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open loop AFR threshold

Old 02-01-2006, 11:46 PM
0.5 BAR
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Join Date: Feb 2004
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Default open loop AFR threshold


I went on dyno, tuned my car in open loop mode. I've kept closed loop disabled (gives smoother throttle reaction). What is the safe threshold AFR on low load? (e.g. below 400mbar between 1500-4500rpm). 15.5-15.6mbar on 288mbar still safe?

As far as i know for very low load (under 300mbar) 15.2 is ideal.
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Old 02-02-2006, 12:11 AM
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Default Re: open loop AFR threshold

run like low 15's in low load. theres some simple chart from uberdata i saw a while back, im trying to find it, but basically it just shows that as you transition into medium load conditions you transition into mid 14:1 land, then transition into 13:1 land as you get into heavy load...naturally aspirated of course.
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Old 02-02-2006, 08:26 AM
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Default Re: open loop AFR threshold

But what about the safe limit? In case the timing is acceptable, there is no knocking, can i tune the low-mid rpm 288mbar column for 15.5-15.6 AFR? It saves a lot of fuel in city meanwhile open loop mode keeps great throttle reaction.
Boosted application, not NA. But i don't think it means much difference in low load (upwards toward the atmospheric it does for sure).
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Old 02-02-2006, 01:10 PM
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Default Re: open loop AFR threshold

the leaner you go, the more timing you can run.

I know at 11" vacuum @ 3000 rpm in Crome, 37.50 was the number + 20 degrees at the dist., I was getting 53 mpg too!!!!!!

The fuel/timing went back to normal below 10" vac and above 3200 rpm. with next tune (thanks blundar!) the tuning will be upped to 3600-3700 rpm since I'm running the close ratio gearbox now.
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