Quote:
Originally Posted by Grip Ronin
so what exactly does timing compensation per cylinder do?
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What the per cylinder timing compensation does is allow for different ignition timing for different cylinders. In our case on a standard map, it retards timing in cylinders A and B, which I'm pretty sure are the rear 2 cylinders, but I'm not 100%.
As to why, there is plenty of speculation out there but I guess that no-one bar Subaru/Toyota actually know. From my reading the possible list is (and may not necessarily be just one of below):
Knock Sensor Location if only 1 sensor - So that the cylinders closest to the sensor are the ones that will knock 1st, knock detection is easier.
Heat - Maybe the cooling (oil &/or water) systems are more efficient in some cylinder than others, making some more knock prone
Manifold Design - Both intake and exhaust, possible flow differential between cylinders require a change in the timing
There's a good long debate on RomRaider and there is no defined answer. There's definitely signs that on older STi's, cylinder 4 was more advanced (ie positive values in the PCC) than the rest and was more often the 1st cylinder to go. Others have 2 cylinders more advanced, and that is usually 2 and 4 (same bank).
Now, I don't know where the knock sensor is on the FA20 so I don't know if cylinders 1 and 2 being retarded is for the same thing, as that would mean the knock sensor is on the front of the block - assuming the layout is:
R
1 2
3 4
F
This is why I asked Shiv why he thinks this is a good idea. It seems (from other reports) that the car will run better with the compensations zero'd out, so I don't see why you couldn't/wouldn't do this on any tune but 1st of all I'd like to be sure why it's there in the 1st place as it could protect the longevity of your engine. If it is knock related, I would be looking to have a completely knock free tune before you change the PCC.