MoTeC Global Forum

OK...not a Motec problem as such.

2002 STI AVCS, 2.35, PT63 turbo, biggish build etc etc M800 pnp


Pretty much, no matter what we do, the car hits a brick wall at 6500rpm.

Ive tried cam timing from 0, to 30deg, ign timing is at a safe 16 deg, 1 bar boost only ( wastegate pressure ). The cam readouts do appear to say the cams are doing what the cam map suggests ( I assume the rear sensors do give actual cam position on the motec ? )

AFRs go very rich at this brick wall, with no obvious reason for it on the fuel map. If anything, the drop between 6000, and 6500rpm, it should be going very lean.
So fuel map isnt the cause. Something verys trange is happening.

ive tried dwell time from 3.0, to 5.0 on the ignition side...no difference.

I hate asking about stuff like this, as I know its impossible to diagnose over the net....but its so strange. Its almost like a rev limit....but the rev limit is set well above this ( 7800rpm last night...but he tried higher today while I wasnt there, no change )

Aside from this problem, the car seems to perform ok, and drives perfectly fine everywhere else. It just will not rev ??


Any thoughts ?

Did you datalog all parameters under "cut levels" in datalogging setup.
See if any of them is triggered.

As much as I'd like to datalog.....Ive never used logging on the Motec before...and I think Im right in saying, its a cost extra with this ecu ?

Which was not purchased at the time.


Just thinking out loud here. the car had previously been running fine on the V23 software/firmware...but with this new build, I upgraded to V34 before we started on it.
And its always had this problem now...


Is there any chance something got messed up in the changeover ?

Just to add...here are the trigger settings being used ( although they read same on old V23, as they do V35 )

Curious.....


does the motec rely on the cam/crank signals all the time ?

This motor is a custom built thick liner block....so the block has been decked, heads also, non-stock head gaskets, and aftermarket billet crank.

If somehow, the crank to cam relationship wasnt where it was supposed to be with regards to triggers...what affect would it have ?

We do occasionally get some crank/cam sync errors. I'll try and get a snapshot of the error screen later.

Could this be an issue ?

PM sent to admin.....

Hi Stevie,
You would be surprised what can be diagnosed by e-mail when you have a data log file! It is an option on the ECU but not a very costly one, you can save a lot of time if you familiarise yourself with it.

The ref sync mode is designed for standard engines, on these engines it is prone to giving problems on an engine that has been modified in this way (deck height, aftermarket cam belt etc). This is because the triggering edges for both ref and sync are very close as standard and modifying the deck height can be enough to cause them to occur at the same time. If this is the case you will see ref/sync related errors when the engine missfires. You will need to take a ref sync capture to varify that this is the problem. If it is the best way to fix it may be to install al hall sensor in place of the mag sensor for sync.

mmm Alternative ecu in place ( aftermarket ) and rom is no raised to 7000rpm, but its the same problem.

Logs show no crank/sync errors, and the ecu seems to be telling the engine to do what it should be.

Still wont rev.

Motec was 6500rpm....Simtek 7000rpm, but exact same problem. So so weird.


help !

Hi Stivie,

Might be kinda late reply, but I had similar problem on 2.0 and 2.5
highly moded STIs. Traced the problem to the mag sensor levels
setup. Had to rescale mag sensor table to have more resolution
in mid and high RPM and use higher V levels. If I remember
correctly its the Sync sensor that was giving us the trouble.

Traced it by logging the Ref/Sync errors and Ref/Sync min/max
vales. So Ross is right please get the logging option activated.
It saves a lot of time if troubleshooting some werid behavior
and helps a lot when calibrating the ECU.

Alternatively you could scope the Ref/Sync sensors with a scope
and check the actual voltage levels and any noise that may interfere.

Hope this helps
Best regards
Alex

Hi Alex, and thanks.

We havent looked at this car for some time now....so no updates.

We did try an alternative ecu into the car, and the problem still existed....albeit at a higher 7000rpm for some reason. With the Motec it was nearly always at 6500rpm.

We did log the scope trace, and Ross confirmed it was ok. With the alternative ecu.....cam/crank logging showed no problems at all. We also turned off the cam once above 1000rpm or so, and the problem was still there.

This engine is a full custom build....with an aftermarket crank.

Is it possible that if the crank keyway wasnt where it should have been........the cam timing error could cause such a problem ?? All std AVCS pulleys on the car.

What cams are you using? OEM or aftermarket?

The problem we had on 2.0 cars (GC and GDB)
with bigger displacement blocks (2.5) is cam timing.
Hitting about 6-7k rpm similar to some cut.
Solved by retarding the IN cam using adjustable cam
gear on GC and using less advance on GDB.

Disconnect AVCS solenoids and check what your
cam position readings with Motec recommended
settings. If readings 0 +/- 3 deg its correct 0 position,
if readings are different need to adjust the offset
to get 0 reading.

What is the power rating of the PT63?

Cheers
Alex