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Originally Posted by generalconfusion
I went out and rechecked the throttle position at wide open throttle...went back to the manual and here is what it says....here are the results;
REL TPS(0-100%)- Relative Throttle Position is the normalized relative throttle position. My Jeep at WOT shows 76%
THROTTLE CMD(0-100%)- Command Throttle Actuator Control is the position of the throttle. If throttle is closed the percentage will be 0% and if wide open 100%. My Jeep at WOT shows 76%
THROTTLE POSITION(0-100%) - Absolute Throttle Position is the position the throttle is closed. The more the throttle is closed the less the percentage is shown. My Jeep at WOT shows 86%
ACC POSITION(0-100%) -Accelerator Position represents normalized distance the gas pedal is pressed. My Jeep at WOT shows 91%
So what this tells me is in fact that we are seeing about 3/4 throttle opening and in my case the pedal is pressed 91%. The book shows what the IAT sensor does and it in fact affects fuel and timing. My timing shows at WOT about 22 deg then at shifts drops to 17deg and climbs back to 22deg. Throttle never moves during shifts but one thing I did notice is that it does not move that fast from the time you floor it to the time it opens to its maximum.
Maybe someone with more experience with this could shed some light.
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First this is a complicated system, we are more like passengers that have control of these vehicles than the masters of it.
There are two modes of operation of the tables by the PCM
Open Loop and Closed Loop.
I don't have my notes home but there are about 6 parameters monitored by the PCM in Open Loop.
Coolant temp
IAT
OAT (input by FCM)
MAP
Crankshaft position sensor
Camshaft position sensor
(Not to even mention the 20-30 Can Bus inputs like shifter node position)
There are about 8-10 parameters monitored by the PCM in Closed Loop operation
All of the above under the open loop plus
all (4) O2 sensors.
(again not to mention 20-30 Can Bus inputs)
The Key point when the PCM goes from open to closed loop at idle condition is coolant temperature.
I have yet to specifically define the magic number but after digging into DC files it will be some goofy number like 187.4 degrees F as opposed to say 185 degrees F
(If you notice some of the RPM/Fuel/timing tables at engine off cold, target High idle speed is around 1426 RPM) Who would pick a goofy number like that??
DCX is who.
There are a few scenarios of open loop.
(1) When the engine is cold as in first startup that is a open loop.
(2) WOT at any coolant temperature is a open Loop operation.
(3) Sudden Deceleration.
Ok I'll try to unravel whats happening one thing at a time.
(1) First we all know we have throttle by wire.
(2) When you jam your right foot to the floorboard you are only suggesting to the PCM you want WOT, the PCM will decide for you what you are going to get depending on the parameters it sees and what you would like it to do.
(3) The accelerator pedal node and the throttle body motor are not directly connected for linear operation.
(So every single person here depending on the PCM style/type will see some disparity in the percentage of opening. BUT I GUARANTEE no one will see 100 Percent as defined by myself as the throttle plate to throttle body at 90 degrees presented as the least amount of cross section of the throttle plate)
OK I gotta get running for this AM
I'll add more this PM
Jeff
You are the man!
Linear Mode
