ESE's works engine tuner

[Frits Overmars]

hey frits what about widening the port as much as logically possible before raising the roof to the clouds . perhaps rtech power loss is from the power stroke being reduced a bit to much, which seems like it would mean less cylinder pressure at exh open and less pressure differential between cyl and pipe, (less suction and plugging ) ?

In general widening any port trumps raising it, but widening the exhaust port will also increase the risk of short-circuiting, especially with those H2-transfers.

I don't follow your reasoning about reducing the power stroke. Raising the exhaust roof means opening the exhaust port earlier, when the cylinder pressure is higher, generating stronger pipe action.

[jonny quest]

In general widening any port trumps raising it, but widening the exhaust port will also increase the risk of short-circuiting, especially with those H2-transfers.

I don't follow your reasoning about reducing the power stroke. Raising the exhaust roof means opening the exhaust port earlier, when the cylinder pressure is higher, generating stronger pipe action.

And that's why you fill in the A ports with epoxy by the ex port to shape them like modern A ports. A right trapezoidal shape.

[peewee]

frits if the spark lead is at 15atdc there must be a limit to how high the port could be. otherwise going beyond the limit, wouldnt the egt go down because the port opens before combustion gets far enough along ? and cyl pressure goes down as well because again , combustion process is still to early. thus less pressure difference between cyl and pipe ? maybe rtech is already beyond the limit

[TZ350]

... if the spark lead is at 15atdc ...

15 deg ATDC. is that a realistic thing???

[Grumph]

15 deg ATDC. is that a realistic thing???

You wouldn't think so - But Irving quotes the range of movement given to outboards with coupled throttle and ignition controls as varying from 35deg before to 10deg after TDC...So special circumstances can alter cases. But not, I would think, on an H2.

[TZ350]

.
Took the GP/NSR110 beast apart tonight. Been getting hot. It happens when you forget to turn the fan's on ......

I am impressed by the way this thing survives a good overheating.

Also, reeving it way past its blow down limit with excessively retarded ignition and lean mixture looking to get big over rev did not help. Plenty of burnt goo in the transfers. With EFI and its precise fueling I was able to extend the over rev way past anything I have been able to do with a carb.

I just love this engine, its a real trouper.

[HenkS]

rtechracing,
If you don't get the right information, I'm ready to make the right calculation for you.
Which will show exactly what is wrong, but only directly and without any information to this forum.

I would definitely try it
But I hope that you will post the result here anyway

[peewee]

15 deg ATDC. is that a realistic thing???

i meent btdc

[TZ350]

You wouldn't think so - But Irving quotes the range of movement given to outboards with coupled throttle and ignition controls as varying from 35deg before to 10deg after TDC...So special circumstances can alter cases. But not, I would think, on an H2.

With my water cooled Beast I have a range of 28 BTDC to near zero to get heat in the pipe, but I am not to sure its that good for the engine.

[TZ350]

Finding your optimum ex duration is easy. Start at 190 degrees, dyno, go to 191, dyno, 192, dyno... until things get wacky. Easy ;P

Did this on the air cooled engine and the interesting thing was, that the difference between ultimate "good" and "wacky" was about the thickness of one 0.5mm cylinder base gasket. For my engine, 200 deg Ex duration = good, 204 = wacky. Take the base gasket out and we are back to good.

[jonny quest]

Did this on the air cooled engine and the interesting thing was, that the difference between ultimate "good" and "wacky" was about the thickness of one 0.5mm cylinder base gasket. For my engine, 200 deg Ex duration = good, 204 = wacky. Take the base gasket out and we are back to good.

Yep... it's a very fine line when you get there. And then when you first get in the "wacky" zone... you mess with transfers to see if power starts to come back.

[Frits Overmars]

Frits, you talked about how the blowdown requirement was different for methanol / ethanol engines, once. Model aircraft engines. Or was I mistaken?

Sorry for my late reaction Neil. Somehow I must have overlooked your question yesterday.
The blowdown requirement for those model engines is not different because of the fuel, but because of the way it is distributed (relatively big blobs), because of the very short time available for evaporation and because of the dreadful glowplug ignition.
Because of all these factors the combustible mixture in these engines needs to be preheated by way of Exhaust Gas Retention. If you give them a 'proper' blowdown,
they become very temperamental. And in a glowplug engine without permanent external heating one missed firing cycle can mean a total engine stop and a lost race.

frits if the spark lead is at 15atdc there must be a limit to how high the port could be. otherwise going beyond the limit, wouldnt the egt go down because the port opens before combustion gets far enough along ? and cyl pressure goes down as well because again , combustion process is still to early. thus less pressure difference between cyl and pipe ? maybe rtech is already beyond the limit

You had me searching for quite some time: "Where on earth did I write 15˚ aTDC?" But that has been cleared now.
Nevertheless your original question deserves a reaction.
WOT combustion may take somewhere between 43˚ and 60˚. Ignition delay is the time or the number of crankshaft degrees between the occurence of the ignition spark and the first instant when a temperature and a pressure rise because of combustion can be observed.

I took the values of the Aprilia RSA and a more mundane 125 cc engine for comparison.
Power @13000 rpm . . . . . . . . 54 . . . . . . . . . . . .40
ignition timing bTDC . . . . . . . .14˚ . . . . . . . . . . .18˚
ignition delay. . . . . . . . . . . . . .7˚ . . . . . . . . . . . .9˚
combustion duration . . . . . . . 46˚. . . . . . . . . . . 60˚
combustion completed aTDC . .39˚ . . . . . . . . . . .51˚

You can see that, even for the relatively slow-burning 'mundane' engine there is no combustion any more at 51˚ aTDC.
Its exhaust timing would have to be at least 260˚ before you could hope to see a glipse of a flame in the exhaust port.

... the difference between ultimate "good" and "wacky" was about the thickness of one 0.5mm cylinder base gasket. For my engine, 200 deg Ex duration = good, 204 = wacky. Take the base gasket out and we are back to good.

Did you keep the compression ratio and the squish gap constant during these gasket changes? Changing the squish gap 0,5 mm can have the same effect as changing the ignition timing several degrees.

[SwePatrick]

because you are very good at that.

*lol*, that means we guessed right

[lucf]

I would definitely try it
But I hope that you will post the result here anyway

Yes, you will see, were many other needs much text bla..bla (good or bad)
I need only one calculation and tell him exactly what to do.
I did this in the past years more than 1500 times, one of them was a super kart:

TM K9c in the European Cup Superkarts at Hockenheim, april 2012

The experiences of a team that rides for the European Superkart Championship. Rider Fokko Zoutman in a kart with two 125cc TM K9c motors, one at each backwheel. No usual setup, but proven effective. The team asked me in the end of 2011 or improvements are possible, on standard factory concept initially for the exhaust and combustion chamber. In the calculation I soon discovered that, oddly enough, the original factory exhaust was not optimal for the cylinder, so the answer was soon ready. Also a significantly improvement to the combustion chamber was possible. Actually I found that the cylinder itself should be updated too, but one wanted to keep it unchanged at that moment.

feb 17, 2012 (after approx 2 months)
Hi Luc,

We have already tested on a short runway kart engines at circuit Pottendijk. This was a good test. On the long course, it may be different of course. Full throttle for much longer straights. We will see. I keep you informed what will happen. Greetings, Henri Tiben

April 20, 2012
Hello Luc,

Still getting better. The rider is now a European Championship race in Hockenheim. We can take on with the fastest speed in the whole field. The driver should be a little better, but that is on the driver. It's been laughing about how they talked in the padock that he can just have it right away by the fast guys. Greetings, Henri Tiben

One calculation . . . . ! (no bla bla, no gessing ! )

[Frits Overmars]

. Took the GP/NSR110 beast apart tonight. Been getting hot. It happens when you forget to turn the fan's on .. I am impressed by the way this thing survives a good overheating.

So it didn't seize and the piston crown didn't cave in, but how about the piston ring? I've seen engines that ran hot with no apparent ill effects, only they were a pig to start afterwards: the piston rings had lost much of their tension.