Knocking in 4th

[white01ss]

Anyone have any recommendations for some knock I'm getting in 4th gear? I was at the track last Friday and all four 1/4 mile runs had knock starting at 4900-5000 RPM. Knock varied between 1-4 degrees. Attached is a log from one of the runs. Should I...

a) Lower base timing (currently at 20 degrees)
b) Reduce timing based on IAT
c) Increase fueling (already well under 12:1)
d) Check for plug fouling and proper gap
e) Use colder than NGK TR6 plugs
f) Get water/alcohol injection to reduce IATs
g) All of the above

Thanks in advance for any advise!

Dan

[joecar]

Also try:
- reducing plug gap a little,
- make sure PCV plumbing is not pulling oil.

I'll be able to view your log when I get home tonite.

[white01ss]

make sure PCV plumbing is not pulling oil.

Got that one covered already. It was initially installed with PCV going to the inlet hat on the supercharger (per ATI's instructions), but that was sucking in engine oil. Caught it pretty early and now I have all PCV lines going into a single AMW catch can.

Even after adding the catch can, the dipstick continues to pop up after hard driving which indicates there's still too much crankcase pressure. Maybe I need a can for each side or just a real big one to handle the blow by? Would an LS6 breather setup help?

[white01ss]

I'm going to try a combo of a, b, and e. I got some colder plugs (TR7IX) because it couldn't hurt and the worse that could happen is they foul a little quicker. Lowered base timing almost a full degree and increased the effect if IAT based retard.

I talked to a tuner from the shop I bought the kit from and he said to use race fuel and/or back off the timing. Also, adding a alky/meth injection system would also lower combustion chamber temps and raise octane. He says the cause of the knock is a combination of high combustion chamber temps that goes up as you bang though the gears and increased load.