ESE's works engine tuner

[katinas]

All pistons, from Rygerised to RGV, made from the same 2618 T6 alloy. I like to made them from lower linear thermal expansion 4032, but cant get rod easily. With 2618, more clearance needed.

Honda for GP racers pistons used EN AB 48000 ( add pdf ), for cylinders EN AB 46200 http://www.trimet.cz/en/sv_EN_AB-46200.php
https://ntrs.nasa.gov/archive/nasa/c...9990019483.pdf
http://blog.jepistons.com/2618-vs.-4...al-differences
http://www.aluminiumbozen.com/en/cms/54/4032.html

Add two photos of the same piston for NS cylinder that changed through two years of testing and ended with fallen spark plug ceramic

[MotleyCrue]

The picture of the F750 exhaust back on page 2199 shows the merge point of the exhaust from adjacent cylinders quite a long ways from the port, to make the 4 into 2 exhaust. I don't know much about that engine, but my question is not about that engine. My question is about where the ideal location is to make the merge on a normal twin cylinder engine. On twin cylinder engines it was my understanding that a 2-1 exhaust should have the merge as close as possible to the engine without making crazy bends. But what would happen if the merge was not until way down the exhaust say near the end of the diverging section, in a case where the rules demand a 2-1 exhaust but are not specific. No merging at the stinger is not an option, that would get tossed out for sure. Would making the merge much farther along the exhaust be better, or worse than making it close to the engine ?

Also if the best location for the merge is deemed to be right after a short length of head pipe, is there a best angle to merge the two head pipes into one and ideally how much bigger should the single pipe be than the individual pipes right at the merge? 50% bigger in area ?

[Muciek]

Maybe those photos will help somewhat with your question. It was designed way back (by Kevin Cameron for Daytona) but it worked. Next option would be spending some time with Engmod...
http://www.natsforum.net/viewtopic.p...tart=290#p3252

[husaberg]

Maybe those photos will help somewhat with your question. It was designed way back (by Kevin Cameron for Daytona) but it worked. Next option would be spending some time with Engmod...
http://www.natsforum.net/viewtopic.p...tart=290#p3252

Cameron used second hand rusty sheet steel for his as it was all he had about at the time. Its mention in a TDC in CW or the book or both
Some art lady wanted to exhibit it as artwork.
click three times

[MotleyCrue]

Maybe those photos will help somewhat with your question. It was designed way back (by Kevin Cameron for Daytona) but it worked. Next option would be spending some time with Engmod...
http://www.natsforum.net/viewtopic.p...tart=290#p3252

Thanks for the link. I would guess that it doesn't work on twins and that's why no one uses it, just thought that Wobbly or someone might have tried it or knew of someone that did and knew what the results were. I guess what I'm saying is that I'm not trying to re-invent the wheel (Engmod etc.) the factual knowledge is surely already out there.

[diesel pig]

The picture of the F750 exhaust back on page 2199 shows the merge point of the exhaust from adjacent cylinders quite a long ways from the port, to make the 4 into 2 exhaust. I don't know much about that engine, but my question is not about that engine. My question is about where the ideal location is to make the merge on a normal twin cylinder engine. On twin cylinder engines it was my understanding that a 2-1 exhaust should have the merge as close as possible to the engine without making crazy bends. But what would happen if the merge was not until way down the exhaust say near the end of the diverging section, in a case where the rules demand a 2-1 exhaust but are not specific. No merging at the stinger is not an option, that would get tossed out for sure. Would making the merge much farther along the exhaust be better, or worse than making it close to the engine ?

Also if the best location for the merge is deemed to be right after a short length of head pipe, is there a best angle to merge the two head pipes into one and ideally how much bigger should the single pipe be than the individual pipes right at the merge? 50% bigger in area ?

Your best bet is to look into snowmobile and jet ski tuning web sites as some of them use twin engine single pipe set ups.

[wobbly]

Trouble is we are seeing engines with 2:1 pipes that are pairing different cylinder phasing.
There are the 180* firing pairs , and pairs firing together.
Trying to deuce what " works " is thus a nightmare.
All I know is that I spent months in EngMod trying to logically work thru the possible combinations for a Yamaha fan cooled 180* twin used in a miniature aircraft.
What I leaned was that huge Ex port duration's are mandatory , short Y headers work the best , and finally , that no matter what you will never approach the power of individual chambers.
You can " cheat " the system by having the Ex port bottoms open with the pistons at TDC , but at the time I did this we were using pumper carbs.
Fuel injection would work - carbs I seriously doubt it.
Jet skis use 2:1 for simplicity of packaging and cost.But they can recover alot of the lost power using clever water injection strategies.
Not much help I know , but thats all I got.

[MotleyCrue]

Trouble is we are seeing engines with 2:1 pipes that are pairing different cylinder phasing.
There are the 180* firing pairs , and pairs firing together.
Trying to deuce what " works " is thus a nightmare.
All I know is that I spent months in EngMod trying to logically work thru the possible combinations for a Yamaha fan cooled 180* twin used in a miniature aircraft.
What I leaned was that huge Ex port duration's are mandatory , short Y headers work the best , and finally , that no matter what you will never approach the power of individual chambers.
You can " cheat " the system by having the Ex port bottoms open with the pistons at TDC , but at the time I did this we were using pumper carbs.
Fuel injection would work - carbs I seriously doubt it.
Jet skis use 2:1 for simplicity of packaging and cost.But they can recover alot of the lost power using clever water injection strategies.
Not much help I know , but thats all I got.

180 firing pairs is what I was thinking of. Since the power is not as high as with individual pipes. snowmobile and jet ski engines sites don't seem to really have a lot to offer, not at the level that is normal on this site. Assuming a short Y header is there any sort of rule of thumb as to how big the single pipe exiting the merge should be?

In a way it would seem like at the merge the cross sectional area of the single pipe should be equal to the cross sectional area of pipe 1 and pipe 2 summed up, but then with a different train of thought it seems like maybe the cross sectional area of the single exit pipe should be the same as just one individual pipe at the merge. I think in practice people have the cross sectional area of the single pipe as somewhere between 1 and 2 times the cross sectional area of one individual pipe, but there must be an optimal value or range I would guess?

[Haufen]

Happy New Year to everyone!

Anyone else going to attend the two-stroke engine conference in Paris mid February?

2-stroke engine conference

Edit: you can also download the 2018 presentations here

[husaberg]

Geoffrey Cathcart
Chief Technology Officer at Orbital Australia Pty Ltd
Perth, Australia

[jbiplane]

We saw exist V engines where angle beetween cylinders differs from 90, says 112 with 24degree pins offset.
Just curious may be says 168 degree boxer will be a bit less violent engine than 180?
Then it will be a bit shifted ignition in both cylinders less crankshafl loads and probably smoother torque?

[wobbly]

That idea may , just may have some technical merit , but trying to package a 168 V 2T into a real bike would way offset any advantage gained by the configuration itself.

[Vannik]

Does anyone have the crankcase volume or primary compression ratio for a Maico 440? And is it inclusive or exclusive of the transfer port passage volumes?

[flyincat]

The picture of the F750 exhaust back on page 2199 shows the merge point of the exhaust from adjacent cylinders quite a long ways from the port, to make the 4 into 2 exhaust. I don't know much about that engine, but my question is not about that engine. My question is about where the ideal location is to make the merge on a normal twin cylinder engine. On twin cylinder engines it was my understanding that a 2-1 exhaust should have the merge as close as possible to the engine without making crazy bends. But what would happen if the merge was not until way down the exhaust say near the end of the diverging section, in a case where the rules demand a 2-1 exhaust but are not specific. No merging at the stinger is not an option, that would get tossed out for sure. Would making the merge much farther along the exhaust be better, or worse than making it close to the engine ?

Also if the best location for the merge is deemed to be right after a short length of head pipe, is there a best angle to merge the two head pipes into one and ideally how much bigger should the single pipe be than the individual pipes right at the merge? 50% bigger in area ?

I'd look at snowmobiles for latest and greatest design for twins. Just about everything for the last 15+ years has been parallel twins (180* firing) with 2:1 single pipe.

The example, below, is the way NOT to design a y-pipe. This stock OEM design was one of the worst in modern two stroke snowmobiles. Speculation chalked the poor design up to noise/emissions regulations dictating the less than stellar design. It's interesting to note the indented area on the top and bottom, likely trying to maintain cross sectional area at the merge. Quite a few OEM y pipe designs have similar indents.



Below is an aftermarket replacement for the above poor stock design. This design is known to gain a quick 6% HP! Interesting to note is the generous bend going into the outlet....much larger radius than the stock design. Also, the indent is removed, top and bottom. I'm not sure if the indent removal has much effect or was left out for fabrication reasons.



Finally is another aftermarket design, below. This has similar gains to the other aftermarket unit. The biggest difference here is the much longer runners and even straighter angle into the outlet.



I would guess the Stock design loses major pipe energy at the merge into the single outlet with the steep angle, much greater than 90* between the legs at the merge.

[dutchpower]

Does anyone have the crankcase volume or primary compression ratio for a Maico 440? And is it inclusive or exclusive of the transfer port passage volumes?

820 cc incl.transfer