fbody_brian

Not sure if it's engine or trans related.
Not sure if I should have put this in trans section or LT1 section, because I don't have a clue as to what it is.

I logged a run at the track last night. Car ran slower than I expected, could be several things that changed. One of the most concerning things to me at the moment is what's going on in third gear.

The car feels like it's pulling strong, but looking at the log, something is going on. The rpms climb and drop, and the knock count just goes crazy, incrementing by the thousands. This doesn't happen in 1st or 2nd, just third. I Do get a small amount of knock count at gear shift 1-2.

anyone have an idea of what's going on?

here's a pic of the rpm in third vs 1 and 2:



I'd really like to get into the 12s, and if I can get this figured out I'm pretty sure I'll be there.

bowtienut

iTrader: (1)

I think you've already answered your own question. It's detonating in 3rd gear. It's on the ragged edge for timing; by the time you're into 3rd, the loading is at its max and you've put enough heat into the chambers by that part of the run to make it more likely to knock than it does in 1st and 2nd gears. Either run better fuel or tune it for what you're running.

VoyagerCamaro

Shell 93 octane has never pinged/knocked/detonated on me. I swear any other brand of gas, when my car was bolt on if I ran any other brand of gas Hess, Sheetz, BP etc... On the 2-3 shift it was just bust out and then finally shift at what seemed an eternity... But when I had 93 Shell it never would. Weird?

fbody_brian

Interesting
I ran chevron fuel previously. This time I ran some from the kangaroo station. Probably bad gas. I always run 93 octane.

Iat temps were way up too, I think about 20°.

I also just replaced my fpr, now I need to verify fuel pressure, possibly running leaner.

junkLT1

I would say too much timing. The motor is not happy there. Pull a couple degrees out and you will likely pick up et/mph.

Kevin97ss

Can you feel any surging in 3rd even though it continues to pull hard?

I had a similar issue that effected 3rd gear @ WOT. It would pull hard but had a slight surge. I tried the things suggested here, fuel, timing but it only continued to get worse. Eventually it started to effect the top of 2nd gear and I felt like a bobble head in 3rd. New valve springs went in...no change.

Then I noticed the water pump started to leak. While I was in there I figured I should take a peek at the opti and bingo! Even though this car had only 34k miles, the factory opti had loose rotor screws. Reassembled using Loctite and its perfect to 6500 in 3rd.

Root cause, doing a cam swap and not replacing the O-rings on the optishaft.

bufmatmuslepants

iTrader: (3)

At the end of your run what was the coolant temp? Try a 160 t stat and pure water with water wetter and see if it stops.

fbody_brian

I'm going to pull some timing and see if it helps. I didn't change the timing between the last time I went and ran .2 and 3mph faster than this time though, so I'm trying to figure out what's going on. It was a way better DA this time too, like 300 vs 1700 kind of better. I was hoping for high 12s and ran a 13.58.... I've got some adjusting and testing to do. Going to get a wideband and make sure my afr is good, make some timing adjustments, etc.

I didn't really feel a surge at all. Also the opti if fairly new and I did locktite the rotor screws. I'm hoping that's not it, but I guess it's possible.


It was 200 deg from the start to the finish. It only got up to 201 after the run ended. I did order a 160 deg thermostat, we'll see if that helps.