VEMS Tuning Issue - breakup above 4k RPM

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VEMS Tuning Issue - breakup above 4k RPM

Postby jretal » Sun Sep 30, 2018 7:34 pm

Hey all,

So, after my little bit of a fiasco leading up to (crashed 034 Ic ECU updating to latest firmware and deciding to just upgrade to VEMS and rewire the harness in a day) and continuing at Carlisle trying to get my car tuned, Marc was able to get my car tuned fairly well given that we weren't able to rev over 4K rpm b/c of a trigger error (60-2 wheel on the crank pulley that no matter how I adjusted it wouldn't keep signal).

For amusement - FLAMES! :guns:

That being said, after swapping over to the OEM trigger sensors in the bell housing after Carlisle (courtesy of Marc), I've finally had time to take the car for a few rips.

Unfortunately, I'm still getting breakup issues at full boost (26 psi) above 4k RPM. There are no trigger errors, but it seems like an ignition or timing issue. It will essentially sound "flat" b/n 4-6K RPM and feel like it's going, but not really... and backfire as well. This is only at WOT and full boost (26 psi). If I do part throttle and keep to 15-18psi, it will pull cleanly to redline.

So, I've attached a video of the backfiring/hesitation, as well as three logs. Sorry for the weird angle. For some reason, despite being on its side, my phone didn't rotate correctly when recording.

I'm still "figuring this all out" as I go w/ VEMS and what not, so if there's a better way of me doing the logs, tell me and I'll go take the car for another rip. It's great to get it out again, and I only narrowly escaped the local law enforcement on the local highways... lol. But I'll do what I need to to get this running! I have a track event on Saturday (6th), so I'm motivated!

I have replaced all plugs this week as well as a new distributor. Rotor is damn near new, and wires still look good (magnecore).

Let me know thoughts! Appreciate the help/insight!

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Re: VEMS Tuning Issue - breakup above 4k RPM

Postby ChrisAudi80 » Mon Oct 01, 2018 12:43 pm

You said distributor, what coil are you using? It could be you don't have enough spark energy above a certain boost level so might need a stronger coil.
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Re: VEMS Tuning Issue - breakup above 4k RPM

Postby audifreakjim » Tue Oct 02, 2018 7:23 pm

Or the opposite, you have too much dwell and are saturating it. I's play with the dwell and see if it changes the RPM range. Then you will know if you are on the right track.
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Re: VEMS Tuning Issue - breakup above 4k RPM

Postby jretal » Tue Oct 02, 2018 7:48 pm

It's an MC1 coil I believe (its been a while!!!).

Which menu has the dwell settings in VEMS?

Funny part is, if I roll into it, it will hesitate more than if I just go straight WOT... so it'd make sense it's coil related!

What are good settings for dwell?

Thanks all!
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Re: VEMS Tuning Issue - breakup above 4k RPM

Postby DE80q » Wed Oct 03, 2018 10:38 pm

I was running the later NG/7A coil with my old dizzy setup. I can look up what dwell I was running in the morning if you want.
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