Ref/ Sync capture - occasional backfiring on crank

Discussion and support for MoTeC's previous generation ECUs.

Ref/ Sync capture - occasional backfiring on crank

Postby Natetune on Tue Aug 10, 2021 6:02 pm

I have been tuning and working my way through various issues on a dodge viper gen 2 engine that was already fitted with a Motec M800 ecu. These issues are wide and varied from poor power feeds to awful mapping.

It is now 90% sorted but I am struggling to get a clean and consistent start. Occasionally the engine pops or backfires through the inlet or exhaust. It sometimes does this when running too. I have checked all the physical causes, ht leads, plugs, coils, air leaks etc and the fuel/ignition timing seem ok. I suspect noise on the sync sensor.

Please can someone have a look at my ref/sync capture file and tell me if the noise I am getting is acceptable or likely to be causing issues?

Much appreciated.

Kind regards
Nate
Attachments
Viper V10 gen 2 tune file 10 08 21.e35
(72 KiB) Downloaded 107 times
running waveform ref and sync.rsc2
(64.45 KiB) Downloaded 106 times
cranking waveform backfire 3.rsc2
(64.45 KiB) Downloaded 106 times
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Re: Ref/ Sync capture - occasional backfiring on crank

Postby SDean on Wed Aug 11, 2021 10:54 am

Hi,

In the actual triggering voltage range for the signal it looks clean in these captures. There are a couple of small spikes above 4V but these are outside of the trigger range for the sensor.
Stephen Dean
MoTeC Research Centre Melbourne, Australia
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Re: Ref/ Sync capture - occasional backfiring on crank

Postby Natetune on Wed Aug 11, 2021 7:33 pm

Hello Stephen.

Thank you for your reply, much appreciated. I am certain there is something wrong with the ignition setup/ ref sync setup as the car backfires/ kicks back on cranking and sometimes spits flames on rapid acceleration. Everything else seems to check out ok. I Have checked the base timing with a timing light so know the CRIP is correct. The number of teeth per crank rotation was set to 20 when I began fault finding this car despite this actually being 10 per crank rotation. The engine ran and was being driven like this despite running poorly, I have checked the odd fire TDC angles are correct and the coil dwell. Do you have any suitable base settings/base map for the 96-02 viper engine to compare to?

Kind regards
Nate
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Re: Ref/ Sync capture - occasional backfiring on crank

Postby David Ferguson on Fri Aug 13, 2021 10:46 am

I suggest you verify the IGN expanders are wired to the coils in the correct firing order. With that many cylinders, it's easy to make a mistake, and yet the engine still runs.
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