For several months now, I've been noticing that when I do a tuning session, the first pull always has some knock, and then later pulls have less. Has anyone seen also seen this when tuning? Here is an example from this morning. Two pulls back-to-back, same tune.

First:


Second:

 

I notice this too. After cruising for a while if i get on it i will see knock, but on another pull shortly there after nothing.

 

I say all you got to do is first your peak stuff
drop peak boost down 1 from 25 to 24psi
increase timing from 1 to 3
richen a/f from 11.5 to 11.2

then your 4500-5500RPM mivec might need some tweaking.Post your mivec map

 

I get the same and just accept it. Otherwise you end up detuning.

 

same here

 

can u plot the 2 AFR's together? got any temp stats?

perhaps after the first pull the engine is hotter and thus temps are different thus the ECU is going something slightly different for the the second pull ?

 

I get the same thing. The first log is the log that I discard.

 

I also noticed that my car is particularly prone to very back knock count spree's if I start the pull from around 2250 and stab the throttle. I usually roll on it real fast and it doesn't knock. Anyone notice this?

 

Yes to both, I always had knock on the first pull.
Also stabbing the throttle seemed to be worse even though boost doesn't hit right away.
Eventually it was tuned out but the differences between the tunes are very mild.

 

Ahh..I'm not crazy,lol. I get this every single time. I always do a 75% pull just to "clean the pipes", if you will. I did notice that this issue was FAR less when I was running at 15.5AFR closed loop which made me wonder if it was some sort of carbon deposit thing which would explain why a good burst of 15+psi seemed to clean out the issue.

I've wasted countless hours trying to detune because of this and once I realized I just need to do a "clear the throat" pull first before logging...all is well and consistent.

I also get low load knock during cruising if I never get on the throttle during my trip. Opening it up just once minimizes the cruising knock most of the time for me.

 

I dont think its "clear the throat" at all. I dont see how that can be?
in stock form my evo never did that on the 1st run,
my current tune doesn't do it the 1st run either.

 

more than likely has to do with the buffer if you will on the knock algorithm. IIRC the routine compares current sensor "noise" to a background noise value. If you mash the pedal for a wot run after a bit of low rpm cruise the "background" noise level that the ecu is comparing current noise level too is very low hence you get knock sum.

 

thats a thought, I will have to test that out. do a 20 min no WOT cruise then mash it and see if I experience it.

 

I usually have the issue when I go from a cold start-up, reach operating temps and then make a pull after a 5 minute drive to my favorite on-ramp. I get anywhere from 5-7 counts of knock starting at 3K RPM. If I start my pulls from 2.5K RPM I seem to get 1-4 counts of knock no matter what I do so I just don't start that low anymore. Once you get the knock, it seems to linger throughout the pull which is beyond annoying.

 

I don't get that much, but I do often get more on the first pull after cruise.

I've seen it on other turbocharged engines as well after cruise. It might be carbon deposits.