2007 WRX STI AVCS Issue

[dazdavies]

Hi All,

I've just finished a rebuild due to a cracked cylinder head.

Car is a full forged build with Cosworth 278/274 Cams and currently pushing out 450 WHP at 21psi

Anyway I noticed last night that my LH Inlet cam was not syncing. Aware of the issues with the oil filters in the oil banjos i removed them completely and also replaced both the solenoid and the sensor.

Fired the engine up and still had the same issue.

As the heads are different to the originals (same heads just a different pair) I thought I'd adjust the offset in the trigger set up for that cam. I've added 3 degrees from 126 ATDC to 129 ATDC and it has now synced perfectly. Although for some reason it occasionally presents an extra tooth error but when driving its stays in sync.

The one thing I have not looked at yet is whether that particular cam pulley is a tooth out but there is no indication of this as the car drives superbly well and idles exactly where it should be. There's no flat spots or missing of any kind and have around 3000 kms on the car since the build

There were absolutely no symptoms I just happened to spot the error when I looked at the run time values out of curiosity.

Is 3 degrees enough to indicate that the pulley is indeed a tooth out?

I've attached a log file from a quick 10 minute run around the block.

ECU is a V88 Plug in.

Please can somebody put my mind at rest and tell me that it is all working as it should and it was just slightly out of sync due to new machined heads.

 

Thanks in advance

Daz

2007wrxsti.llg

[Scott]

How many teeth does the camshaft wheel have for the cambelt? The VVT offsets are in crankshaft degrees, and as the crankshaft rotates at twice the speed of the camshaft that means the camshaft would have to be out 1.5 degrees. This would mean your camshaft wheel would have a minimum of 240 teeth. So I think it unlikely your cam is out by one tooth on the belt. When using the VVT cam test function you will notice a small difference in numbers with engine speed, this is most likely due to mechanical movement and stretch of cambelt.

[dazdavies]

As said my initial problem was that the LH inlet cam was showing a sync error in the runtime values and as a result the VVT wasn't working as it should.

I knew the timing belt was fitted properly as I fitted it myself when i built the engine. The belt was new and all the relevant markings were lined up.

So have I done the correct thing by adding a few degrees of VVT offset to get it to sync which it now does or have i just worked around the issue?

I know on my last ECU which was a Syvecs you could fine tune the cam sensors to take account of head skimming and different thickness gaskets etc.

One thing I have noticed now that its syncing is that its a little leaner lower in the revs. I'm assuming that now advance is working is needs a little more fuel to account for this?

Apologies for the questions but I'm new to the Vipec and am just learning all of this stuff.

The car will be properly tuned in the next couple of weeks I just want to make sure its ok to drive in the meantime.

Once again thanks for your help its very much appreciated.

 

Edited February 18, 2016 by dazdavies

[Simon]

Yep resetting the offset is the correct thing to do as you will have slight differences due to the distance between the cam and the crank pulleys from the machining and head gasket differences.

Your mixtures will change a bit from the compression change I suspect. Assuming all other things are the same.

[dazdavies]

Awesome thanks for confirming.