LT1 24x Conversion - No knock retard, ever.

Hello,

I have a 383 LT-1 which has been converted to run a 411 PCM with coil per cylinder ignition. The problem is, no matter what I do to the tune, I never see knock retard. This has me worried and thinking I've messed something up in the tune or knock sensor wiring.

For example, I tried the trick of hitting the block with a screw driver and still got zero knock retard.


Can anyone provide some tests I can do? If I backprobe the knock sensor pins, is there a voltage or resistance I can look for?

How about some screen shots of your tune? Do you hear detonation?

I'm experiencing the same thing. Will be following this one.

Resistance should be 93K-107K ohms, voltage should be 5v on harness terminal with key ON.

AdsoYo, I'm assuming you did those tests on your knock sensor and its good to go?

correct, and it's a brand new sensor. Since I have a 94, I had to buy an OBD2 sensor. I downloaded the stock 2002 TransAm file from the repository and copy/pasted the knock settings, changing the number of sensors to one. My next move was going to be changing detection mode to global from cylinder. I don't know what that does exactly but I'm out of ideas. I've also never heard any knock though. I'll post my tune and a recent log with highway, city, and wot driving.

If you never heard knock it is a tough call maybe there is nothing to detect.

Is there a gradual way I can about creating a knock situation as a test? The only thing I have tested it a screw driver next to the sensor, and I slowly maxed the timing to 50 degree at idle with no retard.

Great thread guys. I think the 411 PCM is less sensitive to knock than the LT1 PCM was. This is based on having heard LS1's on the dyno that sure sound like they're knocking and the PCM doesn't see it. That and there isn't the constant "how do I get rid of this false knock retard" threads that you saw when tuning and LT1.

Any update on settings etc?

Jason

Are you guys running 1 knock sensor on the block or 2??

Quote:

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Originally Posted by jahajazz

Is there a gradual way I can about creating a knock situation as a test? The only thing I have tested it a screw driver next to the sensor, and I slowly maxed the timing to 50 degree at idle with no retard.

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The only other thing I can think of is maybe using a hammer instead of screwdriver.

Quote:

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Originally Posted by JasonS5555

I think the 411 PCM is less sensitive to knock than the LT1 PCM was. This is based on having heard LS1's on the dyno that sure sound like they're knocking and the PCM doesn't see it. That and there isn't the constant "how do I get rid of this false knock retard" threads that you saw when tuning and LT1.

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This is another reason I'm more than a little interested in this issue. Before 24x, I was getting all kinds of knock counts and seemingly random knock retard. Cruising down the highway? 5* pulled out of nowhere. Idling at stoplight? Good time to pull 0.5*! Sometimes WOT had no retard, sometimes it pulled all kinds of whacky numbers.

Quote:

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Originally Posted by Ben Charles

Are you guys running 1 knock sensor on the block or 2??

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1 sensor on the block.

Yeah 1 knock sensor on the block

Finally had a dry day to drive the car. I set the knock detection mode from "cylinder" to "engine" and that fixed the problem. Now I have knock retard ALL THE TIME, more in line with how the car was before 24x :(

Tried many different things today to get rid of the knock retard. Raised the values to near max in all 3 "knock sensor level" tables. Doubled the decay, halved the attack. Finally reduced timing by 8* in all spark tables. Didn't make any amount of difference whatsoever. The PCM pulled the max amount of timing in all cells at all times. Finally just turned the knock sensor back off. After 3 months of 24x, I've only heard actual knock once anyway.

Jahajazz: get it working yet?