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Subaru Shift Knock

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Hi Andre I noticed particularly Subaru seems to have this shift knock issue,

it usually happens when u are accelerating on wot to redline shifting into next gear and it will hit a minus 2.8 degrees of knock.

I can solve this by retarding the timing a little on the knock area but I don't understand why always the up shifting will cause this behavior? I don't see this shifting knock on the EVO platform just on the Subaru noticed its very common if using pump gas

On E85 I dont experience any shift knock at all from Subaru. It's definitely Ign timing related since whenever I retard the trouble map area the knock goes away.

I think I probably covered this a little in today's webinar but let me expand on that a bit.

I can't give you a rock solid explanation for what causes tip in knock. I've found over my career that it has been a very minor problem seriously affecting just a handful of cars so it probably hasn't seen my full attention. I remember the biggest issue I had with it was on an EVO 7 production race car running an old autronic SMC. it was fine during a wot pull but knocked heavily during a full throttle transient from 4000-5000. Ultimately I put the issue down to map sensor latency hanging the engine up in a lower load/higher advance portion of the ignition map momentarily. I coul partially eradicate it by retarding the part load timing map which gave weight to that theory.

It's quite likely that the same result could be achieved with a factory MAF as they do show some latency on large transients dependent on their location in the intake track. Some OE ecus actually switch to the map sensor momentarily during transients as they react faster than a MAF.

Here's the thing though. Most tip in knock I've experienced has ultimately occurred at or very shortl, after the throttle is hit. This is while boost is still climbing and MAP is still quite low. Ultimately this means the actual specific power the engine was making at the time was also quite low and hence the chance of doing damage is also very minimal. I would suggest you might be worrying too much about it. Allow the knock control system to do its job and provided you're not seeing sustained wot knock you are going to be fine. If you want to be really scared, check out how active the knock feedback is on a 100% stock Subaru! And that's a tune the manufacturer backed to last 100,000km!!

When it comes the Subaru stock engine piston, I tried to avoid any knock possible since piston do seem to even fail at stock power. I find whenever I retard the timing map on that specific gear it will cure the shift knock but i loose a lot of power for fixing these knock issues. Which at the end makes the tune feel slow and not fun to drive anymore, reliabiility and speed is really hard to pick for me now.

Do you mean if i switched to speed density tune, my tip in knock issue will be solved? I find evo x never experienced this problem and evo x is a hybrid maf and map system on airflow caluclation.

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