AFR Question...
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AFR Question...
Since the other thread was closed and my question can't be answered 
I thought I'd pose my question here.
Shiv said
And my question was...
Would an A/F ratio of 11.5-11.6 change at all with factors like high or low temps (90+ or -10 degrees F), humidity or elevation possibly causing the engine to run leaner?
You'll have to excuse my for my ignorance as I am not very mechanically inclined ....but trying to learn
I thought I'd pose my question here.Shiv said
Originally Posted by shiv@vishnu
Not really. Furthermore, I can't for the life of me understand how people can say that X tune is safer than Y tune because the AFRs at full throttle are richer. There is more to it than that folks. Not only is ignition timing the biggest factor in what is "safe", partial throttle mis-mapping will also spell death for any engine. I've seen a lot of reflashes (no, not from turbotrix) that attempt to run ignition timing numbers 4-5 degrees past the point of MBT. It may get a strong one pull on the dyno, but on the street it feels inconsistent and always on the verge of knock--- regardless of how rich the logs on the dyno suggest.
My 2c,
shiv
Not really. Furthermore, I can't for the life of me understand how people can say that X tune is safer than Y tune because the AFRs at full throttle are richer. There is more to it than that folks. Not only is ignition timing the biggest factor in what is "safe", partial throttle mis-mapping will also spell death for any engine. I've seen a lot of reflashes (no, not from turbotrix) that attempt to run ignition timing numbers 4-5 degrees past the point of MBT. It may get a strong one pull on the dyno, but on the street it feels inconsistent and always on the verge of knock--- regardless of how rich the logs on the dyno suggest.
My 2c,
shiv
And my question was...
Would an A/F ratio of 11.5-11.6 change at all with factors like high or low temps (90+ or -10 degrees F), humidity or elevation possibly causing the engine to run leaner?
You'll have to excuse my for my ignorance as I am not very mechanically inclined ....but trying to learn
In a word ... Yes. My car was originally tuned in Colorado. Shiv tuned it to ~10.5 AFR. When I took it back to Chicago it leaned out ~.3 or so. Air density definitely seems to affect AFR, and, I am guessing so does vehicle speed, since the faster you go, the more air is forced into the stock intake. I wish I had a place where I could test this, because I'm guessing that if you tune your AFR right on the verge of knock, then a top speed run would probably put it over the edge....
l8r)
l8r)
A MAS based system typically uses a MAP to sense changes in air density caused by elevation or whatever and calculates actual air density accordingly. If the EVO uses a MAP for this purpose, I do not know.
Likewise, MAS equipped cars typically have a IAT to measure the actual air temp in the MAS, and compensate accordingly.
Likewise, MAS equipped cars typically have a IAT to measure the actual air temp in the MAS, and compensate accordingly.
