Octane Vs. A/F ratio
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From: Ft Lauderdale, FL
Octane Vs. A/F ratio My car has run 12.2:1 A/F (motor) on my wideband since I have had it and yesterday I put some 110 octane in the car for the spray and on motor it dropped to 11.4:1 A/F ratio. Would you imagine this is due to the fuel? Also the car is tuned for 93 octane. Thanks,
Joe
Joe
I would imagine that this is due to the lead in the 110 screwing with your wideband. However, if your local street fuel contains alcohol, the reading may be correct, depending on whether or not the 110 is oxygenated.
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Joined: Nov 2001
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From: Lake Zurich, IL
^^^ that sounds accurate
Another thing I was thinking... though this is just a theory, not sure if it's accurate...
Higher octane fuel is harder to ignite... so if you command 28* of timing, but now it takes until the piston is 20* before TDC to ignite and start the flamefront... I wonder if it's possible not all the fuel gets burned due to the late ignition?
Another thing I was thinking... though this is just a theory, not sure if it's accurate...
Higher octane fuel is harder to ignite... so if you command 28* of timing, but now it takes until the piston is 20* before TDC to ignite and start the flamefront... I wonder if it's possible not all the fuel gets burned due to the late ignition?
Originally Posted by 1999TransamWs6
My car has run 12.2:1 A/F (motor) on my wideband since I have had it and yesterday I put some 110 octane in the car for the spray and on motor it dropped to 11.4:1 A/F ratio. Would you imagine this is due to the fuel? Also the car is tuned for 93 octane. Thanks,
Joe
Joe
The higher the octane, the richer the wideband will show. It has nothing to do with lead. The mix of chemicals is not the same as pump gas. Even the oldschool carb guys have to lean down for race gas.
Race gas has a different specific gravity or density, and doesn't contain 10% ethanol like pump gas does.
These factors are cumulative.
Even comparing pump gas (each with 10% ethanol) you should see a change in A/F by switching from 92 octane to 87 octane.
The chemicals that increase the octane rating apparently change the stoich point as well.
It has been like that as long as I can remember.
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From: Ft Lauderdale, FL
I really appreciate this guys I drove my car all day so I could burn up the 110 because im going to the track tomorrow and the fuel made a big difference in performance (worse) this is the first time I have run race fuel with my tune so the car is completely freaked out. I am going to throw 93 back in tonight and pray all is well. Thanks again for the help guys. It should go right back to normal when the 93 is back in correct? Thanks,
Joe
Joe
