Troubleshooting Knock Correction Advance

[Brando]

RomRaider logging/graphs:

I'm working through tracking down knock correction advance. I have checked and made sure nothing is loose and rattling against the motor.
If I decelerate or keep a constant throttle there is no knock correction advance. When I accelerate hard I get knock correction advance of 9* in first, 7* in second, 5* in third.
The knock correction seems to run in sync with the amount of throttle + load on the motor.
If I am in neutral and blip the throttle I will get a 4* correction advance but it's just a spike and if i hold the throttle it goes away.
If i ease into the throttle there is little to no knock correction advance.
My graph for Feedback Knock Correction stays flat-lined while the knock correction advance is spiking, so that would mean the correction isn't due to an actual knock, is that right?
I'm still learning about all this crazyness, but doesn't that mean something else like the MAP is responsible for the knock correction numbers?

I have a data log if it helps
https://docs.google.com/spreadsheets/d/10w_nTPTyDWeRQKIODDMr3SAFiYhqk85ZIU7zAJ5uWM8/edit?usp=sharing

[JeromeS13]

If RomRaider is anything like the Cobb software, a positive value of knock correction actually indicates an advance in timing. If you were getting actual knock, the value would be negative to indicate pulling timing away. If this is correct, everything looks fine (aside from the Right and Left side AVCS not being in sync).

[Brando]

Good to know, thanks Jerome.
So now, about that AVCS ;)

[Bob_n_Cincy]

When I accelerate hard I get knock correction advance of 9* in first, 7* in second, 5* in third.
The knock correction seems to run in sync with the amount of throttle + load on the motor.


Hey Brando,
Stand on the tail of your transmission. Mine goes down and hits the frame.
300ftlbs of motor torque times 1st gear ratio ~ 12 = 3600 ft-lb of axle torque.
I guess that the rear mount is about 2 ft away so there is a downward force of 1800 lbs. (SLAM)

The hook ends of the mount hit the ffr flat mount. On the Subaru cross member there is nothing under the hooks.
34755

Edit: this is a picture of a group N trans mount. My car has oem. I hope the Group N trans mount and group N motor mounts will fix our problem.
Bob

[Turn In Concepts]

Agree with Bob that stiffer mounts need to be used on these cars. let us know as we have a full compliment.

Your logs look fine. The ECU has a 3 part timing system. Base timing, Knock Correction advance and Dynamic Advance Multiplier. The knock correction column should indicate positive values under load and 0 at cruise. If it start to drop from the 9 range into less and eventually negative then you have a problem. If it drops into the negative range enough it will start to lower the dynamic advance multiplier. When that happens you know you have something wrong. Depending on the engine and ECU you are using the DAM will either be a max of 1 or 16.

Tony

[Pearldrummer7]

Another vote for what Bob said. The flimsy stock mounts don't hold up well in normal driving applications, let alone the more....spirited ones you partake in with the 818.


I bought (and installed) Group N motor and transmission mounts on both my street WRX and my 818. Hopefully they'll do the trick. They're quite a bit more rigid than the stock ones. Here's a Google pic of them side by side (I've encountered similar results with WRX's myself):
http://www.rallysportdirect.com/user_submitted_content/photos/STI%20D1010FE020_2.jpg

Unless you've already upgraded motor and trans mounts...in which case, I'm in need of new ones! ;)