High rpm issue

[jmackisback]

I recently took my bone stock 1991 TSi and added a handful of items such as FMIC, 255 pump, wideband o2, turbo back exhaust, intake, MBC @12 psi, boost gauge and SAFC. For some reason when I hit around 6k rpms the car will backfire and hit a wall....no boost leaks, but it does spike to 15-16 psi occasionally at WOT. What could be causing this? the AF ratios seem appropriate unless I am not noticing a split second change. The car pulls hard until that point.

 

[steve]

Perhaps you're hitting fuel cut.

You say no boost leaks, but how much pressure are you testing at and how long does it hold pressure after you remove the air? Anything leaking out will cause the MAF counts to be higher than they should be and can lead to triggering fuel cut.

 

[jmackisback]

Perhaps you're hitting fuel cut.

You say no boost leaks, but how much pressure are you testing at and how long does it hold pressure after you remove the air? Anything leaking out will cause the MAF counts to be higher than they should be and can lead to triggering fuel cut.

Hmm ok i will do further testing and report back. Thanks

 

[jimsgsx]

You still runnin the 450's?

 

[DSTSI]

You added 255 pump did you increase the injector size?

 

[SrKegler]

I don't see any AFPR on your list. Is it possible he's overrunning the stock FPR with the 255 pump.

Can't see why he would have to change injector size just for putting in a 255 pump.

 

[DSTSI]

Can't see why he would have to change injector size just for putting in a 255 pump.

I didn't mean he had to change them, I was just tiring to find out more info, apologies for not being clear

 

[steve]

I don't see any AFPR on your list. Is it possible he's overrunning the stock FPR with the 255 pump.

Overrun is largely a problem at low rpm/load where the engine isn't consuming much fuel. Once the consumption rises the pump isn't overrunning the FPR anymore. Unless he's free revving to 6k, which it doesn't sound like, you would need a bigger pump to still be overruning the FPR.