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Old 06-19-2019, 10:49 AM
ShagWagon ShagWagon is offline
350 Buick
Join Date: Apr 10, 2016
Location: Oregon Coast
Posts: 872
Originally Posted by babywag
The factory settings for AFR are pretty rich.
Increasing them should result in a mpg increase.

A tuned carb vs. tuned efi HWY MPG should be =
A tuned carb "" CITY MPG will be much better w/ efi due to more efficient use of fuel.
With "tuned" implying it is attempting to hit 14.7 target.

If you want even better HWY mpg increase cruise AFR.
Anything lower than 14.7 will waste fuel/decrease mpg.
Cruising I've gotten excellent results running ~15.5 AFR.

But GM TBI has a lean cruise hack

You read my data log? That’s at idle for 60 seconds or so.

I think I tried to lean out the settings last year and one of them ( I can’t recall) had some lock on it where I could adjust it max lean. I reset it all after I installed a new o2 sensor so that’s all factory computer learned tuned or whatever.
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