lean at low rpms

[cjpp78]

Ok I have had this issue for a while now. Under 3 thousand rpms while at wot My car runs lean. I have the fuel pressure at 45psi(vacume not connected) and im adding around 25% on the safc in that area of rpm band. At these settings im still at like 12.3-12.5/1 air fuel ratio. As soon as it gets past 3 grand it richens to the 11.3-11.6/1 range. With the base fuel pressure that high im not taking out much afm signal in the high rpm range and this is causing me to hit fuel cut at around 18 or so psi. Also have afm screw backed all the way out.

Does it sound like I have a problem or does the stock fuel maps not run that rich in that rpm range? Granted im not making a whole lot of boost down there,seems like I should be able to get it richer under wot.Dont like the fuel pressure that high or adding that much afm signal, guess its killing my timing down there.

mods related to this issue- sp58gt turbo,lexus afm, 550 injectors,aremotive fpr, walbro 255 fuel pump.

 

[sneakypete]

12.5 under 3k rpm isnt too bad. for that split second at wot, the engine load isnt that much until you start building boost.
im at 13.6 at that same rpm at wot, but im running a bigger turbo.

 

[grimreaper]

i see similar af ratios. Im building boost in this range (5-7 psi) but still shy of full boost. add fuel or leave it alone?

i see 13's af ratio and they work there way to 11's once i cross the 3000rpm range...

 

[cjpp78]

Thanks for the replys. Ok so its normal for it to run this lean in that rpm range. In that case ill take out some of the afm signal in that rpm range, dont like running +25%. I should gain back some timing doing that. No matter how much I turn up the safc it wont richen up past 12.3/1 anyway. Ill pull it back till 13/1 air fuel ratio.

 

[cjpp78]

ok I just noticed where I made this comment in my first post....


With the base fuel pressure that high im not taking out much afm signal in the high rpm range and this is causing me to hit fuel cut at around 18 or so psi. Also have afm screw backed all the way out. (quote first post)

Dont know what I was thinking, had that backwards. The extra fuel pressure should have me running even richer in the higher rpms but im not. I should have to be pulling more afm signal up top, this would help with fuel cut but im pulling very little up top to get the 11s af ratio. It hasn't always been like this..In the past there has been times when I was pulling 15-18% afm signal to get into the 11s, now im only pulling like 5-7%.

 

[grimreaper]

something changed then, like pirate air perhaps?

 

[cjpp78]

yeah, ill try and look for any places that air could be getting in. I have a few rubber caps in some spots, maybe they are leaking. Afm screw is backed out as far as it can be as well. Maybe some air is being pulled in from around that screw as if its no longer seated in the threads good, worth a check I guess. May just screw it back in anyway, at this point fuel cut is no higher than before I screwed it out.