TPS % always above 20?

[03worthy4link]

Recently purchased a modded ZL1, playing with the aeroforce gauges I noticed that the Throttle position sensor percentage does not go below 20% even at idle. The car does have some mods and a tune, is this perhaps how to tuner got rid of skip shift or is there another possible explanation? Just a curiosity.

[RobZL1]

Normal. You'll find the max is 84% as well. I don't have an interceptor, but if you can select another PID with it, you'll be able to find one that spans 0-100

[silversleeper]

I think they didn't get the software quite right in converting the voltage or resistance to the actual throttle position displayed on the tuner info. I don't recall the ranges I saw, I was thinking it was 90 some percent max. It wasn't as low or as high as I expected, like 0 or 5% or 99 or 100%.

[RobZL1]

On the SCT, there are PID's that run 19%-84%, as well as PID's that run 0%-100%. So, the data is in there, it's just extracting it- not sure if the aeroforce can grab all of the available channels or not?

[ABADZL1]

Originally Posted by silversleeper

I think they didn't get the software quite right in converting the voltage or resistance to the actual throttle position displayed on the tuner info. I don't recall the ranges I saw, I was thinking it was 90 some percent max. It wasn't as low or as high as I expected, like 0 or 5% or 99 or 100%.

Rob is correct. Max TPS% is 84. The "software" is not converting any voltage. It is simply displaying exactly what the ECM is seeing directly from the databus. Cars that are modded with cams will read slightly higher than stock percentages at idle due to the requirement to increase base running airflow in the tune file. Kinda like an idle set screw.

[silversleeper]

Originally Posted by ABADZL1

Rob is correct. Max TPS% is 84. The "software" is not converting any voltage. It is simply displaying exactly what the ECM is seeing directly from the databus. Cars that are modded with cams will read slightly higher than stock percentages at idle due to the requirement to increase base running airflow in the tune file. Kinda like an idle set screw.

So you figure it's a mechanical link from the throttle plate to the display and not an analog voltage that is being read and processed with code, aka software...ooookay.


I just went out and checked mine with a OBDII dongle and I get as low as 18% at idle. And like Rob said you can select from a different PID data port that the computer uses different algorithms to display a value. All done mechanically of course.

[RobZL1]

Not at all what he said. The gauge is simply repeating real time data being captured by the ecm. TPS reads about 19 to 84. It has to do with percent of voltage span I believe. If you log ETC pedal position (or other PID's), you'll get 0-100%. This is well known on e38's, e67's and other late model gm ecm's. Do a Google search on hptuners or efilive forums for confirmation if you are still skeptical.

Edit: I didn't see your edit until after I posted. All I was saying is he was making a comparison to a mechanical system for explanation purposes.

[silversleeper]

That's what I said.
http://www.camaro5.com/forums/showth...ight=tuner+tps
There is a thread where people are getting 89% at full throttle. IIRC my handheld or HP tuner broke into 90s but that isn't the point. The point is that as it's converting the reading from the TPS sensor which at least used to be OHMs of resistance which was transmitted to the ECM as a voltage reading according to throttle opening. The ECM which runs code / software, and it is output via the "PIDS" as values. You can use code aka software to change the value from metric to standard etc if your reader or gauge supports that. Why the commonly used TPS PID doesn't go 0-100 is beyond me, but it is a code thing inside the ECM.
IIRC the MAF sensors use a heated wire and as more airflow cools it the value is converted to a frequency that is sent to the ECM.
So the software in the ECM doesn't display a 0-100 value where you expect and the software in the unit is not reading the correct PID for the data you actually want to view. That's what I said. But if someone wants to think there is no software involved. whatever.

[ABADZL1]

silver, There are many PID's related to throttle body that you can log. TPS% is just one of them. TPS% is the main one I use for tuning cars. Here is a list of all your options to view. Some of them are 0-100%. But not the TPS% one.



An image of my scanner at WOT.

[DGthe3]

Makes sense that a running engine would never see 0% throttle as that should close off all air going into the engine. It makes less sense to me why a system would be calibrated to read '0' at idle.

[silversleeper]

Originally Posted by DGthe3

Makes sense that a running engine would never see 0% throttle as that should close off all air going into the engine. It makes less sense to me why a system would be calibrated to read '0' at idle.

Yes, that part makes sense. But why "wide open throttle" it would be 8x% or 90% doesn't sound like a logical value. And you'd think at idle it would be more like 5% or less. Not 18% or 20% as it is from that PID. I know throttle opening isn't completely linear to hp, but imagine 20% of 580hp at idle. Over 100hp to drive the alternator oil pump and friction, not hardly.

[ABADZL1]

Because it's a ratio. TPS% ratio is used by other tables in your tune file. For example; it's used for the Power Enrichment TPS% vs. RPM table. If this "ratio" were not correct, you would have issues when you step on the throttle. TPS% ratio is also used bigtime on the engines that have AFM.
If you want to look at something that is 0-100, then log throttle actuator. No one here should be wasting time on why it seems illogical to work the way it does. Been working like this since 1996