Low RPM boost A/F

[supradjza80]

Guys,

First I will list the modifications done to the car
BIC DDP to 3.5" Straight pipe
Apex Intake
Apex AVC-R tuned to 10-11 psi
Cooleeze 2.5" hardpipes
Innovate LC-1 with DB gauge
stock turbo, stock intercooler, stock fueling/AFM

So with the wideband installed and calibrated and the boost controller ramping up boost as quickly as possible I noticed that when starting a "pull" in 4th/5th gear from 1500/2000 rpm the car will jump into boost and be up near 10/11 psi and until about 3500 rpm I am getting A/F in the 12-12.5 range. After 3500 to redline the a/f drops down all the way to 10.3 right by the limiter (pulls to the limiter done in 2nd/3rd not enough road/lack of traffic to do 4th/5th).

I am aware that 12-12.5 is still safe but I am wondering if I should be worried about it while still being with stock ECU and timing. I am aware that the fuel pump switches to 12 V at some point (probably 3500 RPM based on A/F's) and I am wondering if I should run 12 Volts all the time to try lower A/Fs in 2000-3500 rpm range.

What is everyone's thoughts on this? Is it fine for stock fuel/stock ECU to see those A/F's under boost at lower RPM's? Should I be doing the 12 V mod to make it more rich down low? Should I bite the bullet and buy an SAFC even though I really don't want to mess with fueling, (could richen down low and lean it out up top). Right now I am unsure of what is the best thing to do and I was thinking of backing the AFM screw out to help lean the high RPM zone out but fear the effect of doing that on the low RPM A/F's.

Discusss

 

[gaboonviper85]

So pretty much your car is stock and all you did was add a down pipe and up the boost....you're fine as fuel cut will save your ass....if you actually modified anything then I'd be worried but your on a stock afm and turbo so you're fine.

 

[supradjza80]

Any other opinions on this?

 

[mkIIIman089]

So pretty much your car is stock and all you did was add a down pipe and up the boost....you're fine as fuel cut will save your ass....if you actually modified anything then I'd be worried but your on a stock afm and turbo so you're fine.

+1

 

[CajunKenny]

So pretty much your car is stock and all you did was add a down pipe and up the boost....you're fine as fuel cut will save your ass....if you actually modified anything then I'd be worried but your on a stock afm and turbo so you're fine.

+2

I would NOT mess with the AFM screw. Also, keep in mind that you're pushing/stressing a very old fuel system...

 

[supradjza80]

Guys, i understand that fuel cut saves my ass once the airflow meter measures past what it can "safely" support. My question is in the low RPM range under boost, is it really safe to be running all the way up to 12.5-13 A/F up to 3-3.5k rpm where it really richens the fueling up? Is this something the running the pump on 12V's all the time would fix?

And I realize my car is not modified nearly as much as most peoples on here, I just want to make sure my A/F's are ok under boost low in the rev range since I can make 10+ psi by 2250/2500 RPM while A/Fs are mid 12's sometimes 13.0 even.

 

[mkIIIman089]

I run ~12.2 all the way to redline.

 

[supradjza80]

I run ~12.2 all the way to redline.

I would be happy with that, I just am a little uneasy with seeing 13 while in boost @ 2-3k rpm, but maybe that is just what the stock calibration is on these cars

 

[kmfdmk]

I don't worry about AFR's that lean until I hit 5psi, once I get to 5psi I try to nail them down to 11.5 or richer, but I am running MAFT-PRO as well...

 

[supradjza80]

I don't worry about AFR's that lean until I hit 5psi, once I get to 5psi I try to nail them down to 11.5 or richer, but I am running MAFT-PRO as well...

yeah, thanks for the input, thats where im nervous since it is at 5-10 psi when this is happening.

 

[CajunKenny]

Are you sure you're not just seeing the tail end of the car switching to open loop?

The afr's will be lean (14-15.5) then when the ECU switches, it'll go rich. This transition is pretty quick; but, maybe what you're seeing is the tail end of that switch...?

 

[supradjza80]

Are you sure you're not just seeing the tail end of the car switching to open loop?

The afr's will be lean (14-15.5) then when the ECU switches, it'll go rich. This transition is pretty quick; but, maybe what you're seeing is the tail end of that switch...?

No, I do not think im seeing the tail of the ecu switch to open loop. At cruise/idle it is 14.5-14.9 consistently. When this is occurring (WOT, rpm in the 1500-3000 rpm range) the A/F's are in the mid 12's to thirteens, and it appears the car is running open loop at this time.