Sorry to start another 'chasing knock' thread, but this one has me a bit stumped.

Basically I've been getting knock during spoolup and peak boost on this car and have been trying to get rid of it. I started with 2* at peak boost and am now at -2* which seems to have cured the knock at spool/peak, but now it's knocking further down the rpm range where there was no knock before.

Firstly, I just wanted to know if -2* was considered OK for timing at peak boost (~4200rpm on this setup)? As you will see in the logs below, it appears to have cured the problem in this case, (or pushed knock further up the rpm range)

Here's the details on the car:
1998 Evo 5
CeddyMod v1.2B flashed stock ECU
FP HTA Green
TurboTech bleed valve at 24psi tapering to ~21 at redline (seeing about 260 load peak)
Walbro pump
FIC 1050's
Upgraded o2 housing + TXS 3" exhaust
HKS pod and intake pipe
reversed stock BOV
Tuning on Aussie pump 98 (roughly equiv. to US 93)

Here's a pull with -1* timing around peak boost at ~4300K. As you can see, it knocks and sorts itself out.


So I pulled another degree of timing at 4250 down to -2, and as per below, the knock there appears to be gone. Problem is, it now starts knocking at around 5K as timing starts to ramp up and knocks for the remainder of the pull to redline.


Am I on the right track here and just need to pull timing further up the rpm range now?

 

Do you know if it was actual knock or false knock?

You shouldn't have negative timing in your load curve, it will lead to loss of power as well as higher egt since it is firing the spark plug after TDC.

 

Pretty sure it's genuine knock. It doesn't knock there when free revving the engine or anything and previous rom updates where I've reduced timing on spoolup have reduced/cured knock.

Sounds like negative timing is a no go then... I started at 2* peak boost, so perhaps I need to go up to cure the knock.

 

Can always throw in couple liters of race fuel or octane booster to see if it goes away. Then you would know if its real. Also, check to see if you have anything loose on your engine. eg brackets, bolts etc causing false knock. Finally make sure your timing curve is smooth and there are no values more than 2 degree increments. Hope this helps

 

Have you adjusted the knock multipliers as I think on the ceddy they lower the the standard and should adjusted up to 21

 

for me, timing seems too low 4-5.5K rpm. give there at least additional 2-3 degrees and try it.
FIY car can knock from too low timing too

-2* isn't ok at all and also maby it's just me but for HTA green spool seems bit late. which gear is that 4250rpm/260 load log ?

 

Log knock voltage side by side with the knock sum. How much boost and what grade of fuel?

 

I had encountered something similar, the reason was high engine compression ratio, (engine was built for autocross racing) I kept boost at 19psi (stock turbo) rather than having to reduce timing too much at higher boost.

 

Thanks for all the info guys. I ended up giving the car back to the owner to get him to have a good look over the setup, do a leak test and see what might be the cause. It was just completely inconsistent and was doing my head in. He's found one of his engine mounts was busted which is hopefully the main cause of the random knock. His TB seals are also leaking. He's also installing a new wastegate actuator which should hopefully help with spoolup as the HTA green still seemed a bit lazy on a 2L to me.

Thanks John. I did have this log with knock voltage. Not sure how you tell if it's real knock or not though? Boost is about 24psi tapering to 21 and fuel is Aussie pump 98 which is similar to your 93.



Anyway will let him sort the issues on the car out and hopefully finish the tune in the new year

 

Load looks pretty low and it's rather rich on spool. Really doesn't look like true knock, try a splash of E85 and see if that changes things.

 

Doesnt look like its real. Remember the knock sensor can pick up misfires as well. The voltage right before the indicated knock is very low, it hasnt even started to pull timing yet. If there were big spikes previous to it or after it I might think it was real.

93 octane at 24psi on an otherwise stock motor shouldnt knock at that timing level. I can run more on 92 octane and 28psi. Check for rattles, things that can interfere and transmit sound, a loose knock sensor, etc.

As Burgers said throwing in some racegas or e85 without changing the tune will tell you a lot as well. I think I'd probably adjust the knock filters at that point.

aaron