Being that the ECM is supposedly able to "autosense" the calibration of the TPS feedback every time the car is started... what is a normal TPS reading at idle? I'm thinking around .5vdc? Then let's talk about wide open throttle.. It's a TTL logic circuit with a max value of 5vdc... so if the throttle is fully depressed you should see somewhere in the neighborhood of 5vdc, right?

Now we get into the scan tool details in relation to the max TPS throttle voltage and what the ECM considers to be wide open throttle coz my stupid AutoXray scanner doesn't show throttle as a relative percentage to the throttle position. In other words.. 100% throttle is ~5vdc, right? So, if my car (all things considered, pedal alignment, throttle body bracket alignment, ASR cable alignment,etc) only sees 4.1vdc at wide open pedal FULLY depressed throttle, is this enough and does the ECM see 100% throttle?

So, how do I know if I'm not leaving myself short a tenth or two in the quarter mile? If 4.1vdc is not enough to signify 100% throttle position (the throttle body blades are for arguments sake all the way open) is there some way to adjust this out? (No oval slots in the TPS, remember, it's self calibrating through the ECM)

 

I'm probably the last guy to try and answer this...

If the computer goes open loop, even with the lower TPS voltage, then I would think it has entered PE mode.
If so as long as the throttle plates are all the way open, it whould be running at max power for the programing in the chip (Speed Density).

I don't know for sure if that is right or not, but it sounds correct

Just a thought.

 

Yeah, but, how does the ECM know whether it's actually at full wide open throttle.? I would guess, that at startup the ECM samples the "idle" voltage of the TPS, and then figures on adding maybe 3 to 3.5vdc for a w.o.t. condition to exist? I mean how else does it know that the throttle is wide open?

 

See I told you I'd be the last guy to try and answer.

I don't know for sure how the 'puter decides that it should be in PE mode.

I would think that the TPS is a big part of that, but if it's a percent of the voltage that it see's from start up or a fixed constant, that I don't know.

Sorry

KBK

 

If you look at the ALDL datastream ther is another value called %TPS - this is actually how all the tables are scaled in the computer.

To determine percent TPS the computer samples the voltage at key-on. This is 0% TPS as long as it is between 0.1 to 1V (0.1<TPS<1v). If it's out of this range a code is thrown.

WOT is achieved at 4v TPS. Extra voltage past this is fine until you hit 5v, at which point an error code is thrown.

So from Idle to 4v determines the range of tps. 0.5-0.6 are the normal settings you shoot for at idle, though honestly it doesn't matter to much.

 

Chris, thanks for the heads up on the TPS calibration. I've developed a minor problem with the ASR (probably the mechanics of the unit itself) in that the ASR to throttle body cable is pulled in at intermittent lengths dropping a tenth or two off of the the wot tps reading. That being said, knowing that full throttle is "seen" by the ECM at 4vdc, gives me a little wiggle room with the adjustment of the TPS and/or throttle linkage as a band aid (for the interim).. The t.b. butterfly and it's position difference for that .1vdc or .2vdc loss is next to not noticeable by the naked eye... what I'm getting at is that max flow is still achieved, but the TPS isn't necessarily feeding back the same... a little tweaking and it'll be a-ok.

 

To verify just look at the %TPS value. That is what the rest of the program actually sees - nowhere are any tables scaled vs. TPS volts. So as long as you hit 100% TPS you know you are fine. (which should correspond to over 4v).