Is it KNOCK or NOT?

[epfatboy]

Just started tuning a Gen3 6.0 DBW with a 4L80E. It's been gone thru and is a cammed 6.2 with flat tops, 317's, .600/228 ish cam, 50# injectors. Tranny has been gone thru and has a 3200 single disc converter. It's in a '74 C10 with 3.73 gears and 29" tires, new everything.

This is the 2nd real tuning pass.

I have some knock going on when I first roll into it. I only pick it up under initial load, if I "pedal it" I don't seem to pick it back up but obviously the load changed so there is that....

Anyway I started with the stock tune and haven't touched much more than Idle Air, VE, and a few tranny parameters.

Should I decrease Knock sensitivity or should I pull some timing?

About 1:48 in you'll see some KR start.

short dr sd6.1.hpl
C10 Gen3 6.2 V4.4.hpt

[RDF1]

What fuel are you using?

[abc]

Do you here it knock?
Have you looked at the plugs and scoped the cylinders and look for signs? Typically the signs will show up on the plugs, top of cylinder bore, and top edge of pistons.
As mentioned already, what fuel?
You could pull 5 degrees across the board and see if the signs are exactly the same. If the signs are exactly the same, it's very likely false and you can de-tune the sensors.
To verify as much as possible you will need to listen to the engine with a knock ear setup.

[epfatboy]

Do you here it knock?
Have you looked at the plugs and scoped the cylinders and look for signs? Typically the signs will show up on the plugs, top of cylinder bore, and top edge of pistons.
As mentioned already, what fuel?
You could pull 5 degrees across the board and see if the signs are exactly the same. If the signs are exactly the same, it's very likely false and you can de-tune the sensors.
To verify as much as possible you will need to listen to the engine with a knock ear setup.

THIS!

pulling 5 and assessing was testing methodology I was looking for but couldn't get there on my own...

it might be the gas, I put 10 gallons of 93 in, what was in there was fresh but it might have been 87... This scan has the mixed tank but not much time on it, basically drove home from the station. I know it's 10.8 ish compression.... thought I'd see alot more knock if the gas wasn't up to the task.


I will check the plugs too, it's about time too look at them anyway and dump the oil.

Thanks for the help.

Oh and I could not hear it knock, but I'm as deaf as I am daft!

[Alvin]

87 would be tough to make work on 10.8 compression.

You plan on staying with 93 right?


BTW. when you go speed density with these it defaults to the low octane table. SO you are knocking that hard and already in the low octane table. You can either copy high octane to low or run a custom OS which is supposed to fix that default low octane in SD mode.

[epfatboy]

87 would be tough to make work on 10.8 compression.

You plan on staying with 93 right?


BTW. when you go speed density with these it defaults to the low octane table. SO you are knocking that hard and already in the low octane table. You can either copy high octane to low or run a custom OS which is supposed to fix that default low octane in SD mode.

YEP, 93 for sure.

And that answers another Q, I thought default was high octane, which it is... until I'm in SD... wa wa waaaaa.

So I did the following before reading this to setup the table and a quick 10 minute drive saw no knock.
- Copy Low Oct to High Oct
- Remove a degree or less from specific areas in the high oct table
- Copy high oct to low oct (didn't want them to be diff just in case)

I pulled plugs but nothing to see there so I believe KR is doing it's thing... plus it's being driven a few miles after the event occurs so there is that too.

I'll keep monitoring, hoping a full tank of 93 gets me more excitement.

FYI my plan is to NOT run SD so I do plan to setup the High/Low tables appropriately when the time comes.

[epfatboy]

So, I had a little real KR here and there and that problem is solved.

BUT

I see KR and alot of it consistently when the converter is locked and unlocks as I lean into the throttle, doesn't have to be me leaning hard either. Its almost always a max event (-8) too.

AND

I think I have a little "tingling" coming from the converter/tranny (new FIT single disc ~3Kstall, rebuilt 4L80E local shop) I thought it was lifter noise at first but after running it while I was under it I really think its coming from that general area. I also can be accused of hearing tingling on just about everything I build and can't really spot noise or leak location, pretty sure that's normal for most of us.


The local shop that did the rebuild was reputable while the owner was alive, he is not so there is that. Also the tranny was stored in my shop for 4 years after the rebuild.. maybe a problem but it runs down the road and shifts as it should.

So could the tranny/converter be slapping/banging and causing KR when it's locked and unlocking? I don't hear/feel anything going on when it happens.

I have validated the converter bolts have not moved as they have been torqued/locktite'd/painted, same for the flywheel bolts, I learned that lesson once.

[abc]

Sure, lots of things could be out of the factory calibration range to cause the KR. To verify as much as possible you will need to listen to the engine with a knock ear setup.

[epfatboy]

OKAY.... getting back to this.

Added "4 points" to the knock sensor sensitivity tables across the entire range. Added 2 to start and still picked up some KR at low RPM while the tcc was locked. Added 2 more (4 total) and got 0 KR. Still running the low octane spark table but given this I'm pretty sure I'm not detonating so I'm gonna start adding some advance back in.

So about adding 4 across the range... now what leave it or?

[Alvin]

I don't ever do that..

Did you consider replacing the sensors first. When knock sensors go bad they either pick up nothing or every little bump in the road.

[abc]

OKAY.... getting back to this.
I'm pretty sure I'm not detonating

In short, you can listen for knock and look for the signs or lack there of or hope you guessed correct with the sensitivity of your knock system and structure of your ignition tables.

The thing with Knock is: The engine can possibly tolerate intermittent bouts and live a normal long life. The engine can possibly have intermittent bouts and cut the useful life of the engine in half by beating the big end of rods up, destroying the tops of the pistons, destroying the top portion of the bore, destroying the combustion chamber and so on. Some engines will tolerate constant knock, the only way to know for sure is to test it. The best possible way to eliminate knock as a potential destructor of your engine is to test for it or in this case and in most cases in the aftermarket is to listen for it.
As far as I know, trusting the factory knock sensors (especially on the older systems) once you have changed any part of the engine that will have an effect on the density of the long block as a whole, is a crap shoot. Add in the reports of aging sensors, after market sensors, and other variables with the system, now it's anybody's guess if you should desensitize the knock system in your situation.

[mychevyisntheavy]

i am fighting the same things. knock. i cant hear nothing and i seem to see it in the scanner at around 4000 to 4400 rpm range. i have long tube headers to a y pipe. thinking hard on going back to the stock manifolds. just alot of work. smh. i even got those blocks from ict billet to move the knock sensors out of the middle of the engine. i think mine is false knock. i had other people that are tuners to look at it wth out me saying a word as they tune he said i believe i was getting false knock. there would be months go bye with no sign of it then i get months of this crap. i cant hear no pinging i know what it sounds like.

[abc]

When I mention about listening for knock, I mean to do it with the proper tools. Either make your own with a mount to the engine, some tubing, and a cheap set of ear muff ear protection or move up the food chain as far as cost goes to suit your taste. Search "knock ears".

[Vbb1994]

Has a single plug or piston dome been inspected ? Or are we still speculating and trusting sensors and scanners?