Shift shock timing reduction?

[fishbone]

I've got a quick log snippet but am at work and can't post it. I think after many years of trying to hunt down this issue, today I've got a clear picture.

The question is whether or not this sounds like "true" knock that can be potentially destructive, or finnicky behavior.

This is a stage 2 automatic. Scenario is this.

3rd gear at a moderate pace, torque converter is locked up (this is important since it eliminates hydraulic play), anywhere between 3-4K rpms or so, if I stay in gear and let off the gas and the car does a good bit of engine braking, right as I let off the gas the AP will throw up a good bit of feedback knock correction, in the vicinity of -6 to -8, sometimes -10. It starts decaying right away, but if I get back on the throttle before it goes down to 0, it will stop decaying, and hold at whatever value it was when I got back in the throttle.

 

This happens in cold temperature only. During the summer, I can never get knock, no matter what I do. If I keep doing this kind of stuff, eventually what the car does is drop IAM somewhere to .875 and may stay there for a long time. I've "inadvertedly" done this once and actually managed to get IAM down to zero. Even in cold temperature, the car does not knock if I run through the gears, nor if I do a 3rd gear pull. But as soon as I am in manual mode and am playing around, getting in and off the throttle, it'll go apeshit.

I've had this issue for more than 6 years across many, many tuning revisions.

The kicker is, this current tune is for 91 octane gas and have since moved to Texas which has 93 everywhere. I see the exact same behavior all over again, exact same knock corrections.

Any thoughts? Input?

The tune is a custom tune based on Cobb Stage 2 OTS 91. Got it nailed down for all the other seasons except winter.

This is just further evidence that, since the engine has refused to grenade in all these years, I truly am the owner of the unicorn Legacy.

[technicalgarage]

Any logs showing this behavior?

[fahr_side]

Does this spike in FBKC correspond to boost error? There is code to pull timing via FBKC in response to overboost.. preemptive knock control. A log would help a great deal.

[technicalgarage]

Does this spike in FBKC correspond to boost error? There is code to pull timing via KBKC in response to overboost.. preemptive knock control. A log would help a great deal.

 

I was under the impression that the preemptive FBKC was introduced on the 07+ models.

[fahr_side]

I'm not sure which year in the Legacy model.

[fishbone]

Thank you gentlemen, I haven't had a chance to pull the logs off the AP but will try to do so soon. Just got tied up in other stuff.

I didn't know about FBKC in regards to overboost. Not sure if my logs will have boost error logged and I doubt this to be the issue because the timing pulled happens at part throttle, so not under full load/boost. Here's the other annoying part about this. It seems to go away once the engine is really warmed up. For example, the first part of my drive home I would get consistent -4 degrees FBKC pulled sometimes as soon as I would touch the throttle at 40mph. Then as I almost got home, it wouldn't do it anymore. Flooring it in 3rd gear at 2K rpms to redline, no knock whatsoever. I'll see about those logs.

 

I really want to say this could be induced by the stiff trans mount I have possibly transferring noise to the engine. It's an automatic. The mount is stiff as hell when it's cold outside, but it softens up once the transmission fluid warms up.

[fahr_side]

-4* is a lot. Check for rattling stuff. Do you have any FLKC racking up?

[technicalgarage]

For what it's worth, I've had a shift knock problem (manual trans. though) for years on my setup.

Never managed to resolve it but it hasn't blown up my motor yet.

I sort of left the tune alone but have recently felt like revisiting the issue. I will post here if I find anything that works for me.

While it may not be terribly useful (maybe even a different collection of problems entirely), here's a link to my past thread http://legacygt.com/forums/showthread.php/shift-knocki-195070.html

[fishbone]

-4* is a lot. Check for rattling stuff. Do you have any FLKC racking up?

Unfortunately I have an APV2 so I can only see one parameter at a time. Thus far I've opted to watch FBKC but I'll switch and look at how FLKC is doing. This morning I chose to watch knock sum instead and I did not see anything incrementing wildly other than the usual stuff. What I mean by usual stuff is knock sum increments during shifting. I can sit at a red light and drop it in and out of D and watch it increment.

If you think -4 is a lot, what about -8 and -10 and advance multiplier modified dropped all the way to 0.