Air/Fuel Ratios
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
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From: Winchester Ontario
Air/Fuel Ratios
What are the best optimum ranges for air/fuel ratio?
I heard that naturally aspirated it's 12.8 - 13.2 ish and for nitrous injected try to attain around a 12.5.
Is forced induction similar to the nitrous injection as far as air/fuel ratios go? Is 12.5 too lean, should I try richer like 12:1?
I heard that naturally aspirated it's 12.8 - 13.2 ish and for nitrous injected try to attain around a 12.5.
Is forced induction similar to the nitrous injection as far as air/fuel ratios go? Is 12.5 too lean, should I try richer like 12:1?
Burning Brakes
Joined: Apr 2005
Posts: 1,109
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Ray Bohacz wrote :The term "stoichometric" identifies the ratio offering the most complete burn. For unleaded gasoline, it is 14.67:1, which is commonly rounded to 14.7:1. The stochiometric value for other fuels varies with their energy content, but our discussion will be limited to the requirements of gasoline.
Safety Car
Joined: Apr 2001
Posts: 3,525
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From: Houston TX
Measured with wbO2. I like to run mine at 11.8 through about 12 psi and then I gradually drop to 11.4 up to the mid 20s. High vacuum to WOT, no boost, ranges from 14.6 to 12.9 A/F.
I hope this helps.
Aaron
I hope this helps.
Aaron
Melting Slicks
Joined: May 2007
Posts: 2,382
Likes: 2
From: Kathleen FL
You can only run the 14.xx stoichiometric A/F ratios on light acceleration or cruise. Running a stoichiometric A/F ratio under heavier acceleration could cause drivability problems. Most N/A cars need an A/F ratio richer than that for power production, usually between 12.5-12.8:1. A/F on boosted cars should be richer than that, like 11.5:1. You can measure A/F ratios accurately using a wideband O2 sensor. They are expensive, >$1,000, but very necessary for tuning the A/F ratio at different rpms and loads.
Instructor
Joined: Sep 2006
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From: Yorkville IL
Race Director
Joined: Jun 2004
Posts: 13,961
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From: WI
Not a wideband but there is plenty of room yet.
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From: WI
Instructor
Joined: Sep 2006
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From: Yorkville IL
The guage I bought (and most others I know of) comes with the proper sensor, which is different than the ones that our in our vette's, those are narrow band.