Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB - View Single Post - Cannot solve transient knock issue high RPM when letting of throttle (boosted)

brosifSmith · 07-08-2020, 01:12 PM

First some info, I'm tuning using Ecutek with RaceRom. I've got my maps pretty dialed in for my 2015 brz with the SBD turbo kit installed. I am targeting 6 psi of boost, my AFR's are on point.

I rarely have knock under load, and it pulls hard! everything seems well and good.. EXCEPT, I notice I always have what looks like transient knock after I do a pull, and when I begin to let off the throttle, but before I downshift.

so for instance, second gear pull, go from 2k rpm up to 6k rpm, throttle % falls to about 10 percent, load falls to .6 ish and the timing starts to climb because of the falling load, but then immediately I get Knock correction. sometimes -1 degree, sometimes -3 or -4 degrees. Those ones scare me, it's always when the load is pretty low like .6 and .7 but RPM is still high because I just let off throttle but have not downshifted. but I don't know if I should be concerned... Someone please advise, this is the opposite of tip in knock it seems...

Log so you can see what I'm talking about - https://datazap.me/u/brosifsmith/pur...zoom=3191-3359

this one is also very concerning. I've tried retarding transient a lot and seemingly no effect -
https://datazap.me/u/brosifsmith/pur...g=0&data=13-32

07-08-2020, 01:12 PM	#1
brosifSmith Member Join Date: May 2018 Drives: 2015 BRZ Limited Location: Utah Posts: 38 Thanks: 2 Thanked 8 Times in 6 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Cannot solve transient knock issue high RPM when letting of throttle (boosted) First some info, I'm tuning using Ecutek with RaceRom. I've got my maps pretty dialed in for my 2015 brz with the SBD turbo kit installed. I am targeting 6 psi of boost, my AFR's are on point. I rarely have knock under load, and it pulls hard! everything seems well and good.. EXCEPT, I notice I always have what looks like transient knock after I do a pull, and when I begin to let off the throttle, but before I downshift. so for instance, second gear pull, go from 2k rpm up to 6k rpm, throttle % falls to about 10 percent, load falls to .6 ish and the timing starts to climb because of the falling load, but then immediately I get Knock correction. sometimes -1 degree, sometimes -3 or -4 degrees. Those ones scare me, it's always when the load is pretty low like .6 and .7 but RPM is still high because I just let off throttle but have not downshifted. but I don't know if I should be concerned... Someone please advise, this is the opposite of tip in knock it seems... Log so you can see what I'm talking about - https://datazap.me/u/brosifsmith/pur...zoom=3191-3359 this one is also very concerning. I've tried retarding transient a lot and seemingly no effect - https://datazap.me/u/brosifsmith/pur...g=0&data=13-32 Last edited by brosifSmith; 07-08-2020 at 01:22 PM.