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Porsche 994 turbo trigger error

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Hi everyone, so I currently have a 944 turbo on my dyno and I am having a trigger error at 5000rpm. the vehicle is running a new Link G4+ storm and factory crank sensors, I have tried changing filter settings and arming voltages but neither help. The crank uses a 132 tooth pickup and a 1 tooth per tdc pick up. both are VR sensors and mounted very close to each other, I will put a trigger log up of when it is missing then the trigger error counter is increasing.

My main observation is that the voltage levels from the sensor are very high even at low rpm could this cause an issue??

thanks

Casey

Attached Files

As weird as it sounds check your ignition option dwell time at the point where the misfire occurs, I've seen some maps ramp up the dwell to the point it causes misfires usually around 5000-5500rpm

I have just tried moving the dwell either direction with no luck :( it seems to misfire earlier under no load

I have solved the issue by changing trig1 to hall/optical in the setup, the car starts and revs freely now but I am woundering if anyone can see any potential issues that may arise from this

thanks

Casey

The porsche 944 trigger system is pretty fussy at the best of times due to the high tooth count. When everything is in perfect working order it can and will give acceptable results, however all it takes is damage to a tooth on a flywheel or some runout on the flywheel and it can become problematic. even in good working order the factory trigger system will also limit you to waste spark/group fire too since the trig 2 input is also derived from the flywheel.

While it's a lot of work, I'd strongly recommend fitting a suitable aftermarket crank trigger system.

Had the same experience with the 944s I setup with MoTeC M4/M48 some time ago. Also check the air gap from the sensor to the tooth as I found this to be out often and it caused a missfire around the same rpm and setting it to the factory gap fixed the problem mostly.

We have had the same problem on a 944 Turbo with a Link G4+ Xtreme about two years ago.

The real problem was the flywheel itself. The original one seems to be fine, but if you try fitting an aluminum flywheel to those cars, you can see the whole voltage curve from trigger1 move up and down like a sine wave.

The sensor gap on the customers setup was also to large, and once we have dialed that in, it worked and the car revved fine to over 7000rpm.

But as it has already been mentioned, moving to a proper crank trigger is the real solution.

Sorry I forgot to update, After talking to Link when they opened up again. The problem was the sensor was being saturated due to the high tooth count, to solve this I started to taper Trig1 arming threshold down after around 3000rpm so the table now tapers up from 0.7v at 0rpm to 4.5v at 3000rpm then down to 1.9 at 7000rpm.

This seems to have solved the issue and I have had no timing drift or sync errors. Oh and it is set back to both sensors being magnetic with low filtering.

Thanks for the help guys :)