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Please explain O2 readings to me, Thanks

What are we measuring and why does it matter.

I understand that a HIGHER READING means more likely to pre-detonate.

Why?

I have heard 13.7 is optimal but too risky. I have had automobile people tell me they shoot for 13.7 and that would be using 85 octane.

I need some help understanding what it all means so I can make some desicions.

Does the optimal reading change with higher octane fuel or not?

I want my TApex to run and run hard but I want it to run hard for years.

I am running 18lbs and using straight 110 Sunoco

We ride 8000 to 10,500 in elevation

Thank you for your Help!
 
13.7 is a none boosted # & leaner you need fuel to make power & to cool the motor 11.5-12.5 if optimal lower # is richer higher # is leaner iam not 100% positive on oct rating vs af ratio.with mater meth or alcohol you can run higher # because of the cooling effect these have on the motor.here this explans the a/f#
http://www.aa1car.com/library/2004/cm100428.htm
 
What are we measuring and why does it matter.

I understand that a HIGHER READING means more likely to pre-detonate.

Why?

I have heard 13.7 is optimal but too risky. I have had automobile people tell me they shoot for 13.7 and that would be using 85 octane.

I need some help understanding what it all means so I can make some desicions.

Does the optimal reading change with higher octane fuel or not?

I want my TApex to run and run hard but I want it to run hard for years.

I am running 18lbs and using straight 110 Sunoco

We ride 8000 to 10,500 in elevation

Thank you for your Help!

Chuck, you are measuring the percentage of oxygen in the exhaust. As mentioned the higher the number, the leaner or more oxygen left.
Also like mentioned, different fuels have a different burn rate. So different fuels can run on different readings without problems. However, if you are that close to the line of safety, a nice drop in temperature could mean the difference in running or not. Play it safe, and keep the numbers down. The power difference will not but noticable. I run mine at under 12 all the time, everytime I am under boost.
As for your fuel question, lots of folks with the rear mounts have ran 17lbs on Avgas, with just a head shim. The front mounts lack the charge tube, so I would either leave it richer, or loose a pound of boost to make that happen. 18 lbs with a head shim on any 110 race fuel will be more than suffecient. I would not hesitate to run 20 either.
Give me a call sometime. Sounds like you picked something different up?
 
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