What makes things even more "complicated" is the fact that when you use the
15-second "Reboot" on the computer, that does the same as the 5-10 minutes.
;) (And that's already been proven at the local Dyno shop when we ran a
"reset" test on the parameters to see what the computer is doing before and
after the relearn curve.)
- Bernd
-----Original Message-----
From: owner-dakota-truck@buffnet.net
[mailto:owner-dakota-truck@buffnet.net]On Behalf Of Tim Berry
Sent: Tuesday, September 12, 2000 7:28 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
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:54:32 EDT