What do you guys think... Everything being equal,(timing, IAT, gms/cyl, rpm) is an engine more likely to knock in 3rd gear WOT(more load) than 1st or 2nd gear(less load)?

Reason I ask is I always get KR in 3rd gear with timing equal in all gears. My IAT's are highest in 3rd, so I was wondering if the IAT's are what does it or if more load plays a part too. I want to know if I need to tune my timing based on IAT's only, or if the gear I'm in will need to be accounted for also.

 

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" is an engine more likely to knock in 3rd gear WOT(more load) than 1st or 2nd gear(less load)?"

On a different supercharged vehicle I always found it more likely to knock in the higher gears as well due to the higher load. Realistically everything is getting hotter too the longer you are at WOT so there could also be potential problems with pre-ignition if you had any hot spots. Colder plugs helped with the pre-ignition a little but didn't do as much for the knock/detonation in third and higher. For that I needed to back off on the timing and make sure AFR was really proper. In the lower gears I could get away being a little leaner and with more advance but it would catch up to me in third and above.

Shawn

 

Just went out and did some logs. My truck can easily handle 20 degrees of timing in first gear, IAT's at 70 degrees. It can only handle 17 or so in 2nd gear with 70 degree IAT's. Only 15 in 3rd at 70 degrees. I let the Iat's cool down to ambient, then did a 40 roll punch to test 2nd gear, cool down again, then a 75 roll punch to test 3rd gear. So I guess the answer is, more load can't take as much timing.

I'm trying to tune so IAT vs load will drop timing as The Iat's go up and as It goes through the gears. So it will start at ~20 in 1st, And end up at ~15 at the end of the 1/4.

After this test though, it looks like I'll have to use a lower timing table for roll races where I start at a low IAT from a high gear. Or just go from a dig only.