Timing jitter... ... ?

defiance · Post by **defiance** » Wed Aug 09, 2006 10:40 am

I've got some wierdness I'm trying to track down in the charger, and wanted to see if anyone here had any suggestions... Basically, the car is on a megasquirt V3 board, running MSnS-E 29q2, input direct from a locked MSD distributor VR sensor into the V3 board VR circuit. The output is driving an MSD-6A box with the circuit from the MSnS-E page. I've got the car actually running pretty well, but it has about 5* either way jitter in the timing. I've got the input trigger at 5*, If I set fixed angle output at 15*, it will jitter between 10* and 20*. RPM doesn't seem to make much difference. I know the distributor isn't the problem, because if I feed the 6A box the direct distributor VR signal, it is DEAD on (I can't see any jitter at all). Also, the tach signal seems very clean; it doesn't show any RPM spikes or wierdness...

Any idea what could cause this? I'm guessing maybe it's something in the VR circuit, but I don't understand how it could be inconsistent, but still hit every single time, you know?

Also, I know the polarity is correct because when I connect to the 6A box through the MSD harness (the harness is polarized), it fires at exactly 5*, as expected.

defiance · Post by **defiance** » Fri Aug 11, 2006 4:26 am

Any ideas? I'm still searching periodically, but haven't found anything

bleoh · Post by **bleoh** » Fri Aug 11, 2006 4:56 am

I don't have the same setup, but on mine the timing gets jumpy if I am not using the Last Algorithum (sp?) predictor.

muythaibxr · Post by **muythaibxr** » Fri Aug 11, 2006 7:14 am

that's only on ms2...

Try turning the VR sensor conditioner potentiometers on the V3 board all the way counter-clockwise.

64Vair · Post by **64Vair** » Mon Aug 14, 2006 11:19 pm

May be off base here, but any chance the reluctor has the polarity reversed going into the MS??? Perhaps if you switched the wires around it would make a difference?
Tom