djm_e22

iTrader: (2)

Been tuning with the cats tuner. Have decided to go with an open loop tune only for various reasons. Open loop runs really good except for when I slam on the gas pedal it hesitates briefly with AFR dropping to around 17.5:1 then immediately goes to around 12.5:1.

Also when driving normally after each shift it will lean out and take a second or two before it goes to the afr setting I have it set for. Now when I shift at WOT there is no leaning whatsoever during shifts. Just when shifting during normal driving. Anybody know what could be causing this? Is there something in Cats Tuner I can do to fix this. Thanks for any help.

1toofastlt1

iTrader: (4)

Is your car stock? Let me know more about the car.

djm_e22

iTrader: (2)

No its not stock. I have a fairly big cam. Can't remember the size off the top of my head but it"s a custom one from Lloyd Elliot. I know its bigger than the 306 cam that I used to have. I also have LE3 heads and of course all the bolt ons. From what I remember I have a 3800 stall. Didn't go to high on the stall because I eventually will shoot nitrous.

My fuel injectors probably have less than 3000 miles on them. Also a have a fuel pressure guage hooked up and there is no problem there either.

I just can't seem to figure out these lean spikes. Especially when I shift in normal driving. Not sure why it leans out right after the shift?

1toofastlt1

iTrader: (4)

So when the trans shift from say 1st to 2nd it goes lean for a sec then come right back? I had a similar issue when I would hit the gas it had a lean tip in. I'm on a 2 bar SD tune but I fixed it by lowering my injectors size in the ture and then making the corrections on the ve table. I'm running 60# injectors but the 2 bar tube needs me to scale them in half so I put 30# for the injectors but still had a lean tip in. I now have them at 21# had its gone.

djm_e22

iTrader: (2)

Really! Man I hope this will fix the problem. I stopped messing with my car for months because I got tired of dealing with it. Mine is a maf tune, but when I tryed ve tuning it did the same thing. Sucks that I'll have to retune it, but if it fixes the problem I'm going to feel like I won the lottery. Thanks for the suggestion. Can I ask how exactly does this fix problem? Just curious.

1toofastlt1

iTrader: (4)

With it thinking it has a smaller injectors then it really does it adds more fuel. So that lean spot needs more fuel and it will get it but so will everywhere else. Thats why you will need to adjust everything accordingly. Try this.... Say your running 36# injectors... Scale that by .90 taking 10% off the injectors will add 10% more fuel. Then scale your ve and maf tables by .90 taking that 10% off fuel added out and you should be close... You will need to try different amounts to get it right. Remeber to save this new tune as something else just in case it doesn't work for you

djm_e22

iTrader: (2)

Thanks man! Hope this works. I'll let you know.

nitrous2fast

iTrader: (2)

The reason you have lean spikes is because when you rapidly change throttle angle the vacuum changes rapidly as well and the computer looks at the VE tables to predict the amount of fueling required. The MAF has a lag on amount of air it reads to the time it reaches the valves. You need to make changes to the VE table on those specific circumstances to properly correct the problem. I could be wrong though....

gregrob

iTrader: (8)

You guys are over thinking this in my opinion.. When you let off the throttle to shift my guess is you're hitting DFCO for a second, which if the engine is still turning, it's only pumping AIR. Therefore its going to show a "lean spike". Nothing to worry about.

djm_e22

iTrader: (2)

Hey what's up gregrob? I have dfco disabled. Plus this lean spike also happens when I smash the gas pedal. There is a very noticeable hesitation.

1toofastlt1

iTrader: (4)

It's an auto so no lifting to shift

gregrob

iTrader: (8)

It says M6 in your sig. Are you closed loop? If so what are your fuel trims?

1toofastlt1

iTrader: (4)

Oh Greg I thought you ment djm car. Mine is an m6 and it would go lean when I would punch the gas. I think its called a "lean tip in"

1toofastlt1

iTrader: (4)

No I'm not closed loop. I'm still working on the tune but with the bad weather it makes it hard. I have the wide band reading around 14.2 cruising and 11.3 wot. I'm running a 2 bar Speed density tune

LopeyZ

iTrader: (2)

I used to have lean spike off idle with throttle tip in. By running in PE mode at idle to 1100 rpm, I cured that problem. In PE mode, you are able to add or subtract fuel without the PCM compensating like it will do when making changes in the VE table. Not only was I able to add fuel off idle to cure the lean spike but I was also able to cut fuel at idle to dramatically reduced the raw fuel smell you often get with larger cams.