Here's my problem. I'm running a large cam. My O2's are tuned reasonably well as the LTFT's are close to 0 the whole time from idle to WOT. However when the car sits idling in the garage the fumes are rich enough to make your eyes tear. I understand why this is happening, but I'm looking for the best way to correct it. For example, how can I make the PCM aim for an AFR of say 15.5 instead of 14.7 only during idle? Is the VE table the key?
John
John,
Why is it happening actually? Besauce of the lope of the cam and the size of the injectors? My car (MP112/ S3 Nitrous cam) is the same way. Maybe about -1.5 @ idle, but I sure can smell the gas. Would leaning out idle a bit more, and then adding more PE,and or AE make up for it? Just throwong out some idea's.
-Scott
Scott,
My understanding is that you get a few misfires so you're getting some unburnt fuel out the exhaust. I think it's made worse by the O2 sensor interpreting the free uncombusted oxygen as lean so it fattens up the mix some more.
PE wouldn't help. You're not in PE at idle. What's AE?
John
I knew it was something with the cam and misfire-lol. although I thought having 50# or bigger injectors had something to do with it. Anyway, PE-Power enrichment, and I thought AE-(Accelerate enrichment?) was-ummmm. Let me look it up again. one of them dumps fuel in right as you hit the throttle a certain %, and stays in that mode till the tps is is below certain %--that is PE i thought. AE is just a shot of extra fuel for a second etc..to stop you froim getting blip's of KR. Ill try to find where I found the info and get back to ya. Say you wouldnt have a pic of your snout brace that you could email me would you?
Scott,
What version of HPT sw are you running. I don't think I have accelerate enrichment, or maybe I'm not looking in the right place? If it works as you describe, it wouldn't help with idling either.
I don't have any close up shots of the snout support other than what I posted on ClubGP a few months ago. Have you seen those?
John
I might have seen those pics, but if you can email me one that be great, or a link to it. I pm'ed you earlier.
Scott
I am not running HPT yet, but I will be in the next few days.
Scott YGM
Thanks.
Hey John,
What is your idle speed?
Rob
Rob,
For normal temps, it's 900 in P/N and 850 in gear.
John
In my hotrod days with big cams, the idle was above 1000rpm of course depending on the exact combo.
I have my idle @900 all the time. It seems to like it better.
If yourcam is that big, try a higher idle and maybe that would help.
I'll never forget the nova I heard, very lopey idle, looked at the tach, 1200rpmHe said it wouldn't idle below a 1000.
Just a thought. Oh yea HPT doesn't have the tables we need to adjust what you want.
for tuning big cam idle, forget the scanner #'s as they are unreliable. Add timing and tune for quality.. Watch your histograms to target the right timing and VE cells. Also watch out for those AFC's
I would say up your idle too, I run the Vs cam which isn't that big of a cam and I went up about 100 rpms between 175 dg. to 235 dg. I think it helped me out alot, I know it is sounding and running better.
1996 Camaro 3.8 M5 to A4 conversion, VS cam, 3" exhaust, 9:5.1 forged pistons, Clev.77 bearings, Comp 130lb springs/.105 pushrods, Manely modded retainers, Walbro 255, PLX wideband,65lb injectors, Every Suspesion mod. alot of other mods- GT35R Turbo.http://www.cardomain.com/ride/2441235
2008 Silverado LTZ 6.0 L76 Dynomax exhaust K&N intake
Rob, what table do you think is needed here?
WCP, would added timing help lean out the idle? How?
ssms, I'm not having a problem with a bad lope. It actually sounds and behaves fine. My idle is already 150 above stock, and I think it sounds pretty good. I'd just like it better if it didn't idle as rich.
John
it wont lean out the idle, but it will help burn the fuel better. Also remember that running too lean will also cause the same troubles..
That makes sense. Now if only I could get to the Base spark tables. But since I can't, I should be able to add some timing during idle by adding a few degrees to the left cells (low air/cyl) in the IAT spark advance correction table.... I'll try it. Thanks.
John
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