Fuel consumption signal

[itix]

Hi!

I am researching trying to figure out if I should buy the UT-comp pro and associated sensors or not. I have a Subaru impreza wrx sti 2008. It's a family mobile and a street car so any modifications have to retain original functionality to 110 percent. The ECU is very programmable and support everything from flex fuel sensors to bigger injectors etc. I like the idea of the ut-comp very much as I can see a lot of parameters that the ECU cant see like EGTs, continous oil pressure, potentially transmission temps etc.

I like the idea of a display as well. Despite having an android stereo and possibility to run info through there, I want a display for when I play music or have naviagtion up on the screen. This require me to use the only space available which is where the clock/outside temp/fuel consumption display lives today. Modifying this space to fit the 3.2 display is not a problem and will look OEM but it will obscure the old display. All the OEM functionality has to stay - I am quite adamant about this so my idea is to move the data to the new display.

Clock - not a problem, outside temp - not a problem, fuel consumption... problem. There is a fuel consumption signal to the clock micro computer today but it comes via can bus from the instrument cluster (of all locations) who presumably gets injector signals from the ECU via can bus. The UT-comp doesn't do can bus from what I have understood so my thought was to use injector triggers but when I read the wiring diagram they are controlled by the ECU by switching the earths. If I splice into the wires it will be a constant 12V so completely useless (and I didn't really like the idea of altering the impedance in that circuit anyway no matter how insignificantly).

Is there something that I can use to read the magnetic field surrounding the injector leads (like an amp-meter or timing light does) and maybe amplify that signal to the UT-comp? I used my best google fu but came up empty handed.

[ArT]

(...) The UT-comp doesn't do can bus from what I have understood so my thought was to use injector triggers but when I read the wiring diagram they are controlled by the ECU by switching the earths. If I splice into the wires it will be a constant 12V so completely useless (and I didn't really like the idea of altering the impedance in that circuit anyway no matter how insignificantly).

UTCOMP-PRO does not support can bus, but injectors controlled by ground is exactly what you need. You have 2 wires connected to injector, one is +12V constant, second is +12V controller with GND (injection opening) - you should connect the second wire to pin A10 and it will work. Please check manual page 17 for more details https://www.reveltronics.com/downloads/ ... manual.pdf

[itix]

Aha!
I read the manual but couldn't figure out that it was designed to be grounded together with the injector by the ECU.
For some reason I understood it like the ut-comp was expecting a 12v signal when the injector was opening.

So I assume the utcomp is designed with a high impedance output to the injector ground on the ecu and that's how it gets its signal?

That helps a lot, thanks. I'll definitely purchase one now

[ArT]

Exactly, it's high impedance input and you can connect injector signal in parallel. It's working also with injector +12V controlled - in settings you can choose type of signal, PWM- (ground controlled) or PWM+ (+12V controlled).

[gtbtdi]

Hi!
I have similar problem, but with 2003 (AVF) TDI passat.
Pin for fuel consumption signal was empty in the instrument cluster, so I spliced signal from one of the PD(piezo)injectors.
I searched for signal waveform and it looks like this:https://www.picoauto.com/images/uploads ... orm-01.png
If I change injection const. in Utcomp I can make idle consumption same as instrument cluster, but when driving consumption is like 10% compared to instrument cluster.
Also RPM display goes through the roof, idle shows 16000rpm.

[ArT]

You need to connect consumption signal from ECU.
Signal from PD injector will be not accurate without measuring fuel pressure.

In AVF ecu you should have fuel consumption signal at pin 20 (white-blue wire)

[gtbtdi]

I switched wire to the pin20, now utcomp shows only zero l/h.
There is another white-blue wire in pin 21. could signal be there? I don't have pinout for ECU so I'm afraid to just try.

[ArT]

Did you have white-blue on pin 20? or only at pin 21?
Please send me your ECU picture (connectors) before testing it on pin21.

Please note also that you should set PWM (+) control signal in settings - otherwise it will not work.

[gtbtdi]

I connected wire only to the pin 20. Utcomp is set for PWM(-).
I noticed that utcomp shows readings while car is moving, but I think they are not consumption related. For example rolling downhill with gear on, instrument cluster goes to zero while utcomp is showing readings.
When I stop utcomp display goes to zero.

Brown-Yellow goes to the utcomp pin A10

ECU_pins.jpg (74.47 KiB) Viewed 8605 times

ECU_connector.jpg (26.14 KiB) Viewed 8605 times

ECU.jpg (39.8 KiB) Viewed 8605 times

[ArT]

It seems that pin 20 is programmed to speed signal in this ECU.
Please check PIN 28 - it should be yellow wire.
And please set PWM+ in settings.