I knew that would turn some heads. Basically the four major factors that
control how the computer tunes the fuel curve are the map sensor, iat
sensor, coolant temp sensor, and then the input from all of them is compared
to the biggest factor, the dreaded o2 sensor. With the help of a dodge tech
I know, I've wired up a small panel of 3 potentiometers (i think i killed
the spelling on that) with switches on them. Each one is in loop with one of
the first three sensors (map, iat, coolant). the computer reads the
resistance off of each and that tells it the reading for that device. When
the switch for each is off, the signal runs to the sensor bypasses the
potentiometers, and goes to it's next point just like normal. when I want to
adjust my fuel mixture ( I only really do this to richen up the mixture
right before racing, but like I said, it can be used to lean it out also) I
simply flip the switch for each potentiometer on, then the signal goes from
the each one of the sensors to it's designated potentiometer where I can
adjust the resistance, which allows me to tell the computer the sensors are
reading whatever I want them to read. Normally this wouldn't do much because
everything comes down to the o2 sensor. this is where the coolant temp
adjuster comes in. It's actually kind of a neat trick. By turning down the
coolant temp far enough, it's tells the computer that the truck is still
warming up and it goes into open loop mode. The cool part is, in open loop
the o2 sensor is bypassed till the truck warms up! Now you can adjust the
next biggest factor, the map sensor. Basically, you want to adjust it to
where the computer thinks the engine is pulling more vacuum than normal at
WOT. finally, you adjust the iat sensor to compensate for whatever the
coolant temp was adjusted too so that the computer thinks everything is
normal, this also has a small effect on fuel mixture. Now, no too engines
can handle the same amounts of fuel to run best even if they have the same
mods. this is why potentiometers are used instead of resistors.
potentiometers are adjustable and resistors aren't, so you can tune it for
factors that change. Such as weather temp, or when adding new mods. The
thing about it is whenever you adjust it, what feels good at WOT might not
feel good at part throttle. The way mine is set up is fine for me because I
only need a set mixture for WOT while I race, then I turn them off for
normal driving. you can set up a system that adjusts automatically in
conjunction with how much throttle your giving it, but it wouldn't be cheap.
now that my fingers hurt, I'm gonna stop. there's more info but if anyone is
interested let me know and I'll write privately.
Aaron
99 318 manual cc
"5.2 liter 5.9 eater"
----- Original Message -----
From: Dave Scelfo <macncheesemonster@hotmail.com>
To: <dakota-truck@buffnet.net>
Sent: Tuesday, March 21, 2000 12:03 PM
Subject: Re: DML: R/T MPG
> I'm afraid I have no idea what you're talking about. Please elaborate.
>
>
> >well, I have a 318 that I can adjust my fuel mileage on the fly
> >electronically. but I didn't want to say anything to tick off you r/t
> >fella's. you can't override the computer, but you CAN get around it. :)
> >
> >Aaron
> >99 sport 318 CC
> >12 sec or bust
> >
> ______________________________________________________
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>
>
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