Syvecs Forums

I'm mapping my car and hitting what has the symptoms of a rev cut at high RPM. But before the rev limit.

I'm not seeing anything untoward in the logs, no limp mode, no trips and its staying in 720 sync.
But the logs do show revCutActive coming on and off repeatably after 5000 rpm. The logs show that the rev limit is 7200 and that the rev limit active is always idle.

I just don't know why the ECU is enabling revCut.

Any help would appreciated, at the Dyno now.

I've increase my rev limit on everything to 20000 and it's fixed the issue.

Any ideas what's going on

log it and see.

it should state the reason for any limiters or cuts if logging the right things.

And without any logs/cal to see...anyone here will be guessing.

and rev cut and rev limit are two separate features.

Understood, I was a little flustered earlier as I was on the dyno.

Here is a log of the event.
Thanks for looking.

I can see it very intermittently becoming active around 5k, but as you say, it is logged as cut at being 7200rpm.

No limps or trips or anything though, very strange.

In fact...viewing again, the entire time above 5100rpm, both on and off load revcutactive is repeatedly switching between idle and active, even though rpm trace seems reasonably smooth above this level, although perhaps not quite at 5100rpm.

Definitely no cal switch reductions or something for the rev cut ? although it isnt actually being a full rev cut...because it isnt staying active.

No rev reduction is set on any of the cals.

Rev cut was set to 8450 and rev limit set to 8000.
When I set all limits to 20000, so RevCut, RevLimit, all limp mode RevLimits, then the problem went away and I was able to continue mapping on the dyno.

I'm going to re-introduce the rev limit and then the rev cut and see when the issue re-appears, I'll report back on that.

I found on my GR Yaris that if rev cut was set to either instant cut on fuel/ign (I think also with a instant rpm detection) it would randomly pull injection pulses at certain engine loads / rpms. Went mad trying to find the cause. You could see injectors being cut on high speed logs but no trqfuelsrc indications. I think that on certain engines, harmonics tell the ECU RPM is varying wildly within one rotation. Instant RPM detection measures every 60degrees or something. When I set rev cut back to no instant cuts and average rpm detection.....all good!