Help, I either need new engine or new knowledge!

[kwhiteside]

I've been tuning my track 2001 Z06 for a while now and have it to where it runs pretty well within what I thought I was supposed to be doing. The tune I inherited was knocking like crazy. I would drop the spark down each time I found knocking. I have ended up with a fairly safe tune that only has 19 degrees of advance when flying full throttle at high speed. The difference in speed and how hard the car pulls during a full throttle straight is greatly noticed from when I first inherited the car. Originally my high spark table was 25 degrees advance in the full throttle 100mph + ranges. Now I've subdued the knocking, but my car is much slower.

I've been researching a bit and have come to find that 25 degrees should be easy for my LS6 engine at full throttle. The 6 degrees I've lowered is giving up a ton of speed and the engine still knocks a bit. I'm thinking either something is mechanically wrong, or I'm ignorant about some tuning process.

I've attached a couple screen shots showing that when I get on it full throttle coming out of a turn, I sometimes trigger knock. Actual and Commanded AFR are pretty close. Sometimes .2 lean. The LTFtrims also concur that I'm pretty close as they are usually kicking in only 2-4% more gas.

One piece of info to consider is that my 01 LS6 suffers from the infamous ring flutter problem where the scraper ring allows some oil up into the chamber. I sometimes get black flagged for smoke upon decelleration coming out of a high speed straight because of this. I also have to keep adding oil (about 1.5 quarts over 2 days and 100 laps)

I've also recently ran some carbon buildup cleaner through my engine.

What causes knock? from my research, running lean, hot spots from carbon build up. How about burned up valves? Oil in the combustion?

Well, I don't seem to be running very lean if at all. My engine is old and I have already done the carbon cleaner (bg44 I think). I recently had my car compression checked and all cylinders were with 7 pounds of each other. Very consistent compression, so reason to believe my valves are ok.

All in all, I need to get the car pulling @ almost 25 degrees like they are supposed to and knock free.

Tune, Log, pics attached. Your help greatly appreciated. Don't worry about offending me. Just educate me and I'll take it humbly.

[joecar]

Other causes of knock (in addition to what you mentioned):
- lower octane fuel,
- hot intake air,
- oil ingested thru PCV system.

What gasoline are you using...?

When you ran top engine cleaner did you see the crap come out (infamous smoke cloud)...?
Did you let it soak for a while and then wring out the motor...?
If you have a borescope ($100 from most online tool houses) you can look inside each cylinder via spark plug hole... condition of piston tops may tell you something.

Have you tried setting your AFR to 12.6...? In some cases changing the AFR slightly may make a difference.

Other factors: condition of spark plugs, plug gap (GM revised gap from 0.060" down to 0.040"... my understanding is that this had mostly to do with misfires... but it may have some influence on knock when CC temps are high).

If you are seeing knock at WOT at the same RPM then there are several possibilities:
- if that is the peak torque (which it is not on the LS6), then CC temperature and pressure will be the highest (which promotes knock);
- it may be to mechanical noise and/or resonance that is being picked up by the knock sensors (valvetrain, bearings, piston rocking, mounts, exhaust/chassis interference)...

i.e. it may or may not be knock related, and it may or may not be engine related... the knock sensors are picking it up.

There's a tool called Chassis Ear which lets you remotely listen to any component of the car while driving (i.e. you clip the microphone clamp to the engine case, and you remotely listen from driverseat while driving)... this may also come in handy.

[kwhiteside]

Other causes of knock (in addition to what you mentioned):
- lower octane fuel,
- hot intake air,
- oil ingested thru PCV system.

What gasoline are you using...?

When you ran top engine cleaner did you see the crap come out (infamous smoke cloud)...?
Did you let it soak for a while and then wring out the motor...?
If you have a borescope ($100 from most online tool houses) you can look inside each cylinder via spark plug hole... condition of piston tops may tell you something.

Have you tried setting your AFR to 12.6...? In some cases changing the AFR slightly may make a difference.

Other factors: condition of spark plugs, plug gap (GM revised gap from 0.060" down to 0.040"... my understanding is that this had mostly to do with misfires... but it may have some influence on knock when CC temps are high).

If you are seeing knock at WOT at the same RPM then there are several possibilities:
- if that is the peak torque (which it is not on the LS6), then CC temperature and pressure will be the highest (which promotes knock);
- it may be to mechanical noise and/or resonance that is being picked up by the knock sensors (valvetrain, bearings, piston rocking, mounts, exhaust/chassis interference)...

i.e. it may or may not be knock related, and it may or may not be engine related... the knock sensors are picking it up.

There's a tool called Chassis Ear which lets you remotely listen to any component of the car while driving (i.e. you clip the microphone clamp to the engine case, and you remotely listen from driverseat while driving)... this may also come in handy.

I had a shop do the engine clean so don't know.

I will be changing the plugs soon and will get a boroscope to see.

When you say change timing to 12.6, do you mean in the PE table?

I'll look into the Chassis Ear thingy.

BTW, I'm not hearing any knock, and it doesn't happen every time. Some times it makes a pull knock free which confuses the heck out of me.

Ken . . .

[WeathermanShawn]

You look a little lean (AFR). As Joecar stated, I would slightly richen up you WOT to ~12.5-12.7 AFR. Your LTFT's at WOT are also indicating the need for a little more fuel.

I run a catch can. That helps a lot with carbon buildup. It is amazing how much oil that catch can can carry.

The only other thing that sticks out is your ECT at WOT. Your at ~ 207F. My thermostat runs at ~ 190-195F at WOT. I also have opened up the intake..the 'Free Ram Air' Mod.

My WOT Spark Advance is ~ 22-24 degrees, depending on how hot is is (IAT).

I would try the catch can, richen up your AFR at WOT, cool your ECT, etc.

[kwhiteside]

You look a little lean (AFR). As Joecar stated, I would slightly richen up you WOT to ~12.5-12.7 AFR. Your LTFT's at WOT are also indicating the need for a little more fuel.

I run a catch can. That helps a lot with carbon buildup. It is amazing how much oil that catch can can carry.

The only other thing that sticks out is your ECT at WOT. Your at ~ 207F. My thermostat runs at ~ 190-195F at WOT. I also have opened up the intake..the 'Free Ram Air' Mod.

My WOT Spark Advance is ~ 22-24 degrees, depending on how hot is is (IAT).

I would try the catch can, richen up your AFR at WOT, cool your ECT, etc.

I am curious to see your results. Good luck!

..WeathermanShawn..

I'm already running a catch can.

I have a Dewitts perfect fit Rad/EOC combo unit and it was only about 77degrees outside that day. I also have a Vararam Cold Air Intake system already. I have not altered my thermostat to a lower temp. Should I look into that?

I will richen up my PE table to 12.6.

Could you post up your tune or send me a copy just to compare?

These are some very real things I can attack. But as you see in my tune, I'm at 19.5 degrees WOT and still picking up some knock. In your experience, do you think richening up from 12.8 to 12.6 and dropping my ECT could make enough difference to put 3 degrees of advance timing back in?

[WeathermanShawn]

As a side note..I change tunes about 2 times a week, just to see how different parameters work. But, this has been a solid tune that has taken 1 1/2 Years to get it to my satisfaction. My current PE Table shows 12.8 AFR. but normally I will run ~12.6 - 12.7 AFR on the street.

And on this tune I have smoothed out the Spark Tables. Normally I will just run ~22 degrees at WOT, but this week I am trying something different.

I rarely get any knock, and even at this altitude..this car has some pretty good pickup.

Hope everything works out for you. Looks like you have a nice ride. You are free to try any portion of my tune.

[WeathermanShawn]

I do not know if iust lowering your ECT, or richening up your WOT will cure your knock problems.

I think it is a little unusual to have that amount of knock on a engine like yours. Do you hear it pinging or knocking? Mine makes a very distinctive pinging sound, that I can hear even over the exhaust sound. And when I lower the timing at that RPM and DYNCYLAIR the pinging sound goes away.

So, I trust my knock sensors. You might try desensitizing them or check that they are operating normally.

[kwhiteside]

Do you hear it pinging or knocking? Mine makes a very distinctive pinging sound, that I can hear even over the exhaust sound.

I have not heard knock in a while. I do know what it sounds like and have heard the detonation sound before when running lean on 100 degree days. Maybe the helmet prevents me from hearing it at the track, but I still have not heard it on my tuning runs where I get up to 110mph.

I read about the C6 having over sensitive knock sensors and some HPTuner guys talked about dulling them out, but I've not read about C5 guys having that problem, nor anybody on this forum under Type III LSX.

Ken . . .

[mr.prick]

Have you tried reducing {B6202} 25% from stock and
increasing {B6207} 50% from stock?

[kwhiteside]

Have you tried reducing {B6202} 25% from stock and
increasing {B6207} 50% from stock?

Ok, that makes sense on how to desensitize the knock sensor. Thanks.

Question is, should one do this. Sounds very dangerous to make the assumption the knock is false. If lots of people found this to be a recommended treatment, that might ease ones mind.