SMOKINV8

iTrader: (6)

Just checking if anybody else has run into this before I start checking wires and pulling intakes. This reminds me a lot of how 97 and 98 LS1's acted when they had bad knock sensors. Anyway...

This is on a 2005 Cadillac CTS-V with an LS7, from I believe 2007, swapped in. This means extensions or adapters were used for the cam sensor, map sensor, and knock sensors (running LS7 knock sensors). It has a small cam, 232/238'ish with .590'ish lift. Perfect manners, quiet valvetrain, no issues, except this false knock. I'll attach a screenshot from what I'm running into, but it's literally right as you enter PE, it maxes out the knock to 10* and stays there. Very repeatable and very annoying.

If anybody has experience with this issue please speak up, I'd appreciate the help. Also, ignore the wideband gauge, it was not used at the time.

scatillac

iTrader: (12)

Check to be sure that the knock sensors are really LS7 units, which are 2-wire. Most LS2/7 adapter/sensor relocation harness setups are for the LS6 sensor, which is a 1-wire.

Assuming that you are running 24X/2X timing and the original ECM, you should be using the earlier Gen 3 knock sensors (LS1/6 type) instead of the Gen 4 (LS2/7) as the newer versions are not compatible with your ECM.

You'll have to enlarge and re-tap the existing sensor holes to M10-1.5 to install the earlier sensors.

ringram

Burst Knock...

NicD

iTrader: (7)

I don't see any big airflow transitions in that area to cause burst knock, and I don't believe burst knock would be spiking 10 degrees either. Looks to me like it thinks there is a fault with the knock sensors and is defaulting to max timing retard at WOT. Run the correct knock sensors like scatillac said and try again.

SMOKINV8

iTrader: (6)

I'll look into the knock sensor issue and go from there. I didn't do the swap myself, but I'll update with what I find.

I backed off the burst knock already, and I was rolling into the throttle to lessen the likelihood of that being the culprit. Not saying it isn't possible, but I don't think it's likely.

Thanks guys.

SMOKINV8

iTrader: (6)

Verified with the builder it has LS7 knock sensors. Supposed to be swapping new ones in this weekend.

jimmyblue

iTrader: (11)

Burst knock should not persist after the step-air event, but
I don't know the newer PCMs. If it does persist there will be
a decay table for it.

Similarly KR has attack and decay tables. On the LS1 motors
the attack was excessively aggressive (fast jump to full -10*
retard) and the decay was stupid slow, to the point that you
couldn't tell how much real knock you had because the KR
would bury any info for a long time.

Reducing attach and increasing decay rate will make the KR
more tolerable, go away quicker and let you see if there is a
real knock burst or if it was just a transient fuel shortage
(which could be an indicator of a poor SD fit in the region
you stepped off from, or through - SD is exposed on throttle
transients in a stock tune with the MAF.

Is PE delay out of the picture, and ramp rate abrupt? If no,
you won't get enriched as soon as you need it.

SMOKINV8

iTrader: (6)

Verified with the owner, no knock sensors in their bosses.

Going to delete the knock sensors for now since he'd have to pull the motor to swap in the sensors. The cradle in the caddy is a little prohibitive.

Slowhawk

iTrader: (12)

That's the problem. Lol.

Just be carefully with the timing as you probly already know. Ls7's do not like much timing.

SMOKINV8

iTrader: (6)

Yep, he was on the phone with me while we were talking about where they were supposed to be. We were both laughing a little about it, but he had a "SOB" undertone to his laugh.

I've not had a lot of LS7's roll across my plate, but I figured a conservative number compared to the others would be around 24 at wot with a dip to 22 at peak torque and an aggressive IAT modifier. The other files I had looked like 25 was as high as I ran on any of them.