understanding knock w/ direct scan


Active Member
The last time I ran my car at the dragway, I pulled off a 12.4 @106. However, my Caspers knock guage hit the red every time the car shifted and then dropped back down to green, (I didn't have the Direct Scan that night). I'm confused because I don't know if I'm getting real knock or not. I got the Direct Scan working, took the car for a spin on the street today and jumped on it here and there. I got knock counts around 3 or 4 and they accumulate until I shut the car off and restart. What do these #'s mean. I don't want to blow the motor, however, I don't want to turn down boost or turn back timing thinking it's real knock when it's not.
The guage usually hits the read after shifting even with low boost driving normally. And mostly going up hills. However, knock retard never goes above 1.8 and quickly drops back down to 0 so I guess I'm O.K.
Real knock escalates. IOW when your in the middle of a gear and you see the lites climb... LIFT.

Check your motor and tranny mounts. Downpipe, etc.. anything that can shift while running the car or shifting.

My other TTA on the 1-2 shift would show 40 degree's.. from the band clamping the drum violently. Some chips have knock ignore especially on downshifts. The Extender is one.. but the knock guage will pick it up since its connected straight to the ESC line...

So as said above.. if its on shifts.. dont worry bout it.
I replaced the motor mounts and trans mount when I had the motor out to be rebuilt. The knock is usually half throttle starting around 5PSI of boost going up hill when it climbs hitting every light on it's way up to the red so fast it's in the red by the time I catch it and let off. I don't get it, can I blow the motor at only 5PSI? It also used to do this when the car was stock with the stock chip. However, under WOT at 25PSI with Methanol I get no knock.

You have a heavily modified car. Is the EGR still in place? Detonation control is one thing these are good for.Beyond that, I can only say that you might have crappy fuel or exhaust obstruction, probably neither, huh? I had an '01 Chevy truck in my shop last week, knocked and bucked like it was the end for the poor old thing,ended up being a plugged exhaust. I never would have thunk.....
Yeah, EGR is still in place and it's new. If I'm not running 100-104 Octane I have 94+ the Alky. It has a strange little stumble/hesitation at idle and the transmission slips under a heavy load but other than that, things are normal.
Best way to determine if the knock is false is put in some race fuel, preferrably 116, and if it still registers knock at the same intensity, its false. Mine develops about 3-4 degress only on the 2-3 shift after getting the tranny rebuilt cause it shifts very hard on the 2-3.
It doesn't seem to matter what Octane I have. With 110 in it I get the red under the same conditions every time. The guage drops back down if I stay in it however and like I said the DR only shows 1.8 before dropping back down.