ESE's works engine tuner

[fatbastd]

There doesn't appear to be much front suspension travel..

[Lucas M]

Thank you guys for your response and sorry for answering late. At the weekend, there was the first race this year for me. The engine works great. I had a lot of fun during the race.

The message of the diagram posted by Frits was already in my head. I´m able to switch gear later, and because of this, the next gear starts with the same hp, but at higher rpm. For the first look, the new power diagram don´t seem to be like a benefit. While driving, I recognized it is a benefit. Thank you for your confirmation Frits and Neels.

Variable ignition is allowed, but it´s really expensive. I know that this would be a big improvement for the engine.

Frits, joining the German forum don´t seem to be easy. Someone have to do a suggestion with a new member and after that, there is an election, so I don´t see a way to get in there.

[Muciek]

Thank you guys for your response and sorry for answering late. At the weekend, there was the first race this year for me. The engine works great. I had a lot of fun during the race.

The message of the diagram posted by Frits was already in my head. I´m able to switch gear later, and because of this, the next gear starts with the same hp, but at higher rpm. For the first look, the new power diagram don´t seem to be like a benefit. While driving, I recognized it is a benefit. Thank you for your confirmation Frits and Neels.

Variable ignition is allowed, but it´s really expensive. I know that this would be a big improvement for the engine.

Frits, joining the German forum don´t seem to be easy. Someone have to do a suggestion with a new member and after that, there is an election, so I don´t see a way to get in there.

Check few pages back there was discussion about "simple" retarding unit for CDI (for pvl one and regular CDI). You can do some variations with it just need to have a strobe lamp for setting ignition. Using NE555 and some relay You could build a poor man 2 map ignition.(Switching by hand or by frequency). ;)

[FastFred]

Hi Lucas, take a look at Ignitec ignitions, this is the model that Team ESE use on their singles:-

181 Euro for the CDI box then another 30-40 Euro for wiring harnes and CDI Coil etc,

http://www.ignitech.cz/en/vyrobky/dccdip2_race/dccdip2_race.htm

311192

[Yow Ling]

Hi Lucas, take a look at Ignitec ignitions, this is the model that Team ESE use on their singles:-

181 Euro for the CDI box then another 30-40 Euro for wiring harnes and CDI Coil etc,

http://www.ignitech.cz/en/vyrobky/dccdip2_race/dccdip2_race.htm

311192

CDI-P would work fine in Lucas's bike , I have one on my bucket, unless you have fuel solenoid, TPS, and powervalve you wont need cdip2 race and save 80 Euros as no special loom required and only 145 euro for the CDI

[RomeuPT]

Hello Everyone.

I kind a ask my self sometimes, why some bikes use a steel exhaust flange and then use springs to hold the pipe, I understand that in some models the flange might need to be centered or something, that a aluminium flange may help cool the end gases and give some increase in performance, that it might even get's easier to change the exhaust just taking off springs, to do oval to round transitions, alow pipes to be simplier and rotate a bit to fit better or something etc etc.

But for example Aprilia RS have a steel flange, a round exit exhaust duct, no step between the exit and flange entrance, no need to center the flange, has much has I know rear fitting is the same and is ajustable, some complain about leaks in the flange connection with pipe, the standard exhaust springs are not very acessible and hard to take off, same to bolt on the flange, and my guess is it would be possible to bolt a pipe without much more effort than the flange alone with common tools. Why is this not done?

[husaberg]

Hello Everyone.

I kind a ask my self sometimes, why some bikes use a steel exhaust flange and then use springs to hold the pipe, I understand that in some models the flange might need to be centered or something, that a aluminium flange may help cool the end gases and give some increase in performance, that it might even get's easier to change the exhaust just taking off springs, to do oval to round transitions, alow pipes to be simplier and rotate a bit to fit better or something etc etc.

But for example Aprilia RS have a steel flange, a round exit exhaust duct, no step between the exit and flange entrance, no need to center the flange, has much has I know rear fitting is the same and is ajustable, some complain about leaks in the flange connection with pipe, the standard exhaust springs are not very acessible and hard to take off, same to bolt on the flange, and my guess is it would be possible to bolt a pipe without much more effort than the flange alone with common tools. Why is this not done?

Flexibility and vibration plus ease of removal
http://www.gifflix.com/wp-content/uploads/2014/07/1295896692361.gifhttp://i0.wp.com/www.brobible.com/wp-content/uploads/2013/12/michelle-5.gif?resize=512%2C288

http://i.ebayimg.com/00/s/Mjc3WDUyNQ==/$(KGrHqJ,!qoE-ZHeJINWBP2KcVZZQg~~60_35.JPG

[Frits Overmars]

http://www.gifflix.com/wp-content/uploads/2014/07/1295896692361.gifI can still do that, and I don't get the amount of help from gravity that she does.

[Dutch Fisher]

Thats reminds me,, i must go out and milk the cows

[seattle smitty]

Holy cow, H-berg, I watched for quite a while hoping she'd have a wardrobe malfunction . . . well, that's inspiration for another day of labor.:eek:

[ken seeber]

Holy cow, H-berg, I watched for quite a while hoping she'd have a wardrobe malfunction . . . well, that's inspiration for another day of labor.:eek:

Smitty, dunno how virile you are, but would that be "hard" labour?

[husaberg]

I can still do that, and I don't get the amount of help from gravity that she does.


Thats reminds me,, i must go out and milk the cows


Holy cow, H-berg, I watched for quite a while hoping she'd have a wardrobe malfunction . . . well, that's inspiration for another day of labor.:eek:

Well it was the best way I felt I could convey the need for both vibration control and the importance of flexible of mounting.
The best slip joint flanges I have seen include O rings. I are surmising one of the correspondents will have pics of the Aprilia or Super Kart set ups.
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=303315&d=1413013578
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=303316&d=1413013580
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=303318&d=1413013584
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=303317&d=1413013582
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=236593&d=1302726963
Combination of both MR WOB
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=303012&d=1412478918
http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1129955411#post1129955411

[Frits Overmars]

The best slip joint flanges I have seen...Let's not go there, Husa. We must think about our young readers. And spare the hearts of the old-timers.

[chrisc]

Let's not go there, Husa. We must think about our young readers. And spare the hearts of the old-timers.

"Practice safe 2 stroking, always use a slip joint" :crazy:

[seattle smitty]

What was it the dirt riders' wives used to say . . . "An enduro rider is just dirty boots at one end, and a dirty mind at the other."

Thanks for the pipe photos, H-berg; somebody is doing some gorgeous work.

[seattle smitty]

There must be some general principles on the gapping of spark plugs that I'm missing. One of my interests is in improving the fuel efficiency of my daily driver, work truck, camper-van, road bike, etc.. According to years of reading articles for laymen, improvements to Kettering battery-and-points ignitions got the desirable gap for factory automobiles up (bigger) to about .035" (let's see, about 0.9mm). The advent of inductive and CD electronic ignitions allowed gaps as big as .060" (1.5mm) to light off relatively lean mixtures.

So I got to thinking that it is desirable to have the biggest gap, short of misfire, that your ignition could handle. But these days I hear that the newest alcohol-burning outboards, with the best ignitions they can find, want very small gaps, down to .011 or .012" (0.3mm). So what is the deal here, for racing engines? Do you want the biggest plug gap that the engine/ignition combination will take without increasing misfire (or overheating the ignition), or are there other considerations?

[wobbly]

The amount of energy available to be used in the spark process sets the gap that can be used.
Other elements that come into play are the plug efficiency ( an arbitrary term to denote the use of rare earth metals for the centre and earth electrodes )
and the mixture to be ignited ( rich and lean are harder to fire ).
When the ignition system initiates the gap ionisation this uses a set % of the energy available, and the wider the gap the greater the energy required to
establish a spark.
The remaining energy is used to create the "burn" phase that establishes a growing flame kernel.
So having a wide gap may use up too much of the available Joules, and the burn phase ends up not creating a sufficiently large kernel to have this spread thru
the chamber and consume all the combustible mixture ie a misfire.
Firing rich Alcohol mixtures is one scenario that needs alot of available energy, and if this isnt the case then close gaps can as a band-aid ameliorate the lack of power
to both ionise the gap and then create the kernel.
To do this well you have to resort to using a CDI system like the Ignitech, and fire both channels into a single coil that has a large inductive reactance.
The combination of plenty of energy storage in the twin capacitors and plenty of inductance to increase the burn period allow super rich highly compressed mixtures to be
burned with no combustion events dropping out.

[peewee]

i was told by a few people on other forums to decrease the spark gap for my alcohol engine. i tried .018" and .024" (which is what they are out of the box), i never could tell any difference with seat of the pants. maybe a dyno would of picked up the minor differences but i couldnt tell so i just used the standard gap from the box. maybe on another engine with less powerful ign it would of been more noticable

[seattle smitty]

Once the arc is established, doesn't the resistance to current flow drop dramatically? Of course, if you have to establish the arc with a CD system's short duration discharge, I guess the arc wouldn't stay established for long in any case . . . .

[speedpro]

I built a battery powered, points triggered, CDI for my old AC50. I went from about a .3mm gap, even with a big coil as that was all the gap it would spark over, to 1mm. In the lab the CDI would fire over a 10mm gap with a vicious bright blue spark. Using a pulse generator to trigger it we ran it up to equivalent of a V8 doing 10,000rpm without losing any output. The charging pulses looked like a picket fence on the scope and the inverter was drawing about 10A from the supply. We doubled up the capacitors from the original design and upped the inverter/rectifier output to 400V. It was definitely something you kept fingers off if it was powered up.

Never had a problem with misfiring. Back in the good old days.

[wobbly]

With the Alky system I tested the arc over voltage was around 28KV, and this dropped to around 12Kv during the burn phase.
This CDI system with double the capacitors and a really big coil ( a Crane as used in NASCAR ) had 4 times the burn duration of the stock
single CDI setup, it pulled around 5A from the DC supply where a single was all out at 1.5A.
I read somewhere that the limiting factor in a CDI is the capacitors ability to supply the required power fast enough, this being a quality set by the ESR
of the part, so I would imagine that the actual power supplied to the gap ie Watts = V*A is close to constant.
Thus when we have over twice the gap voltage at arc over, we would have less than 1/2 the current, and during the burn - visa versa.

[senso]

In my limited testing, low ESR and low ESL is the key for a good spark.
I have already tested some metalised foil caps, rated to 630v, and 1uF makes a nice spark, but two in parallel makes a sweet blue spark with a nice sound to it.
From my simulations and for the intended stator the best value for maximum charging is 4uF.

[peewee]

i never could figure out why a methanol engine can run fine even with raw fuel pouring out the end of the pipe. gas engine will only run for a very brief time in the same situation

does anyone care to explain why high performance engines always seem to use alot of oil in the gas ? i believe jan once said he used about 5% oil. i use about the same. what is the advantage of 5% versus something lower like 3 or 2% ? does the extra oil transfer heat to the cylinder walls better ? do the rings seal better ? does it lower the temp of the intake mixture ? better combustion in the head ? does it cool down the piston top more ?

[speedpro]

Dyno tests I've heard about more oil equalled more power. Do you really need to know why?, apart from curiosity of course.

[husaberg]

Dyno tests I've heard about more oil equalled more power. Do you really need to know why?, apart from curiosity of course.

Bell covers it with Dyno tests.

[peewee]

gordon jennings also did the oil ratio tests back in the day with castor oil. his conclusion was it gave more power but do synthetics oil work the same way ( more oil=more power) ? besides more power is there other reasons , like the piston has less chance of siezing ? if you look at a service manual like ktm they say to use only about 2.5% oil even for the 125cc mx engines. im trying to understand why this is. to me 2.5% doesnt seem like enough

i just remembered something from jennings oil test which was alot of years ago but didnt he say the more oil=more power may not be true for synthetics because of the cleaning agents and stuff they use ? granted the new oils are probly a bit different

[F5 Dave]

2.5% is 40:1 and what I run in big bore trail bike. Its peachy and never wears, but you're (I'm) never on the gas for that long so there's always some oil about.

125mx in the hands of a fearless kid? Well perhaps KTM want to sell some parts.

[TZ350]

i never could figure out why a methanol engine can run fine even with raw fuel pouring out the end of the pipe. gas engine will only run for a very brief time in the same situation

My take on it is that the raw methanol that is pouring out the end of the pipe is un-vaporised fuel so is not contributing to the fuel/air mix. When that happens you need to reduce the latent heat of evaporation of the methanol by blending it with acetone, ethanol, or unleaded petrol so the motor runs warm enough to properly vaporise the fuel load. It is possible to run a 2T so cold that the methanol is running lean on the plug but pouring wet out the exhaust pipe, richening it up only makes it colder and leaner while wetting the riders behind. Been there done that.


does anyone care to explain why high performance engines always seem to use a lot of oil in the gas ? i believe jan once said he used about 5% oil. i use about the same. what is the advantage of 5% versus something lower like 3 or 2% ? does the extra oil transfer heat to the cylinder walls better ? do the rings seal better ? does it lower the temp of the intake mixture ? better combustion in the head ? does it cool down the piston top more ?

My take on this is, apart from the apparent truism that more oil = more power, there is the time it takes for the oil to pass through the engine to think about. A high revving engine will pass its oil load quite quickly compared to something more sedentary and is why the performance engine enjoys a richer oil mix and feels properly lubricated compared to the way it would feel using a suitably lower oil mix from something more pedestrian.

Team ESE run 20:1 or 5% and when I was running a TZ it was 20:1 Castrol R on short circuits and the factory recommended 12:1 for running in and 16:1 for demanding conditions, I guess like when you're on WOT and peak rpm for a lot of time. It was basically, use as much oil as you can get away with.

[ken seeber]

does anyone care to explain why high performance engines always seem to use alot of oil in the gas ? i believe jan once said he used about 5% oil. i use about the same. what is the advantage of 5% versus something lower like 3 or 2% ? does the extra oil transfer heat to the cylinder walls better ? do the rings seal better ? does it lower the temp of the intake mixture ? better combustion in the head ? does it cool down the piston top more ?

When I was with Orbital and working with Mercury on what was to become the Optimax, they told us a story of when they used to run (carb V6 engines) in a 24 hour boat race in Rouen, France. They had lots of seizing issues, eventually solving it by running on 8:1. To assist starting, they drained the carbs and refilled them with straight petrol. Can't comment though on if they had more or less power.

If there aren't any deto issues, then one could imagine it shouldn't be any worse as the calorific value for most fuels and oils are quite similar. This statement doesn't take into account the stoichiometric nature of each though.

[Muciek]

Wobbly, have You tried something like this?


http://www.youtube.com/watch?v=lKwhPeQ0lSg

Just need powerfull inventer in CDI module (don't know will ignitech could handle it) module and 2 HV (4 in twin engine) microwave oven diodes.

I was testing similiar one but signal generator failed somehow.

[senso]

With such a big spark isn't there and extre risk of melting a hole in the piston due to the added heat?
Or even the spark jumping from the sparkplug to the piston crown?

[Frits Overmars]

With such a big spark isn't there and extre risk of melting a hole in the piston due to the added heat? Or even the spark jumping from the sparkplug to the piston crown?No, and No. But the plug electrodes will disappear while you wait.

[Muciek]

With such a big spark isn't there and extre risk of melting a hole in the piston due to the added heat?
Or even the spark jumping from the sparkplug to the piston crown?

Spark it's not long like it appears on video , it's just A LOT brighter and fatter and as You could hear a lot nosier.

You can see it better on my video https://www.youtube.com/watch?v=QgmKHk5OOfc



No, and No. But the plug electrodes will disappear while you wait.


Frits is right (as always :msn-wink: ) here are photos of standard plug after some use (Nyemi photo)
311287

[wobbly]

I did a series of tests on full synthetic and semi syn oil for KT100, the results are in here somewhere.
Bottom line is that for very high temp Avgas or aircooled running unleaded, the full synthetic is useless.
The ester based castor/synthetics like Elf 909 or Motul Kart offer much better protection when pushed really hard in hi temp end uses.
They used to run R30 at 16:1 in karts, but now with unleaded the 909 at 20:1 makes more power, and there is very little wear.

Methanol will make no less power when run +20% over stoichiometric, petrol wont even run at this level.
You can run insane levels of com with a rich Methanol mixture as the unburned fuel cools everything and stops deto.
The effective octane of rich Methanol is over 130, and with its very high latent heat its great for all types of 2T, especially Aircooled.

I have not tried the huge Plasma type sparks, with such good results with the twin CDI thing and big coils, I don't see the need.

[speedpro]

Methanol will make no less power when run +20% over stoichiometric, petrol wont even run at this level.
You can run insane levels of com with a rich Methanol mixture as the unburned fuel cools everything and stops deto.
The effective octane of rich Methanol is over 130, and with its very high latent heat its great for all types of 2T, especially Aircooled.

Old air cooled 4Ts with a turbo like methanol as well. I made a little valve for mine that opened with boost and tipped in methanol. My mates blown big block ran 100% methanol and crazy compression and boost. At pre-launch revs it had fuel pouring out the headers and at idle(1500+rpm) in the pits it formed ice on the intake manifold. As mentioned tuning methanol has a few quirks. Real rich made the plugs stay pure white as the fuel washed them then as you leaned it off you got a little bit of colour and if you kept going they got coated with melted aluminium. We tuned until the coating on the plug threads was burnt off the first 2 threads. Kept an eye on the pyro data logger as well of course.

Anyway, , back to 2Ts .

[kel]

Methanol is over 130, and with its very high latent heat its great for all types of 2T, especially Aircooled.

But its toxic as hell (even more so for children). A cumulative poison which leads to blindness and eventually death that pours out of exhausts :no:, thank goodness its banned from use in buckets! Now Ethanol's a different story, if we used E100 we could mix the left overs at the end of race day with a little coke ... :drinkup:

[TZ350]

Page ... 1170


Lots of good info on engine/gearbox oil here:
http://www.ducatimonsterforum.org/index.php?topic=1912.0


311963

What do you think about roller bearings in this transmission ? one behind the front sprocket and one behind the clutch basket. i dont see any reason not to do it, although they would need a ring groove cut in them.


I don't see any basic problems for a roller bearing behind the sprocket, but it's a different kettle of fish behind the clutch basket. The remaining ball bearing on the clutch shaft will have to cope with the full force of all the clutch springs. Is it up to that?

EDIT: There are no big axial forces working on the secundary gearbox shaft (unless you have bevel gears driving a cardan shaft), but it still has to be kept in place.
So although you could use a roller bearing behind the front sprocket, it would require that the remaining ball bearing on this shaft is axially fixed in both directions, and in the cases as well as on the shaft. Could complicate things....

EDIT # 2 (it takes a while, but once I've got my brain in gear, it won't stop): unless you have a primary transmission with straight-cut gears, there will be axial forces acting on the clutch shaft in both directions, depending on whether the engine is driving or being driven. Violent up- and down-shifts, you know...


Re the gearbox bearings - its common to have a roller on the output as there is no axial load and the chain pull is a heavy load easily coped with by the rollers.
But with or without helical drive there is still a heavy axial load on the input shaft from activating the clutch,this is why there is a double row ball on a RD/TZ/RZ etc
behind the clutch, with a full circle circlip into the case - not a 1/2 clip like the mains.

311962Original posted by Husa




From memory there was some comment made about the inertia of the gas column in the transfer duct and that one with a smaller cross section was easier to rapidly accelerate into the cylinder than a large fat one.I thought it was short and fat is better than long and skinny? A gas column with a smaller cross section has to accelerate more rapidly in order to transfer the same amount of air/fuel mass as a column with a large cross area.
But the rate of acceleration depends on the pressure difference between crankcase and cylinder, which in turn depends on the blowdown time.area and the efficiency of the pipe. At high revs, when the available time for transfer becomes shorter and shorter, small transfer cross sections may be less than desirable.



I don't have the cylinder yet, so this will be an educated guess at best; what would yield the best results here? Case transfers are too wide - widen cylinder transfer duct entry 5mm on each side or epoxy the case to match?

311314
As always its impossible to say what would be a good mod if only half the info is available.

Grinding or epoxying would depend entirely on the case com ratio.

If its already way too small then grinding is needed as the case com ratio would have a way bigger positive effect than the cross sectional change may be a downside.

But that cylinder for sure needs a big radius on the duct/bore edge.

Re the gearbox bearings - its common to have a roller on the output as there is no axial load and the chain pull is a heavy load easily coped with by the rollers.

But with or without helical drive there is still a heavy axial load on the input shaft from activating the clutch,this is why there is a double row ball on a RD/TZ/RZ etc
behind the clutch, with a full circle circlip into the case - not a 1/2 clip like the mains.



Rule of thumb ex-port size maxed out thoughts.

Lets assume a single ex-port taken as wide as can be done between the the tight studs and still not up to the "% of bore" you like to have.
OK, let's assume the studs are in a square, so close to each other that they almost touch the bore. Even then you can fit in a 70% wide exhaust port, which is the optimum width anyway. That single exhaust port may not give you sufficient blowdown angle.area, but widening it will not help either because wider ports require bigger corner radii to keep the piston ring happy, and those bigger corner radii would eat into the upper part of the port area, where it counts.


With the ex-port/header area at approx 90% of the effective port already, would it still be advisable to rise the duration to gain blowdown STA even if this gives a "higher ex duration then desirable"?
From a resonance point of view 180° effective exhaust timing is optimal; that will be 190° geometrical, or a tad more. The RSA's 202° is the best compromise between resonance, blowdown angle.area and rpm. Not because it's a racing engine but because of the laws of physics. And sufficient blowdown is not only important for power; it also lessens the risk of spent gases entering the transfer ducts and overheating the cylinder.


The max Ex port width is dependent upon the bore size as well. when dealing with small pistons like 50cc or similar.
You can safely go out to 75% as the bore to supported ring section ratio is skewed in the small pistons favor.
This is a proven safe width in many small engines, but at the end of the day you will be limited by the worst STA number.
If this is the transfer ports, then over spec'ing the blowdown will simply make the thing peaky and hard to tune.
The actual Ex STA is pretty much irrelevant, except to match its effective area to the outlet size.


True. The Honda NSR50 engine as standard has a single port whose width is 77% of the 39mm bore, and they can be and are thrashed mercilously with total reliability

[Kickaha]

thank goodness its banned from use in buckets!
Didn't you see my proposed rule change?

[TZ350]

Didn't you see my proposed rule change?

Methanol for 2T's open fuel for all Buckets, anything goes including nitro, I would love that, absolutely ... :woohoo: ... lets get rid of all the unnecessary restrictions so Buckets can be the preeminent development class again ... :D

[lodgernz]

Methanol for 2T's open fuel for all Buckets, anything goes including nitro, I would love that, absolutely ... :woohoo: ... lets get rid of all the unnecessary restrictions so Buckets can be the preeminent development class again ... :D

But it wouldn't be. Instead of a class where leading edge technical development was taking place, it would be a class where cranks and rods and crankcases and barrel and head mountings got beefed up to use increasingly crazy fuels.
Porting and timing and scavenging and CRs would all become very removed from the diminishing real world of racing 2-strokes that we are trying to improve.

[TZ350]

But it wouldn't be. Instead of a class where leading edge technical development was taking place, it would be a class where cranks and rods and crankcases and barrel and head mountings got beefed up to use increasingly crazy fuels. Porting and timing and scavenging and CRs would all become very removed from the diminishing real world of racing 2-strokes that we are trying to improve.

True, but the blowups would be spectacular........ :laugh: .... we could learn about using alternative fuels and how to apply the sustainable fuels like natural gas, methanol, ethanol and hydrogen.

[seattle smitty]

Methanol can be made from garbage, so two problems are addressed. (Not advocating anything in particular; just sayin'.)

Outboard and Inboard racers in the USA, with decades of being around rich-running methanol fueled engines both on the course and to some extent in the pits, are growing old while retaining their eyesight (as much as any old people) and such brains as we ever had. In the Twenties and Thirties, board-track auto racing was a popular sport in the US, with grandstands full of spectators exposed to the alcohol-burning racecars and motorcycles, but I have never heard of any revelations of health problems related to that. But you certainly have to be aware of your fuels, and it should be regarded as one of the responsibilities of racing organizations to make certain their members are educated about the risks and the needed safety measures. One such risk is that a fire involving straight alcohol is colorless, and possibly the first clue that you have a problem might be the interesting sight of things melting for no obvious reason . . . .

I love the story of Karl Benz, when he was building some of the very first I.C. engines. At that time (1870s-80s), as I understand it, gasoline had no commercial application, and was considered merely a laboratory curiousity. Benz had procured some, and one evening, just before closing up the shop, he decided he make a first quickie experiment. He had a brass casing from an artillery shell, and into this he put one good big drop of gasoline; then he put a cork in the open end of the shell casing and waited for the gasoline to evaporate.

Benz described (my recollection of his account, not his exact words) the moment he removed the cap from the casing and passed a match across the open end: "There was a loud report that startled me greatly; the shell wobbled drunkenly on the table for a moment before falling on its side, . . . and in that moment, I knew I had found my fuel!!"


But given its various dangerous properties, if gasoline were just now being proposed as a possible fuel to be put into very widespread use by ordinary citizens, do you really think government regulatory agencies would allow it? Not a chance! Think of all the useful substances that have been taken away from us for our ostensible protection (at least in the US): zinc chromate primer for aluminum, pentachlorophenol wood preservative, carbon tetrachloride and Stoddard solvent for cleaning, just some of the things I could use when I was a young man but not anymore. I'm not saying that these things, or methanol, are to be dealt with casually, nor am I trying to diminish Kel's legitimate concern by offering a different perspective.

[seattle smitty]

(double-post, deleted) (I once asked a librarian, after yet another rage-inducing computer experience, if she thought anyone would mind if I smashed my laptop to bits against a nearby post. She said that yes, some would surely be annoyed by the disturbance, but that others might stand and applaud . . . ).

[Kickaha]

Methanol can be made from garbage
So we can make it out of two stroke motorcycles then?

[TZ350]

Methanol can be made from garbageSo we can make it out of two stroke motorcycles then?

............ :laugh: ... so true

[husaberg]

Found this never seen them on the site two rings though and unlikely to be a commonly stocked item either.
http://www.tkrj.co.jp/goods/m-AS8060X-21A04-21A14.php.
They are supling the RG500 ones as well same deal.

I am picking they will both be in 2 ring config though.

[adegnes]

I don't have the cylinder yet, so this will be an educated guess at best; what would yield the best results here? Case transfers are too wide - widen cylinder transfer duct entry 5mm on each side or epoxy the case to match?

311314

[speedpro]

One you can undo the other you can't. I know which one I would be trying first. Well actually you could devcon the transfers if grinding them didn't work so well. There is of course a preferred taper and ratio between the bottom of the duct and the port at the cylinder.

[peewee]

wobbly what do you think about roller bearings in this transmission ? one behind the front sprocket and one behind the clutch basket. i dont see any reason not to do it, although they would need a ring groove cut in them

i picked up some skf roller crank bearings with polymer cages at a good deal. if i was to weld the center crank pin (not around the full circumference of the pin but just one spot on each side opposing each other) do you rekon enough heat would transfer through the cheek and melt the bearing cage ? i didnt even give this consideration until just today.

[speedpro]

But its toxic as hell (even more so for children). A cumulative poison which leads to blindness and eventually death that pours out of exhausts :no:, thank goodness its banned from use in buckets! Now Ethanol's a different story, if we used E100 we could mix the left overs at the end of race day with a little coke ... :drinkup:

Of course Toluol which is about 30% of unleaded fuel is completely safe, and unleaded fuel combustion products are safe(r) as well than leaded fuel combustion products. Provided that those combustion products are passed through a "working" catalytic converter. If not then more worse than the original leaded fuel exhaust if I recall the paper I read correctly. Not sure how petrol engine exhaust compares with Methanol engine exhaust as far as toxicity goes. Be interested to find out from someone educated in these matters.

[adegnes]

One you can undo the other you can't. I know which one I would be trying first. Well actually you could devcon the transfers if grinding them didn't work so well. There is of course a preferred taper and ratio between the bottom of the duct and the port at the cylinder.

That's a good point!

[Frits Overmars]

wobbly what do you think about roller bearings in this transmission ? one behind the front sprocket and one behind the clutch basket. i dont see any reason not to do it, although they would need a ring groove cut in them.I don't see any basic problems for a roller bearing behind the sprocket, but it's a different kettle of fish behind the clutch basket. The remaining ball bearing on the clutch shaft will have to cope with the full force of all the clutch springs. Is it up to that?

EDIT: There are no big axial forces working on the secundary gearbox shaft (unless you have bevel gears driving a cardan shaft), but it still has to be kept in place.
So although you could use a roller bearing behind the front sprocket, it would require that the remaining ball bearing on this shaft is axially fixed in both directions, and in the cases as well as on the shaft. Could complicate things....

EDIT # 2 (it takes a while, but once I've got my brain in gear, it won't stop): unless you have a primary transmission with straight-cut gears, there will be axial forces acting on the clutch shaft in both directions, depending on whether the engine is driving or being driven. Violent up- and down-shifts, you know...

[peewee]

thnx for a response frits. the crank and clutch basket gears do have slanted cut teeth originally, i think theyre refered to as helical spur gears ? but im replacing those two primary gears with hinson straight cut spur gears.

as of now the clutch shaft has a ball bearing behind the basket and a needle bearing at the other end

the front sprocket shaft uses the same. a ball bearing behind the sprocket and a needle bearing on the other end

my plan was to keep the needle bearings but replace the ball bearings of both shafts with roller bearings.

i have done this same procedure on one of my ktm engines and its working well and the roller bearing usually has a far higher load rating than a similar sized ball bearing

[peewee]

That's a good point!

maybe my memory went bad or i simply misunderstood what he said, but i thought wobbly said several times that there wasnt much power difference between transer ducts that have high or low ratios between the entrance and exit ?

[TZ350]

what would yield the best results here? Case transfers are too wide - widen cylinder transfer duct entry 5mm on each side or epoxy the case to match?

311314

From memory there was some comment made about the inertia of the gas column in the transfer duct and that one with a smaller cross section was easier to rapidly accelerate into the cylinder than a large fat one.

[adegnes]

From memory there was some comment made about the inertia of the gas column in the transfer duct and that one with a smaller cross section was easier to rapidly accelerate into the cylinder than a large fat one.

I thought it was short and fat is better than long and skinny? I'll do a search.
Kinda ironic - I fabricated this case partly because nothing with wide enough transfers for the cylinders I planned to run was available (mainly to use a rotary valve though), now this cylinder would actually fit a "stock" case with minor modications.

Maybe go for the malossi mhr team 50cc for derbi ebe050 instead, cheaper, the right width, and should be up there powerwise. It also shares stud pattern with the Emot cylinder.

[Frits Overmars]

.. the roller bearing usually has a far higher load rating than a similar sized ball bearingYeah, a far higher radial load rating; a roller bearing's axial load rating is about zero.



From memory there was some comment made about the inertia of the gas column in the transfer duct and that one with a smaller cross section was easier to rapidly accelerate into the cylinder than a large fat one.A gas column with a smaller cross section has to accelerate more rapidly in order to transfer the same amount of air/fuel mass as a column with a large cross area.
But the rate of acceleration depends on the pressure difference between crankcase and cylinder, which in turn depends on the blowdown time.area and the efficiency of the pipe. At high revs, when the available time for transfer becomes shorter and shorter, small transfer cross sections may be less than desirable.

[wobbly]

As always its impossible to say what would be a good mod if only half the info is available.
Grinding or epoxying would depend entirely on the case com ratio.
If its already way too small then grinding is needed as the case com ratio would have a way bigger positive effect than the cross sectional change may be a downside.
But that cylinder for sure needs a big radius on the duct/bore edge.

Re the gearbox bearings - its common to have a roller on the output as there is no axial load and the chain pull is a heavy load easily coped with by the rollers.
But with or without helical drive there is still a heavy axial load on the input shaft from activating the clutch,this is why there is a double row ball on a RD/TZ/RZ etc
behind the clutch, with a full circle circlip into the case - not a 1/2 clip like the mains.

[Grumph]

Re the gearbox bearings - its common to have a roller on the output as there is no axial load and the chain pull is a heavy load easily coped with by the rollers.
But with or without helical drive there is still a heavy axial load on the input shaft from activating the clutch,this is why there is a double row ball on a RD/TZ/RZ etc
behind the clutch, with a full circle circlip into the case - not a 1/2 clip like the mains.

What is not generally realised either is that most if not all of the double row races behind the clutch are actually angular contact bearings.
IMO there is probably a point below which it would be possible to use conventional ballraces but without actually measuring the side loads i'm not going to guess where that comes...

[peewee]

so keep the double row ballbearing behind the basket but use a roller behind the sprocket ?

[speedpro]

I'm asking myself why bother? Has something failed? Triple the horsepower? Measurably less losses with rollers?

[peewee]

hard to say how much power it will have but as far as im concearned you can never over build it.

anyone try a set of these reproductions ? i thought about resleeving some yamaha cylinders but for the same price i figured i would try some of these

[F5 Dave]

So no PV banshee copies? Not keen on CPI mono block? Many different types now.

[peewee]

i know theres better options but i wanted the challenge of working with a 30yo cylinder to see how much better i could make it run. it will be good tuning practice as theyre only $300. down the road i can simply drop a different cylinder on if i want

[seattle smitty]

i know theres better options but i wanted the challenge of working with a 30yo cylinder to see how much better i could make it run. it will be good tuning practice as theyre only $300. down the road i can simply drop a different cylinder on if i want

My kind of man!!

But Peewee, only 30yo, that's awfully recent, are you sure it will be a sufficient challenge for you?

[adegnes]

A gas column with a smaller cross section has to accelerate more rapidly in order to transfer the same amount of air/fuel mass as a column with a large cross area.
But the rate of acceleration depends on the pressure difference between crankcase and cylinder, which in turn depends on the blowdown time.area and the efficiency of the pipe. At high revs, when the available time for transfer becomes shorter and shorter, small transfer cross sections may be less than desirable.

Sounds like a win for short and fat to me!


As always its impossible to say what would be a good mod if only half the info is available.
Grinding or epoxying would depend entirely on the case com ratio.
If its already way too small then grinding is needed as the case com ratio would have a way bigger positive effect than the cross sectional change may be a downside.
But that cylinder for sure needs a big radius on the duct/bore edge.

I know, I'll be back with the numbers when I've got the cylinder in hand. And yes, those sharp edges are ugly, I don't get why so many of the manufacturers do it like that.

[Frits Overmars]

A gas column with a smaller cross section has to accelerate more rapidly in order to transfer the same amount of air/fuel mass as a column with a large cross area.
But the rate of acceleration depends on the pressure difference between crankcase and cylinder, which in turn depends on the blowdown time.area and the efficiency of the pipe.
At high revs, when the available time for transfer becomes shorter and shorter, small transfer cross sections may be less than desirable.
Sounds like a win for short and fat to me!That depends. Short and fat will fill the cylinder in a hurry. It also means the crankcase pressure will fall in a hurry. At revs that are too low for this setup, the transfer flow may come to a stop and then reverse before the transfer ports close.
Moreover, the positive exhaust return pulse that arrives too early at 2/3 of max.torque rpm, can do more harm because the lower inertia of short transfer columns offers less resistance to being shoved back into the crankcase.
Both these disadvantages can be balanced to some extent by lowering the transfer timing. But this is really a balancing act: lower the transfers too much and you loose the advantage of the short, fat transfer columns.
What you certainly don't need, is a combination of short, fat transfer ducts and a long transfer timing.

Between you and me: this may be the second reason (apart from upsetting the scavenging balance) that the Aprilia RSW and RSA cylinders respond so poorly to enlarging the entry of the B-transfers. Their inflow can certainly be improved, but that would reduce the column inertia and their timing is already 132°...

[adegnes]

Thanks to all of you! I'll shurely be back for more advice when I get the cylinder...

[husaberg]

hey guys has anyone attempted to move the piston rings locating pegs with any sucess ? i heard people do it but it failed. surely there must be a way


Well they aren't cast in there so the manufacturers manage it. Talk to a toolmaker.


Pete used to tap the original pin into the piston so it didn't interfere with the ring and then drill another hole in the new position and insert a pin he'd retrieved from an old piston. You just have to make a hole with the desired press fit for the pin, OR, do like others do and press it in from on top into a 2nd larger hole below the ring land and bend the end of the pin so it can't come out. Depending on the method you will need to get the right rings.


me at 17 was cutting pins out of old pistons and setting them up in rg50 pistons for my rd50 , never had a promblem , get a old piston and get some practice in


Pressing the pin in from above and then bending the lower end is the tried-and-trusted Yamaha method. But it requires a rather soft steel for the pin, or the bending force might cause loss of press fit in the vertical bore.
310193310194

Emot recently developed a variation on the theme: the pin is pressed in from above, after which the top of the vertical bore is closed by welding.


I have relocated pins without problems. I used the same method as EMOT. Just ensure that the top end of the pin is 1- 2 mm below the piston crown.

The pin was a needle 1.5mm dia out of a little end bearing into a 1.45mm ish hole. You may need to use a mill file to dress off the outside of the piston at the position of the pin after fitting the pin .


No need to demolish bearings or old pistons in order to obtain pins. One piano or guitar string will provide you with hundreds of pins in any diameter you want.
311486
Posted By Ken in another thread


Our AR pins are 8 mm long, and Ø1.54, tapered at one end and have a longitudinal groove to prevent hydraulic locking should the drilled hole have coolant remaining. Using these, the hole should be blind to prevent any combustion pressure leakage via the groove.
.

[peewee]

that reminds me, i found a machine shop that will relocate the ring pegs for me. probly send the pistons out sometime this week. according to what wiseco told me the pin is just regular carbon steel with .002-.003" interference fit

[peewee]

wobb you got any advice about the roller bearing behind the sprocket. would a NJ style work fine or NUP be better ? im sure you know the difference but incase you dont, NUP has the seperate collar on one side, collar integrated into the bushing on the other side, so theres a collar on both sides . NJ just has the collar on one side as part of the bushing

[Frits Overmars]

wobb you got any advice about the roller bearing behind the sprocket. would a NJ style work fine or NUP be better ? im sure you know the difference but incase you dont, NUP has the seperate collar on one side, collar integrated into the bushing on the other side, so theres a collar on both sides . NJ just has the collar on one side as part of the bushingThe Aprilia RSW crankshaft bearings initially had bushings with integrated collars. These collars sometimes broke. After switching to separate collars the problem went away. I'm not saying that the same thing will happen with transmission bearings, but you never know until it happens.

[jonny quest]

Look at parts diagram of a 2013 KTM SXF250. They use rollers for crankshaft and output shaft bearing.

[husaberg]

Look at parts diagram of a 2013 KTM SXF250. They use rollers for crankshaft and output shaft bearing.

Many KTM's from the 85SX up have at least one Roller bearing on the crankshaft. The easiest way to see is look in the Pro X Catalogue.
Quite a few use the same bearing size as the Aprilias including quite a few karts.
On the original Honda 100/125 Four Strokes they had a Roller on the Ignition side they deleted it to save costs, when they went to the 185 and 200's they then had to run bigger bearings.
I guess it was still cheaper than rollers.

Here is the crankshaft of the week.
Any ideas to what it is from?
According to the author he had never seen one with worn bearings.
The rollers ran in steel sleeves in the cases.

[marsheng]

Finally got my Maico on the Ashburton Dyno.

It is lean at 6k and just slightly rich at 9k. Where do I start to fix this, Exhaust, transfer ports, crank case volume? Does ignition timing change this at all.

Or is it just typical 2 stroke.

What we did find was that there was not much difference between 3/4 and full throttle. It is running 36 and so a 34 may be better, however, could the limitation be the reed block ? 36 does not seem overly large for a 250.

[speedpro]

I would go bigger in the main jet to get the mixture right in the middle and then go bigger on the air jet to lean out the top, with a recheck of the middle afterwards. Rob is the guru with this stuff. Presuming tests done at full throttle only so the needle is non-effective.

[Muciek]

Many KTM's from the 85SX up have at least one Roller bearing on the crankshaft. The easiest way to see is look in the Pro X Catalogue.
Quite a few use the same bearing size as the Aprilias including quite a few karts.
On the original Honda 100/125 Four Strokes they had a Roller on the Ignition side they deleted it to save costs, when they went to the 185 and 200's they then had to run bigger bearings.
I guess it was still cheaper than rollers.

Here is the crankshaft of the week.
Any ideas to what it is from?
According to the author he had never seen one with worn bearings.
The rollers ran in steel sleeves in the cases.
Jawa enduro engines had bearing like this, it was almost impossible to get that bearing here in 1980s....

[TZ350]

Finally got my Maico on the Ashburton Dyno. What we did find was that there was not much difference between 3/4 and full throttle. It is running 36 and so a 34 may be better, however, could the limitation be the reed block ? 36 does not seem overly large for a 250.

311572 100-90-80-70% throttle position runs.

Its been our experience too, not much difference over 75% throttle. And a bigger carb often did not add much.

311576

Back to back comparison on my Suzuki GP125 of a 24mm OKO carb (Red line) vis a 30mm (Blue line) one.


It is lean at 6k and just slightly rich at 9k. Where do I start to fix this, Exhaust, transfer ports, crank case volume? Does ignition timing change this at all. Or is it just typical 2 stroke.


I would go bigger in the main jet to get the mixture right in the middle and then go bigger on the air jet to lean out the top, with a recheck of the middle afterwards. Presuming tests done at full throttle only so the needle is non-effective.

Yes, that is what I would try, bending your fueling curve down by drilling out the air correction jet to get the 9K area right and plump up the mid range with a bigger main jet.

Anytime you drill out the air correction jet you will need to compensate with a bigger main. On our 125's the air correction Jet is about 1.2mm and the range seems to be anywhere between 1 to 2mm. Smaller engines seem to start about 0.8.

[husaberg]

Jawa enduro engines had bearing like this, it was almost impossible to get that bearing here in 1980s....

Which explains why I can't find a picture of one on the net either LOL
But no the crankshaft is not Jawa.
Pretty sure the Jawas did have nice long rods though.

[husaberg]

Well I’ve managed to engineer myself into a corner with SE bearings again. I have a 50.75 barrel I am running in the interim on my MB so I ordered a ye olde YZ100 piston to check out. Good luck finding online info on a ‘76 piston.

Arrived on my desk this morning so yet to check it at home.

Single 1mm ring that is pegged looking like far enough away from boostport not to have to move. Bit heavy as 3rd oversize & suitable for single port only. But heck it will keep this interim cylinder working ok & is far & away better than the MB one.


Whoops, 16mm pin. 14 is std. rod is 19mm ID. Yams usually run thin SE bearings, but 16x20 is their size (same as RD250 apparently so don’t yell foul yet).

I forgot to order a pin, it was a mission enough to find rings & piston from same seller who would ship. But that should match up with something else easy enough or be shortened.

So can someone point me in the direction of a reasonable resource (can’t seem to find a decent site, maybe I should try PeteSalesbearingcatalogue.com?) for finding if a 16x19x## bearing is indeed made? 1.5mm rollers? Mammy!

Looks like Jawa does Dave. not that it helps you now
Better late than never though.
http://www.jawashop.com/Crankshaft-and-Piston

http://www.jawashop.com/Detail/10999
16mm 19mm 20mm little end bearings

[Frits Overmars]

It is lean at 6k....Maybe. But who told you so? Not the lambda sensor. It only tells you if there is unused oxygen in the exhaust gases. But this O2 can stem from a lean mixture, from washed-through mixture, from unburned mixture due to ignition problems, even from mixture that is so rich that the ignition fails to ignite it.
What I'm trying to say here: you may well be right, but don't jump to conclusions.

[jonny quest]

If I wanted to purchase and try one of the Bosch oil filled coils like used on the RS125. .. how would I know which one to order? I'm from USA

[Frits Overmars]

If I wanted to purchase and try one of the Bosch oil filled coils like used on the RS125. .. how would I know which one to order? I'm from USASorry Jonny, I can't find the part number any more. It's too long ago.

[jonny quest]

Thank you For reply

[richban]

Hi Guys.

Well after re building the top end of the 300 and gaining loads of power with the new barrels we have a little problem. The piston dome top on the bottom barrel is caving in. Its running 16:1 comp and seams happy with advance. The plug tip is close to the top of the piston crown. Like 7.5mm from memory. It shows no sign of det. We have had this problem before on other bikes. My old setup did it as well but it took quite a while to show.

Any ideas welcome. They are wiseco piston's. I will post a pic today.

Maybe not enough advance?

Aside from that I had a good weekend with 3 podiums and a pb lap time.

[F5 Dave]

What are your plugs?

[richban]

What are your plugs?

Spark:rolleyes: BR9ECM. Other bikes were running the fancy expensive ones.

I think it is a combo of maybe not enough advance little bit lean and port timing not ideal.

I have some better egt gauges now so will be able to get better on track readings.

[F5 Dave]

The melting the centre away if that ia what it is doing is usually too advanced ignition somewhere in the range or too hot of a plug.

[husaberg]

Sagging is caused by excessive Heat, its the what caused the excessive heat you need to figure out.
One of the advantages of forged pistons is they will sag before failure.
As they have a better grain structure and higher density due to how they were formed under pressure.
They have been surpassed in a lot of applications. but not in I believe forced aspirated engines due to this advantage.

[peewee]

hey guys a very good thing happen yesterday. i get to my house and this was waiting there :wings:. now i can weld cylinders and expansion chambers or anything else. the argon bottle should be here in a couple days

[richban]

Sagging is caused by excessive Heat, its the what caused the excessive heat you need to figure out.
One of the advantages of forged pistons is they will sag before failure.
As they have a better grain structure and higher density due to how they were formed under pressure.
They have been surpassed in a lot of applications. but not in I believe forced aspirated engines due to this advantage.

Yes I think with out the forged piston it could be messy. The problem is more prominent on the bottom cylinder.

Time for a bit more testing. First port of call will be advance. The plan is to run it up on the dyno and log the egt temp when fuelling is good. Then add advance and see if that temp comes down while watching for det. The last engine ran all year with only a slight bit of sag in the bottom piston. Also that ignition curve had 1 more deg of advance.

Dave: I didn't get a good plug chop in so can't tell if it was plug but I think its fine as that was what I was running last year. But I will certainly be looking at that again. We know to get the blow down correct the barrels will need to be lowered by 1.2mm. So this also could be helping build heat.

[F5 Dave]

Maybe a 10 and a fine wire while you're at it.

[husaberg]

Yes I think with out the forged piston it could be messy. The problem is more prominent on the bottom cylinder.

Time for a bit more testing. First port of call will be advance. The plan is to run it up on the dyno and log the egt temp when fuelling is good. Then add advance and see if that temp comes down while watching for det. The last engine ran all year with only a slight bit of sag in the bottom piston. Also that ignition curve had 1 more deg of advance.

Dave: I didn't get a good plug chop in so can't tell if it was plug but I think its fine as that was what I was running last year. But I will certainly be looking at that again. We know to get the blow down correct the barrels will need to be lowered by 1.2mm. So this also could be helping build heat.

But don't you have a few more HP now?


Maybe a 10 and a fine wire while you're at it.

10 char
Pretty sure a std NSR150 would have a NKG9 So your one is a bit more highly tuned now.
I can't find the post but unless its a lawnmower nothing below 10 or 10.5 on the track was Wobs rule of thumb He recommended a funny numbered plug in another few posts.

The old BR10EGV isnt prone to ceramic cracking at all, and the 7376 at 4 times the price of those is virtually indestructible.
I get the plugs off Amazon as well when a good deal comes up occasionally - best i have done was 52nzd landed.
One retailer i saw wanted 300nzd for the genuine shorty NGK plug cap for RS125, that is why I went searching and contacted NGK in USA who told me about the
exact same configuration plug with a normal body shape.

I have got R7376 several times for around 35USD, about 1/3 of the cost of the shorty Honda style.
And I would never use an Iridium plug again in a real race engine.
They seemed like a great alternative till we lost several engines in a row, including dropping an earth electrode on
the last corner of the last lap - to take a 125 kart title 3 in a row.
The Iridium centre ceramic will crack and fall off the instant you see even the smallest amount of deto, and the reason the R 7376 style plugs are expensive is that the rare
earth ground strap is laser welded to the body - I have never seen or heard of one failing, and the ceramic can crack occasionally, but again I have never seen one drop out.
Its one of those things, just accept that you pay for what you get, and buy the best when it really matters.

Plain old Iridium plugs are a brand name, and yes they have Iridium fine wire centre electrodes.
As I said, these will drop the ceramic at the slightest provocation.
The R7376 has the Iridium centre, but also has a Platinum earth fine wire strap.
The construction is completely different, and is dead reliable..

The new type 7376 plugs are ideal for bead blasting after every meeting.
As I insist on plug chops after every race and change the jets at least 3 times a day when doing "real "racing, reading the insulator and ground strap
is impossible if the thing is covered in oily shit from idling around - at all.

Jetting



Finally got my Maico on the Ashburton Dyno.
It is lean at 6k and just slightly rich at 9k. Where do I start to fix this, Exhaust, transfer ports, crank case volume? Does ignition timing change this at all.
Or is it just typical 2 stroke.
What we did find was that there was not much difference between 3/4 and full throttle. It is running 36 and so a 34 may be better, however, could the limitation be the reed block ? 36 does not seem overly large for a 250.

.
You should see him setting up a carb. Talk about pain staking, he starts with a main jet so big the bike floods at about half throttle (apparently this proves the oriface of the needle/needle jet combo is big enough) and then he slowly step by step works back until it runs clean.
Most people start at the bottom with a carb and work up, He starts at the top and works backwards.
.


best bit of carb advice is you are both right, as they have overlapping circuits. personally that's why EI and similar carbs are intersting, because they don't.
this is one of the best bits i have seen.Cameron
http://books.google.co.nz/books?id=J7tQp2LtsYIC&pg=PA61&lpg=PA61&dq=Carbs+are+complex+because+of+their+overlapping+ kevin+cameron&source=bl&ots=qdU5EuhyxB&sig=ypUCl-6ePjegQmrw1WZLeuRB4Ko&hl=en&sa=X&ei=QpeaUpyhKYjoiAegyIHIAw&redir_esc=y#v=onepage&q=Carbs%20are%20complex%20because%20of%20their%20o verlapping%20kevin%20cameron&f=false
Hopefully the link should work if it doesn't let me know I will scan it.

Pics for the Maico Bimota below for those that don't know what Marsheng is doing.

[seattle smitty]

Congrats, Peewee. Once you get a welder (or a metal lathe, same experience) you will wonder how you ever got along without one.

Gents, you all have to see this: Google "lawn tractor pulling" and when it comes up, click on Images and scroll down through the page of photos . . .

[wobbly]

Anyone that runs a 9 in a racebike is a complete Wally - the NSR250 road bike runs this heat range, does this indicate something ?
Honda RS125 ended up with 10.5 as whenever they got tuned to the edge the plug would overheat and sag the piston centre, does this indicate something ?
All this is helped by cooling the plug thread effectively, but nothing will save you if running a 9 on purpose - SToP IT. NoW.

[richban]

Anyone that runs a 9 in a racebike is a complete Wally - the NSR250 road bike runs this heat range, does this indicate something ?
Honda RS125 ended up with 10.5 as whenever they got tuned to the edge the plug would overheat and sag the piston centre, does this indicate something ?
All this is helped by cooling the plug thread effectively, but nothing will save you if running a 9 on purpose - SToP IT. NoW.

I have been told. :mad: They are never going in the bike again. As usual poor attention to detail hurts the poor we bike.

[husaberg]

Anyone that runs a 9 in a racebike is a complete Wally - the NSR250 road bike runs this heat range, does this indicate something ?
Honda RS125 ended up with 10.5 as whenever they got tuned to the edge the plug would overheat and sag the piston centre, does this indicate something ?
All this is helped by cooling the plug thread effectively, but nothing will save you if running a 9 on purpose - SToP IT. NoW.

So for the V twin with the front wheel near the head is this the ones he needs?

NGK R5300A-105
http://www.inkasboesso.it/images/ngk_r5300a_105.jpg

Or is it these ones
R7282-105
http://web-karting.fr/4194-large_default/bougie-ngk-r7282-105.jpg

[Neal]

So for the V twin with the front wheel near the head is this the ones he needs?

NGK R5300A-105
http://www.inkasboesso.it/images/ngk_r5300a_105.jpg

Or is it these ones
R7282-105
http://web-karting.fr/4194-large_default/bougie-ngk-r7282-105.jpg


Either one will work with the correct plug cap . I used the 7282 with no problems

[peewee]

smitty i think my next purchase will be a small 3 in 1 mill, lathe, drill press. that should be good enough to machine heads and other small projects. i simply just dont have the available space for full sized independant machines. im very excited to be able to weld most anything now , right in my garage.

anyone tried one of the ck micro tig torches for very tight spaces ? that might be whats needs for getting inside of transfer ducts. everything else can probly be done with the standard size torch

[husaberg]

Straight intakes for those using cr125 Honda RS reeds.

I think these are 36mm but I don't know much about Mircolights.
Or bing Carbs. But it seems the carb od 49.5mm
311655

JBM Industries has created tooling for this carburetor socket boot for MZ engines.
The material is TSR compound. It is designed to fit the popular BING 54 carburetors used in LSA
aircraft with MZ 202 engine. These parts use a rubber covered steel plate with 6mm mounting
holes. Rubber cover is .070 thick, so no gasket is required. 52 X 72mm hole locations.
These rubber boots are found on the engine or cylinder inlet manifold on MZ 202 ultralight
or light sport LS power units. These rubber carburetor sockets have the locking rib and internal
size for the Bing model 54 carburetor used on ultra-light or micro-light aircraft. This boot is used
for heat and vibration isolation. This part is NOT made by the original manufacturer, but is made
in the USA and designed to fit. It may fit other models and engines.
MZ 202 Engine Carburetor Socket Boot for Bing model 54 carb.
Designed for 6mm bolts 72 mm by 52 mm centers. 37 mm overall height.
http://jbmindustries.com/MZ_Socket_Boot.html
http://www.ebay.ca/itm/MZ202-to-BING-54-Carburetor-Intake-Manifold-Rubber-Socket-Boot-Isolator-MZ-202-/331506114271?pt=Motors_Aviation_Parts_Gear&hash=item4d2f4ddedf&vxp=mtr


This is the NF4 and NX4 intakes
http://www.risingsuncycles.com/images/carb-parts/botmveiw.jpg


This place also does Carb Diaprams
http://jbmindustries.com/Dimensions.html
Plus a lot of other manifolds.
http://jbmindustries.com/RubberFlange.html
http://jbmindustries.com/HOLDERS.html




Either one will work with the correct plug cap . I used the 7282 with no problems
Cheers

[Sketchy_Racer]

I am also running the NSR300 and am having the same issue with the piston crown sagging even though i've got the wanky NGK 10.5 race plugs in.

I had a lot of teething issues on its first track outing, with one being the stock cylinder heads I machined out cracked and let all it's water into the cylinder so I thought I better do it properly and machined up a 2 piece head loosely based off the VHM products. I'm going to do the insert a little different this time though and modify it so I can get some more water around the spark plug as the VHM style seem to have the thickest wall section at the spark plug.

311668

[speedpro]

With all this talk of carb mounting flanges it just occurred to me - why don't we use 4T style mounts? Typically only 2 bolts but that works on 4Ts, and often we have an adaptor somewhere in the whole carb/reedblock/engine assembly so why not have one screwed to the reed block and then the carb mount to the adaptor? Mostly nice and straight. For a "real" race bike it would add undesirable length but as an option for us it would seem OK.

[Sketchy_Racer]

So the question has been asked about piston rings, 1 vs 2.

I remember reading a post from Frits (Im sure it was him!) that made comment about the extra ring just adding more friction to the job and not succeeding in removing heat from the piston or have I got this all wrong? Anyone know how to find the post?? Husa Help!! ;)

Cheers,

Sketchy

[husaberg]

So the question has been asked about piston rings, 1 vs 2.

I remember reading a post from Frits (Im sure it was him!) that made comment about the extra ring just adding more friction to the job and not succeeding in removing heat from the piston or have I got this all wrong? Anyone know how to find the post?? Husa Help!! ;)

Cheers,

Sketchy

309064309065309066309067
A couple of head designs. The finned one is from the current benchmark in superkart engines. DEA & the other with the passages about the plug may be a Thijs Hessels design.
Frits the DEA head seems to go against what has been described for performance, however this engine is extremely powerful. Given your friendship & confidential nature with Andrea I hope it wouldn't be asking to much to have you explain how / why this style is employed within the DEA inline engines.
Thanks in advance

Or two. Front and side views of a double-finned insert and cover: 309036

You won't. You can't.



Seeing as Frits said it you could click on his name and then click view forum posts.
Or you could use those same words in a forum search top right.
Or I will find it in a minute.

It seems I just can not let go of the thought of the rings dissipating heat from the piston. Thus - two rings should dissipate more heat than one ring. At the same time, I've got the impression the ability of the heat dissipation from the rings might be overrated.


I've had a std head machined down as much as possible (0,5mm), but this only brought down the squish band from the usual 1,8/1,9mm to 1,3mm. The VHM heads are said to dissipate heat much better than the stock 122 heads. Maybe I should get a VHM head for domed piston and machine it to the desired specification. Thanks.




Young, definitely. Velkommen, ung mann.

I can't let go of the thought that a ring rubbing against a cylinder bore generates heat :rolleyes:.


hello. 1 ring! there is no need for a second ring. good 1 ring pistons with the ring peg at "18 o clock" position (so you can widen the b ports) are easy available for this engine.

i dont know why but i doubt this vhm heads a little bit. i think it would be better to not use a flat piston and have a stock head machined to desired specification.


Hi, I'm a 48 year old (Or, is it young?) Norwegian. I've been lurking around this thread for some time now. I'm currently in the process of building a tuned Rotax 122 engine. The bike will be used mostly for fun on road and track days. My only concern is getting as much power as possible from the engine.

The cylinder has been reworked by a known UK tuner. To go with this I've got a VHM head for use with flat top piston. And a good selection of different reeds, carbs, std and custom exhausts, different ignition CDI's, etc.

I just can't make up my mind if I should go for a 1 or 2 ring piston. It seems to me both have their pros and cons and I would appreciate very much any advice. For now, I'm thinking 1 ring is the best.

Thank you.

With all this talk of carb mounting flanges it just occurred to me - why don't we use 4T style mounts? Typically only 2 bolts but that works on 4Ts, and often we have an adaptor somewhere in the whole carb/reedblock/engine assembly so why not have one screwed to the reed block and then the carb mount to the adaptor? Mostly nice and straight. For a "real" race bike it would add undesirable length but as an option for us it would seem OK.
Like this?

[Sketchy_Racer]

Thanks Husa,

I did search his posts in this thread but alas I couldn't find that post! Or I glossed over it. Turns out Frits has 33 pages of awesome information in this thread, brilliant!

So to clarify the consensus is that 2 rings add heat? The response was a little bit cryptic haha

Cheers,

Sketchy

[husaberg]

Thanks Husa,

I did search his posts in this thread but alas I couldn't find that post! Or I glossed over it. Turns out Frits has 33 pages of awesome information in this thread, brilliant!

So to clarify the consensus is that 2 rings add heat? The response was a little bit cryptic haha

Cheers,

Sketchy

My take was Two rings adds friction, friction equals heat and two stroke rings transfer bugger all heat to the bore anyway.
I recall there was a Seatle Smity question as well I didn't see it in the search though.

[Sketchy_Racer]

The most powerfull 125 known to man quite happily got rid of the heat generated thru a single ring.
There have been cases of huge overbored ie oversquare cylinders that had piston heat trouble and twin rings
did help in this particular scenario, but that was a special case where the real issue was lurking elsewhere and the rings just
ameliorated the symptoms.

Well this sort of sums it up. Although the NSR300s are over square, so it might be a case where having the extra ring might help "ameliorate" the problems of our over heating pistons?

[Sketchy_Racer]

My take was Two rings adds friction, friction equals heat and two stroke rings transfer bugger all heat to the bore anyway.
I recall there was a Seatle Smity question as well I didn't see it in the search though.

Yes, that's how I read it, and I suppose the bloody rings aren't touching the cylinder walls for quite a lot of the time given that there are a lot of holes in the side of it!

[husaberg]

Yes, that's how I read it, and I suppose the bloody rings aren't touching the cylinder walls for quite a lot of the time given that there are a lot of holes in the side of it!

Yeah Bell did tests on the dyno (I think it was on a YZ80) it gained under 9000 from better sealing and lost out over that. seeing as they likely don't spend much time under 9000 it would be pointless.
From memory the bore wears faster as well with two rings but on a road bike the two sealing surfaces offer a longer service life. (Not an issue on a competition engine)
Wob has mentioned that Dykes rings wear the bore faster and cost high rpm power.
The dykes rings were the answer until thin piston ring technology caught up, But I think they still have a place on Blown engines as they seal better.

Maybe Frits or Wob could tell us if the higher the ring is the more power it makes, until (I guess) it gets too hot due to its location it fails or does too high a ring location eventually lead to detonation?

The ring on the RSW look to be only about 0.6-.8mm thick at a guess.
Here is a few KTM and Aprilia piston pics
http://i301.photobucket.com/albums/nn78/axxexs/DSCN0748.jpg

[Frits Overmars]

Maybe Frits or Wob could tell us if the higher the ring is the more power it makes, until (I guess) it gets too hot due to its location it fails or does too high a ring location eventually lead to detonation?
The ring on the RSW look to be only about 0.6-.8mm thick at a guess.From memory the RSW and RSA rings were 0.7 mm thick.
The higher the ring, the more power. The limit is not the ring temperature but the piston top land temperature, because the cross sectional area through which heat is transported from the top land to the bulk of the piston, becomes too small. Then the alu weakens and the ring will hammer the ring groove out of shape, causing leakage.
In the RSW and RSA this did not cause detonation, just loss of power.

[F5 Dave]

With all this talk of carb mounting flanges it just occurred to me - why don't we use 4T style mounts? Typically only 2 bolts but that works on 4Ts, and often we have an adaptor somewhere in the whole carb/reedblock/engine assembly so why not have one screwed to the reed block and then the carb mount to the adaptor? Mostly nice and straight. For a "real" race bike it would add undesirable length but as an option for us it would seem OK.
Used one on the 50 for decades but that was easy as not full reed.


The 100 has the shortest 4stroke inlet I could (Z750 i think) find bolted to a 10mm plate bolted direct to the reed with some filler in the reed corners to blend nicely. I couldn't use Frits` idea of the O-ring plate as that made the carb clash with the cases.

[wobbly]

As Frits has said the higher the ring position the better, up to the thermal limit of the supporting land.
The higher you go the less unburned trapped mixture there is in the clearance crevice.
In a back to back test of 1mm stock ring with a 0.8mm so called A Kit ring, the thin ring was worth around 0.3Hp from 8000 to 13,000
so in this case the friction reduction gave a power increase, with no apparent issues of loss of heat transfer.

Wossner have made some special pistons for me with 8 radially placed gas ports in the top of the ring groove.
This piston combined with a very low tension ring pressure on the bore, is worth around 1 Hp at 8000, dropping to 0.3 Hp at 13,000
due to the drop in friction, and the better ring seal at lower rpm reducing blowby.
Thus you can pick up around 1 1/2 Hp simply with small details in the piston assy.

[husaberg]

Used one on the 50 for decades but that was easy as not full reed.


The 100 has the shortest 4stroke inlet I could (Z750 i think) find bolted to a 10mm plate bolted direct to the reed with some filler in the reed corners to blend nicely. I couldn't use Frits` idea of the O-ring plate as that made the carb clash with the cases.

311699311701311700

[F5 Dave]

.. . .
In a back to back test of 1mm stock ring with a 0.8mm so called A Kit ring, the thin ring was worth around 0.3Hp from 8000 to 13,000
so in this case the friction reduction gave a power increase, with no apparent issues of loss of heat transfer.
.

Erm in the same piston with an extra .2 clearance? would have thought the ring would have been more prone to twist. Or a dif piston with other variables?


. . .
Wossner have made some special pistons for me with 8 radially placed gas ports in the top of the ring groove.
This piston combined with a very low tension ring pressure on the bore, is worth around 1 Hp at 8000, dropping to 0.3 Hp at 13,000
due to the drop in friction, and the better ring seal at lower rpm reducing blowby.
Thus you can pick up around 1 1/2 Hp simply with small details in the piston assy.
If I'd seen this on an A'mercan website I'd have sneered & filed it with rifled squish areas. But it didn't & I trust what you've posted, so I'd have to ask -what is happening? the ports create more seal, but pressure being equal how does this push the ring further into the bore at lower revs when pressure is lower? And what in particular is a low tension ring?

[wobbly]

Yea right, so I put a thin ring in a wide groove, don't think so.
Honda did the A kit pistons with thin rings, so I wanted to see why.
They also had the ring pin at the back so the B ports could be made large and symmetric, that made a heap more power than could be gained from the vanilla customer piston.

The gas ports allow the combustion pressure down in behind the ring to create a better bore seal,quicker, at lower rpm.
There is a very limited vertical clearance to allow this, so the ports work well in combination with a ring that doesn't need as much static
radial tension on the bore to create a natural seal action without the gas pressure - thus less friction when the gas seal has been dissipated below EPO.

[husaberg]

Yea right, so I put a thin ring in a wide groove, don't think so.
Honda did the A kit pistons with thin rings, so I wanted to see why.
They also had the ring pin at the back so the B ports could be made large and symmetric, that made a heap more power than could be gained from the vanilla customer piston.

The gas ports allow the combustion pressure down in behind the ring to create a better bore seal,quicker, at lower rpm.
There is a very limited vertical clearance to allow this, so the ports work well in combination with a ring that doesn't need as much static
radial tension on the bore to create a natural seal action without the gas pressure - thus less friction when the gas seal has been dissipated below EPO.

Wayne are we talking about ports like a Oil control ring on a four stroke (Bottom of pic)or to the top of the piston like in top of this picture?
Edit he does say combustion......
311742

[wobbly]

If you look at the pic I posted you can see they are 1/2 moon slots cut into the top of the ring land to transfer combustion pressure
to the space behind the rings back face.
At lower rpm there is more time for this pressure to build and be effective, at high rpm it doesn't seem to work as well - I believe simply
due to the lack of time.

[F5 Dave]

Yea right, so I put a thin ring in a wide groove, don't think so.
Honda did the A kit pistons with thin rings, so I wanted to see why.
They also had the ring pin at the back so the B ports could be made large and symmetric, that made a heap more power than could be gained from the vanilla customer piston.

The gas ports allow the combustion pressure down in behind the ring to create a better bore seal,quicker, at lower rpm.
There is a very limited vertical clearance to allow this, so the ports work well in combination with a ring that doesn't need as much static
radial tension on the bore to create a natural seal action without the gas pressure - thus less friction when the gas seal has been dissipated below EPO.

So this would happen sooner after TDC when the pressure is pushing the piston down & the ring hard against the top of the land after swapping from the bottom of the land (on the way up).. . .No hold on, the piston would be taking the ring for a ride after Ex Port opening, but the pressure would be trying to blow past the ring at TDC pushing the ring down driving the piston as well. . . Now my head hurts.

But you are saying the piston ring ports would swap the ring to bottom of the land bearing pressure quicker reducing time of blow by I guess. I'm still not sure how the low tension ring is made differently but you are saying that for >190degrees there is less friction.


Have you tried just milling some ports on a conventional set up to see how this would work? I mean how much is less friction of this open EX port time? & how much is decreased blowby?, which has to counter the downside of more area lost to combustion, similar to having the ring slightly lower.

Does sound compelling to try this, thanks for sharing.

[husaberg]

The conformability of the rings increases exponentially as the thickness of the rings is decreased. If you reduce ring thickness by half, conformability goes up 8X. Plus, the reduced tension reduces frictional losses.

reducing the ring-to-piston vertical and groove back clearances can aid in reducing cylinder pressure loss. But he warns it is possible to go too far. “The top compression ring needs combustion pressure behind it to hold it out against the cylinder wall during the high pressure portion of the combustion cycle.

Gas ported pistons (vertical or lateral) also help with ring sealing. The ports provide a more direct path for cylinder pressure to get behind the top ring. Gas pressure helps force the ring out against the cylinder wall. In high rpm applications, gas porting helps thinner, lighter rings be more stable, reducing the tendency to bounce or flutter in the ring groove (which can break the seal).

As a rule, the higher the power output of the application, the more end gap you should allow for thermal expansion.
Foul stroke tid bits
http://www.enginebuildermag.com/2011/02/how-piston-rings-affect-horsepower/

* Gas porting: consists of drilling small holes through the tops of the pistons, which allow cylinder pressure access to the back of the top ring to force it out making it seal more tightly to the cylinder wall. They are most effective with tight ring grooves and high ring positioning. I do not recommend vertical gas porting (holes drilled through the top of pistons) for street applications. First, the engine probably doesn't develop enough cylinder pressure to unseat the rings and second vertical ports plug up with carbon in a street engine after a short time. which will be a potential source for pre-ignition. Also, you most definitely do not want one or two to plug up and apply unequal force circumferentially around the piston. As a result vertical gas ports are most often use for drag engines and horizontal ports (drilled through the side of the pistons) are used on circle track and road race engines (and on street engines...sometimes). Unless you have 600 hp or more, do not to worry about gas porting. Gas porting is needed in race engines, but it’s done because of the type of rings used and the absolute need for total ring seal at high rpm. Titanium and Chrome nitrite top rings are typically the type used, and in a 1.2 mm size. Both of which last very well, but are difficult to seal. Gas porting gets them to seal. Molly seals very well, but will not last in a race engine for very long. Also, machining the gas ports is a trick best left to the manufacture. JE happens to be my favorite and I’ve never had an issue with them, ever. Wiesco is a back up. Leave it up to them to determine placement, size and number of ports for the ring type, ring size and how long the race is. I’d also recommend that if you do go this route, coat the bottom of the top ring land, or the bottom of the ring itself with a dry film molly lubricant to keep the ring from welding in the grove. Make sure you use a good Indian stone to de-bur the groves too. Just hit the edge lightly. You’ll also want to take an exacto knife to the ports to make sure that there are no bur’s that will promote carbon build up, or hot spots. Make sure you do all this port and land prep before you mock up the assembly. Bur’s throw off your measurements. And don’t forget to polish the piss out the pistons with a light scotch bright buffing wheel. The deal with gas ports is they allow tighter ring land clearance since pressurization is accomplished with the ports. This tighter clearance is how flutter is controlled, this can be worth 20 to 30hp since it allows higher rpm with out ring seal loss.This also adds power by taking less piston movement to start building pressure,similar to moving top ring up on piston.Lateral gas ports are more street friendly since they wont carbon up as quickly as vertical ports. Ifin you still want to do this..get a gas port drill kit from Goodson..they make all kinds of trick stuff for race car engine builders...


https://www.physicsforums.com/threads/piston-ring-sealing-pressure.316225/

[TZ350]

311758 311759 311760

Ring tension is nowhere enough on its own, gas pressure behind the piston ring is necessary to ensure ring sealing against compression and combustion pressures.

http://alfatune.fi/cms_naytasivu.php?sivu=100

Simplified description of compression ring fluttering.
In the normal engine operation, the cylinder pressure on compression and on power cycle should keep the first compression ring steadily pressed downwards against the bottom of the piston ring groove. The pressure above the piston ring will find its way back of the piston ring, which again pushes the piston ring against the cylinder wall and securing the sealing. In standard applications, the pressure will be directed via the ring to groove clearance. In some applications this occurence may be helped by arranging more direct paths for the cylinder pressure to penetrate behind the piston ring using specific gas ports. The gas ports may be drilled vertically from the piston top or grooved laterally on the top surface of the piston ring groove.
The cylinder pressure fights against inertia of the piston ring and cylinder wall friction. Inertia of the piston ring is related to piston acceleration and to weight of the piston ring. If these opposing forces become greater the piston ring loses its contact to the bottom land of the piston ring groove, thus pressure behind the ring will escape under the ring and the force against the cylinder wall is lost. In standard application also the pressure path behind the piston ring will be closed and the pressure area above the ring is reduced making the problem even worse and last longer on the power stroke. This malfunction is called as piston ring fluttering.

Causes of piston ring flutter.
When the piston ring fluttering happens, rings lose their contact and result will be excessive blow-by. Furthermore the oil control does not work right anymore and these malfunctions cause long list of problems, including following:
- Power losses by excessive blow-by
- Ring and groove wear or failure
- Oil in burning chamfer will provoke knocking which may cause several mechanical failures
- In endurance applications high oil consumption may lead to lubrication problems and related failures
- High blow-by may pressurise the crank case and cause oil leakages and further power losses

[ken seeber]

Rings and heat rejection from the piston.
For many years, perhaps mistakenly, I was of the understanding that a very large percentage of heat from the piston was passed thru the ring. This in part was due to us (when I was at Orbital) dealing with some large vehicle manufacturers in working on the durability of the injected 3 cyl 2 stroke engine. They went on and on about the heat path via the ring, but they maybe were influenced in their thinking by their experience with diesels which had/have lots of compression rings and oil scrapers.

Since my resurgent interest in performance 2 strokes, I am starting to have other thoughts. One thing that I still believe in though is the fact that if the oil gets to be above 290 or so, it will carburise and if this occurs within the ring groove, the ring will stick and then, the sadness.

There is also no denying that the hottest part of the piston will be the crown, with the temp down the skirt, pretty much the same as the bore temp.
So, where does all the heat get dissipated to? My thoughts are:
1. Contact with the parts of the piston that are hotter than the bore to the bore. In this case, namely the ring and the top land.
2. From conduction down the piston behind the ring groove and bosses to the rest of the lower skirt and then to the bore and also to the pin bearing and rod via the piston pin
3. Radiation both upwards and downwards. Obviously if the underside of the crown and upper internal bits are around 250 or so, they are going to kick out some heat. There is going to be some thermal radiation from the pin and big end bearings, but I suspect these would be minimal and easily dissipated by the mixture.
4. Convection. There is a high level of gas flow under the piston, capable of removing lots of heat. This is in conjunction with the latent heat of vaporization of the fuel within the mixture. Also there is the flow across the piston crown during the transfer period.

To me, the biggies are the contact and convection, followed by the conduction and then radiation.

For max contact, I consider the fact that the ring land and ring spend a big percentage of the cycle at TDC and BDC at very low velocity, giving more time for heat transfer. As these have the highest temp gradient relative to the bore and rest of the piston, then these have the most opportunity to dump the heat. This is why the focus of cylinder cooling should be at TDC and BDC. BDC means the cooled water from the radiator passing under the exhaust port (in addition to cooling, or at least minimizing the thermal input, of the unburnt charge in this passage prior to being returned with the reverse exhaust pulse) and also underneath the cup handles of the A & B passages, which in addition can assist in cooling the mixture passing through these passages. Again at TDC, it is desirable to have a ring of coolant passing around this level prior to passing into the head. I often wonder why there isn’t an internal horizontal baffle in the cylinder to force the coolant around this path, instead of potentially short circuiting into the head.

Convection cooling. Knowing the airflow and therefore being able to infer fuel flow, one should be able to determine the convection effect, given temperature rise. So, it would be interesting to have the thermocouple readings, say between the carb and reed valve, just downstream of the reed and then in the transfer passages. Assuming there is a temp rise, then one could calculate the thermal input into the mixture. Still, it’s just one bit of info one could have, but unless we know the heat input into the piston, one could not calculate the heat loss via the contact and radiation.

Gas ports in pistons. The primary function of a ring is to seal compression and combustion pressure from leaking down past the piston. To achieve this, the ring must both seal against the bore and also its seating face. Sealing against the bore is achieved using both the spring force in the ring and gas pressure acting behind the ring, in the case of a common kart piston, the 1.0 mm height. To seal against the seating face, this means the gas pressure acting downwards on top of the ring, in the case of a common kart piston, the 2.2 mm radial depth. All going well, as the pressures rise above the piston, the pressures proportionally rise in the ring groove to act on to the ring. To achieve this, there must be a gas flow into this area. However, there are things that can prevent this from occurring as it should:
• Too great a gap behind the ring. Obviously this will require a greater gas flow to fill this volume, this will take longer and retard the sealing.
• Too tight a ring side clearance. If there was no clearance, there would be no gas flow, hence no sealing. However, in reality, it appears that most manufactured clearances, although pretty tight, seem to have adequate flow area. A heavily carboned ring and groove might create this effect however.
In saying all this, a Dykes ring offers almost no restriction to the gas flow to behind the ring.
I always thought that the gas ports were mostly used in nitro dragsters where the charge is heavily liquefied and that this might prevent a responsive pressure force acting on the ring. Hence the gas holes provide more access for the gas/liquid flow. An example of this is that small aero motors, like Frit’s 6.5 cc engine, don’t have rings, sealing is performed by the viscous film between the piston and ring. So, pretty interesting to see Wobbly’s thoughts. Certainly easy to try.

Ring tension. To me, this is a function of the ring gap, prior to fitment. All things being equal, a smaller gap will create a lower tension ring.
My thoughts anyway.

[Frits Overmars]

Rings and heat rejection from the piston... where does all the heat get dissipated to?
Convection. There is a high level of gas flow under the piston, capable of removing lots of heat. This is in conjunction with the latent heat of vaporization of the fuel within the mixture. Also there is the flow across the piston crown during the transfer period.I don't know about the high level of gas flow under the piston, but there certainly is a high level of gas flow over the piston. Jan Thiel found out that this makes all the difference between a borderline and a thermally sound high-performance engine.


I often wonder why there isn’t an internal horizontal baffle in the cylinder to force the coolant around this path, instead of potentially short circuiting into the head.So do I. But the baffle need not be in the cylinder; it can also be in the head, or the baffle role can be performed by a suitable head gasket.
Coolant, rising from the crankcase and passing along both sides of the exhaust duct, can all too often move straight up into the head, so there is hardly any horizontal coolant circulation in the upper part of the cylinder. Blocking the flow from cylinder to head right above the exhaust and opening a path to the head above the C-port will force the coolant flow to take the long way. Once in the head, it should then flow closely along both sides of the spark plug hole. This will usually take some more baffling and some venting.

Gas ports in pistons: even a tiny bevel from the top land to the ring groove caused detonation in the Aprilia engines. Any place where mixture could hide from the direct flame, was detrimental. So gas ports, either radially inward like Wobble showed, or axially top-down as used in nitro dragsters, were out as far as Jan Thiel was concerned.


The primary function of a ring is to seal compression and combustion pressure from leaking down past the piston. To achieve this, the ring must both seal against the bore and also its seating face. Sealing against the bore is achieved using both the spring force in the ring and gas pressure acting behind the ring... However, there are things that can prevent this from occurring as it should:
• Too great a gap behind the ring.this is in line with our findings. The ring should be able to just disappear into the groove radially; the less the better. But too shallow a groove will cause the full thrust force to act on the ring instead of on the piston skirt. Then we have a very efficient oil scraper and the mother of all seizures.


• Too tight a ring side clearance. If there was no clearance, there would be no gas flow, hence no sealing. However, in reality, it appears that most manufactured clearances, although pretty tight, seem to have adequate flow area.We found that a really tight fitting ring brought a considerable amount of extra horsepower. We start with a narrow groove and a ring that won't fit at all.
Then the ring thickness is ground down in tiny steps and retried over and over until it will barely enter the groove. It may sound like a lot of work, but it is one of the easiest ways you'll ever discover of finding power.


a Dykes ring offers almost no restriction to the gas flow to behind the ring.Those 100 cc direct-drive kart engines of yesteryear all depended on Dykes rings, or L-rings as they are called over here. Detonation was hardly a problem as the cylinder filling of these engines was modest, in return for an ultra-broad power band. But with a good cylinder filling the gas volume above the L-ring will cause detonation problems.


.. small aero motors, like Frit’s 6.5 cc engine, don’t have rings, sealing is performed by the viscous film between the piston and ring bore.Viscous film, you can say that again, Ken. The obligatory fuel is methanol with no less than 20% oil.
But wait, there's more. The cylinder bore is not cylindrical but very slightly conical. When the engine is cold, it can hardly be turned over by hand because the piston will literally jam near TDC. At running temperature the piston will just be able to move, with zero clearance.

[wobbly]

The real trick to getting the benefit of the gas ports in a 2T is the low radial tension of the ring that is allowed due to the extra
( quicker ) access of the combustion pressure into the clearance volume behind the ring.
This radial tension is created when the ring is manufactured, and a low tension ring has a smaller gap when relaxed, out of the bore.
Thus when assembled, it does not have as much natural static spring force on the bore surface.
Reducing the friction component of the ring when it isn't subjected to gas pressure for sure gains power, as my testing has shown.

I am next going to start working on the VHM piston/head idea of a radius on the timing edge as they are selling these as a kit to fit into KZ2
125 race engines and the published power tests show an improvement.
How much is due to the effective port timing change, as opposed to the flow bench improvement remains to be seen.
But as to why a radius on the timing edge doesn't deto, and Jans tests showed that a chamfer did seems at odds.
Except to say that the VHM head squish shape conforms to the piston shape, thus no extra trapped end gas is invoved.
The KZ2 engines will deto at the drop of a hat, so this effect needs to be tested to death before using it in a race situation.

[Frits Overmars]

..why a radius on the timing edge doesn't deto, and Jans tests showed that a chamfer did seems at odds.Maybe we misunderstood each other Wob. I didn't mean a chamfer on the timing edge, but a bevel (albeit ever so slight) at the upper edge of the ring groove.

[F5 Dave]

The real trick to getting the benefit of the gas ports in a 2T is the low radial tension of the ring that is allowed due to the extra
( quicker ) access of the combustion pressure into the clearance volume behind the ring.
This radial tension is created when the ring is manufactured, and a low tension ring has a smaller gap when relaxed, out of the bore.
Thus when assembled, it does not have as much natural static spring force on the bore surface.
Reducing the friction component of the ring when it isn't subjected to gas pressure for sure gains power, as my testing has shown.

I am next going to start working on the VHM piston/head idea of a radius on the timing edge as they are selling these as a kit to fit into KZ2
125 race engines and the published power tests show an improvement.
How much is due to the effective port timing change, as opposed to the flow bench improvement remains to be seen.
But as to why a radius on the timing edge doesn't deto, and Jans tests showed that a chamfer did seems at odds.
Except to say that the VHM head squish shape conforms to the piston shape, thus no extra trapped end gas is invoved.
The KZ2 engines will deto at the drop of a hat, so this effect needs to be tested to death before using it in a race situation.

Ahh thanks for explaining the low tension ring, I only really thought of it as being in the bore with a particular gap. But you are perhaps saying that if you used a low tension ring that in itself might be a bad choice, but in conjunction with ring ports creates less friction when ex port open & can seal real well when it needs to.

So manufacturers actually make low tension options for some applications? Or you could perhaps heat it and position it to take a set at a lower tension position.

[wobbly]

Ah, sorry Frits, yes I misunderstood simply jumping to the comment about the extra end gases causing deto.
Ring tension in the bore is a factor that can be spec'd when the rings are made, but it usually involves huge quantities for anything special..
54 bore is super common, so I assume Wossner had access to these from their normal supplier already.
The VHM setup uses a flat top piston, and makes better power, but in my experience the flat top only makes better power when combined with
a full toroidal chamber, with the plug pulled down close into the middle of the combustion space.
This cant be done in KZ2 as its then near on impossible to measure the assembled chamber cc to the regulations, so maybe the radiused timing edge itself is making
the whole difference - not the combination with the flat top, will have to test and see.

[husaberg]

DETONATION vs PRE-IGNITION



DETO!
By Kevin Cameron The Cellar Dweller

I first encountered detonation back in 1966, and I didn't know what it was. Fortunately for me, it was a light case, and the only symptoms were small holes being eaten into the edges of a motorcycle cylinder head's squish band.

Later, pushing to higher compression, I would generate my share of pistons that were detonated away until their rings hung out into empty space. I would learn to look out for the tiny, ash gray flake of quenched aluminum on a spark plug, or in water-cooled engines, for the sudden and otherwise unexplained rise in engine temperature. And I would still be curious about those dusty holes, eroded into cylinder heads.

Books will tell you what Harry Ricardo learned back in 1918; that detonation is not the same as preignition. Preignition is lighting of the charge before the spark , by some hot object in the combustion chamber usually the overheated center wire of a spark plug whose heat range was too hot for the application. Preignition soon provokes detonation, so the confusion is understandable.

Detonation, by contrast, is self ignition of some of the last parts of the charge to burn the so-called "end gas" out at the edges of the combustion chamber after the spark has already ignited and mostly burned the charge. This self igniting endgas does not then burn normally, as a flame front spread by turbulence at the usual speed of a few tens of feet per second. This gas burns at the local speed of sound, which is very high because the temperature is high. This form of combustion, called detonation, forms a shock front, a sudden jump in pressure that propagates at thousands of feet per second.

When it hits parts, it hits hard. If we hear it al all, it is as a high, dry, irregular clicking, not unlike the reverberating sound of rocks struck under water. Detonation's pressure front can damage bearings by its hammering shock, but the real problem is what it does to an engine's natural, internal insulation.

In any situation in which gases move next to solid surfaces, there is a layer of significant thickness that remains largely stagnant because it is attached to the surface. In internal combustion engines, this boundary layer quite effectively shields the engine's metal internal surfaces from direct contact with combustion gas, keeping them cooler than they would otherwise be.

When detonation begins even light deto this boundary layer is scoured off by the impacting shock waves, and heat transfer from hot gas to cool metal accelerates. In only a very few detonating cycles, piston temperatures rise dramatically, and the rest of the parts exposed to combustion gas aren't far behind.

What is strange to many people is that as this happens, exhaust gas temperature falls. This seems odd because people associate detonation with heat, and heat with failure. But the fact is that as you jet an engine down, its exhaust temperatures peak, not when the mixture becomes lean (that is, too little fuel to react with all the oxygen in the air charge), but when the mixture is chemically perfect. Exhaust gas temperature falls when detonation begins because the engine's internal insulation is destroyed; that being so, some heat that would otherwise go out the exhaust is now being diverted into the piston, head, and cylinder walls. Because those parts are getting hotter, the exhaust gas becomes colder.

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. Often, in a modified engine with high compression, this detonation begins even before we reach correct mixture and peak flame temperature. Then the engine really heats up. This leaves us with the idea that leaning down the mixture raises engine temperature, in a straightline relationship.

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 engines 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 lay well cooled engine that is not detonating, you can jet down until it starts to slow down.

Now back to detonation. The above explanation is the common one, but it leaves important questions unanswered. For example, why does detonating combustion travel at the local speed of sound, and not at normal burning speed? Why does the endgas auto ignite, rather than simply wait there like a stand of trees in the path of a forest fire? Understanding how this comes about helps to understand how the variables that affect detonation generate their effects and it helps to fend off the phenomenon that sets the upper limits on performance.

There are two basic forms of combustion, deflagration and detonation. In deflagration, the propagation of combustion is carried out by simple convection; the hot combustion gas heats what is ahead of it, raising its temperature to the ignition point. Because this process of heating what lies ahead takes time, it is relatively slow. The burning of a quiescent gasoline air vapor is in fact slow only a foot or so per second. Combustion in an engine cylinder is much faster than this because of turbulence, which so wrinkles the flame front that its area becomes hugely enlarged. This area, multiplied times the slow quiescent combustion speed, computes out to a very large volume combustion rate.

Detonation is a different animal, and not all gaseous mixtures will support detonation. It is a form of combustion in which the unburned material is heated to ignition at least partly by shock compression, as the detonation wave moves a the local speed of sound through the medium. This has to happen very quickly, so fuels with simple molecules or those with low stability lend themselves to this form of combustion. Now how does the endgas ignite by itself? It does so when its temperature is raised by any combination of effects to some critical value in the range of 900-1000 degrees F.

In a running engine, air is drawn in at some ambient temperature, and this air then begins to pick up heat from the hot internal engine surfaces it contacts. Finally it enters the actual cylinder, where is it heated by even hotter surfaces. Trapped there, it is heated again by the process of compression.

In this heating process, some little discussed chemical reactions begin to occur in the fuel. Called preflame reactions, these take the form of slow, partial breakdown of the least durable types of fuel molecule. Fuel hydrocarbons have three basic forms; straight carbon chains, branched chains, and ring structures. Temperature is a measure of average molecular activity, but there are always some gas molecules moving significantly faster than the others. These faster moving molecules hit and break some of the less durable fuel molecules, dislodging some of their more weakly bonded hydrogen atoms. This released hydrogen is very reactive (normally hydrogenous travel in bonded pairs, but his is atomic hydrogen) and instantly pairs with an oxygen from the air to form what is called a radical, a chemical fragment that is highly reactive because if contains and unpaired electron. Its attraction for the missing electron is so great that it can snap one out of other chemical species it happens to collide with, thereby breaking it down as well.

At some point in the compression stroke, the spark ignites the mixture and combustion begins. The burned gases, being very hot, expand against the still unburned charge, compressing it outward into the squish band. This compression rapidly heats the unburned charge even more, accelerating the preflame reactions in it. As a rule of thumb, the rate of chemical reaction doubles every seventeen degrees F. All this while, the population of reactive molecular fragments radicals is increasing in the unburned endgas. If this process of heating takes long enough, and reaches a temperature high enough, this population of radicals becomes great enough that its own reaction rate one radical creating more and more through further reactions accelerates into outright combustion. This is autoignition.

Now why does this heated, chemically changed endgas detonate instead of simply burning? The fuel in the endgas is no longer ordinary gasoline. The preflame reaction that have taken place in it have changed it into a violent explosive much like a mixture of hydrogen and air, or acetylene and oxygen. It is in a hair-trigger state, being filled with reactive fragments from preflame reactions. When it autoignites spontaneously, combustion accelerates almost instantly because the material is so easily ignited now. The combustion front accelerates to the local speed of sound, igniting the material it passes through simply by suddenly raising its temperature, through the shock wave it has now become.

STOPPING THE SHOW

Anything that contributes to lowering the temperature that the endgas reaches will make detonation less likely. Anything that slows the process of conversion from normal gasoline into a sensitive explosive, will make detonation less likely. Anything that speeds up combustion, so that is it completed before the conditions needed for detonation can develop fully, will make deto less likely.

Therefore the following will work;

(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.

(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
Plus an interesting related spiel on Fuels


Studies have shown that if the fuel is divided, simply, into light, medium and heavy components, by the time the mixture reaches the combustion chamber, 70% of the light ends have evaporated, and only 30% of the heavier components have evaporated (thanks to Kevin Cameron who found that study last Sunday). Then, if that mixture of vaporized fuel in the combustion chamber is between 10/1 and 17/1, clean burning can begin, creating heat, and the eventual vaporization and burning of most of the rest of the fuel. And probably those “tail ends” help cool the piston, as they are the last to evaporate when all of the oxygen has been consumed in 13/1 mixtures. If you’ve seen the Youtube videos of combustion taking place in an engine, you can see that it’s not an explosion—it’s more like a controlled bonfire—ignition of mostly front end vapors takes place while droplets of heavier ends are still flying about, then the droplets seem to disappear as they finally become vaporized and burn as the piston continues to move through TDC and downward, and if tuning and fuel is optimal the highest pressure should occur at about 18 degrees ATC.

Below is something I glued together also from Cameron but a lot less wordy and it has pics.

[jonny quest]

I've often wondered if a piston machined in such a way that only a slight edge of the periphery of the crown was made to have a slight interference fit with the bore. It would act like a molded in ring... and with careful break in conform and wear to cylinder shape. It would still use a conventional ring underneath.

[Frits Overmars]

DETONATION:...I won't quote husa's complete text here; I'd just like to say that I could not find anything wrong with it :niceone:.

[husaberg]

I won't quote husa's complete text here; I'd just like to say that I could not find anything wrong with it :niceone:.
Other than it has a lot of Four stroke stuff.
In some other more Four stroke related stuff he wrote the EX temp actually goes down when deto is occurring.

I found something interesting that was written a few years ago about forged pistons heat vs Cast
I know cast technology would have improved a lot since but I do wonder if some of the generalisations still hold true.
I will scan it and add it soon.

[ken seeber]

Good stuff Husa. You must be in the lead for the most productive Googler for the year so far.

[husaberg]

Good stuff Husa. You must be in the lead for the most productive Googler for the year so far.

As long as I get to keep my least productive bucket engine builder and KB soft porn King titles.

The bit that interested me was on Page four to do with crown and ring land temps.
As always keep clicking on them to get them easier to read.

[seattle smitty]

Could be I didn't see it, but the comments I've seen here on the ring groove gas-ports (whether drilled down vertically from the piston crown to hit the back of the ring groove, or horizontally above the ring as in Wobbly's photo) miss what I understood as the original idea . . . which was that in the event that the ring got to "floating" up to the top of the groove and thereby pinching off the gas pressure in back of the ring, leading to blow-by, these ports would always offer a continuous path for the gas pressure to the back of the ring. For what that's worth, LOL.

Frits' description of the ring-groove findings at Aprilia certainly blows big holes in what I thought I "knew" about prudent practice as related to ring groove dims and placement. But that's why I'm here!!

One thing does seem (emphasize that word) clear: Wobbly's suggestion that the area of the water jacketing of the head that lies directly over the squishband should be cooled as effectively as possible would seem to address several problems here. You want to minimize the "crevice volume" of trapped A/F mixture above the ring by various means, including placing the ring as high as possible, and reducing groove dims to a minimum per Frits/Thiel (scary to me!), for a power gain. Cooler squish area, so cooler and thus mechanically-stronger piston edge, should allow high placement of the ring without piston failure there, right?? And a cool squish area (and piston edge) ought to tend to quell detonation of whatever "crevice" gases remain. This idea of Wobbly's just seems to me like the deal sheneille for water-cooled two-strokes, a win-win, and easy to accomplish if you make your own two-piece cylinder head and water-jacket cover.

Wobbly, when your piston-builder does those tiny half-moon gas-ports, they make them before turning the groove, right? And do they drill them or use an end-mill that small? IF it's an end mill, I wonder if they could rotate the piston slowly, without breaking that itty-bitty endmill in this high-silicon aluminum, to make slots instead of just half-holes, which might address your finding that the holes become less effective at high rpms when there is less charging time . . . ???

[wobbly]

The super cooled squishband concept has now proven itself beyond doubt in one application that needs it the most
My KZ2 race engines with a straight line analogue ignition, that has way to much advance at peak and beyond, are now deto free.
Under normal circumstances the squish gap would have to be held way big up at 1.3mm or the piston would begin to be eaten away
over the boost port side with no provocation at all.
Now I am down at 0.8mm with no divergent taper and its a mm wider as well - this would have spelled instant deto death previously due to the trapped end gases
being overheated by the failing boundary layer conditions between the piston and head.
Next step is the radiused piston with matching cool head squishband area, and yes I am hoping the two ideas will be synergistic ( better word for the day than ameliorated ).

I havnt asked Wossner about the machining process, but I would imagine that the 1/2 moons are machined after the groove is done, as trying to keep the
groove surface finish high when bouncing thru radial drilled holes would be nigh on impossible.

The Celler Dweller is probably one of the most insightful engine technology commentators we have, and anyone would be hard pressed to find anything he has written that could be deemed suspect.

[husaberg]

I havnt asked Wossner about the machining process, but I would imagine that the 1/2 moons are machined after the groove is done, as trying to keep the
groove surface finish high when bouncing thru radial drilled holes would be nigh on impossible.

I wonder what order are the Pegs done then, they often overlap too.
Where's Ken. Get him out of Bed.
This is a kit the V8 crowd use.
One of the DIY threads mentioned using a SS Hose clip as a drilling guide
http://www.goodson.com/Repl.-Drill-Bit-.040-5-Pkg/
311883311884


Thanks for the posts. For some reason I don't get emails when others post!! Need to look into that.

The suggestion is exactly what I needed. Sounds like it's worth a try.

Cheers Wallace

Its on your setting one minute please caller.
311887

Added a few Maico Pics as well :)
Disk Valve.
311896311897





The Celler Dweller is probably one of the most insightful engine technology commentators we have, and anyone would be hard pressed to find anything he has written that could be deemed suspect.

Sounds like a holiday Challenge but all to easy the answer, tis the pipe opening reeds but he was adamant he got that from Macolloch guy (brooks?)

[marsheng]

Thanks for the posts. For some reason I don't get emails when others post!! Need to look into that.

The suggestion is exactly what I needed. Sounds like it's worth a try.

Cheers Wallace

[lodgernz]

The Celler Dweller is probably one of the most insightful engine technology commentators we have, and anyone would be hard pressed to find anything he has written that could be deemed suspect.

I agree. Kevin Cameron wrote the following letter to someone named Muir in Australia a long long time ago.
I was given a copy in 1976 or 77, so nearly 40 years. You might be surprised at how insightful he was that long ago.
Apologies for the quality. Copiers were pretty crap in those days. Well worth a read though.
311898

[lodgernz]

In another letter from Kevin Cameron to Mr Muir about 1975, he draws a diagram of how to create what we now call Boyesen ports, from the reed block to the transfers.
Interesting that Boyesen patented this idea in 1975. I wonder who thought of it first?

[2T Institute]

I asked Murray Sayle he's bound to know

[Grumph]

In another letter from Kevin Cameron to Mr Muir about 1975, he draws a diagram of how to create what we now call Boyesen ports, from the reed block to the transfers.
Interesting that Boyesen patented this idea in 1975. I wonder who thought of it first?

Given that the US karters were adding reed blocks and additional carbs over the transfers very early on, probably one of them who didn't want to do the welding...

[ken seeber]

Where's Ken. Get him out of Bed.

Better get up I guess. :zzzz: Well, up already as we were casting this morning.

Side holes. For our anti rotation pins, we put the hole in prior to the ring groove. This does mean an interrupted cut, however there is a subtlety. After drilling the hole, we make a first pass cut, using a 0.9 mm diamond tipped tool, Interrupted, but seems to be no bother. Then we do a second cut, to finish off the seat, in our case for a 1.0 mm groove, we move the tool down on the Z axis and repeat, making it a 0.1 depth cut. Then instead of withdrawing the tool directly we come away in a 45 deg angle, by around 0.05 from the seat. This removes and possibility of having scrolling or a spiralled groove as the tool withdraws.

Have a squiz at http://www.strikeproducts.com.au/features.asp. Somewhere in this is a feature we did ages ago on how we make pistons. Quite a few changes since then though.

In reality, there are tons of ways to do the side holes, whether they be for anti-rotation pins or gas holes and I know of some that are done in a separate operation after the groove and skirt are done. Clearly though, one needs very rigid tools and/or guide bushes to prevent deflection if cutting down the side of a groove.

We also don't cut the groove into the piston side in a square fashion. When one considers the running temperature gradient, there might be a 200 deg temp difference between the skirt and ring groove area. So, when a cold piston heats up, presumably to a nominal parallel and round shape, from a cold machined "tapered" and cam shape, a square cut groove has a tendency to be angled or coned downwards, albeit by a very, very tiny amount. So, we cut the groove in on a very, very slight angle. We called it RLTC, Ring Land Tilt Compensation. Wouldn't know if it makes any difference, but it is very simple on an NC to programme it in.

Kevin Cameron. My scribe heroes were the man KC, Gordon Jennings (early Cycle World) and Vic Willoughby in the UK "Motor Cycle Weekly". This used to have absolutely beautiful engine cutaways drawings, well before 3D CAD was even thought of. This dates me.

[peewee]

hey guys heres my first ever attempt at using a tig welder on alloy. its pretty ugly but after 30min i was doing alittle better. ill get alot more practice over the weekend :laugh:. will probly order a pyrex setup as that should allow me to see whats going on alittle better. any of you welders have some pointers ? i been watching alot of youtube videos so i can get headed in the right direction

[TZ350]

<iframe width="560" height="315" src="https://www.youtube.com/embed/Vaa96_WVdEE" frameborder="0" allowfullscreen=""></iframe>

https://www.youtube.com/watch?t=22&v=Vaa96_WVdEE
​



Mt Wellington from the air.

[ken seeber]

It's just so green. Do you guys have rain over there?

[seattle smitty]

I havnt asked Wossner about the machining process, but I would imagine that the 1/2 moons are machined after the groove is done, as trying to keep the
groove surface finish high when bouncing thru radial drilled holes would be nigh on impossible.

Yeah, which would indicate they make the half-hole with a little endmill; I was wondering how they might sequence the machining so as to leave the smallest amount of burring to deal with.

[F5 Dave]

Wow who owns the drone?

[twotempi]

It's just so green. Do you guys have rain over there?

Yes - Don't you ????:yes::yes:

Oh sorry - hadn't noticed that you were from Perth !!

[speedpro]

Wow who owns the drone?

For a day there bucket racing at Mt Wgtn was pretty flash. Apart from the usual real time lap scoring and lap times available via WiFi in the pits we had overhead coverage via drone mounted camera.

[AndreasL]

Rule of thumb ex-port size maxed out thoughts.

Lets assume a single ex-port taken as wide as can be done between the thight studs and still not up to the "% of bore" you like to have.
Crappy old 2 port transfers with way to high duration for the intended use.
Maybe we can get a reed and old style boost in there as wobbly already suggested.

Still, not enough blowdown STA to match up to the rest of the engine. Transfer duration…

Lets, for the sake of the argument, say that no welding/adding of material is doable to put things straight. Shiming the bottom of the barrel will not work either due to perfect match of piston timing edge and lower edge of transfer port.

To the point.
With the ex-port/header area at approx 90% of the effective port already, would it still be advasible to rise the duration to gain blowdown STA even if this gives a "higher ex duration then desirable"? (I'm aware this is the single most important number to make power so…) I guess it is but at the cost of a narrower power band. Or maybe the impact may not be that big even if aiming at the same rpm as for the lower duration concept.

Better run some EngMod sims but think I have answered my self already.
The question about the theory behind it all still interests me though.
It worked at the RSA, but that was a racebike. Mines not. :innocent:

[AndreasL]

Thanks Frits!

Played around with your guidelines on ex-ports in my CAD model. It certainly makes sense.

Hear what you say about the 70% and stud spacing. My biggest problem in reality is a to thin ex-port wall. For this one I was thinking to do the most of it without any welding etc.
Managed to up the % a fair bit after analyzing the casting more carefully and following your guidelines.

Yes, I really hope my engines follow the same rules of physics as the RSA. :)
My concern for adding to much duration is to end up in a useless rpm range. Your Power Range feature will be a great help hear I think. Finding the best compromise will get us a winner.

Really appreciate the point of increased blowdown (may) reduce the transfer blowback and what that does to temps. Very helpful.

[wobbly]

The max Ex port width is dependent upon the bore size as well. when dealing with small pistons like 50cc or similar.
You can safely go out to 75% as the bore to supported ring section ratio is skewed in the small pistons favor.
This is a proven safe width in many small engines, but at the end of the day you will be limited by the worst STA number.
If this is the transfer ports, then over spec'ing the blowdown will simply make the thing peaky and hard to tune.
The actual Ex STA is pretty much irrelevant, except to match its effective area to the outlet size.

[lodgernz]

The max Ex port width is dependent upon the bore size as well. when dealing with small pistons like 50cc or similar.
You can safely go out to 75% as the bore to supported ring section ratio is skewed in the small pistons favor.
This is a proven safe width in many small engines, but at the end of the day you will be limited by the worst STA number.


True. The Honda NSR50 engine as standard has a single port whose width is 77% of the 39mm bore, and they can be and are thrashed mercilously with total reliability

[Frits Overmars]

OK, let's assume the studs are in a square, so close to each other that they are almost touching the bore. Even then you could fit in a 70% wide exhaust port, which is the optimum width anyway. That single exhaust port may not give you sufficient blowdown angle.area, but widening it will not help either because wider ports require bigger corner radii to keep the piston ring happy, and those bigger corner radii would eat into the upper part of the port area, where it counts.I never said 70% is the maximum width. Metal permitting you can make it much wider than 70%; it just won't do the blowdown angle.area much good.

[peewee]

i practiced on some junk cylinders i had. alittle more practice and i should be ready to weld on the good cylinders :Punk:

[F5 Dave]

For a day there bucket racing at Mt Wgtn was pretty flash. Apart from the usual real time lap scoring and lap times available via WiFi in the pits we had overhead coverage via drone mounted camera.

Actually there was a drone camera chap at Kaitoki yesterday, had a quick look at it, pretty cool.

[Drew]

Actually there was a drone camera chap at Kaitoki yesterday, had a quick look at it, pretty cool.

Was his name Mathew?

[F5 Dave]

Dunno. Sign written ute. Eyesky or something. Scraggy long grey hair.

[Drew]

Dunno. Sign written ute. Eyesky or something. Scraggy long grey hair.

Diferent dude then.

[lodgernz]

SkyEye. He said he'll post some video on www.flying.pictures for us. Don't know if there are strings attached.
Unintended double entendre there

[adegnes]

Lots of good info on engine/gearbox oil here:
http://www.ducatimonsterforum.org/index.php?topic=1912.0

[lodgernz]

I never said 70% is the maximum width. Metal permitting you can make it much wider than 70%; it just won't do the blowdown angle.area much good.

Absolutely. Even with 77% of bore the NSR50 blowdown STA is still crap.

[FastFred]

312063312064312065

Recent goings on at the Team ESE house of speed.

Chambers is water cooling a sleeved down 100. He is retaining the original Suzuki GP head and cylinder. Non of this store brought stuff for him. Its just like the rules say it should be .... its all made from a none competition engine.

Proper Bucket engineering using DIY hand skills is his approach ... the down side is, that it takes a lot of time and effort compared to the store brought stuff, but the up side is, its the real deal Bucket racing engine anyone could be proud of.

Great work ... :clap:

[lodgernz]

Is it a 2-piece head? I can't see how he's going to keep the water in.

[peewee]

have you guys seen the new 125 ktm engine ? http://www.ktm.com/us/mx/125-sx/

[chrisc]

have you guys seen the new 125 ktm engine ? http://www.ktm.com/us/mx/125-sx/

All I see is a power valve, 6 speed and 2 ring piston (which I was surprised by). Am I missing something else here?
I'd be interested to see the port layout. Beautiful bikes those KTMs!

[F5 Dave]

Well it's light. Wheelbase is a little long & the suspension seems wildly long with goofy bodywork and quite raked out steering geometry. And those tyres? Are they some sort of wets?:wacko:

[husaberg]

All I see is a power valve, 6 speed and 2 ring piston (which I was surprised by). Am I missing something else here?
I'd be interested to see the port layout. Beautiful bikes those KTMs!

Its a stacked engine redesign.
old
312073

New
312074

Looks like the KTM65, 50 09 redesign has filtered through.

[peewee]

it almost looks like the intake is angled slightly upward but its hard to tell. rear transfers look like they sweep far around to the back also. probly be a while before theres any cylinder photos unless one of you guys are buying one in the next month or so ?

[Yow Ling]

it almost looks like the intake is angled slightly upward but its hard to tell. rear transfers look like they sweep far around to the back also. probly be a while before theres any cylinder photos unless one of you guys are buying one in the next month or so ?

I guess you could use the sparkplug in buckets

[senso]

The plastics/fairings/bodywork seems a bit strange, almost as if KTM saw the chinese replicas and decided that they had good looks, but its all in the name of weight reduction.

[Muciek]

Words for today nonsmoking 125cc 2t 70HP @ 17-18k rpm

Here's picture 312083

Frits could shed some light on it , but like he said other place he have a confidentiality clause.

[wobbly]

Its got a long rod in it - check the spacer under the cylinder.

[Flettner]

Probably not a picture of the actual engine, I expect that will be hidden for a while yet.

[Frits Overmars]

Probably not a picture of the actual engine, I expect that will be hidden for a while yet.The internals will probably remain hidden for a while yet, but this is an actual engine. Don't you love it when it looks so simple and so familiar?

[crbbt]

that would go alright in my NX4!

is the powerband very narrow?

[Frits Overmars]

is the powerband very narrow?Not at all. And that's the last I will say about it for now.

[richban]

Not at all. And that's the last I will say about it for now.

Can you make me a 250 please :innocent:

[2T Institute]

The engine is a VM 125 ICC kart engine , will be interesting to see what Ryger have come up with 80% less emissions too.

[senso]

70Hp from a 125cc engine, now I feel really dumb, and amazed at the same time.

[wobbly]

As the pic shows the engine in a kart, then we can assume the power is measured at the front sprocket.
The Aprilia did say 55 Hp at 13,000, add 10% for the two gear sets and chain and round to 60 Hp Crank = a BMEP of 16.5 Bar
This engine makes 70, add 10% = 77 @ 17,000 = BMEP of 16.25 Bar.
So all that has been done is to move the same torque level up from 13,000 to 17,000 to achieve the extra Hp.
Of course that is alot easyer to say than do,but we could happily assume there is 24/7 hiding in the front end to help things dramatically.
Though with the piston speed up at 26M/Sec I doubt the 54.5 stroke big end bearing of the stock engine is going to last all that long.

[F5 Dave]

And is it physically achievable to cram enough port area to achieve that BMEP at those revs? That seems unlikely doesn't it?

[Flettner]

Am I seeing things or does it look like two reed systems? One clearly is cylinder reed and if you look real close you can see what looks like a case reed hiding behind the breather bottle thing.

[husaberg]

Am I seeing things or does it look like two reed systems? One clearly is cylinder reed and if you look real close you can see what looks like a case reed hiding behind the breather bottle thing.

I think it has both less than two and maybe even less than one carb operational.
I can also see two entries though.

[Haufen]

Words for today nonsmoking 125cc 2t 70HP @ 17-18k rpm

Here's picture 312083

Frits could shed some light on it , but like he said other place he have a confidentiality clause.

Would you mind sharing your sources with us?

[husaberg]

Would you mind sharing your sources with us?

Right click copy code search as an image using the words.


As the pic shows the engine in a kart, then we can assume the power is measured at the front sprocket.
The Aprilia did say 55 Hp at 13,000, add 10% for the two gear sets and chain and round to 60 Hp Crank = a BMEP of 16.5 Bar
This engine makes 70, add 10% = 77 @ 17,000 = BMEP of 16.25 Bar.
So all that has been done is to move the same torque level up from 13,000 to 17,000 to achieve the extra Hp.
Of course that is alot easyer to say than do,but we could happily assume there is 24/7 hiding in the front end to help things dramatically.
Though with the piston speed up at 26M/Sec I doubt the 54.5 stroke big end bearing of the stock engine is going to last all that long.


One site suggested 23000 rpm............
If Frits is reading as soon as I seen those RPM's I thought of a Scotch crank.
If you recall I mentioned a British project of the late 60's the Excalibur I am almost certain that was to use a scotch crank and some form of moving sleeve.
like I posted on the oddball page recently.


Fridays best use of wood in a two stroke engine
The boost port is blocked with a hand fitted balsa strip. This one has survived a full seasons flying. It isn't glued in just a firm fit in the crankcase.
312106

What the heck i know it will be a glow engine but what the heck........
The slot has been machined exactly 1.15 deep to match with the 1.15mm thick mild steel sheet that I plan to make the shield from
312109


The plug shield is made from 1.15mm mild steel and is 3mm wide by 26mm long. Ideally I would have used 1mm thick but didn't have any to hand. I don't believe that this extra few thou of thickness will make any difference. It is very important that the groove is exactly the right depth for the material used to ensure that there are no leaks. I painted a little bit of Loctite 601 into the slot before pressing the shield bar into it.
312107


The head modifications are finished off by fitting a 0.6mm thick aluminium shim over the steel strip. I coated the mating face with a very thin skim of JB Weld to ensure that the resulting assembly was fully sealed. I chose 0.6mm as I had removed 0.4mm already and needed to put that back and on my other engines I had 0.5mm of shims in addition to the head gasket. I expect to need another couple of shims possibly up to 0.4mm to get the compression back to an ideal setting.
312108
http://www.machineconcepts.co.uk/aeromodelling/st51/st51-3.htm#top

[ken seeber]

Like many I am sure, I have looked at the pic and am not sure what I am looking at. Is it a reed block housing on the cylinder, which looks very much like VM’s current engine? Or is the housing in fact not a housing, but a part of the return of the beading of the seat behind? The crankcase looks like their standard crankcase with the forward facing reed block. As Wob says, there is a thick spacer under the cylinder. Maybe they are getting the thing ready for the 2016 homologation. Never any good at this forensic stuff.



Where's Ken. Get him out of Bed.
Husa, out of bed, we need more pics and info.:not:

Another thing. If it was revving to 17k, there would be two noticeable external features:

1. The exhaust would be shorter. Does this one look any different to a regular KZ exhaust?
2. Assuming the gearbox internal and primary drive ratios were generic KZ stuff, the secondary chain drive ratio would be 17/13 = 1.3 times greater.

Husa, we need more info!

[husaberg]

Like many I am sure, I have looked at the pic and am not sure what I am looking at. Is it a reed block housing on the cylinder, which looks very much like VM’s current engine? Or is the housing in fact not a housing, but a part of the return of the beading of the seat behind? The crankcase looks like their standard crankcase with the forward facing reed block. As Wob says, there is a thick spacer under the cylinder. Maybe they are getting the thing ready for the 2016 homologation. Never any good at this forensic stuff.

Husa, out of bed, we need more pics and info.:not:

Another thing. If it was revving to 17k, there would be two noticeable external features:

1. The exhaust would be shorter. Does this one look any different to a regular KZ exhaust?
2. Assuming the gearbox internal and primary drive ratios were generic KZ stuff, the secondary chain drive ratio would be 17/13 = 1.3 times greater.

Husa, we need more info!

Most of it has seemingly been scrubed from the Internet. It appears to be a mop up and clean excersize. just saying............
http://forum.pyrotherm.rs/forum/index.php?/topic/4015-ryger-engine-125cc-30000-rpm-70-bhp/page__pid__91798
Pretty sure it is not 30000 RPM though maybe the rev counter is in lira?
There seems to be a mention of it in the Search for this page but maybe only for Friends. bet lozza is a facebook friend of his though
https://www.facebook.com/luc.foekema/media_set?set=a.1761099246360.71824.1805454134&type=3Special

Ryger engine 125cc, more than 80% less emission 30.000 rpm 70 bhp A................Again? the same info
http://www.rygerengine.com/index.emissions.htm
its all German to me.......

http://www.rygerengine.com/
I had another page but I can't find it (I think I looked under cached pages)
....... have you looked on pitlane Ken?
I do know how to find obsolete and deleted information.. but not tonight.
Frits will be along soon to explain all.......... LOL


I haven't either?

Marketing
Create a buzz
Peak peoples interest
Limit information available.
What better advertising than word of mouth.

Just saying...........

[F5 Dave]

Most of it has seemingly been scrubed from the Internet. It appears to be a mop up and clean excersize. just saying............
http://forum.pyrotherm.rs/forum/index.php?/topic/4015-ryger-engine-125cc-30000-rpm-70-bhp/page__pid__91798
Pretty sure it is not 30000 RPM though maybe the rev counter is in lira?
There seems to be a mention of it in the Search for this page but maybe only for Friends. bet lozza is a facebook friend of his though
https://www.facebook.com/luc.foekema/media_set?set=a.1761099246360.71824.1805454134&type=3Special
Again? the same info
http://www.rygerengine.com/index.emissions.htm
its all German to me.......

http://www.rygerengine.com/
I had another page but I can't find it (I think I looked under cached pages)
....... have you looked on pitlane Ken?
I do know how to find obsolete and deleted information.. but not tonight.
Frits will be along soon to explain all.......... LOL


I haven't either?

Marketing
Create a buzz
Peak peoples interest
Limit information available.
What better advertising than word of mouth.

Just saying...........
Sounds like a job for the waybackwhenmachine

[wobbly]

Just noticed that the emissions tests on the KZ2 engine and the so called Clean 2T were done at 5000 rpm - what a joke.
Makes me wonder about the whole thing when you see that sort of skewed ,make it look good at any cost bullshit.

[husaberg]

Sounds like a job for the waybackwhenmachine
Yes but I might be an advertising bot for them.
But yes that and some similar stuff was what I was going to use.

[RAW]

The Ryger 125.
I'm under the impression that the crankcase is sealed from the cylinders transfer ports ( thus the spacer ) also the crankcase is oiled like a conventional 4 stroker ( note puke can ) now if i recall correctly there was some trickery with pressure balancing the crankcase with some other part of the engine, this again if I recall correctly freed up some form of resistance.

[husaberg]

The Ryger 125.
I'm under the impression that the crankcase is sealed from the cylinders transfer ports ( thus the spacer ) also the crankcase is oiled like a conventional 4 stroker ( note puke can ) now if i recall correctly there was some trickery with pressure balancing the crankcase with some other part of the engine, this again if I recall correctly freed up some form of resistance.

Scotch yoke anyone? I don't want get egg on my face mind you.
It would allow the separation of the crankcase from the confines of petrol oil lubrication.
Just to be clear I have no knowledge of the internals of this engine.

[TZ350]

Page 1180 .....


here is a rule of thumb: a racing two-stroke consumes about 7 cc fuel per hp per minute.


Some good viewing in here from TechGP on facebook
https://www.facebook.com/media/set/?set=a.254892271379265.1073741826.254890808046078&type=3

M50-A Cylinder.


Here's the iame m50 cylinder, got it a few days ago. It's so tiny it's ridiculous!

312442

Meassured primary volume @tdc is about 242cc, will probably end up around 250-255 if I add material to the cylinder and match the ports to my case, or around 230-235 if I weld up the case transfers. Hmm... What to do?


Here's the port map, I couldn't find my pencil sharpener, and was tired so kinda rushed it - rough and not super accurate, but should give an idea of things. I cut out the ports from the paper I used to trace the bore and transferred the "holes" onto graph paper, with the blunt pencil it didn't turn out very good, oh well.

312443

Axial angles:
A = 25°
B = 7°
C = 55°

312444

Radial angles:

If anyone is bored and need something to pass their time...


With those huge auxiliary exhaust ports and the conservative timing, it's going to have very good blowdown STA. As Frits and Wobbly have been saying for a long time, this is the most significant factor in an engine's performance. I'm guessing that's why it can rev so high to make that incredible power.



312445
Here is the STA analysis of the M50. About as accurate as the drawings allow, but shows that the Blow STA is on the money, the transfers too small - but as they flow so well in the right directions this is not holding back the power production badly.
So, this engine needs an additional 21% exhaust port area to meet the targets?


Ha Ha, sorry not even close.

The Exhaust STA is basically a redundant measurement.

As it has been alluded to in many pages here, reducing the Ex duct volume,by lifting the floor and filling in the bottom corner radii at the port face has a way positive more effect - due to the velocity increase and a reduction in A port short circuiting. Same effect at the duct exit into the header, where the rule of thumb for a 3 port is 75% exit area of the total port effective, works a treat.

Its the combination of the Blowdown STA and the Transfer STA ( modified by the discharge coefficient created by the duct shape and the port orientation ) that sets the power making potential of any 2T setup.

Forget what Cameron and Blair etal said in the literature last century, and take heed of what Thiel found in the dyno cell.



Here is the STA analysis of the M50.
About as accurate as the drawings allow, but shows that the Blow STA is on the money, the transfers too small - but as they flow so well in the right directions this is not holding back the power production badly.
All the ports are actually about 1mm higher than what I managed to show in my crappy portmap, they're nice and symmetrical to Seem's to be a well made little cylinder - maybe I should leave those transfer ducts alone for now, in fear of screwing up the "harmony". I was going to widen them 5mm.

Could someone share how they manage to get an accurate port map? I obviously suck at it, though bad equipment has to take part of the blame. Do you use graph paper when you trace the bore? My graph paper was too stiff to use.


Well the port heights seemed fine in that the stroke length of 39.4 works on the graph paper as the height from tdc down to the bottom of the EX measures right on that.
So the EX timing at 23mm = 92.5 atdc = 175 duration, lift it 1mm = 22mm = 89.5 atdc = 181 duration.
But we need alot more accuracy with the transfers as lifting them all 1mm makes them way too big.

You should use a long stroke dial gauge sitting on the piston, zeroed at tdc. I took the transfer widths off the radial angle diagram, as this is the most accurate. You do realize that using graph paper in the bore and doing the old "rubbing " thing doesn't give the true chordal widths, and that the chordal widths are also not the actual " flow " widths needed.



Ha Ha, sorry not even close. The Exhaust STA is basically a redundant measurement. Forget what Cameron and Blair etal said in the literature last century, and take heed of what Thiel found in the dyno cell.
Some more reading on the subject: http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130292202#post1130292202


Thanks for the tips! I'll be back with more accurate numbers!


Hey guys, I have a question, I yesterday measure the base advance of my engine, and it is 8*.I was discussing this with a friend and he advised me to modify it for 15*,but when I asked him why should I do this, he couldn’t answer.

So I was thinking what exactly is the base advance doing? I have an Ignitech, not standard CDI, so changing the base adv won't change the whole curve in degrees.
Also, what is happens when the lobe passes through the CPS.. why some flywheels have wide lobe and some others short?
Cheers!


This is as accurate as I can get it:

Iame m50 cylinder

Stroke = 39.4mm
Bore = 40mm
Stud pattern = 57x57mm

312448

"Cylinder rubbing":
(to show radius of port corners)

Port heights:
Main Exhaust open = 22.4mm atdc Height = 17mm
Aux Exhaust open = 24.1mm atdc Height = 7.6mm
A-port open = 31.2mm atdc Height = 8.2mm
B-port open = 31.7mm atdc Height = 7.7mm
C-port open = 31.7mm atdc Height = 7.7mm

Axial transfer angles:
A = 25°
B = 7°
C = 55°

Radial transfer angles:

Exhaust port widths and shape of aux exhaust outer wall:
millimetre graph paper.

Transfer port widths: millimetre graph paper

Exhaust duct is 27x20mm at the flange.

Hope this can benefit others in search for a 50cc cylinder to, not just me.


In reply to the question about the base timing. This number is irrelevant to anything except that under 300rpm when the flywheel first starts moving, the spark fires, by default at the base timing. 7* or 27* makes no difference, except a big single would probably break your ankle if kicking it over at 27* firing.

This simply tells the ECU where TDC is in relation to the mechanical triggering point on the flywheel.
Changing the base advance ( without moving the trigger ) DOES change ALL the timing points.
As you increase the base advance you are retarding ALL the actual programmed spark events.

The lobe length is also pretty much irrelevant, as an Ignitech fires off the trailing edge point - its less susceptible to RF noise being a dropping trigger signal.. A very long lobe causes problems in that the waveform created by the bump upwards being closer to the trigger pole, decays to zero and you can get random misfiring, but this can be accounted for in software.

312446

And here is the STA analysis with the better data, now we see the guys doing this were pretty close to the money.


Well here is what is easily possible with this cylinder - all the ports are widened and lifted ( except the boost port ) and the stagger increased to help widen the power spread ( no PV ).

This keeps the Ex timing in the range for good superposition resonance tuning as well to help with no PV.

Lots of detail in the mods, and that would need a full sim run in EngMod, ( like duct exit area etc ) but that doesn’t happen for nothing.

[Flettner]

The Ryger 125.
I'm under the impression that the crankcase is sealed from the cylinders transfer ports ( thus the spacer ) also the crankcase is oiled like a conventional 4 stroker ( note puke can ) now if i recall correctly there was some trickery with pressure balancing the crankcase with some other part of the engine, this again if I recall correctly freed up some form of resistance.

Sounds like a suitable scenario.

[teriks]

Fridays best use of wood in a two stroke engine...

Are you flying control line stunt?
Kind of odd things to do to an engine otherwise..

[husaberg]

Are you flying control line stunt?
Kind of odd things to do to an engine otherwise..

Not I...... did I not link it? still best use of balsa wood, it was a corker.
So its not a common glow plug thing to do then?............
http://www.machineconcepts.co.uk/aeromodelling/st51/st51-3.htm#top
ps I have no idea what control line stunt means or why it would be needed. So explain how it works and why you would block a transfer and shield a plug.

oh yeah....... the crankshaft of the week answer is 1960's 250cc Greeves Silverstone.
312137

[Flettner]

Sounds like a suitable scenario.

I feel like another test cylinder is needed, forget the crank case althogether, I have other plans. Now where did I put that 250 fourstroke engine? Don't worry I won't be using cams or valves.

[ken seeber]

Hooser, you’ve got a lot to answer for. Couldn’t help thinking if a scotch yoke could be fitted into the VM. Well I reckon it could, with a lot of work and chomping.
So, the assumptions. 50 * 54 *100 rod in conventional format (see left side of sketch) and the spacer is 25 (rhs). Scotch crank uses a Ø20 pin, 30 square slider, 6 plate thickness rising by 12 or so at the centre of bracing (super random guesses).

312146

Presumably the scotch yoke would need to be supported at both ends to resist the bending moment and this would be done with a Ø15 or so piston rod. This is supported and sealed at the spacer plate. Would obviously also be supported on the underside as well. The scotch mechanism would be lubricated separately from the piston.
At TDC, the scotch engine has a deck height of 25 higher (spacer thickness). At BDC there is almost this amount for the piston to clear the spacer plate of the arbitrary layout in the sketch.

Irrespective, it raises lots of points:
1. To clear the yoke, there would be lots of clearance required within the crankcase
2. The reciprocating mass wouldn’t be less than trivial
3. The “crankcase volume” below the piston would be very small, defying the current trends, but, as Wob says, it maybe could be using a 24/7 inlet
4. The motion would be sinusoidal. Could be good or bad, up to the EngMod types to make this call
5. My thoughts are that it would need a lower piston rod for support, requiring a projection housing out the bottom of the crankcase

So, in my opinion, possible but unlikely. However, as always, there are lots of smarties in the world, and maybe this is a product of them. On the other hand, maybe the whole 70 hp and 17k is bullshit and we have just wasted a lot of time

[husaberg]

Hooser, you’ve got a lot to answer for. Couldn’t help thinking if a scotch yoke could be fitted into the VM. Well I reckon it could, with a lot of work and chomping.
So, the assumptions. 50 * 54 *100 rod in conventional format (see left side of sketch) and the spacer is 25 (rhs). Scotch crank uses a Ø20 pin, 30 square slider, 6 plate thickness rising by 12 or so at the centre of bracing (super random guesses).

312146

Presumably the scotch yoke would need to be supported at both ends to resist the bending moment and this would be done with a Ø15 or so piston rod. This is supported and sealed at the spacer plate. Would obviously also be supported on the underside as well. The scotch mechanism would be lubricated separately from the piston.
At TDC, the scotch engine has a deck height of 25 higher (spacer thickness). At BDC there is almost this amount for the piston to clear the spacer plate of the arbitrary layout in the sketch.

Irrespective, it raises lots of points:
1. To clear the yoke, there would be lots of clearance required within the crankcase
2. The reciprocating mass wouldn’t be less than trivial
3. The “crankcase volume” below the piston would be very small, defying the current trends, but, as Wob says, it maybe could be using a 24/7 inlet
4. The motion would be sinusoidal. Could be good or bad, up to the EngMod types to make this call
5. My thoughts are that it would need a lower piston rod for support, requiring a projection housing out the bottom of the crankcase

So, in my opinion, possible but unlikely. However, as always, there are lots of smarties in the world, and maybe this is a product of them. On the other hand, maybe the whole 70 hp and 17k is bullshit and we have just wasted a lot of time


Yes but fun anyway, as Frits mentioned in his normal way it was the engine, but maybe it was not the entire engine maybe it carried a FOS cylinder.
With the Scotch yoke it would need to be modified a little as to dwell longer at BDC which is readily achievable.
yes the "crankcase"volume is small but then again if there was a form of additional pumping (like the other end) it would not be an issue.
But I have scotch yoke on the mind at the moment its a burden but you will have to grin and bare with me.

Pretty sure you will have experience with the bottom end of two strokes that had pressure feed four stroke like bottom ends
They only seem to work with a form of forced induction, more food for thought. It was mentioned earlier about something along those lines.... which might account for cleaner burning and substantial power output

[teriks]

Not I...... did I not link it? still best use of balsa wood, it was a corker.
So its not a common glow plug thing to do then?............
http://www.machineconcepts.co.uk/aeromodelling/st51/st51-3.htm#top
ps I have no idea what control line stunt means or why it would be needed. So explain how it works and why you would block a transfer and shield a plug.


Ahh, thought you had done that yourself.

No, none of them is a common thing to do if you want any kind of power to speak of :)

Control line, well that goes back to the days before radio control.
The plane is attached to an handle with two lines, flying in circles around you.
The two lines allows you to control the elevator, and that's the end of the control you have (when I tried I really really wanted engine shut off too :sick:).
CL stunt is doing aerobatics with control line models, limited to a hemisphere of course.

One thing they try to achieve is constant speed, where I think is where at least the shielding comes into play.
If you place the tank a bit backwards from the throttle, you can get the engine to run rich in level flight, damn rich when diving, and lean out to a best power setting climbing.
The shield would be there to prevent the glow-plug from being drenched by fuel droplets in the rich conditions.
I don't know, but would guess the boost port is plugged for the same reason. -If you dont scavenge the top of the cylinder you wont have the raw fuel there either..

[Haufen]

Just noticed that the emissions tests on the KZ2 engine and the so called Clean 2T were done at 5000 rpm - what a joke.
Makes me wonder about the whole thing when you see that sort of skewed ,make it look good at any cost bullshit.

Also, the KZ2 engine was run richer (CO values) and, depending on the load and ignition timing etc., would be more likely to miss a couple of ignitions at 5000 rpm than the (c)leaner engine which would then explain the different HC values easily.

[peewee]

hey guys i cut this head open to see what it looks like and drilled some holes to see how much material there is. it appears to be plenty thick. i want to make a chamber shape like what jan did :niceone:. somehow i just have to calculate it so i get the correct volume

[Muciek]

hey guys i cut this head open to see what it looks like and drilled some holes to see how much material there is. it appears to be plenty thick. i want to make a chamber shape like what jan did :niceone:. somehow i just have to calculate it so i get the correct volume


Finished Webco reproduction heads for RD350/400 with Wobbly designed combustion chambers :niceone:

309101309102309103309104

Wouldn't it be better to do it like this ones for RD ?

[Frits Overmars]

Took the Ryger-kart for a little spin today.
God Almighty!
312179 312180 312181

I've got a fairly good idea of what to expect from a 125 cc kart. But this....
The revcounter could hardly keep up with the crankshaft but in any case it revved much higher than a normal 125 and I reached the end of the straight-away much quicker. What a rocketship!

[wobbly]

Perfectly chosen pics there Frits.

Re the head inserts - here is a TZ350 with these fitted after machining away the original material completely.
This setup also had a plate welded onto the top of the cylinder to redirect the water flow correctly.

[Flettner]

Frits, you are taunting us.

[adegnes]

I haven't been this excited in a long time!

[Grumph]

Perfectly chosen pics there Frits.

Agreed - I think we'll all recognise the van now.....

[ken seeber]

Ryger engine.
If you go to http://www.deraceheldenvanweleer.nl/index.php?wap2 then to full version and then to Engine Talk, from Page 76 or so onwards, there is more on it. Banter and speculation, but CDA limited.
Still, it'll be good to see what it is in the end.
A rotary/reed engine winding up from 8k to 22k gives me goosepimples, dunno what the same would do going to 30k. Dampness?

[husaberg]

Ryger engine.
If you go to http://www.deraceheldenvanweleer.nl/index.php?wap2 then to full version and then to Engine Talk, from Page 76 or so onwards, there is more on it. Banter and speculation, but CDA limited.
Still, it'll be good to see what it is in the end.
A rotary/reed engine winding up from 8k to 22k gives me goosepimples, dunno what the same would do going to 30k. Dampness?

Ken we have been trying to keep that one a secret........:laugh:
I haven't looked at that forum for about 6 months either
Even worse it looks like I am bloody right about the crank.
If its got an upside down piston that extends into the head and a bottom ex port I have just wasted 2 weeks.

[Frits Overmars]

Perfectly chosen pics there Frits.They are not selfies Wob; I didn't take them. I had no free hand in choosing them either. But in case you want to see more details of the van, I can ask :D.


Frits, you are taunting us.I can't help it. I'd love to tell y'all much more but I'm not yet at liberty to do so.


I haven't been this excited in a long time!Same here!

[peewee]

Perfectly chosen pics there Frits.

Re the head inserts - here is a TZ350 with these fitted after machining away the original material completely.
This setup also had a plate welded onto the top of the cylinder to redirect the water flow correctly.

ive seen guys machine out the whole chamber on the stock heads and use a removable cool head style chamber insert, like your photo. problem is most shops around here only know how to cut standard hemi style chambers so ill likely be stuck doing the calculations myself. any tips on what my comp ratio should be ? atleast that would give me a idea where to start with the head chamber. its 64x58 dimensions. ive got it loaded in engmod but i was using it mostly just for guidance on the STA values

on to another project. its got honda rod, piston and exh manifold. this one ill put in engmod in the next few days but im not sure what to do on the A, B,C axial angles. should A=30*. B=20*. C=10* ? and which way do i stagger the timing ? thought i read it should be A first, then B next and C/D last. i think ive got the cylinder spaced up correctly. piston just pops above the deck a few mm but not enough so the top ring will pop out of the bore. that leaves me with 182/122 timings which is a good place to start so i can have plenty of material to get a good axial angle on the A port (ktm put all the side tranfers at 5*).

[chrisc]

Some good viewing in here from TechGP on facebook
https://www.facebook.com/media/set/?set=a.254892271379265.1073741826.254890808046078&type=3

[wobbly]

The only reason to use normal stagger, ie A open first is if you have no powervalve, and need the inherent power spread of that type of porting layout.
As seen in KZ2 for example.

[Flettner]

Words for today nonsmoking 125cc 2t 70HP @ 17-18k rpm

Here's picture 312083

Frits could shed some light on it , but like he said other place he have a confidentiality clause.

That top reed block is quite high up the cylinder, looks like it goes straight into the back of the cylinder at transfer height, ie straight into the transfers.

[adegnes]

That top reed block is quite high up the cylinder, looks like it goes straight into the back of the cylinder at transfer height, ie straight into the transfers.

I've been playing with the idea of a cylinder with short runners inside a plenum around the bore in place of the regular vertical transfer passages, hope this is something similar - would make me feel kinda smart.

[ken seeber]

Well, I reckon the cylinder is pretty much the same as a standard VM (see http://www.magtune.com/magtune/VM_MOTOR.html), but with the addition of a reed block which is very much the same as a Rotax Max and some early Kawasaki 125 motocross engines. This certainly dumps into the base of the B & C passages.


I've been playing with the idea of a cylinder with short runners inside a plenum around the bore in place of the regular vertical transfer passages, hope this is something similar - would make me feel kinda smart.

Going on to Adegnes's suggestion, there was a bloke on pit-lane last year who posted this:

“There was an engine in the 1930s called the Petter Harmonic engine. A low rpm engine that had the exhaust valves in the head and a long resonant length pipe. Can be seen via Google.

To me there are 2 options for the next quantum power jump in performance 2 strokes:

1. A ring of exhaust ports around the bore with valves in the head, maybe even passive reed valves, cooled each time during induction

2. Go with a RSA type port layout, but have a diversion valve, say in the B ports that allows this to be connected to a short (throttled?) duct from atmosphere, ie direct inlet to the cylinder, bypassing the crankcase. Even the diversion valve could be eliminated by simply dedicating the B port to external air (& fuel?) only, leaving the A & C ports to provide sufficient flow for starting and getting up to the tuned speed when the B port passage could be opened”

[husaberg]

I thought I had cracked it with the cupped piston but now can see it will not work with out a sleeve valve controlling the ex.
Left field But I feel the cylinder is very different with a sleeve valve shutting the exhaust port on the rise to tdc and opening it on the fall to BDC.
That is assuming it is "cylinder" supercharged.

Ken as for two stroke like engines with Valve I think this is pretty cool
312246312247
Bourke engine
312244312245 312248

[ken seeber]

Husa, I reckon that the only way for a high performance exhaust to work is to have rapid opening, such as the piston in the bore (ie conventional stuff). Any poppet valved thing just cannot get the opening rate anywhere near that of the piston. The Petter thing was just old stuff, the point it was raised was the fact that an engine could run without passing air through the crankcase. Sleeve valve engines might be able to show advantages, but I think they will be thermally limited, ie poor piston cooling.
I guess we'll just have to wait.

[husaberg]

Husa, I reckon that the only way for a high performance exhaust to work is to have rapid opening, such as the piston in the bore (ie conventional stuff). Any poppet valved thing just cannot get the opening rate anywhere near that of the piston. The Petter thing was just old stuff, the point it was raised was the fact that an engine could run without passing air through the crankcase. Sleeve valve engines might be able to show advantages, but I think they will be thermally limited, ie poor piston cooling.
I guess we'll just have to wait.


My little mussing was based on it only shutting on the upstroke it would be normal on the opening of the ex.
I was trying to get it to work in my head for the last two weeks with two separate ideas that were in an old KG Draper book.
with the New engine why wait?
Do as I did and look at the link you provided and search the patent application this morning.:whistle:
you need to just search the numbers to see what is there. the original link did not work.
Pretty sure one of them even had drawings.....
I must admit to only skim reading it and I have reputation for being a little slow.
Its bloody wordy
http://www.google.com/patents/WO2013185802A1?cl=en
312249312250312251



Never noticed these before
NSR500V the 500 twin Below the reed intake?

[ken seeber]

Well done. The sumobrain link didn't work for me yesterday. Yep bit of reading required.

[breezy]

Took the Ryger-kart for a little spin today.
God Almighty!
312179312180312181

I've got a fairly good idea of what to expect from a 125 cc kart. But this....
The revcounter could hardly keep up with the crankshaft but in any case it revved much higher than a normal 125 and I reached the end of the straight-away much quicker. What a rocketship!

seems like the hand over the spark plug , is placed as an obstruction , something behind ??

[adegnes]

Here's the iame m50 cylinder, got it a few days ago. It's so tiny it's ridiculous!


312254312255312256312257312258

Meassured primary volume @tdc is about 242cc, will probably end up around 250-255 if I add material to the cylinder and match the ports to my case, or around 230-235 if I weld up the case transfers. Hmm... What to do?

[adegnes]

seems like the hand over the spark plug , is placed as an obstruction , something behind ??

What I'm thinking to...

[Grumph]

Do as I did and look at the link you provided and search the patent application this morning.:whistle:
you need to just search the numbers to see what is there. the original link did not work.
Pretty sure one of them even had drawings.....
I must admit to only skim reading it and I have reputation for being a little slow.
Its bloody wordy


Well I think I see the air/oil separator...You may have cracked it husa. Doesn't mean that all the optional bits in the patent are actually on a race motor though, you'd only want the power producing stuff, the very green options can wait for a road motor.
I'm a bit dubious about the pumping diaphragm in a race engine...supercharging ?

[Flettner]

I've been playing with the idea of a cylinder with short runners inside a plenum around the bore in place of the regular vertical transfer passages, hope this is something similar - would make me feel kinda smart.

Good idea I think. Cast your own cylinder?

[adegnes]

Good idea I think. Cast your own cylinder?

Thanks! I want to when time/money/knowledge allows it, hopefully not in a too distant future.

[Frits Overmars]

Do as I did and look at the link you provided and search the patent application this morning...Its bloody wordy
http://www.google.com/patents/WO2013185802A1?cl=en Don't bother deciphering that patent; it's not the Ryger-patent. The Ryger engine is much simpler.

[husaberg]

Don't bother deciphering that patent; it's not the Ryger-patent. The Ryger engine is much simpler.

Thank God........
I have pieced a few things together though.


We do not work with a high supercharging but create a balance between the upper and lower side of the piston, thereby, inter alia, there is less resistance. Into a storage container
I have seen mention of Bellows or a bellowed chamber

Before the fuel-air mixture enters the transfer ports is the compressed once already. into the separate chamber?

The ryger is no oil combusted which you have already made considerable gains. separation chamber

Next point: your Aprilia consumed per revolution already sucked mixture volume of approximately 1.4 times the cylinder hold.
This was not due to the pumping action of the crankcase, but for the most part to the suction effect of the exhaust pipe. You remember surely have the test at Aprilia where a 52 hp engine, the exhaust pipe was disassembled. Then the ignition and carburetion were again perfectly tuned for the new pipe desperate situation, and the engine was measured again: 17 hp. A good pipe, the capacity thus tripling!
A sump pump can not, even if he pumped the double volume.


Also, the guiding of the piston is different so that the piston does not tilt. Scotch Yoke

There is talk of 20,000 revolutions but in my first tile to find the exact information.
With Luc we find a good solution to limit the speed at about 20,000 rpm max is 30,000 at the moment. Scotch Yoke

Indeed, we have a quick and clean stroke with an emphasis on clean and stroke is to keep alive. Leads me to Scotch yoke again

Our 125cc has 70 hp at the rear wheel at 17,000 rpm and a maximum of about 30,000 rpm at 80% less ppm. HC certified by the civil service and now homologated cik fia

What does that knowledge from you is an additional pump to create space under the piston separated from the crankcase space. Scotch yoke again

[speedpro]

Thanks! I want to when time/money/knowledge allows it, hopefully not in a too distant future.

I've thought of that as well. I was thinking of like a donut at a small distance from the cylinder fed by a supercharger and feeding ducts direct to the cylinder at the appropriate angles as now. My idea would be bulky but OK on a single. Crankcase or direct fuel injection of course.

Another thought I've had, about the 24/7 inlet, is that the 24/7 inlet does not have to be the regular reed inlet but could be additional. The little reed could feed the crankcase in some less preferred position and the 24/7 could feed the best location(s) seperately. Would require mamangement and fuel injection of course

[2T Institute]

312249312250312251



Never noticed these before
NSR500V the 500 twin Below the reed intake?

Blanking plates bolt over those holes to stop the water gushing out :msn-wink:

[Frits Overmars]

Another thought I've had, about the 24/7 inlet, is that the 24/7 inlet does not have to be the regular reed inlet but could be additional. The little reed could feed the crankcase in some less preferred position and the 24/7 could feed the best location(s) seperately. Would require mamangement and fuel injection of courseThank god, finally a remark that I can comment on without violating the Ryger non-disclosure agreement.
Yes, you could employ an additional reed. But why would you? The 24/7 valve itself is a reed; how much simpler do you want things to be?

[husaberg]

Blanking plates bolt over those holes to stop the water gushing out :msn-wink:

So its quite different than a RS250 set up then
312347312348312349
got any pics different than what I have here lozza
http://www.kiwibiker.co.nz/forums/album.php?albumid=4953
I thought I had others but I can't be arsed looking.



Thank god, finally a remark that I can comment on without violating the Ryger non-disclosure agreement.
Yes, you could employ an additional reed. But why would you? The 24/7 valve itself is a reed; how much simpler do you want things to be?
No need Frits..... Someone found the actual Patent today......... It was not me either. So no more questions........

[speedpro]

Thank god, finally a remark that I can comment on without violating the Ryger non-disclosure agreement.
Yes, you could employ an additional reed. But why would you? The 24/7 valve itself is a reed; how much simpler do you want things to be?

Real simple

My idea is that the 24/7 port simply has something like a guillotine in it, no reed. The off-pipe reed valve intake remains unaltered throughout engine operation. That way there is no difficulty removing the reed from the intake and maintaining nice port shape, just lift the guillotine and hello, perfect intake.

Actually it wouldn't be hard to make it variable cross-section. The minimum cross-section would be "0" or fully closed and max cross-section would be a full circle, or it could be in steps with the guillotine exposing various cross-section ducts in sequence until they are all exposed with their sum being a round tuned length duct. As with a rotary valve the guillotine opening edge would be profiled to provide certain opening characteristics.

[2T Institute]

I'm not an insider Nick but i can give you this.
The ryger engine has found a way round the age old problem off polluting two strokes.
They have altered the scavenging proces and in this development period spanning 10 years achieved the gain in performance we read today.
No doubt in my mind that the 70 hp is there. 😀
Diverting the exhaust puls to take advantage of the momentum from the puls. Channeld to be added to the intake event thus creating more scavenging volume.
I think judging from the various reply's arround the web. This is key in the engine mentioned.

a little snippet

[teriks]

This will probably drown in the Ryger stuff, but anyway, might lure Frits to say something since he cant comment on anything else ;)
Pipes for this season working good, pretty colors too.
312350

[adegnes]

This will probably drown in the Ryger stuff, but anyway, might lure Frits to say something since he cant comment on anything else ;)
Pipes for this season working good, pretty colors too.
312350

Pretty colors!
Same concept as this guys "torque pipe" it looks like:
http://www.dragonfly75.com/motorbike/bafflemod.html
http://www.dragonfly75.com/motorbike/images/Bext.jpg

What kind of results are you seeing with it?

[Muciek]

Pretty colors!
Same concept as this guys "torque pipe" it looks like:
http://www.dragonfly75.com/motorbike/bafflemod.html
http://www.dragonfly75.com/motorbike/images/Bext.jpg

What kind of results are you seeing with it?


This was already answered by Wobbly.


I have posted link to this in 2013
http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner/page853?p=1130623219#post1130623219

He did updated this exceel sheet few times, but dunno if this works , I tried to put there a pipe which I built for engine and I know how it works and outcome in graphs was way different....


Always amazes me when people make huge jumps of blind faith when trying to explain some fantastic " new " idea they have concocted.
The 50mm piece of tube added to the tailcone will of course smear out the timed return wave, but what was completely ignored was the tuned length is now 50mm longer.
I am sure I could make an even better power curve with a "proper " pipe design that was 50mm longer - if the engines powerband shape actually needed that in the first place.

The volume of the pipe is not something that can be used as a number to shoot for, what is important as Frits said, is the end use use of the finite energy imparted down the header from the
Ex port.
The fatter the belly, and thus the steeper the diffuser, the greater energy that is used to create a depression at the port around BDC.
Thus less energy can be used to create the stuffing pulse.
This can be countered somewhat by a steeper rear cone, and this is what does happen in reality, where I have seen huge 145mm belly 250cc pipes with 30* rear cones.
This approach means the rear cone length is reduced, but the steep angle gives at least some amplitude to the event.

I was sceptical when I was told about " Mr " VSK who worked at Rotax, as I spent several years when in England working at JL pipes trying to get to talk to this mythical pipe
designer - no one knew who actually did do the designs, so I never got to meet him.
But whoever it was, the two stage header was a feature of those later pipes, and must have been dyno tested in house, for them to have been published.
Every pipe I have run thru EngMod makes better power with that design so to me its a no brainer nowdays.

[adegnes]

Found the iame m50.
http://www.chi-motos.de/gambio/product_info.php?info=p1241_iame-cylinder-minimoto-50cc.html

Looks promising indeed!
On the downside it has a cast iron liner but that also makes for easier porting without the constant fear of flaking nikasil. It's not terribly expensive either.

310632310633310634310635310636


Here's a dyno run, performed by someone called "V-man Racing" from sweden, rw hp with the engine mounted in a minimoto.
http://www.minimotoscene.co.uk/forums/showthread.php?58120-New-IAME-Engine-by-Parilla
310637

The peak rpm numbers and graph doesn't match up, don't know what's up with that, either way it looks pretty impressive for an out-of-the-box fifty.
edit: the graph and numbers do match, I was just reading it wrong...
Am I right in thinking that with a pipe better optimized for peak power, sacrificing the massive powerband/overrev, and maybe paired with a rotary inlet and a bigger carb(suited for someone with a variator=me), this could really be something?

I'm exited, ordering one as soon as I can afford it.

Looks even more impressive(and confusing) after meassuring the port timing of this cylinder. Out of the box, 39.3mm stroke, I get 180° exhaust and 121° transfers! What?!


16.5hp from a fifty with that low durations?!

[Muciek]

Could You make a port map? Then someone could calculate it how much STA's it does have.

[adegnes]

Could You make a port map? Then someone could calculate it how much STA's it does have.

Consider it done!

[breezy]

a little snippet

so, they have used the exhaust pulse to increase the fuel or just air flow/charge into the engine, rather than just pushing a small charge back into the cylinder in the traditional way?

[teriks]

Pretty colors!
Same concept as this guys "torque pipe" it looks like:
http://www.dragonfly75.com/motorbike/bafflemod.html
<snip>

What kind of results are you seeing with it?
Looks can be deceiving, it's just a built in silencer on a "normal" rear cone. Performance is good though :)
Can't use the absorption type silencer in this kind of racing, the fuel is regulated to 80% Methanol + 20% Castor oil so the packing would be drenched in no time..

The colors tells a story about how hot the pipe runs, so it's a bit more useful than just being pretty.

[adegnes]

Looks can be deceiving, it's just a built in silencer on a "normal" rear cone. Performance is good though :)
Can't use the absorption type silencer in this kind of racing, the fuel is regulated to 80% Methanol + 20% Castor oil so the packing would be drenched in no time..

The colors tells a story about how hot the pipe runs, so it's a bit more useful than just being pretty.

Aha, I see!
I was going to ask about detonation problems with the dead straight pipe, but I guess the methanol is keeping it at bay.

[adegnes]

Could You make a port map? Then someone could calculate it how much STA's it does have.

Here's the port map, I couldn't find my pencil sharpener, and was tired so kinda rushed it - rough and not super acurate, but should give an idea of things. I cut out the ports from the paper I used to trace the bore and transfered the "holes" onto graph paper, with the blunt pencil it didn't turn out very good, oh well.

312352

Axial angles:
A = 25°
B = 7°
C = 55°

Radial angles:

312351

If anyone is bored and need something to pass their time...

[lodgernz]

Looks even more impressive(and confusing) after meassuring the port timing of this cylinder. Out of the box, 39.3mm stroke, I get 180° exhaust and 121° transfers! What?!

16.5hp from a fifty with that low durations?!

With those huge auxilliary exhaust ports and the conservative timing, it's going to have very good blowdown STA. As Frits and Wobbly have been saying for a long time, this is the most significant factor in an engine's performance. I'm guessing that's why it can rev so high to make that incredible power.

I don't suppose the make a cylinder for the NSR50 do they? :no:

[chrisc]

Looks can be deceiving, it's just a built in silencer on a "normal" rear cone. Performance is good though :)
Can't use the absorption type silencer in this kind of racing, the fuel is regulated to 80% Methanol + 20% Castor oil so the packing would be drenched in no time..

I'd be very interested in seeing how you built the internals of that silencer if you were happy to share.
Thanks for posting the photos. I love seeing where else 2 strokes excel in this world.

[adegnes]

I don't suppose the make a cylinder for the NSR50 do they? :no:

They only make it for their own engine, the m50.
But where there's a will there's a way!

[peewee]

hey guys i know you dont want to see this old junk but i have to show it anyways :bleh:. spent yesterday and today attempting to weld the back corners. it dont look real great but it should be fine after i dress it up. i had a hell of a time as it was the worst cast shit ive ever seen. pin holes all over and 20yrs of oil soaked in. those old yamaha cylinders weld like a dream compared to this one

[seattle smitty]

Peewee, you might know this, but don't ever clean up an aluminum casting by glass-bead-blasting if you plan on welding on it, or if you do, go over the to-be-welded area with a rotary file and skim off a little metal. Some of the glass bead will imbed itself in aluminum, and will drive a welder nuts; you can see the shiny bits under some magnification. Piston ring manufacturers have put out bulletins warning against cleaning up old pistons with glass-bead. (Have I said this here previously? Probably several times!).
:violin: