So i recently trying to troubleshoot trigger noise problems in my FD, and ordered new trigger sensors. turns out my trigger thresholds were too low. I ended up hooking up an oscope at the ecu connectors to measure them. this is cranking rpm:



at cranking rpm, it peaks out at +4V. The noise im getting is almost +1V.. not exactly sure where the noise is coming from, could be the starter, since it appears to disappear when i release the key toward the end of the trace

I also probed the sensors while running, and at idle the voltage peaks at +8V (over 15V peak to peak!), and increases linearly to about +15V (over 30V peak to peak!) at 7000rpm. I tried incrementing trigger threshold at idle until it died, and sure enough it was around +7V. so.. not sure why we set our thresholds so low. haltechs basemaps have it set to 0.25V at idle to 3V at redline

based on these measurements, i would suggest you can go at least as high as 2V at idle to 10V at redline. it gives you better buffer to keep you out of the noise. im currently running 2.5V at 0rpm, linear to 5V at redline with no more problems

note.. after you change these settings, you probably want to re-zero your timing just in case it moved slightly due to triggering on a slightly different point on the voltagecurve. although mine didnt move much at all

 

im not sure why i didnt have this problem with my old trigger sensors, since they worked fine at a threshold of 0.25V. Maybe they loose gain over time, and the new sensors where able to pick up more noise.

anyway, an easy way to find the peak voltage without an oscope is while the car is idling, increase the trigger threshold voltage until it stalls. divide that voltage by 3, and that would be a good starting point for idle threshold, then double it for redline, and linearize between

 

just heard back from haltech aus, i asked them how the older ecu's trigger settings work on the e6k and e8.. apparently the "filter" setting isnt really a filter.. it is actually setting the threshold. so based on that, on the older ecu's you want to set filter to high as possible without missing teeth during crank. if it works at crank, it will work at any higher rpm, since the signal will only get bigger from there, and higher "filter" setting will give you more buffer away from noise

 

What trigger are you using? Stock FC CAS?

EDIT: Sounds like they're aftermarket triggers, nevermind!

 

factory FD, but FC CAS puts out a signal very similar

 

today i measured fc cas output, definately a lot lower than the fd. threshold voltage setting needs to be more like 0.4v at cranking, linearize to 5v at redline
for fc

 

the FC and FD CAS's have way different impedance. i wanna say the FD is high, and the FC is low.

there was a point where i tried to run an FD engine with an FC ecu, and it doesn't work, although we know it works fine the other way

and now we know why! neat