Jumpy RPM Signal

[Greg E]

Other issues yes, mostly idle, certainly not jumpy RPM.

RPM on the ECU comes from pulses out of the CAS. Both you and B-Man have the photo style CAS. While I don't have the solution, that's where I would start looking.

BTW RPM from the tach side comes from the PTU.

[Toni]

OHHH RIGHT, I always forget that one. That must be why my innovate logs are smooth because it's getting rpm from PTU. Hmm I'll have to try logging the CAS separately and see if I can log noise. Could the timing belt be stretching/tightening causing the minor fluctuation since it's run off one cam?

[Greg E]

Nah I doubt that. More probable is the photo sensor itself is dying or the connector is crusty.

[B-Man]

Mmmmm, crusty connector.

Time for a custom wiring harness, Ant!

[Toni]

We'll see. I'll figure this rookie biatch out. Hopefully it's just crustiness. These damn things are expensive. Forgot that I setup a frequency generator to simulate these things (Greg do you remember why I was doing this lol?). Anyway, comes back to the ECU as a 0-5v square wave. I'll just log a run on my scope and see what the ECU is seeing and go from there.

[Greg E]

To test the frequency limit of the ECU.

[KeithMac]

Mines slightly choppy on the Emanage (ecu ignition trigger derived), the joy of the 1st gen cas (along with 2500rpm timing jitter..).

[Hans@GZP]

The dyno sheet won't be effected by the RPM crap you are seeing since it pulls it straight from a spark plug wire. Your curve is pretty smooth on my dyno. You should see the BRZ's that come in here LOL

[Toni]

Ahh, yup. Plotted the RPM in winpep and it's straight up. Also checked out the logs from the MAFT Gen II and they are jumpy. This uses the CAS for RPM so I don't see it being the ECU.

[Toni]

This is what the GEN II is seeing from the CAS