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Subaru warm movement

How to Degree a Cam

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Can someone familiar with horizontally opposed Subaru engines please take a look at the attached log of a 2004 EJ207 with intake-only (Single AVCS) as it's warming up and advise which bank is Cam 1 and which is Cam 2?

I realise the variability with the intake cams can be dialed out with the AVCS control, but the static exhaust position cannot and will lead to a subtle variation in LSA between banks. If I can adjust for the exhaust cams while cold, then the LSA difference between banks should be smaller.

Attached Files

Bank 1 is cylinders 1,3 (right side of car) and bank 2 is cylinders 2,4 (left side of car).

Your ECU should be zeroing them out a few seconds after startup, potentially once the engine warms up a bit. Then above idle they should both be following the same target if set up properly and there isn't a mechanical or electrical fault.

Here's an example. There will be slight variation in how quickly they move to target, but there should not be a noticeable offset like you are experiencing.

It looks like the PID system isn't getting the job done in your log and may need some adjustment.


Thanks Mike, my ECU (Autronic SM4) works a bit different to that. It doesn't zero the parked position and instead reports the absolute value in crankshaft degrees. Adding advance for both cams follows an open loop GPC target in crankshaft degrees, rather than relative degrees. This works perfectly for my ECU.

I am curious what zero actually is in your use-case and does it adjust as thermal expansion moves each bank relative to the crankshaft datum or are you just selecting an advance target at idle?

Since I only log the intake cam position, I have to assume the exhaust cam position skew is the same margin as the intake cam. Someone with D-AVCS logs should be able to confirm this.

All the ECUs I have experience with use a closeloop PID setup that chase the target continously, no matter if the target is 0 or 30deg. If there's an offset for any reasons, the PID will adjust the cam position to match the target.

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