Going lean under boost.

[OneEightSeven]

So I got my powerdyne gripping good and putting out solid PSI. However I'm going lean now. I'm running 65lb/hr injectors, walbro 255l/h fuel pump so fuel should be good. My AFR starts at around 11.0 when I floor it, but starts to shoot up as boost builds to 14.5-15.5 and I back off before I get KR. I am injecting methanol and I'm wondering if that's increasing the AFR, but I thought meth made you run richer, the AEM instructions certainly imply that. It's a progressive controller so as the boost builds it injects more meth. Currently I have my commanded AFR set at 11.0 in the PE table and the PE vs Time vs. RPM table set to do -0.9 accross the board. I still can't rich it out. Fuel pressure seems good. Wtf?

[WarShrike]

Re: Going lean under boost.

What is your injector duty?

Also, are you running a stock FPR or an adjustable setup?

Methanol should be keeping it richer, make sure you aren't pressurizing the meth nozzle/line with air from the SC, preventing methanol from coming in.

Maybe retard timing a little as boost increases to see if your AFR fattens back up?

[OneEightSeven]

Re: Going lean under boost.

Injector duty is under 40% (65lb injectors). I'm running a stock FPR at the moment. I'm going to try dropping the timing back down some more just while I test. Do you think my commanded AFR needs to be even lower?

[ssms5411]

Re: Going lean under boost.

I would check for exhaust leaks too, they will trick the wideband into running leaner.

[OneEightSeven]

Re: Going lean under boost.

ssms5411,

That's actually a pretty good idea. Maybe my TSP rumbler is leaking a bit. Do you think that under boost the leak would be more evident? Because without boost the AFR stayed pretty solid.

[WarShrike]

Re: Going lean under boost.

Where is the wideband located? After the y-pipe and before the cat is preferred.

What are the O2 sensors doing on the fuel trim? Are they trying to add fuel or take it away?

[OneEightSeven]

Re: Going lean under boost.

@ WarShrike, It's just after the Y-pipe. I have no cat. I'll check logging data when I get back home and see what the fuel trim is doing. I noticed the % was kind of high around 10-15 after I got the powerdyne blowing harder :P.

BUT IMO I'm not sure it's really exhaust leak related. I saw some KR from the lean mix (very little) that was not there before causing me to instantly pop off the gas. I think it's jumping way too lean to really be a leak :-/.

[caspernicus]

Re: Going lean under boost.

Are you scanning the MAF frequency in hz? If so what is the peak reading?

[OneEightSeven]

Re: Going lean under boost.

^^ You hit the nail on the head there. MAF issue. Thank you kind sir :D.

People, I figured out the problem. My MAF connector was not on perfectly... No wonder PE table wasn't doing ****. Sadness. Good thing I always log data and even have a camaro police car MDT (laptop) mount on the way. I always back off instantly on bad AFR/KR.

[ssms5411]

Re: Going lean under boost.

Glad you figured it out.

[OneEightSeven]

Re: Going lean under boost.

Yea man, me too =D. I went to the big meth nozzle from the AEM kit now. It really riches the AFR, i got to bump up my command afr about 0.5 points to wind up at 11.4-11.5 at WOT. My boost peaks as high as 8psi and the car feels pretty fast. However now I'm thinking I should have went turbo :-/. I'm going on a trip to europe for a few weeks. When I'm back I guess I'll dyno the powerdyne setup and decide if I want to sell it and go turbo or not.

[97rs4life]

Re: Going lean under boost.

just hit it with a 50 shot of giggle juice for when you really want to get into it ;)