What causes KR?

[stealthy1ss]

This last Friday I made an attempt to tune my car for E85. The problem is that with 93 and E85 the car is still seeing knock. What I would like to know is what are the mechanical causes of knock retard? We have backed down the timing and the car still continues to see knock. It probably doesn't help the the MAF calibrations are way off but I am looking to see if I have possibly caused internal damage with the previous tune. Any help would be much appreciated.

[wrath]

I'm no expert but I've had trouble tracking it down before.

Can you hear the knock? Or is the car just detecting it? Is it seen throughout the full RPM range or is it spike-y? Right after a shift it should get highest if it is true knock.

Have you tried switching to colder plugs?

If it doesn't happen very often it can be related to something mechanical contact. Can be as simple as exhaust hitting something. Or a bad knock sensor. I had to replace one not that long ago because it got ruined by a relative constantly taking it to a carwash.

[theavenger333]

heat, vibration, knock, and misfires

[wrencher]

Might help to understand what a knock sensor is & how it goes about detection.
http://www.autoshop101.com/forms/h38.pdf
Anything that produces sounds or vibrations in the calibrated range of the knock sensors will make them detect a knock.
Also important the knock sensor & circuit is good (proper resistance, correct stable reference voltage ETC) + it is also important that their mounting & or bolt is installed to the proper torque.
Chasing KR is no fun thats for sure.

[stealthy1ss]

I'm no expert but I've had trouble tracking it down before.

Can you hear the knock? Or is the car just detecting it? Is it seen throughout the full RPM range or is it spike-y? Right after a shift it should get highest if it is true knock.

Have you tried switching to colder plugs?

If it doesn't happen very often it can be related to something mechanical contact. Can be as simple as exhaust hitting something. Or a bad knock sensor. I had to replace one not that long ago because it got ruined by a relative constantly taking it to a carwash.

The car is just detecting it and what is weird is that when it picks up knock it is never in the rpm range. One run it will pick it up in the lower end and the very next run it will pick it up in the higher end. The car absolutely hates it when you stab into the gas. If you roll into the throttle it is much happier. I just put brand new plugs in the car when I put in the 80 lbs injectors. We have tried backing the timing way down but it still knocks..


Might help to understand what a knock sensor is & how it goes about detection.
http://www.autoshop101.com/forms/h38.pdf
Anything that produces sounds or vibrations in the calibrated range of the knock sensors will make them detect a knock.
Also important the knock sensor & circuit is good (proper resistance, correct stable reference voltage ETC) + it is also important that their mounting & or bolt is installed to the proper torque.
Chasing KR is no fun thats for sure.

Thanks for the link. I will have to check it out.

[BAD LS1]

Burst knock = anticipated KR, this is what you are seeing. Esp on E85, highly doubtfull its reall knock, esp if you removed timing.. The BK tables will need to get relaxed to fix this. Your Maf transfer table, as mentioned as being off, this will help play into the onset of BK activating too.

[lilws6]

the answer from god himself :goof

[stealthy1ss]

Burst knock = anticipated KR, this is what you are seeing. Esp on E85, highly doubtfull its reall knock, esp if you removed timing.. The BK tables will need to get relaxed to fix this. Your Maf transfer table, as mentioned as being off, this will help play into the onset of BK activating too.

Thanks Tom. If I have other questions would mind helping me with them?

[BAD LS1]

Thanks Tom. If I have other questions would mind helping me with them?

sure no prob, shoot me a pm!

[stealthy1ss]

Thanks to all that help me out. The car is now running really strong so it looks like I might have a date with the dyno on Sunday.

[lilws6]

figured it out finally?