Does anyone have a nice relationship established, to get the % from the volts? Most scan tools display the actual TPS voltage. I think I read that CraigM has this option in his free scan tool. Something like inputing your idle volts, and max TPS voltage, to get the %. I'm sure I could figure this out, but if it has been done before, I would like to see it!

TIA!

This is where MAF and SD differ. The MAF system ACTUALLY uses %TPS too, but, for whatever reason, GM decided to only include the voltage in the ALDL data stream. But, the actual %TPS is there in the RAM for MAF cars.

For SD, GM decided to actually include the %TPS along with the TPS voltage. The SD system is also "self-adjusting" in that it always makes the max TPS voltage (at WOT) that it can obtain 100%, and the minimum TPS voltage (at idle) 0%.

I haven't study the MAF system as much as I have the SD, but from the parts that I have read, internally the MAF system appears to do the same. Just that GM has chosen NOT to include the %TPS in the ALDL data stream.

Just what Glen said.

If you want to see the equations I used for the MAF TPS % as a function of idle and WOT TPS voltage settings, just take a look at the 850b source code, it's in there. Just do a search for 'throttle', in the source code, it'll pop out.

Craig, have you ever considered having a "modified version" of your Scan Tool where you either "sacrifice" a useless/seldom used variable in the ALDL stream. Or, better yet, add the %TPS variable to ALDL data stream?

This kinda goes back to the old 'don't keep your foot on the accelerator when cranking a FI vehicle'.

I know that when adjusting my TB screw my TPS will change. I had the scanner hooked up and even though TPS voltage was increasing, after a blip of the throttle, the scanner reported TPS as being back to 0% even though the voltage was higher. Then, after a certain point and more TB adjusting, it finally froze at about 6% no matter what.

If I did my homework correctly, it appears that the lowest voltage the ECM sees in open loop will be applied as 0% throttle in closed loop. This is the only thing I can think of as to why the higher voltage started to not correlate to 0% TPS. After I shut the car off and disconnected the battery, that higher voltage was once again at 0%.

Is this correct? Not really a problem, but just something I ran into and wondered if anyone had an explanation.

<edit> BTW, SD setup

The program now will log the %TPS I believe as a variable.

As for logging only specific variables, there is the 'abbreviated' mode which only logs the values on screen 4.

I've considered making an option where you could select the specific values you want to log, and then only acquiring those values from the ECM, thus accelerating the comm beyond the refresh rates possible with pulling the whole byte series.

Good info, fellas. I wish the MAF cars worked the same as the SD ecms. I know they use the %TPS in the '165 ecm, there are several other parameters that use it, just a shame that GM wouldn't pull it out in the datastream.

Craig, any tips to where I can find that 850b source code? I'd still like to see your equations.

There is also a table of crank fuel PW multipler VS %TPS, so you could change the multipler at 0%tps to something greater than 1.0, if you were having starting problems. IOW, leave your foot off the pedal when starting!!

Try:
http://ice.prohosting.com/moates/gmecm/index.html
The source code is part of the beta download...
-Craig

Here's the equation:

meas(68) = 100 * (meas(66) - tpszero) / (tpswot - tpszero)

Where meas(68)=%TPS, and meas(66)=TPS volts. The TPSzero is your value, and so is the TPSWOT, these are the values you dial in when you're adjusting the TPS.

Thanks Craig, that is what I was looking for. I will set up a spreadsheet with the formula and the values for idle and WOT. These will in a table with reference to the look-up value.

In fact, I could import the raw data from my scan tool, and input those values to the formula......
Now you got me thinking....

Thinking's good...