LS1 Corvette power dips at 5200rpm after A&A install

[JASON11WS6]

So the car is a 99 Corvette. It has headers and we installed an A&A kit on it. Car runs fine except for a strange issue at idle were it runs pig rich no matter how much fuel I take out of it. Still working on that issue.

Car has new injectors and plugs. It does not show any misfires and again drives fine. At wot you can feel it hit a wall around 5200 rpm. The power dips big time and you can feel it during the pull. I can't see anything in the scan that shows the event is even happening though. Anyone have an issue like this? If I had a misfire pull up in the scanner I could at least have an idea where to start. I don't want to start changing everything and just hope it works better. I'd like to find the issue. I uploaded the last couple tunes and scans.





SETH005.hptSETH004.hptSETH005.hpl

[Frost]

Spikes in the wideband look like misfires. Use NBO2 voltage to get down to the affected side (or look at the side the WB is in). This car needs a 2bar or ZL1 GM sensor and a boost OS; not a MAF. Then you can see belt slip or other boost related issues. It's not even done tuning and the MAF is nearly maxed out and you have another 1K RPMs to go (WOT part stops at 5600ish in log). Transient fuel, min mgs is an IPW lower limit; cut that value down to try and get it to clean up fuel at idle. Swap plugs; they maybe wetted up from fat idling. Use a dyno for spark (and fuel really); no car wants just 19deg everywhere at WOT. It will want more down low, and likely less up top.

[JASON11WS6]

Spikes in the wideband look like misfires. Use NBO2 voltage to get down to the affected side (or look at the side the WB is in). This car needs a 2bar or ZL1 GM sensor and a boost OS; not a MAF. Then you can see belt slip or other boost related issues. It's not even done tuning and the MAF is nearly maxed out and you have another 1K RPMs to go (WOT part stops at 5600ish in log). Transient fuel, min mgs is an IPW lower limit; cut that value down to try and get it to clean up fuel at idle. Swap plugs; they maybe wetted up from fat idling. Use a dyno for spark (and fuel really); no car wants just 19deg everywhere at WOT. It will want more down low, and likely less up top.

The car has stock valve springs so we will be cutting power around 6k. The MAF should cover the tune. The timing was just a base tune before we could power tune. Hitting this wall kind of put a quick stop to the tuning. I'll look into bringing the IPW lower limits and fuel mins down. I pulled the date right from FIC on the injectors though but that's worth trying. I'll see if I can get the customer to invest in a new map sensor.

[Frost]

That brand has killed a LOT of my time. I usually share this with my customers when it comes to drilled injectors: http://injectordynamics.com/articles...-and-dipshits/ If they are passionate about keeping them, I pass on the work.

I'm not saying you WON'T get them to work, but you will have to come up with your own data for much of it.

I still like the 2bar MAP so that I can SEE boost personally. Things like belt slip stick out like a sore thumb!

[waz89]

Why is your tps reading 8.6-9% @ idle?

[bpm]

Um you’re boosted with stock springs and you wonder why it falls flat on its face at 5K?

[Frost]

Why is your tps reading 8.6-9% @ idle?

It's DBW.

Um you?re boosted with stock springs and you wonder why it falls flat on its face at 5K?

It's a centri blower; he's not losing spring seat force from back pressure like if it was a turbo, but it would indeed peak later with just a set of aftermarket springs (and the centri).