Hardware fault on injector circuit. FIXED.

[Nigep]

I have a bit of an odd problem. Built my ECU several years ago, same time as a mate built one to the same spec. Wasted spark, VW 60-2 OEM trigger setup.

Fitted to my ITB`s with the MS1-Extra code and mapped it. The car ran for several years and I didn`t realise I had an issue.

Turns out I was running at 2-squirts per cycle. This wasn`t a problem, the injectors were big enough so duty cycle wasn`t a concern.


Now I`ve gone Forced induction, bought some 640cc Bosch injectors, 4 Bar FPR and mapped it. Was getting over 100% duty cycle at high RPM, so tried to change it to 1 squirt per cycle.

Now we hit the problem. It simply won`t idle smoothly or run well on 1-squirt per cycle. Change it to 2 and it`s as smooth as you like.

I thought it was my setup, so we fitted HIS ECU into my car, runs fine on 1-squirt per cycle.

Fitted MY ECU in HIS car (same engine, VW 2.0 16V ABF with Turbo). It runs smoothly on 2-squirts per cycle. As SOON as he changed it to 1, it runs rough.

He burned his project and map on the the ECU and it`s exactly the same.Won`t run smoothly on 1-squirt per cycle. HIS ECU, on my car, with my project & MAP runs perfectly on 1-squirt per cycle.


We`re convinced it`s a hardware problem in the ECU, but I have no idea WHAT or how to diagnose it.

Any advice please ??

[kjones6039]

Hmmmmmmmmm........

Sounds a bit like injector opening (dead) time settings.........

Just a thought.......

Ken

[Matt Cramer]

Throw an oscilloscope on the injector outputs and see what voltage it's clamping the flyback spike at.

[Nigep]

Hmmmmmmmmm........

Sounds a bit like injector opening (dead) time settings.........

Just a thought.......

Ken

Both cars are running the same injectors and times, which made me doubt that could be an issue?

Throw an oscilloscope on the injector outputs and see what voltage it's clamping the flyback spike at.

Sorry, what ???

I can try and borrow a scope from somewhere. Do I connect it across both wires to the injector or somewhere else ? At the injector end or doesn`t it matter ?

[Nigep]

Throw an oscilloscope on the injector outputs and see what voltage it's clamping the flyback spike at.

Apologies for the delay, but finding a scope I could use took some time. It`s an old thing, but I managed to get the necessary information.

Unfortunately, it doesn`t actually appear to show an issue

For reference. 0V


Connected the trigger wire to the car battery (14V)


2 channels, one at +1CM and the other at -1CM. I`ve added details to the +1V event.

First off, my mates ECU on 1 squirt per cycle. Flyback spike at 36V (as expected ?)



Now mine, on 2 squirts per cycle.



The traces look identical with both ECU`s


As a final check, with MY ECU.

2 Squirt per cycle trace


Changed to 1-Squirt per cycle

1 Squirt per cycle trace. Engine running rough as soon as I switched to 1 SPC on MY ECU, no noticeable difference with his ECU, yet the traces look the same.



Any suggestions please ? I`m stuck.

[Nigep]

Obviously this has never happened before.


Anyway, just to close it off incase it ever happens to anyone else and they are as stuck as I was.

Turns out reflashing the ECU with the firmware has fixed the problem. I had the original files with the correct Easytherm files saved on my PC. Reburned it and it now runs on 1-squirt per cycle, exactly the same as the other ECU.
I`m guessing there was some corruption in that part of the code when it was orginally burned. I didn`t change ANYTHING else, simply connected the laptop, reflashed it, reloaded my tune and when I tried 1-squirt per cycle, it ran just as smooth as the other ECU where it hadn`t before.

Nige.