Time for an update.
The project is almost finished and like always, some new problems popped up.
I got a huge amount of help from Mattias, so a lot of credit goes to him!!
A lot of our problems are due to not having experience with the Vems.
We are newbies to Vems.
The first problem was a big one and due to a lot of unknown factors we ran into it.
When the car was on the rollers we mapped the engine without turbo's connected to the inlet manifold (no boost).
Once that was done we connected the turbo's to the inlet manifold and tuned further.
At a certain point we could not rev the engine past 4700rpm. It hissed and popped, boost was steady at 0.65 bar.
But it would not rev any higher than 4700rpm. full,half throttle, nothing worked.
Hmm, euh, hmm... Think, think, think.
Possible causes (we think): - some setting in VT, - fuel pressure to low, - spark blown out, - noise from the ignition coils, or the coils, - pop off valves leaking, ...
Before, we have tried to upgrade the FW.
This didn't work out well, we had a non-starting car afterwards; so flashed the original FW back.
When we did this we forget to pull the fuse from the coils on one engine bank. So possible we smoked the coils on one bank.
So we bought 6 new coils=> no change.
The new FW where Mattias put a post on the wiki for us will be tried on another project.
For this project we will leave the system as is.
We spend already too many hours and I did not get a green light to rewire the whole thing.
With the help from Mattias we changed a lot of settings in VT, reviewed every setting to not miss anything => no change.
Plugged off the pop off valves=> no change.
Checked fuel level/pressure all ok => no change.
Spark blow out: this was checked with a timing light on a wire placed between coil and sparkplug.
Spark blow out was not the case. =>no change.
Signal noise.
Rewired the grounds according the info given by Mattias. =>no change.
Originally, I wired the 'signal ground' from the coils to the signal ground from the Vems.
Mattias suggested to wire this directly to the engine block as this causes often a lot of noise.
Somebody else told us to connect the power ground from the coils also directly to the engine block with thick wires as short as possible.
Have done that too. =>no change.
We noticed however less trigger errors with the rewiring of the signal ground. So it did do something good.
But still no progress on why the engine would not rev past 4700rpm.
Then we decided to take the whole ignition/injection setup from another car and put this on the engine.
This was a 3 hour job.
After it was done, a real road test => all was good.
Result:
Nothing wrong with the engine/turbo's or whatever, fault lies somewhere in the Vems system or the settings.
As we had now a running V12 with the original system we did some measurements of ignition timing and pulse width on fuel injectors at idle. Remember, on the engine there are no marks at all to check for timing, so we put some ourselves.
As it was only for a comparison and not for the real figures it was good enough.
Now I removed back the original system and put the Vems system back on; again a 3hour job.
With in mind what we had measured with the original system, I checked the timings with the Vems.
Immediately I saw that the ignition timing was not correct: 20 degrees to late. Ooops.
So corrected in VT the item 'TDC after the trigger' from 30 to 10.
This did the engine idle a lot higher; from 850 to 1250rpm.
It also reacted much better on the throttle and it did it in such way that we took it for a road test drive.
Jipeee!! The engine revved happily past 4700rpm towards 9000rpm without any strange thing.
Ok, so it was apparently only the ignition advance and for discovering that we got a day and a half work.
Next: the boost control.
And guess what?
Right, it doesn’t work like it should.
First it would not work at all: no power on the connector. Hmmm.
So dived into the wiring because the fuse of it was good.
After taken out the complete fuse/relay box I found the fault: a cut wire!?!?
Soldered that wire again and in same time looked for the problem of the fuel pumps.
These were running as soon as ignition was switched on. Also this was due to cut wires and some extra wire bridges.
After correcting this it worked like it should: Vems controls the fuel pumps.
We contacted Mattias (again) and started to play with the boost valve.
The crazy thing is that we can't get the boost high enough.
The boost valve regulates between 0.3 bar and 0.6 bar.
We tried to measure the base frequency on the original system but when idling there is no signal, driving when measuring with a scope was not possible, our scope is not portable.
On that boost valve stands: 12V/160. Should that mean 160Hz?
In VT you can only select 125Hz as maximum.
My own car uses a boost valve of the brand SEM and is controlled at 200Hz.
Is there a way to select a higher frequency for this in VT??
Answer on previous post: Yes the box is double height, but there is a 2nd Vems on the other side too!
One controls the left bank, the other the right bank. The only signal that is sheared is the crank signal.
For the rest they work completely independent.
Regards,
Tommy
