jpandes

This is sort of wierd. My car has been in the same state of tune for around 7 months (i.e. no new mods or messing with the PFC maps at all). I used to see a peak knock level of 37-39 during normal cruising and boosting(not WOT w/ upshifts) Lately, I have been seeing peak knock values of 40-44. Why would the knock numbers rise like that? Has anyone here seen their PFC knock values increase over time?

Here are some of my guesses:

I am driving the car harder since I am more confident that she wont blow...
Knock sensor is loose
It's summer and the weather is warmer(i.e. hotter intake temps)

or

my engine is wearing. It now has around 15k miles since being rebuilt.

Any ideas guys?

krackerx7

iTrader: (1)

ralph at groundzero motorsports told me when i asked a similar question that on these cars the knock sensor is really sensitive and its not how high the number gets its the big sudden jump in the number you should worry about

cewrx7r1

iTrader: (2)

If your car was tuned during a short period of consistant weather, then it is not tuned for all year driving. You have to go run AFR/knock tuning at lease for the major 4 seasons.

That is because all of these change: air temp, moisture in the air, barometric pressure, and fuel chemical makeup. All of these affect performance and knock levels.

The most affected table is AIR TEMP vs INJECTOR. This controls AFRs for air temp changes. You use this to control your AFRs for the seasons. You can have a linear plot or what ever you want.

I run linear from 50C down to 10C and richer above and below.

Usually you will have higher knock in winter due to making more power if the timing is a little too advanced. Summer you make less power so timing is not as critical, but intake air temps are.

rx74evers

iTrader: (6)

What do you mean by sudden jump? Are you refering to KNOCK spike under slow boost or boosting? Because I get that too and I have to drive with no boost or at least below 4 psi or I get a KNOCK SPIKE way off the charts sometimes. Depends how far I get on the throttle the bigger the sudden spike I read. I really need to see Ralf when I get a chance.