Knock retard during burnouts???
 

When I was doing a burnout at the track recently, the raised area of my new cowl induction hood was bouncing all over the place due to the vibration caused by the burnout. Then when I launched, I definitely experienced wheel hop -- the top of my hood reacted in the same manner. Can a knock sensor pick up the car physically being vibrated? I think the answer is yes because my Auto Xray indicates knock retard of 11 degrees was at ONE mph? The engine was revving 3,855 rpm's at that time. The succeeding recording (one second later) was at 6 mph. Knock retard was at 10 degrees. Then it drops to 6, 4, 2, then one (at 68 mph). From then on, the knock retard sustained at two degrees. Therefore, I believe the excessive knock retard on the front end was caused by the physical vibration of my car due to wheel hop. Could this be true? Any opinions or ideas here?

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Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
Former Paxton (6-psig): 12.57 @ 111 mph.
Former Paxton (6-psig) & former 50-hp nitrous: 12.04 @ 114 mph.
Current ATI D1SC (Initially 10-psig): Projecting high 11's.
Future ATI D1SC (15-psig): Gotta catch them pesky 26-psig boosted TTA's!!

http://willie.camaro-firebird.org/

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

Yep, my knock sensor is picking up my driveshaft vibration and pulling out several degrees of timing in 3rd gear. It happens at the same mph every time, and it did the same thing on the dyno several weeks ago. I don't get hardly any knock in 1st or 2nd gears, so I'm 99% sure it's not due to the engine. Also, once I get above 88-90 mph, the vibration goes away and I had no knock up to 108 mph on the dyno. https://www.thirdgen.org/messgboard/smile.gif

As a side note, I have my ESC mph enable set to 10 mph, which was the stock setting for the '87 305TPI/A4. This keeps me from getting any drivetrain-induced knock retard from launching.

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Greg Westphal
'87 IROC 305TPI/A4

Greg, pull the knock sensor and use a resistor. You might be surprised to what you hear https://www.thirdgen.org/messgboard/wink.gif