adding boost to lean AFR?

91BLOWNBIRD

Registered User
As of now I am running about half a point rich so...I was wondering if adding boost will lean it up, and if so would that be a good idea?
 
What do you mean you are half a point rich? Who let you decide what the propper air fuel ratio is for your motor? Judging by this question, I'm pretty sure you are not one of the engineers who built it, so don't assume you know what is best for it.

No, boost will not necessarally lean out a mixture, as it would mean more metered air (hopefully), and a totally different scenerio to begin with.
 
I looked on your member page and you have an impressive list of Mods. It saids you have a basic tune on a SCT chip by Dave Dalke. Did he tell you what your AFR is or do you have a way to measure it that tells you you are running rich? I wouldnt ask this question to the rank and file here only because you will get conflicting information or remarks that dont help you in anyway. I would E mail your tuner, Dave , and get his recommendation and follow that only.

Ken
 
It will not necessarily lean it out. The MAF will meter the extra air and compensate. This is not the way to lean out the mixture. YOu need to retune. You could lower the fuel pressure but that is not advisable, And it might create a dangerous situation in the Upper RPMs or might make your idle and start up too lean.
 
As of now I am running about half a point rich so...I was wondering if adding boost will lean it up, and if so would that be a good idea?

Rich in relation to what? Richer than you want, or richer than you have targeted. If it is simply richer than you want, then you'll need to get your tune adjusted to increase the target AFR. If it is richer than what is targeted, then you will need adjust your tune to force the EEC to calculate less fuel than it currently is.

If all you do is add boost, you simply increase the metered air entering the engine and there is no reason to assume that your AFR ratio will change.
 
ok so Dave has my car tuned running at about 10.8:1 and last I heard from him he said I should be around 11.3-11.8:1

This thread was just a general question about adding more boost because I can only run 91 octane and want to get the most from my engine running only 91 octane

I wanted to get a better understanding before I go back to Dave retuning my chip again
 
ok so Dave has my car tuned running at about 10.8:1 and last I heard from him he said I should be around 11.3-11.8:1

This thread was just a general question about adding more boost because I can only run 91 octane and want to get the most from my engine running only 91 octane

I wanted to get a better understanding before I go back to Dave retuning my chip again

If you up your boost with 91 octane you will likely need to reduce timing a bit, another change in the equation. I dont think upping the boost is the answer your problem unless you do that and than go back to dave to tune. With all the Mods you have done to the engine you should not have just a basic tune you should have a dialed in, right on tune. That requires hands on tuning by the guy tuning your car. Otherwise it is all just a guessing game by you and all the guys posting to this thread. Just my opinion

Ken
 
I can't say for sure, but most cars tuned in the last few years were likely set to command around 11.67 AFR at WOT. If you're using a wide band and finding it off more than 3 or 4 %, they would be some value in having Dave take a look.

If it is running 6% lean from target, you may want to first make sure you don't have some unmetered air leaks somewhere. i.e. a boost leak or vac leak. (assuming you didn't change anything since you were tuned). If you are running 6% rich, the first question will be, what did you change. If you fixed a vac leak or boost leak, that could lead to being rich.
 
ok so Dave has my car tuned running at about 10.8:1 and last I heard from him he said I should be around 11.3-11.8:1

This thread was just a general question about adding more boost because I can only run 91 octane and want to get the most from my engine running only 91 octane

I wanted to get a better understanding before I go back to Dave retuning my chip again

More boost will increase the fuel pressure an equal amount and won't really change the ratio. The tune will need to be adjusted.

David
 
thanks guys I appreciate the info...I'll get back to Dave as I am sure he can adjust my tune for what he feels will be good for my setup
 
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