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1jz-vvti erratic rpm signal at higher engine speeds

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Hey guys, I'm hoping someone can help me out here.

I am tuning a 1jz-vvti engine on a link fury ecu. I am having an issue where the rpm signal is jumping from around 6,000 rpm to something like 12,000 rpm erratically. It only happens for a split second but it's enough to trigger the rpm limiter. It doesn't do it at the same RPM every time. It also only seems to do it under load. If I just rev the engine in neutral it seems to just hit the normal rev limiter. I put in a new crank sensor as well as a new cam sensor. The harness is a flying lead harness from link so the ecu side of the harness is all factory terminated and the sensor side looks solid.

I tried all the filtering levels in the software and none of them fixed the issue, some of them just made it worse. i also adjusted the trigger arming threshold tables in the problem areas with no positive response.

I have the cal file as well as a log of the rpm signal spiking if anyone would like to take a look.

Any ideas or have any of you had this issue? Any feedback would be greatly appreciated!

Thank you!

It sounds like you're just running into some triggering issues and my gut feel would be that the arming threshold is possibly set too low at higher rpm. I'd start by performing a scope capture up at higher rpm to see what the trigger inputs look like. A good rule of thumb is to set the trigger threshold at 1/3 of the peak voltage amplitude.

Thanks for the reply Andre, we did end up setting the thresholds up a bit higher then I did the scope I noticed the Cam sensor trigger was backwards so I flipped the wires and resync'd the timing and we were good to go. That explains why the vvti was giving me fits as well!

Thanks again!

Please attach a triggerscope, one done at idle and one done at say 5000RPM.

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