bob-05

I am getting what I think is false knock counts on my 95 since adding roller rockers when I had the heads redone. Installed the LT4 Knock Module and it reduced it, but did not totally eliminate it.

I have been logging with datamaster and sometimes it will get through a WOT run without retard and other times it will pull out up to 10 degrees. You can really feel the difference.

My question is, what is the best way to disable it.

I am thinking about setting "max knock retard vs RPM (in PE) to zero ?

This is the table as viewed from TunerCAT.

Thanks for any suggestions.

Bob

Wheelman

I wouldnt recommend disabling the knock system completely, but if I was going to do it thats the table I would set to zero...

bob-05

Thanks for the reply.

I drive this car infrequently for mostly pleasure, but when I do drive it I tend to drive it hard. I use 93 octane and thought that I would be able to hear the knock if it was really knocking. I have logged with datamaster and noticed that with the same tank of gas, sometimes I get knock counts incrementing and sometimes not, during a full throttle acceleration same day same engine temp etc.

If I slow down to about 25 and then floor it, it will downshift and spin the wheels, but when it pulls timing out it will not break the wheels loose from 25mph. I am looking for more consistent performance, but maybe this unrealistic. Other wise this car runs great. I am new to the C4's used to own a C3. I like hard acceleration and handling but don't need to go real fast mph wise.

Casethecorvetteman

Find out why its doing this and fix the issue, then take it from there. You cant simply turn it off to cover the issue, this wont fix it.

You say you had the heads redone. This could be the issue, how much did they shave off and what sort of head gaskets did you go with? If the compression ratio is up enough, you may need to pull a few degrees of timing out of it in the areas its knocking.

What other mods does this engine have?

bob-05

I don't know how much was removed from the heads, the shop gave me a fel pro kit which included 2 9966pt head gaskets. I think I remember him saying it would have a slight increase in compression.

He also replaced all of the valves, valve guides and springs and gave me a set of Scorpion 1.6 roller rockers.

I was assuming that I was getting false knock because I cannot hear it.

Is this a bad assumption ? The car runs great , if I didn't start playing around with datamaster I would have never know about the knock counts.

Thanks for the reply.

Bob

STL94LT1

I don't think false knock would be pulling 10* of timing.

Casethecorvetteman

No i dont think it would pull out 10* either. If its had that work done, it might just need a tune to fix it.

bob-05

Anyone know of a good tuner in the Southeastern PA area ?

I wouldn't mind doing myself but my continued logging runs on the highway are probably going to get me in trouble.

Atok

It will! I had the same issue that Bob mentioned. I installed GMPP 1.6RR on my 95 LT1 ZF6 (50k miles). I had two cylinders fairly noisy afterwards. Then while working on the tune I noticed huge knock retard. After some tests I could reproduce it sitting in my garage in neutral. While logging if I reved the engine to 1400 - 1800 RPM the knock counts would go nuts. On the road, in 6th gear going up a slight grade at about 67mph, it would kill the power until I got it above or below the "magic" RPM that the rockers/lifters were rattling. It was pulling more than 10* depending on how long I held it at the precise RPM. It only did it with hot oil (Mobile 5w30).

I have since replaced my lifters. It is quieter now but I have not done any datalogging yet to check for false knock. One thing I found in my tests, the LT4 KM made it MUCH worse. So maybe I have a bad LT4 module? Or maybe the lifter/rocker rattle is closer to the LT4's knock frequency.

Bob, I suggest you try the same test I did. Sit in the garage and slowing rev the engine through the RPM range (hot oil) watching for knock counts. Then try your LT1 module and see if it's better or worse.

I will do some data logging soon and report back on if the new lifters helped or not.

STL94LT1

That doesn't sound like false knock either.

bob-05

Thanks for the suggestion, I will give it a try and I may try using octane booster or 100 octane gas.

One thing that I noticed, when going through the logs is that it is only registering knocks at wot, sometimes at as low of an rpm as 1875 other times at 4750. Part throttle (rpm's up to 3500 or so) driving will not register counts, only full throttle. The pcm is trying for 37 degrees at 4700. I am starting to lean towards real knock.

My situation got better with the LT4 module.

Are you happy with the new lifters ? Is it quiet now ?

Atok

Yeah, that sounds like it might be real knock. Mine was detecting knock at any throttle position, it was RPM dependant not engine load.

Yes, the new lifters made a big difference. Much better now. If the false knock is gone then I'll be happy. It pulls strong all the way up so it might be Ok now. Guess I had a bad lifter.

Atok

What's your definition of false knock? What I call false knock is anything that causes knock counts that's not detonation. In my case I think it was a bad lifter. If you just tap a wrench on the side of your head it'll register knock counts - false knock.

bob-05

I think that I will be doing lifters. When I had it apart I inspected all of the rollers on the lifter the bore and checked the cam lift as per my machinist. All of that looked good and I did not think they would have a hydraulic problem that would lead to a noisy valve train. I should have changed them while it was apart. The noise annoys me.

Like yours the noise gets worse as the oil heats up.

Thanks for the reply.

VenkmanP

Bazillions of people have installed RR on LT1s without having to disable knock retard.

Therefore it is highly likely that you have a real problem which needs to be fixed.

mseven

I would not even consider removing spark retard. In mine I would pull some timing out at the specific rpm or add fuel. What I have read all sounds like more tuning is needed.