> -----Original Message-----
> From: MICHAEL CABE
>
> ray
> i will check out all those links. thank you.i guess my thought is,even
> with modest mods (exhaust,air intake)are the factory settings in the
> computer able to make the best of said mods without some sort of
> reprogramming?
The short answer is yes. In part throttle driving the PCM will read the O2
sensor, Intake Air Temp (IAT) sensor, MAP sensor and the Coolant Temp Sensor
(CTS) to determine the proper Air/Fuel ratio regardless of any mods.
During Wide Open Throttle (WOT) the PCM ignores the O2 sensor and refers to
predetermined parameters (lookup table) to adjust the timing and A/F ratio.
Typically, all factory computers (ECM or PCM, whatever you want to call
them) are programmed to be extra rich at WOT to prevent we idiots from
causing any engine damage. For a racer this can be detrimental to maximum
performance but there are external ways to compensate. A mostly street
vehicle wouldn't know the difference.
> i haven't looked at your links yet so maybe after doing so
> i will understand more about "speed density systems"my next question is to
> the group.have any of you reprogrammed for fuel economy or performance or
> both? i would like to stick to the 4.7 on this subject but all
> experiences too.thanks again ray.
> mike
I acquired a Superchips tuner several years ago for my Jeep 4.7. (same one
is used for Dodge truck 4.7s) I've tried the "economy" and "performance"
modes. The fuel mileage difference is negligible. The performance mode
does show a slight performance improvement at the track but it is not
significant enough to "feel" on the street.
FWIW, when I race the Jeep without the tuner I use 87 octane fuel. Higher
octane didn't do anything for it. If I use the Superchips performance mode
I run 92 but can't confirm it really needs it. I've run just as good times
with 89 in most weather conditions.
Hope this helps.
Ray
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