MoTeC Global Forum

Help require to trace very poor RPM signal of a Suzuki Hayabusa turbo installed in single seater race car. With 24-2 flywheel mag crank pickup and GT101 cam sensor.

The car has been running for serval years and has always has a poor idle varying approx. + 300rpm, last year due the noisy rpm signal the engine over revved by >1000rpm causing some mechanical damage to the engine. [ie the rev limit was set to 10,000 actual rpm reached approx 11,500rpm].

Please see attached, ECU config , ECU Log and , CRIP capture, note the rev limit was reduced to 3000 rpm to log over rev [ with out upsetting the neighbours!]

We have recent checked all the earth wiring, the ECU, Ignition amplifier, regulator, fuel pump etc, which are all earthed at one star point on the engine, we can send wiring diagram photos etc it that helps

Many thanks for any help on this

Steve & Dave

Do you have individual throttle bodies or a single throttle and intake plenum? If ITBs, I think you have a manifold leak, or the throttle stop is too high. I would expect 30-40 kPa maximum. 60 kPa is typical for larger intake plenums.

The RPM fluctuations seem to be similar to the MAP changes (so it's hard to say which is the cause / result since they are logged a very different rates. Any chance you can lower the idle RPM by closing the throttle or reducing the ignition timing to find a stable idle.

Your fuel map is very interesting in the idle area - have you tried ignoring the lambda and just tuning the operating area by ear -- see what it wants to run smoothly.

You could also try setting up idle control using just the ignition, so when the throttle was below 1%, the idle control ignition comp would try to remove the timing. You might find it idles smoother at 5 deg timing or less.

Hi David,
Thanks for your in-depth reply.
The engine is using the original throttle bodies with 1000cc injectors, there is plenum above these which the turbo feed in to.
The engine produces approx. 500BHP so I don't think there is any mechanical issues.
The poor/noisy RPM is through range, I was hoping if the idle was fixed, the higher rpm / over rev etc would also get fixed.
I assume the Ref/sync capture is filtered?, as I cant see any noise spikes in the trace.
So is it common for the Hayabusa to have a poor rpm signal? can a poor ECU config cause this issue, or is it more likely to be the wiring?
Cheers
Steve

From your .rsc trace it looks to me that there is a problem with the crank signal. If you look in any of the missing tooth gaps in the crank trace the waveform should go up smoothly to the next tooth. But it usually crosses in the rising direction through 0v then dips back under 0v before rising again, one of those zero crossings is likely causing a miss-trigger event.

Are the trigger wheel and sensor original? Does the waveform have the same pause/dip at cranking and high rpm?

The flywheel pickup is the standard Suzuki type with 24-2 tooth pattern.
would you recommend moving pickup further away to change the cross over?, or change the Ref MAG sensor filter in the ECU?

I don't have experience with that engine / ECU combination so maybe one of the MoTeC people can advise you of the best thing to do.

What is the spacing for the sensor from the trigger wheel? Normally that sort of signal issue occurs when the sensor is mounted too closely to the trigger wheel.