Throttle position question

[mzh29]

I asked about this in another thread, but got no response. Probably because it was in the wrong section, and the wrong thread. sorry guys.

While driving with my superchips data logging, I was using the throttle position sensor monitoring feature. When I floored the gas, it would only go up to about 90% for a split second and then drop down to about 70%. Can anybody tell me why that is? I checked the throttle by putting some weight on the gas with the engine turned off and the throttle plate was as open as it can be. Any ideas why the computer is reading that it's not 100% open?

Thanks.

[robpp]

i dont know exact numbers Matt but I do remember seeing on the red site the SRT8 guys discussing 73% WOT on the sensor.

I dont remember the explanation but I'll go snoop around and see if I can dig it up.

[robpp]

From a post over there: I had the wrong % but point is you will never see 100%

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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.
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[Scottina06]

from what I know.....no vehicle throttles at 100%

[Dylans3960ccs]

is that just the cars with electric throttle?

[hemi.jon]

with the way the throttle blade is slanted at rest, if it opened 100% it would actually impeed the airflow. because of the new "slant" it would be on, the blade stops were it is because it is some what level and letting air move evenly above and below it.


it all makes sense in my head. :D i guess i could draw a picture or something

[Dylans3960ccs]

^^ it makes sense to me.

[ducks unlimited]

picture time! :D

[mzh29]

Ahhhh, I understand exactly what you're saying. Ok, thanks guys.

[hemi.jon]

ok

**disclaimer, im not a mopar engineer, nor know the truth, but this is what was in my head, i do have a good understanding of how things work by just looking, so this is what i think...


im looking at the fact that if throttle position is 100% that it would be a 90 degree turn inside the throttle body. the 90 degree turn would position the plate restricting space in the TB. so if it only opened 70% then it would be in a position were it would be flat and open letting more air across top and bottom.



this is my image, probably a few errors to are hemis..goin off memory..lol...(my head is more detailed...lol)

(image is side view)
http://img33.imageshack.us/img33/6256/throttle.png

[mzh29]

They should calibrate the throttle sensor to read 100% when max air is flowing through the throttle body!

[saleen032]

with the way the throttle blade is slanted at rest, if it opened 100% it would actually impeed the airflow. because of the new "slant" it would be on, the blade stops were it is because it is some what level and letting air move evenly above and below it.


it all makes sense in my head. :D i guess i could draw a picture or something


At 100% it would be optimum...you are thinkining degrees....just for example, if the max throttle opening was with the blade at 90 degrees in relationship to the throttle bore, then that would be its 100% opening point...just because the blade is slanted at rest, that has nothing to do with the 100% opening point....now if you start talking degrees, that is a different story.... Now in your drawing, you are thinking degrees and not percentages....which is what we are talking about....say a throttle was only designed to turn 45 degrees, if it turned the whole 45 degrees, it would be at 100%....so degrees and percentage are much different...

[hemi.jon]

At 100% it would be optimum...you are thinkining degrees....just for example, if the max throttle opening was with the blade at 90 degrees in relationship to the throttle bore, then that would be its 100% opening point...just because the blade is slanted at rest, that has nothing to do with the 100% opening point....now if you start talking degrees, that is a different story.... Now in your drawing, you are thinking degrees and not percentages....which is what we are talking about....say a throttle was only designed to turn 45 degrees, if it turned the whole 45 degrees, it would be at 100%....so degrees and percentage are much different...

thats exactly what i said, i was saying that 100% open would be 90 degrees from were it started. not relation to the bore. so i was using degrees and % together to maybe put an understanding on the whole thing

[saleen032]

thats exactly what i said, i was saying that 100% open would be 90 degrees from were it started. not relation to the bore. so i was using degrees and % together to maybe put an understanding on the whole thing

But the fully open position doesnt have to be 90 degrees from rest, it may only be 85 degrees from where it started..It doesnt have to be 90 degrees, and It can still be open 100% even though it only rotated 85 degrees

[hemi.jon]

but if its stoping flat and thats saying its 70% the extra 30 percent would put it at 90 degrees.

[saleen032]

but if its stoping flat and thats saying its 70% the extra 30 percent would put it at 90 degrees.


It can still be opening the full 100% but the TPS may be misadjusted or may not read correctly

[mzh29]

I guess if I'm not the only one then i'm not worried about it. Rob, does yours do the same thing? Scott?

[Scottina06]

nope....the blade only opens up to about 73% at WOT......its not opening up 100% but only reading 73%. That means the farthest the blade opens is 73% of its 100% capacity.

[jkram]

I would recalibrate the throttle. Then hook it up and see the result.

Key on, press the gas pedal to the floor slowly and release slowly. then start engine. I may not be remembering this correctly. That gives the PCM the full range of the pedal potentiometer.

I could be way off with this, but it is worth a try.