Strange downshift incident with knock


Well-Known Member
This happened about a month ago and it's been in the back of my mind ever since. My car usually runs all day long at 20# of boost with zero knock. I can run it up to close to 22# before seeing signs of KR.

Well, last month I was cruising at about 47 MPH when a ricer came up next to me. He punched it, so my foot reacted immediately without my knowledge ;)

I pulled on him of course but I felt the car nose over a bit for a second and then regain the power. After letting off the gas I looked over at my computer screen (running powerlogger) and I saw a HUGE KR spike. I saved the log file for later review. And I also installed a knock gauge to alert me next time.

It seems that when I floored it, the boost started to build and the tranny didn't downshift right stayed in Drive. In fact, the boost went all the way up to about 22# and the RPMs went to about 5400. The tranny was still in DRIVE at this moment and the MPH was only in the low 50's. It shouldn't see those RPMS until well over 100 MPH. The knock retard spiked to 11 degrees :eek:

At that moment the tranny downshifted into 2nd gear. The RPMs DROPPED from 5400 down to 4650 and the KR immediately went back to zero. What the heck just happened? Was I blowing through the converter? Tranny slipping? As a side note, the knock started to occur at around only 15#, so I'm inclined to think it may of been caused by some mechanical noise rather than true knock.