Throttle Position % Wrong on SAFC, Why?

[DSMRevolution]

I put a APEXi S-AFC in my 1G a few days ago and everything seemed to be okay. Throttle position read correctly along with all other settings. Now yesterday I hooked up my logger and went out and started tuning. After about 30 minutes into tuning I noticed my TPS readings on my SAFC were wrong. If the pedal was pressed to the floor then the AFC would show 100%, which was correct. The problem though is that 0% throttle happens on the AFC when the pedal is only half way roughly. My logger shows the correct reading but the AFC is wrong. It worked fine before which made me clueless.

I took out the ECU again today to check connection. I pulled on it and it was okay (everything soldered) but I did take the wire off and resolder it just to make sure. After resoldering and testing resistance between the AFC and the ECU everything was okay. I installed the ECU along with everything else back into the car and the same problem still exists. I did the "sensor check" mode to make sure it was functioning correctly but it shows the exact reading I got when % was displayed on the previous screen. I am reaching 4.9x volts WOT and 0.00v at half throttle roughly.

Anybody have any ideas? The closest thread I saw that would compaire to my problem is here

Thanks

 

[DaveT]

I believe the AFC looks at the voltage coming from the TPS. It takes the lowest voltage (meaning the throttle plate is closed) and relates that to 0%. At WOT (throtte plate fully open) the AFC reads 100%. What the AFC doesn't know is that the throttle plate is not fully close when the pedal is completely depressed. It's not smart enough ie. wasn't programmed into the AFC.

The ECU on the other hand know that the throttle plate is not completely shut, which results in the pocketlogger displaying 11% or so. I would just go by what the logger displays.

If any of this is wrong, let me know as I can not remember where I found that info, but I hope it makes sense.

DaveT
92GSX

 

[DaveT]

The problem though is that 0% throttle happens on the AFC when the pedal is only half way roughly. My logger shows the correct reading but the AFC is wrong.

But this has me baffled (I had to read through your post again). I am assuming you reinitialized everything in the AFC after you checked the connections. I don't remember everything you have to do to set the AFC up after the install.

DaveT
92GSX

 

[DSMRevolution]

Thanks Dave. That was a big help. Sorry though, I should have clarified what I meant better from your second post. What I ment was:

The AFC reads 0% throttle opening from fully depressed to half pressed. Once I reach the half way point with my foot pedal the AFC reads correctly and I get throttle position from 0% up until I reach 100% which is also shown by the AFC.

I hope that helps clarify that, sorry for the confusion.

I did not reinitialize everything since I checked connections. I wasn't sure if I had to or not. I will however do that after noting settings and update this thread again stating wether this fixed my problem or not. Thanks again for the help!

 

[DaveT]

Once I reach the half way point with my foot pedal the AFC reads correctly and I get throttle position from 0% up until I reach 100% which is also shown by the AFC.

The end of the sentence, did you mean "which is also shown by the pocketlogger"?. So this is what is happening (I'm guessing):

Pedal AFC Pocketlogger
Depressed -> 0% 11%
Halfpressed -> 0% 50%
3/4pressed -> ~50% 75%
Fullpressed -> 100% 100%

Does this make sense?

DaveT
92GSX

 

[MindBlowin03]

Im having a similar problem with my TPS and AFC numbers. My AFC TPS hits 100% at like 75% of actual throttle(via logger). The funny part is that my voltage is fine on the AFC. Starts near 0 and gradually ends up ~4.9+ at WOT. The only thing Ive heard is that the AFC uses 'fuzzy' logic and needs to read the lowest and highest voltage point and learn where to go. Mine has been on for about a week with no luck so far. Sorry I cant be of more help.

 

[steve]

As discussed the SAFC scales it's TPS display based on the min and max voltage it's seen since it was reset.

The 1G ECU outputs the absolute voltage it sees scaled to fit in a 8 bit value 0-5v. With the throttle closed the TPS should output about 0.5v and a datalogger will display about 10%. If you getting readings different than this on your datalogger then you should check your TPS, TB, and cable

What the TPS will output at WOT depends on several things and is non-critical since the ECU doesn't care if the TPS ever goes 100%. Those things are the actual value of the +5v sensor power at the TPS, the resistance of the TPS at WOT, and how far your butterfly acually opens with the petal to the floor.

The mechanical part is the only thing you can somewhat adjust. The throttle cable has a specification of how much slack should be in it with the throttle closed. Too little and the butterfly will be held open at idle, too much and the butterfly won't open as far as it might.

Steve

 

[DSMRevolution]

The end of the sentence, did you mean "which is also shown by the pocketlogger"?. So this is what is happening (I'm guessing):

Pedal AFC Pocketlogger
Depressed -> 0% 11%
Halfpressed -> 0% 50%
3/4pressed -> ~50% 75%
Fullpressed -> 100% 100%

Does this make sense?

DaveT
92GSX

Yeah that is exactly what is happening. I did try to reinitialize the AFC now and it still acts the same as far as TPS goes.

Steve - On my logger (I use MMCD) at idle with the pedal depressed it reads 10.1% so I do not believe the TPS is my problem.

Thanks everybody for the help so far. I did a few test runs and got my tuned pretty well so no problems that the TPS would cause.

 

[MindBlowin03]

The thing I worry about is when you set your min/max, is the AFC going by its TPS or voltage? That means alot in our situations.

 

[steve]

I don't understand your question.

Steve

 

[MindBlowin03]

Here is what I mean for my case. My AFC voltage reads perfectly with throttle, but not the AFC TPS. The AFC TPS reads 100% about 3/4 throttle(although my throttle and actual TPS are fine). So if I want to set my high settings on the AFC to 75%, where do I actually set it? If the AFC goes strictly by its TPS then I need to set it at 100% for it to actually be 75%(remember my actual 75% is 100% for AFC TPS), but if the AFC reads from its voltage then I can set it to 75% without problems(my AFC voltage reads perfect with throttle).

That may seem a bit confusing, but I dont know what to do really. I tried resetting my AFC and ECU several times already with no success.

 

[steve]

Resetting the ECU won't have any impact on this.

Sorry I don't have much else to add. I can only guess that if your SAFC displays reasonable throttle voltage values when using the sensor check function, and you've selected the throttle sensor type, trained the SAFC to the throttle opening, and saved the values by turning the SAFC off, and it still displays wrong percentages you might want to get the SAFC checked.

Steve

 

[DSMRevolution]

Well I went out and played around with my SAFC settings today and got a fairly good log. Car pulls strong and even though it shows that the TPS percentage is off, it didn't seem to have any impact on tuning. I guess I will just see how it goes. It seems to be switching to the correct table (high/low settings) at the correct time (inaccurate, but my foot pedal location) so it isn't worrying me too much. Thanks for the help and if anybody comes up with any ideas then please post here! I will email Apexi (if they have a address of course) and see what their say on this is.