DSmith

At what TPS voltage does the ECM consider as WOT?

I have started playing around with the AFRturner program and to my understanding it only changes fuel at WOT. The reason for my question is that I have notice that my TPS voltage is 4.28 with the throttle blades the way open. With the voltage scale from 0 to 5 this would only be about 86%, just wondering if I need to make adjustments.

RBob

iTrader: (1)

Usually it is based on TPS%, which isn't a straight conversion from the voltage. Normally there is a gain factor applied.

On the MAF ECMs it is critical to set the TPS voltage at idle correctly. And, not have it go too high at WOT. Too high on WOT and the ECM sees it as an error and will drop out of PE mode.

Your data log will show when the ECM goes into PE mode. Can then check the TPS% or even the voltage at that point.

RBob.

Ronny

iTrader: (1)

RBob maybe you can expand on this further.

Lets say I am cruising at 20% TPS. I have PE invoke trigger set to 40%TPS. Does that mean I need to throttle to 60% TPS too see a PE event? Or is the net movement in excess of 40% like moving throttle to 21% further gonna trip PE?

Likewise on AE. There is a AETPS delta table. Again cruise at 20%TPS. If I move TPS quickly to 40%TPS does the look up occur at 20% in table or 40%. Or are there several lookups?

There must also be a trigger on both PE and AE for % of movement over a length of time. Such as a very gradual increase in TPS from say 5% to like 80% that will not trigger AE or PE and yet maintain CL.

RBob

iTrader: (1)

The TPS% threshold for PE mode is a set value. If it is at 40%, then once over that the ECM will be OK for PE mode. I say OK as they may be other qualifiers before PE is entered.

AE is a change in TPS% over time. Completely different.

RBob.

pandin

In TunerPro using the conversion in the xdf "0.390625 * X" will give the % and "x/51" will give the volts. The "X" value is actually the decimal number converted from Hexadecimal.

I have dual xdf for many of the TPS settings, % and volts (same address different conversion) .

This is nice the be able to use, what fits best, as to what you are looking for.

RBob

iTrader: (1)

You do realize that one can't convert between the TPS% value and the TPS volts value unless the gain & offset is used? IOW: what you are doing won't work correctly.

In the XDF you use the .390625 to convert a TPS% BIN value to a percentage. But you can't use the x/51 conversion to convert it to a voltage.

Then in the .ADS file the opposite is true. The ALDL stream has the TPS ADC value (convertable to voltage), but not the TPS% value.

You can do what the ECM does and retain the lowest seen TPS voltage (ADC value), then use the gain term from the calibration, the result being the actual TPS% value. The $6E mask does this, not sure about the $32 mask.

RBob.

pandin

Yes the volts is an approximation not true volts, but it gives a close to real number.

Low volts at .69 and high at 5.00 vs low at .54 and high at 5.00.

I can't hold the throttle steady enough to see the error.

Some people can't visualize the % to volts conversion in their head.

It is just a crutch for the mentally impaired.

DSmith

UMMM...... what was the question again?

anyway, thanks guys. I gonna say I do not have a problem with my TPS and not drive myself nuts wondering why is I need to be converting anything as far as the TPI is concerned.

DSmith

Does this mean that when I set my TPS to .55 it still my be off? I'm starting think there is no point in having this stuff if it not correct.

RBob

iTrader: (1)

Setting the TPS volts during idle to .54 V is correct. On GM 3rd gen TPI MAF setups this is important (note how I qualified which setups ).

In the $6E code the ECM checks and retains the lowest seen TPS value. It uses this as an offset to the current TPS volts. To convert the TPS voltage to a TPS% the code subtracts off this offset (lowest seen) from the current TPS voltage. Then multiplies the result by a gain factor (from the calibration). The result is the TPS in percentage.

So even if the total range is from .54 volts (idle) to 4.05 volts (WOT), the TPS% still goes from 0% to 100%. Note that it won't always go to 100% and sometimes it goes to 100% before WOT is reached. It is all in the gain term.

But at the same time you can change the gain value to make the TPS% go to exactly 100% once the throttle linkage is up against the stop.

ARAP has a gain value of 112 (@ $C3A3), and back converting from volts to ADC counts, for .54 V we have 28 counts, for 4.05 V we have 207 counts.

Subtract the idle counts from the WOT counts and we have 179 counts. Then multiply by the gain of 112 and divide by 64 for 313 counts. Which is over 100% (255). So for those values the TPS% will reach 100% before WOT is actually reached.

A value of about 92 for a gain would be better. This would put 100% TPS right at WOT (4.05V).

Make sense?

RBob.

DSmith

LOL !!!! I think you like spilling all that stuff like you do. It makes my head hurt just reading it but for some reason I keep on wanting to learn more.

Its like a bad drug.

pandin

In the $6E comments:

These are listed under the heading
" FUEL/AIR PARAMS"

"LC3A3 FCB 112 ; 57% TPS, THROT HI - THROT LO"

and the line below it is
" LC3A4 FCB 35 ; 13.7% TPS, Min TPS Throttle Posit
; Arg * 2.56" 35/2.56 = 13.7

the next two lines are
"LC3A5 FCB 1 ; 0.0039, FILT COEF, LOW TPS
LC3A6 FCB 16 ; 0.0625, COOL TEMP COEF
; Arg * 256"

If you divide 112 by 2.56 you get 43.75, so where did the 57% come from?

On my engine right at the 3A3 Dec 112 point (2.20 volts TPS) is were the Power Enrichment starts. Above this point AFR drops to 13:1 and below it is in closed loop (14.7:1).

I was wondering what adjusted this spot ?

and how does the a 92 gain affect the PE value at 1F2?

Thank you for all the detailed explanations.