Excellent info! Thanks !!!
-Doug in Vermont
> -----Original Message-----
> From: Tim Berry [SMTP:coolva1@home.com]
> Sent: Tuesday, September 12, 2000 8:28 PM
> To: dakota-truck@buffnet.net
> Subject: DML: Found info on our Dakota computers!! (must read!!)
>
> I found this on Moparchat.com in a message... (looooonnnnnnnggggg)
>
> Here's a topic I can hopefully help with, Chrysler electronics are my
> specialty.
> As far as the pcm having to relearn after every mod, yes this is true. As
> far as the pcm resetting to factory programmed specs after the batt is
> disconnected (for about 5 to 10 minutes, there is a memory capacitor that
> has to discharge) that is also true. However the pcm is constantly
> "learning" any time it is in closed loop operation, ie O2 sensor(s) hot
> and
> properly sigaling the pcm. (usually takes 20 seconds to 2 minutes after
> startup for the pcm to go into closed loop operation)
> You cannot disable the pcm's ability to learn, nor would you want to.
>
> The reason why your truck runs faster after several drag runs has more to
> do
> with deposits in the injectors and on the pistons/valves than learning,
> because the pcm is in open loop during WOT (wide open throttle)
> acceleration.
>
> Fuel injector deposits obviously are going to cause a slightly leaner
> mixture, the carbon on the pistons will tend to cause slightly higher
> compression, and the carbon on the backs of the intake valves acts like a
> sponge and actually soaks some fuel out of the incoming air/fuel charge,
> which in conjunction with the allready the leaner than ideal mix from the
> injectors, causes detonation, even though it may not be enough for you to
> hear it. Obviosly, the lean mixture does not make as much power anyway,
> even
> if it doesn't preignite (detonate)
>
> DETONATION = LESS POWER
> LEAN = LESS POWER
>
> Obviosly the more high speed runs you make, the cleaner the injectors get,
> as well as burning off carbon deposits on the pistons and valves.
>
> So the old saying about "blowing the carbon out" or making a few high
> speed
> hard acceration back road runs, really does hold true, it is good for the
> motor.
>
> Now to really confuse the issue. You cannot set the timing on 91 up Magnum
> engines. Sure, you can move the distributor, bi\ut the pcm determines
> timing
> based solely on input from the crank position sensor, the sensor in the
> distributor is only there to determine TDC compression stroke for #1
> cylinder during startup. This allows the pcm to properly time the fuel
> injection pulse. In fact, you can unhook this sensor with the engine
> running, and other than the Check Engine light coming on, there is no
> affect, the engine continues to run just fine. Dodge also does not use a
> knock sensor, or EGR valve (96 up) to help control detonation. So
> basically,
> every thing has to be just perfect, or you will get detonation an lose
> power. The cleaner you get everything inside you engine, the closer to
> factory "perfect" it will be, and the less detonation you get.
>
> On to the transmission. 1-2 and 2-1 shifts are entirely controlled by
> pressure. The other shifts are shifted by pressure acting on the valves,
> servos etc, the pcm actually controls the govenor and therefor th
> pressure,
> electronically to get the trans to shift when it wants it to. It has no
> ability to learn when to shift. it simply looks at coolant and trans
> temperatures, throttle position, road speed, acceration rate, and a few
> other variables to shift the trans. Moving the throttle valve cable to
> increase the cables travel (move the cable body towards the firewall) will
> cause a delayed 1-2 shift, and slightly harsher 1-2 2-3 shifts. There is
> no
> affect on 3-4 as it is shifted fully electronically by a solenoid
> controlled
> directly by the pcm. All of this applies only to the RE series
> transmissions.
>
> Those of you who have the 45RFE trans (4.7L only) it is fully electronic,
> all shifts are controlled directly by the TCM (trans controll module) by
> solenoids. With a custom built TCM, it is possible to make this trans
> shift
> any way you want it to.On a side note, Dodges Auto Stick transmission is
> nothing more than the normal fully electronic Caravan or Intrepid
> transmission, with a different tcm that allows the driver to decide when
> to
> shift. (up to a certain point, it won't let you downshift to 1st at 70!)
>
> A little clarification... open loop is when the pcm is running solely on
> preprogrammed fuel, and spark timing maps. closed loop is when the O2
> sensor(s) are awake, and the pcm moduifys the fuel and spark maps
> according
> to siganls from the O2 sensors, this is the mode where the pcm learns.
>
> I know this was a very long post, and probably full of typos, but I just
> wanted to clear up the subjects as mch as possible. As allways, if anyone
> would like to add there 2 cents or ask a question, feel free to emain me
> at
> jirion@triton.net or YAMAROCKET630@YAHHO.COM
> THANKS.
>
>
> ___________________
> Tim Berry
> Chesapeake, VA
> 97 CC, 4x2, auto, 318
> Best 1/4: 13.84@99.33
> ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
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