83# inj - EXT EXTREME - part throttle stumble

[Warp6]

Just put 83# injectors in. Have modded ecm and Extender Extreme. Translator + is set per instructions. WOT is awesome but there is a bad stumble (around 6-10 psi) when going to WOT. Once I get through the stumble the car is brutal! Fuel pressure set at 45# vac line off - 40# line ON. 2nd fuel pump is not active during stumble so I know it's not an issue. At WOT with 18psi I get 730's - 750's on the O2 sensor(fresh denso + 93 octane pump gas) with ZERO knock. Is it okay to drop the base MAF with the Extreme chip? I'm not sure. It's now set to "0" as are the rest of the knobs. Dip switches are set on-on-on-on. (3 1/2" LS1 meter) I'm thinking of dropping the spoolup fuel in the chip. Anyone know if this will affect the spoolup curve while driving? Any advice is greatly appreciated!

 

[salvageV6]

I just put the extender extreme chip and modded ECM in my car yesterday too, mines for 55's.

I thought the fuel pressure was supposed to be 45 psi.?

I'd guess you are a bit lean not rich. Mine runs okay so far. Haven't gone WOT for more than 2 seconds yet.

Just a guess at your problem.

I believe all the controls still work as described with the Extreme chip.

 

[Warp6]

Originally posted by salvageV6
I thought the fuel pressure was supposed to be 45 psi.?

Woops! That was actually a typo I meant to say 45 line off, and 40 line on. I have corrected my original post. Thanks Salvage!

 

[salvageV6]

In that case I have no clue what your problem is.

I'd try Direct Scan if you have it and try to capture the event.

Or look at blms and int during an occurance on a scanmaster.

I'd try to find out what is happening under part throttle boost before I made any adjustments.

 

[Tom Willard]

Originally posted by salvageV6
In that case I have no clue what your problem is.

I'd try Direct Scan if you have it and try to capture the event.

Or look at blms and int during an occurance on a scanmaster.

I'd try to find out what is happening under part throttle boost before I made any adjustments.

good advice. Let us know, I'm interested

 

[rkreigh]

WOT is awesome but there is a bad stumble (around 6-10 psi) when going to WOT. Once I get through the stumble the car is brutal! Fuel pressure set at 45# vac line off - 40# line ON. 2nd fuel pump is not active during stumble so I know it's not an issue.


you say "going to WOT" please clarify what you mean by that.

you might be getting part throttle turbo surge. do you by chance have a big turbo and front mount intercooler to go with those big injectors???

I have exactly the same thing with 72s and the extreme plus. since going to the 3.5 maf, and TE45, the turbo surges really badly at less than WOT at 8-10 psi I get a big "stumble" and then the car picks up again.

try a few experiments, hold throttle a 50% 75% and WOT and see what the car does, I found out that at about 66% throttle as the car builds boost to around 10 psi it surges and stumbles, if I use less or more throttle and hold it, no problem.

also give Bob B a direct scan trace of when the stumble occurs and he can very likely help you out. the man is a genius!!

keep us posted, I finally got my "white gnx" back on the road after a lengthy body/paint job with a similar combo and have the same thing happening.

hope this helps.

 

[Warp6]

I was out yesterday trying to capture this problem on direct scan. That's when I got the backfire (see my other post here ).
It seems fuel related and not really so much turbo surge. I do get the surge you are refering to but the stumble is not a turbo surge.
BTW I have a PTE Stealth (T63E upgrade) and a Cottons front mount. Thanks for the replies

 

[NC87GN]

Low gear spool richens up you fuel mixture to allow the big turbo's to spool faster when staging. Try taking it out of the loop and try. It may be having a difficult time trying to burn all that fuel from intial spool up. Also look at those BLM's, via DS, to see how much fuel correction is needed when your into the throttle. HTH

Mike Banas
87GN