Trip computer - calibrating tank size

[Henka]

So... I calibrated my trip computer according to S2central.com. In my opinion the procedure described on that page is not entirely correct. I got the instructions from Audi Sweden. There are similaritys but they also differ.

First off. The fuel guage should not be set to show full at full tank (!). When the service tool vw1301 in set according to the instructions the guage should be set to point at the third red bar.

Next thing - calibrating fuel reserve. When using the vw1301 tool the trip comp should show the number 80. This number is the same for all S2's, regardless of model (Coupé, Sedan or Avant). It stated on S2central that this reading is how much fuel you have in the tank. That might be - but I don't believe it since the reading should be the same regardless of model - the tank size differs from Sedan/Avant and Coupé (checked it on my buddies RS2 - it basically implies that the sedan has a bigger tank than it actually has).

Maybe the S2Central way works - I can't say it worked all that well for me though.

I'm going to round up the mentioned service tool and check how it works - if anyone wants a write up on the full procedure I'll try to translate the Audi manual on it.


And - I did not write this to bash S2Central - I tried the method described on there, I wrote a mail asking for more directions...and then I contacted Audi Sweden. A very fast reply from them, they sent me the instructions... All I need now is the VW1301 tool.

[S2sedan]

what is this tool, as I changed my fuel pump and use another kind of combustible (alcohol) my gauge is not 100 % accurate anymore.
Do you know the real size from the S2 Sedan ???

Infos would be great.

Cheers Eduardo

[RS2 CQ]

So... I calibrated my trip computer according to S2central.com. In my opinion the procedure described on that page is not entirely correct. I got the instructions from Audi Sweden. There are similaritys but they also differ.
.

If my trip computer is not working does that mean I need to calibrate it? The speed and timer works, but nothing to do with fuel consumption works. This problem occured after engine swap and new program from Minhea.

[Henka]

I really can't tell. I thought that the trip comp only checked the values in the map and multiplied it with speed/distance/time (not sure what variabel though) and the just presented them on the screen. This would imply that no matter what you do the board comp will know how much fuel you use. BUT - this is only true when you have stock injectros and stock fuel pressure. Why? Well, the equation that the board comp solves when calculating fuel consumption has some fixed variabels (FI fuel pressure and injector size). Messing with these variables will make the whole thing go nuts - and that is just too bad. I mean, I use my car daily and I really don't like this. But it's a fact of life. Now - you can calibrate the fuel consumption up to 20% more - but let's face it, on a engine dynoed at 350hp those 20% won't mean squat. There are three resistors (or it might be somkind of locigal circuits) on the instruments that you can adjust to set the fuelconumption - maybe those three components could be changed to get a more accurate reading - it won't be easy to get it right though.

On an engine that has been modified all that is left are the variables used to calculate fuelconsumtion: average speed and time. So there isn't any real life use to have that comp afterall. I just get pissed off looking at the thing as it's just giving information that is totally wrong.

A fuelconsumption reading is very hard to create if you don't just read values from the map. You would need to know how much fuel that goes into the fual rail at every time and how much is returned to the tank. Meassuring flow is expensive and complicated (now, think like you where a car manufacturer!). This means that reading from the map is the only way. Mess with fuel pressure and injectorsize and you're toast.

I hope that there is a way to get this thing working...but I really just think we'll have to accept the fact that our board comp is reding it all wrong...

[porkkis]

Henka, IIRC the fuel consuption signal is 0 to 5 volts from the ecu so the signal could be changed with some resistor or other direction would need an amplifier circuit.

The same applies to the boost signal used on C3 and C4 chassis cars.

[Liam Gallagher]

What is the MAP? I'm drawing a blank on this.

[audiman]

Yep, nothing to do with the ECU changes, its down to engine fettling. My car now does 40mpg on a run with 550cc injectors. LMAO, it is only really 27mpg

[RS2 CQ]

Yep, nothing to do with the ECU changes, its down to engine fettling. My car now does 40mpg on a run with 550cc injectors. LMAO, it is only really 27mpg

So let me get this staight...You guys are basically saying my computer will not work if not running stock everything? I do have a stock RS2 engine....just the program is diferent since the RS2 ECU locks and we couldn't unlock it. But I have a MAP from Minhea, that I assume on the low power setting is similar to RS2 stock. My display reads like 200 for the MPG, dist to empty etc. It almost seems as if it is not gettting some information. Oh well, the timer works and the ave speed works so it is worth something.

[Henka]

Hey... Now that's cool! This means there will really be no problemo fiddling with it to show correct readings. Cool. As I stated above, I believed it was a more complicated system than that.

[Mihnea]

Chris, IMHO this has nothing to do with my chip, IIRC you are using a 7A trip computer, right?

This problem occured after engine swap and new program from Minhea.

[Mihnea]

just the program is diferent since the RS2 ECU locks and we couldn't unlock it. But I have a MAP from Minhea, that I assume on the low power setting is similar to RS2 stock.

The low power program in your car IS stock RS2, the only mod done to it is the removal of the immobilizer (which not many people can do the way I do it) and the boost chip is modded for the WG spring. Your car performs like a stock RS2 in low power mode.

HTH,


Mihnea

[porkkis]

Hey... Now that's cool! This means there will really be no problemo fiddling with it to show correct readings. Cool. As I stated above, I believed it was a more complicated system than that.

That's right. It can't be much more complicated as the same onboard computer unit is used with several different engine types and vice versa same engines are used on different chassis -> different computers.

@RS2CQ
Mihnea is quite probably right. You have another problem with the wiring or the instrument cluster and there is no link to the chips used.

[RS2 CQ]

That's right. It can't be much more complicated as the same onboard computer unit is used with several different engine types and vice versa same engines are used on different chassis -> different computers.

@RS2CQ
Mihnea is quite probably right. You have another problem with the wiring or the instrument cluster and there is no link to the chips used.

So that is good news, thanks. Now I just have to find the wiring problem. Anyone have any ideas? Seems the computer is getting speed and time, so it must have something to do with fuel.

Also from what I understand, when I switch ECU to high boost, the computer will not work....correct?

[Mihnea]

Chris, you got me wrong, if you switch to high boost, the trip computer should work the same as on low boost. i.e. if it's working fine, it's gonna work fine, if it has a problem, it's still gonna have a problem...

This could be due to your early 7A trip computer type only, not necessarily to the wiring, but it could well be that the TC isn't getting any fuel consumption info from the ECU, and that could be the cause of your problems...

HTH,

Mihnea

So that is good news, thanks. Now I just have to find the wiring problem. Anyone have any ideas? Seems the computer is getting speed and time, so it must have something to do with fuel.

Also from what I understand, when I switch ECU to high boost, the computer will not work....correct?

[RS2 CQ]

Chris, you got me wrong, if you switch to high boost, the trip computer should work the same as on low boost. i.e. if it's working fine, it's gonna work fine, if it has a problem, it's still gonna have a problem...

This could be due to your early 7A trip computer type only, not necessarily to the wiring, but it could well be that the TC isn't getting any fuel consumption info from the ECU, and that could be the cause of your problems...

HTH,

Mihnea

Minhea,
Even better news. But how does the TC get the info from the ECU? Could there be a wire from ecu to TC missing? Is the TC actually in the instrument cluster, or is that just a display?

Good to see you around....hope you're not working to much!