve induction) for example, and as such, different maximum cylinder compression ratios are applicable for each one, as well as exhausts, etc.

You say that "supposedly your motor will be better at trapping fuel in the Cylinder........."

That is interesting (and I believe I know how that is being facilitated)...Do you know what scavenge pattern has been applied to your new cylinder?

[TZ350]

Hmm, what compression ratio would I recommend?

Teezee's post-:
So the total dynamic ClearanceVolume is now 10cc’s at 10,000rpm
Dynamic Corrected Compresion Ratio = 6.8
Dynamic Uncorrected Compression Ratio = 13.5

My experience would suggest that the first volume was better in this situation, and perhaps even that could at times be a little high.......

My current head is more this ratio and thought it to low, I will leave it for now and see what others think. Thanks for your reply based on your experience.

I used the term "Dynamic" to indicate the 1cc Clearance Volume lost to rod stretch at 10,000rpm. The compression ratio would be lower if measured statically.

.

[TZ350]

This is from a very early post by Teezee (number 9 actually)-:

Thomas is working on the ports. Rear port angles up 55 degrees, secondaries 45 and mains are angled flat across the bore. All the transfer ports were made to open at the same time, 114 degrees ATDC, duration 132.

The rear port at 55 degrees is pretty much on the money (in my opinion), but where it goes amiss is-:

"And the mains angled flat across the bores"

This is going to give you a pretty crap scavenge pattern really.....because you are losing so much fuel out the exhaust (as you are "short circuiting" the loop scavenge system, by having the mains "angled flat across the bore" )

My experience suggests that with a set up like this, you are not going to get a visible pattern on the piston at all. My work has shown that when I start to get the pattern correct, it becomes more visible on the piston crown (as opposed to the piston having a uniform colour)

Your right, my motor with a flat piston was uniform in colour across the top and the other motors from Taupo with normal domed pistons and ports had visible patterns.

When I can I will draw diagrams showing the horozontal and vertical angles of the ports.

.

[TZ350]

I can't remember ever seeing a pronounced pattern on the head since I started getting the scavenge pattern "more on Par (with-out copying)", and always read the piston. But plenty of other people are well ahead of me........

I said this in an earlier post ( as a broad hint....)

"I would would look at HONDA race engines when it comes to quality scavenge patterns"

Having said that, I was told a while back to take a look Kart Sport patterns as well.

But I have to admit I never did, but just because I was being lazy!

Do you mean your heads or my photo was not clear enough? I will see if there is a better photo. If I take the head of during the race day or soon after I can see a wash pattern in the crud/oil that covers the combustion chamber. It usually doesn’t last long as in handling the head it is easily wiped away. I will draw a picture.

I remember you pointing in the direction of Honda but I could not find anything??? a couple more hints would help, thanks.

.

[TZ350]

This is a link to someone elses thread that talks about suspension setup:- http://www.kiwibiker.co.nz/forums/sh...ad.php?t=93518

After last Sundays points racing where I suffered several bad juddering front end slides. that effectivly detuned me for the day. It is time to start looking at handling and riding technique improvements to go with the engine development.

.

[TZ350]

Thinking of building a Dyno? Check out Geoff's homebrew dyno page:- http://geoffm.sitegoz.com/dyno/DIY_dyno.html

Also a air cooled 2-stroke hotup page/links, mostly RD stuff:- http://geoffm.sitegoz.com/tuning-info.html

A link to Eric Gorrs 2-Stroke tuners page:- http://www.eric-gorr.com/2%20stroke%...erformance.pdf

Typical Kiwi ingenuity. Thanks Geoff

.

[Chambers]

Um sort of the same thing in practice. A layer of plating will still create a thermal barrier, so it would be better to use untreated aluminum, (if it didn't wear of course) but the barrier is considerably less that a steel sleeve, so more heat is passed to the outside ally rather than retained in the sleeve & hence the rest of the engine.

B&S Lawn mower motors had an untreated aluminum bore with a flash chromed piston and rings. I think other motors used this idea too. The early Yamaha racers tried teflon coated bores before going to chrome.

Like B&S and Yamaha, TZ350 was thinking outside the box with his copper head idea, He is in good company.

[Buckets4Me]

Check out that areo cylinder, see how close the fins are spaced compaired to the motorcycle cylinders.

Maybe more for 4-Strokes. Sparkplug pictures, worth a look:- http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html

.

[SS90]

B&S Lawn mower motors had an untreated aluminum bore with a flash chromed piston and rings. I think other motors used this idea too. The early Yamaha racers tried teflon coated bores before going to chrome.

Like B&S and Yamaha, TZ350 was thinking outside the box with his copper head idea, He is in good company.

While "Thinking out of the box" is certainly cool, the copper (or bronze alloy) cylinder head is simply a serious step in the wrong direction in my opinion.

Yes, bronze alloys have great heat transfer properties......ever noticed (or measured) how much bronze alloys EXPAND when heated....now compare that to a high silicone Aluminium (such as the Japanese have been using for the last 20 or 30 years)

I think if you made a cylinder heat for your performace two stroke out of this type of material, you will be replacing the piston before too long.

Just take a look at the detonation starting around Teezee's piston in the photo's from the last race.

Look closely, and you will see a "sand blasted" effect around the outer edge of the crown....

This is detonation.

Detonation starts at the outer edge of the crown.

If this was a 125 water cooled GP bike (that had just finished a race, and hopefully won), then, you would most likely say that "you where on the limit", as far as compression ratio was, take note, and next time you where running at that track, in those conditions, lower it a little.

And ditch the piston.

However, this was caused (in my opinion), by the fact that you had the copper "liner" in the head, which, when it got hot, expanded, closed up the "squish area", and caused detonation (possibly was touching the piston at the top of the revs as well).

Have a complete head from copper, I suspect somewhat more dramatic results.

Looking at the pictures of the head after the race, the head shows the same signs of detonation.

The fact that the copper "liner" isn't pressed into the head is adding to the problem as well.

If a "cast in" cylinder liner ( like a your GP125 is) is better at displacing heat than a simple "pressed in liner", then the same logic applies in this situation.

I really believe, as has been stated much earlier on by a few people, finding an early "radial" head off the last of the air cooled motorcross bike (I.E, designed to cope with lower speeds, higher power), and adapting it too fit would be a wise move)

[Buckets4Me]

Jetting through reading piston wash.

Reading Piston Wash:- http://www.bikemanperformance.com/tech_detail.php?ta=4

and even better:- http://www.snowtechmagazine.com/arti...e/baseline.php

Ist pic Rich, 2nd pic Good, 3rd pic Lean.

[SS90]

Put it on a dyno, stop pissing round. You make a change, do a run, and see exactly what effect the change has had. No bullshit, no guessing, no theories, just cold hard data.

As said by speed pro, week one!

I have to agree 100% on this. I believe that you would be much further ahead if you had done this. When you find a reliable dyno (and experienced operator), your results are always rewarding. Cool idea on building one Teezee, I have to believe though, that spend 3 hours on an existing dyno, (with established limits), as well as existing data for comparison, that you will never look back!

[SS90]

Reading Piston Wash:- http://www.bikemanperformance.com/tech_detail.php?ta=4

and even better:- http://www.snowtechmagazine.com/arti...e/baseline.php

That's not a bad page, the important thing that I am talking about with "scavenge patter", is the "shape" you get. (the "pattern"......I.E the "scavenge pattern)

Try to look for a combustion shape, that "shields" the fuel from pouring out the exhaust (after all, the extractor effect of the chamber is not 100%)

The picture on the left is heading towards one that I would aim for, if I was designing the scavenge pattern for this engine..... You will see how that exhaust side of the crown area is clean..... It's not perfect (you will never get it that way, but it's a very big step in the right direction.