knock event on single cyl. how bad are these events

i have a v8 turbo runing on 95 oct fuel cr ratio 1.10 it is a na block

i run around 0.65-0.7 bar and doing some street tuning

i have had 2 knock events on diff cyl. but induvidial runs and in only happend higher 4 gear

if i do the run in 3 gear i dont have the knock event

the knock detection pulled out 0.2 degree according to the log and the knock is gone right after

i was still full on throttle

is this strange ? i would execpt seeing the very high peak of this 1 cyl. and no a slowly going up trend before the knock event in frequenty

is this a knock event ?

i pulled out 1 degree of timing and lowered the boost a little for know to 0.6 bar and running good without knock events

im in the learning process so all input is very welcome

regards johan

hello Johan,

I have seen knock events on on single cylinder before and looking quite similar to the log.

There are number of causes of single cylinder knock from a failing TTL coil driver to overheated sparkplug electrode or a stack up of tolerances meaning a variance in compression or squish/swirl/tumble effecting combustion efficiency.

I take it the knock occurs around peak torque rpm where we see the highest cylinder pressures which would add to the legitimacy of the knock...?

The baud rate looks to be quite low or heavily filtered so there may be other events that the logger is missing, I'd typically want to be seeing knock at 200-500hz if the logger is capable of that.

Regarding the 3>4 gear pull comparison, there's more tractive effort in 3rd so it may be able to pull through that area of knock faster so its not happening or happening too quick for the logger to pick it up.

Thanks.!

It is not peak torque yet . But this is where NA peak torque would be

I have the standard setting form Maxx ecu for reading the knock signal i will have a look what frequentie it is reading . The limits are put in at a early dyno session with different turbo kit and different heads .

If was on a very hot day . So most extreme conditions

I will try with 2 or 3 Degrees of timing of what is does

Egt's where still not that high i had 850c peak on that cyl. What was 20-30c higher then the others