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charlieRobinson
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Name : Charlie
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PostSubject: Air Fuel Ratio   Tue Feb 28, 2012 8:37 am

I know the answer is out there but I searched and could not find it.
What is the optimum AFR for a stock series II supercharged?
I have seen 14.7:1 AFR since I got the car. Where should I be? Thanks, guys! happy
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96riv
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Name : Dennis
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PostSubject: Re: Air Fuel Ratio   Tue Feb 28, 2012 9:23 am

I shoot for 11.5 on my Regal under boost conditions. 14.7:1 is the proper stoichiometric value.
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deekster_caddy
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PostSubject: Re: Air Fuel Ratio   Tue Feb 28, 2012 9:59 am

It depends on the fuel you are using. With 'old' gas 14.7 is the target idle/cruise. With e10 (most fuel today) stoich is actually 14.2. I like 11.5-12 under boost/WOT. ymmv.
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charlieRobinson
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PostSubject: Re: Air Fuel Ratio   Tue Feb 28, 2012 10:20 am

I use supremo fuel only. Maybe I need to clean my O2 Sensor(s) ???
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deekster_caddy
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PostSubject: Re: Air Fuel Ratio   Tue Feb 28, 2012 11:11 am

Unless you get a tuner and change the stoich setting to 14.2, you are always going to see the computer call for 14.7, except under full throttle. If you are running e10 (which you probably are) you will probably see high ltft numbers in your scanner. If you are going to custom tune, the first thing to do is change stoich to 14.2. Otherwise don't worry about it. You are seeing 'commanded A/F', not actual.
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charlieRobinson
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PostSubject: Re: Air Fuel Ratio   Tue Feb 28, 2012 12:40 pm

That's right. It is commanded AFR. I don't think my scanner (Torque) can read the real time AFR.

By the way, to go off subject for just a moment..
I know our preferred vendors offer a pcm tune for a stock set up. But why is it so expensive?

If someone had the same file couldnt they copy it to my pcm for a handshake and $20 or so?

Just thinking out loud here..

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deekster_caddy
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PostSubject: Re: Air Fuel Ratio   Tue Feb 28, 2012 5:01 pm

charlieRobinson wrote:
If someone had the same file couldnt they copy it to my pcm for a handshake and $20 or so?

Sort of. I have to admit my tune started with an Intense PCM. But knowing what I know now I could have done it myself, and have many times since.

It's always better to start from your OE PCM and go from there.

With HP Tuners I have to unlock your vehicle, and that costs me credits and $. I spent $100 to unlock '98 Rivieras. I also have an "offboard" so if you had a '98 I can take your PCM, apply my changes to your file on my bench, and send it back to you. But, that assumes you have all the same hardware installed that I have, the cams are timed exactly the same, etc.

In reality you are better off to skip the vendors PCM and get a custom tune. All a vendor can give you is some shift enhancements (anyone can do that) and some good guesses at a "better" timing/fueling table. Their good guesses have some experience behind them but there is no such thing as an off the shelf tune that applies to all performance parts.

-Derek
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