ESE's works engine tuner

[WilDun]

So did my Toyota Camry

Didn't Yamaha design the heads for Toyota?

[TZ350]

Didn't Yamaha design the heads for Toyota?

Yep, I had a twin cam turbo Toyota whose head had Yamaha on it so I guess Yamaha designed and actually made them too.

[husaberg]

Didn't Yamaha design the heads for Toyota?

Yep, I had a twin cam turbo Toyota whose head had Yamaha on it so I guess Yamaha designed and actually made them too.

They have a long history of designing not just heads but even complete engines for Toyota starting with the Toyota 2000 GT in the late 60's
Which was borrowed back by Yamaha to create the XS650.

[TZ350]

Looks like you have a fair bit of lash in the drivetrain with the engine speed jumping around like that.

Yes, true.

At 15% throttle it looks like the switching between the small and big injector is causing the misfire, possibly injector settings are a bit squif and when it switches over it jumps richer or leaner. Is it just a straight RPM switchpoint with no hysteresis?

Switching is determined by setting a minimum injector closed time that way you can more or less chose where the switch will occur depending on load/rpm and then there is an adjustable upper and lower ms value for hysteresis. I have been trying to have the small injector doing all the off pipe stuff.

At 50% throttle it looks like it's going too rich as the revs climb and pulsewidth goes up, then stops firing, revs fall, pulsewidth drops, then it kicks on again.

Very good point, I will look carefully at this when I get back to the dyno again.

I think the problem is in fuel delivery not gas dynamics. Guessing it doesn't do it with the carb? Food for thought.

It was definitely gas dynamics in the plenum with its short inlet. Wet fuel was blown out past the front wheel. But I guess that does not mean this is the same issue with the EFI system. But they both had the same blubbering symptoms before coming on the pipe.

Also there is a big lambda delay on these things off the pipe and it always swings lean when misfiring. Is the motor on the rich limit/four stroking? Your lambda values look ok, but they can appear lean when air is short circuiting the motor.

Yes it can be so rich that the lambda shows lean. I can see short circuiting, misfiring and four stroking will all show lean. The less effective the trapping efficiency the leaner the lambda will show even though the air/fuel ratio is correct.

I agree, clearly lambda needs to be interpreted a bit, depending on where in the power curve you are looking.

My motor has a 'rich' point between 4500-5500rpm, 50% throttle and up. I think it's the anti-resonance point of the pipe. Shows the same 12.6:1 AFR as other points but its on the verge of four stroking, heaps of blue smoke, similar to how 10.8:1 behaves (which is about the rich 4-stroking limit on mine when on the pipe).

So i've tuned that area to be about 1.5 points leaner. I am yet to do a plug chop at that point to check, I'm yet to do any plug chops actually, luckily the YZ isn't too picky on mixtures.

Also the VE table is starting to look how I would expect, a lot more natural and smooth, apart from the weird anti-resonance peak. Maximum injector duty cycle of 80% at 9200rpm, full throttle.

The anti-resonance rich point has always been there with my EFI efforts to a greater or lesser degree. I would have thought the power valve would have countered it but that does not seem the case so that is why my thoughts turned to the inlet resonance.

Interestingly things improved when the small injector on time was as wide or wider than the transfer open time. And injection end time was important, I guess so the injection squirt time covered the transfer window.

In the anti resonance area the closer to lambda 1 I got the richer the exhaust sounds.

Lots for me to think about, thanks for your input.

[Martin1981]

This Mazda 787B had an exhaust silencer, deemed necessary even by the most seasoned enthousiasts.

Oh this R26B...Hell of an Engine! Somebody once said it sounds like an f1 engine on steroids Imagine the sound if it could rev to 15000rpm or so....Frits, why does it only rev to about 9000? Is it because of the complicated Way the "pistons" have to go in the wankel engine in comparison to the simple up and down moving in a normal engine?

[Frits Overmars]

Oh this R26B...Hell of an Engine! Somebody once said it sounds like an f1 engine on steroids Imagine the sound if it could rev to 15000rpm or so....Frits, why does it only rev to about 9000? Is it because of the complicated Way the "pistons" have to go in the wankel engine in comparison to the simple up and down moving in a normal engine?

I 'd say the rotors in a Wankel move in a more straightforward way than the reciprocating pistons that we have all become used to.
A Wankel's revs are limited by flame speed; the combustion chamber has a terrible shape with end pockets everywhere and a flow constriction between the two spark plugs. Moreover, the chamber's bad surface/volume ratio is responsible for a lot of heat losses and an unhealthy fuel appetite.

Apart from that, I love Wankels. They may be four-strokes but they sure know how to open their exhaust ports with a bang; not like those poppet valves that open with an initial velocity of zero, but like a two-stroke that opens its exhaust port with maximum piston velocity. Hence the strong useful pulses and the glorious noise.
I've even got a works racing engine. Not the four-rotor B787B (I wish!) but a twin-rotor 13B turbo for touring car racing. The turbo doubles as a fairly effective silencer. Just as well...


The small intercooler in the pictures is the standard hood-mounted RX7 cooler; just substituting it with a larger front-mounted intercooler brought 60 hp more.

[oldjohnno]

...I've even got a works racing engine. Not the four-rotor B787B (I wish!) but a twin-rotor 13B turbo for touring car racing. The turbo doubles as a fairly effective silencer. Just as well...

I always thought the turbo's primary role was to catch the bits of apex seal...

[WilDun]

Yes they were certainly interesting and had some good qualities like no reciprocating forces (ie no piston reversals, also smoothness) but the disadvantages mentioned outweigh all this and I think Mazda have finally acknowledged it.
I can remember (all I do these days is remember!) driving home from work and knowing that there was a Mazda Rotary up ahead even though I couldn't see it! probably much more pleasant driving behind a Trabant!
It's a pity really but as I said earlier lets get back to our little old two strokes and develop them more (in the bucket scene), the "simple" two stroke probably has a brighter future, but that's still a bit difficult to predict through the "haze"!

[Nath88]

Took the bike for another ride last night. Leaned it out a fair bit in the high load areas, a little in the cruise range, and a bit past peak rpm. Made the bike very happy! Was going to be a short one but ended up cruising around the streets for about half an hour because it was running so well, bike never missed a beat. 'Lean' cruise is a funny feeling, it's very smooth, like a scooter, then when you open the throttle it just rolls into normal YZ250 in every way.


The VE table ended up looking like this, load areas tuned by wideband lambda feedback.


This is the exhaust pressure system in action. Just before the cursor position, I blipped the throttle to 20% and the motor didn't respond (no exhaust pulse = no fire), that's the area I need to work on the most, probably a bit rich at closed throttle at that RPM, lambda offers no useful feedback so it has to be tuned by feel. After the cursor, when opening the throttle to 20% for a little longer, the motor has time to clear, then the injector pulsewidth more or less follows the exhaust pressure. You can see it four-strokes a bit then runs clean. Then opening the throttle to 15% goes into constant light throttle four-stroking, again, fuel following the exhaust pulses.

[F5 Dave]

I 'd say the rotors in a Wankel move in a more straightforward way than the reciprocating pistons that we have all become used to.
A Wankel's revs are limited by flame speed; the combustion chamber has a terrible shape with end pockets everywhere and a flow constriction between the two spark plugs. Moreover, the chamber's bad surface/volume ratio is responsible for a lot of heat losses and an unhealthy fuel appetite.

Apart from that, I love Wankels. They may be four-strokes but they sure know how to open their exhaust ports with a bang; not like those poppet valves that open with an initial velocity of zero, but like a two-stroke that opens its exhaust port with maximum piston velocity. Hence the strong useful pulses and the glorious noise.
I've even got a works racing engine. Not the four-rotor B787B (I wish!) but a twin-rotor 13B turbo for touring car racing. The turbo doubles as a fairly effective silencer. Just as well...


The small intercooler in the pictures is the standard hood-mounted RX7 cooler; just substituting it with a larger front-mounted intercooler brought 60 hp more.

Sorry Frits you seem to have posted the wrong photos. That appears to be a helicopter crash.

[Frits Overmars]

I see what you mean Dave. A bit clumbered, isn't it? But if you remove everything that you don't need for racing, what remains is a very compact engine.

[F5 Dave]

I helped move a 12A (I think thats what they are called) across the garage floor. It was like the rest of the car was still attached.

[Peter1962]

I helped move a 12A (I think thats what they are called) across the garage floor. It was like the rest of the car was still attached.

That can be fixed. Racing Beat is producing aluminium housings and flywheel. http://www.racingbeat.com/RX7-1975-1...-Housings.html Saves 50 to 60% of the weight of the original cast iron housings.

[breezy]

Frits, can you tell me what type and name of race fuel was actually used in your world champion winning aprilia 125 race bikes. thanks, nigel.

[Peter1962]

Frits, can you tell me what type and name of race fuel was actually used in your world champion winning aprilia 125 race bikes. thanks, nigel.

breezy, I don't think that Jan Thiel will feel OK with the assumption that he is not the father of the winning aprilia 125.