Help! Stumble/Misfire at WOT

[DSMDEMON93]

Hey guys, my car ran FINE before I installed the GM MAF, new intercooler piping, etc. Everything is nice and tight. I just finished my idle/cruise tune with DSMLINK v3 and am moving on to WOT, but everytime I full throttle it, it starts to buck HARD at around 10psi...where my limit is at 18. I am running 560cc/rewired evo 8 pump on a small 16g. I have no idea why it is cutting NOW! You can review my log below at 90 seconds. Thanks!

 

[97-gst]

your timing dropped like a rock, did you set the injector size on maft to 450 and leave everything else stock? looks pretty rich too

 

[Tiki2777]

Make sure your plugs are good. I had a problem at WOT where it would stutter and buck a little because it was blowing spark. Make sure to get new plugs and get them gapped right. (some people have also needed to get better spark plug wires) When i replaced my plugs my problems at wot went away.

 

[WillRaceForBeer]

A few things stick out to me.

- You have a lot of fluctuation in your MAFRaw Signal starting at 3135 rpms and gets worse

- Your o2 indicates your running very richt at WOT, do you have a Wideband? If not you absolutely need one. Your knock appears to be rich knock.

- Your Throttle Positiong is at 95%, it should be 100% at WOT. You need to either adjust the throttle body itself, or use DSMLink's TPS adjustment to bandaid the problem.

My recommendation, fix the TPS issue, then turn down boost to where you can get a clean run without knock. Then you can dial in your airflow and fix the rich condition, then you can bring you can pull a bit of fuel if you are still too rich, then you can turn up boost carefully.

If the MAFRaw signal issues come back, then you'll need to try swapping Maf's with a known good maf, and go from there.

 

[DSMDEMON93]

Thanks for input guys! Well, my car at wot hits around 11.2:1...then hits stutter and DROPS to 10:1! Im using my UEGO. I will try everything above.

A few things stick out to me.

- You have a lot of fluctuation in your MAFRaw Signal starting at 3135 rpms and gets worse

- Your o2 indicates your running very richt at WOT, do you have a Wideband? If not you absolutely need one. Your knock appears to be rich knock.

- Your Throttle Positiong is at 95%, it should be 100% at WOT. You need to either adjust the throttle body itself, or use DSMLink's TPS adjustment to bandaid the problem.

My recommendation, fix the TPS issue, then turn down boost to where you can get a clean run without knock. Then you can dial in your airflow and fix the rich condition, then you can bring you can pull a bit of fuel if you are still too rich, then you can turn up boost carefully.

If the MAFRaw signal issues come back, then you'll need to try swapping Maf's with a known good maf, and go from there.

Quick question. So right now, instead of say..18psi, drop my boost down to 15psi, tune for 11:1, then slowly turn up the boost per psi?

 

[97-gst]

did you set the maft to 450's? and leave everything else zero

 

[WillRaceForBeer]

Quick question. So right now, instead of say..18psi, drop my boost down to 15psi, tune for 11:1, then slowly turn up the boost per psi?

Yes drop the boost, the lower you can go withough boost creep the better. Your first goal is to get your airflow dialed in properly, there is tons of info and threads on dsmlink forums for that. Once you know your GM maf's airflow signal is calibrated, then it will be much easier to tune for a given A/F. Then turn up the boost, perhaps a few psi at a time. Just make sure to let off when the CEL lights up from knock