7mgte CAS sync loss

[nathaninwa]

Hey guys, had this running on the drill great, but now in the engine I'm getting sync loss like no tomorrow, reason number 11 (to few teeth before second trigger) Once above about 1000rpm the loss gos away. Ive tried a shunted 1k on both crank and cam, and a 10k inline on the crank. This is on a ms3Pro, big block chevy with a 7mgte cas sitting ontop the dizzy

but this engine is running and shows no sign of the sync loss

Any more ideas? Ill try a 1K inline in the morning sometime tomorrow

I didn't properly save the composite and tooth log Ill get those tomrrow

https://youtu.be/S2uw2qTjffo

Edit,just found the cross talk filter, I'll try this tomorrow as well

[nathaninwa]

OK got some logs today. Turned on the nippendso filter with the 10K inline and 1k shunted on the crank signal. Sync loss is still present, but only at the 1000rpm range. Below that at 650rpm idle there is no loss and above that there is no loss

[slow_hemi6]

Can you grab composite and sync loss logs. I would like to see what the cam tooth is doing.

[nathaninwa]

here are the logs Ive put 60 miles on this truck now towing a trailer around tuning the engine and tranny, sync loss doesn't seem to affect anything? Its worth noting, the CAS is mounted to the dizzy Ill bet with some chain slop, but its fixed housing so it should rotate all together

[slow_hemi6]

Might be worth while trying some noise filtering/Period rejection on the Secondary Tach(cam) as there is some noise on it.

[nathaninwa]

Could adding a 1k shunt resistor help with that before I start messing with the noise filter?

[nathaninwa]

So I turned on cam filtering. Used a 500usec time and the sync loss counter has slowed way, way down.

[slow_hemi6]

Here is bad on the left, you see the 2 noise pulses, Vs good on the right.

Screenshot (38).jpg

Keep in mind how slow a single tooth at cam speed is. The good gap is 25.3mS @ the 1070rpm shown here. The noise pulses here are around 1.6mS so a noise filter period for you would be more like 1800uS. You would have to be pulling over 11Krpm for the main/normal cam signal gap to be pushing that 1.8mS filter anyway.

[suberimakuri]

Wow, that's awesome slow_hemi. I never spent the time to figure out how to use it before. Thanks.

[nathaninwa]

Messed around with this some more today. Added time to the noise filter and though it would get better, nothing really remedied the problem, went as high as 4000usec in 200 increments

So I went to the trusty resistors again. Leaving the 10k inline and 1k shunted on the crank signal I tried a 10k inline on the cam and it went back to counting like a clock in sync loss

So I moved the 10k to the shunted position on the cam wire and went back to 1800usec on the noise filter and now I only get a single sync loss during cranking, while running there are no more issues