False knock driving me crazy, help please

[BEATAV8]

That looks much better, even though it's showing such a big number. The knock hits when you spool up and the engine accepts the load, then it's clearing up and going away. That's the kind of thing that a good chip can be programmed to ignore.

Did it spin the tires when you did that?

My car will often do the same kind of thing when the engine accepts load and the tires spin. It's like an unwanted traction control....
The TTSD chip can be programmed to ignore the knock immediately after going to full throttle, based on either time or mph. Then you can look for knock after the engine has "settled in" to full load and you know you can trust the readings better. Also read the plugs to make sure.

 

[BEATAV8]

Here's an example with and without the knock ignore working.
On the left, lots of tire spin and massive false knock.
On the right, same tune with knock ignore turned on to ignore knock for the first 1 second or so after going WOT. The knock data on the right is much more reliable.

 

[blackdeathtrap]

i had even more faulty knock then that though engine was done till i pulled of the motor mounts and found driver side was broken clean in half

 

[Flyin Brian]

That looks much better, even though it's showing such a big number. The knock hits when you spool up and the engine accepts the load, then it's clearing up and going away. That's the kind of thing that a good chip can be programmed to ignore.

Did it spin the tires when you did that?

My car will often do the same kind of thing when the engine accepts load and the tires spin. It's like an unwanted traction control....
The TTSD chip can be programmed to ignore the knock immediately after going to full throttle, based on either time or mph. Then you can look for knock after the engine has "settled in" to full load and you know you can trust the readings better. Also read the plugs to make sure.

Yes, the tires were spinning bigtime and it just shifted from first to 2nd right before the big knock signal. Wideband was not working on that run but the O2 volts were at like 850 and the EGT was at 1220F on E85. No way that could be real knock I hope. I can still roll into WOT in third and get no knock. Got to be something banging around but I cant find it. I like the knock ignore feature on that SD chip. I may end up getting one someday.

 

[Flyin Brian]

Here's an example with and without the knock ignore working.
On the left, lots of tire spin and massive false knock.
On the right, same tune with knock ignore turned on to ignore knock for the first 1 second or so after going WOT. The knock data on the right is much more reliable.

Thanks Steve. It is good to see some log files that look just like most of mine! Now I know I am not just cursed or crazy. I am going to keep working on it this weekend and try to find what could be causing it. The plugs look new due to E85 and there is no sign of detonation. I have a new set of plugs that are a heat range cooler that I am going to put in today before I do test runs.

 

[TurboBuRick]

Trans mount?

 

[blackdeathtrap]

thats another good point all tree mounts could be tired since i changed mine i have 0 knock i also changed the headers maf and all gasquets mine runs like a top now you mint wanna check your mounts once my tranny mount had lost both bolts i never noticed until it started getting false knock

 

[Flyin Brian]

thats another good point all tree mounts could be tired since i changed mine i have 0 knock i also changed the headers maf and all gasquets mine runs like a top now you mint wanna check your mounts once my tranny mount had lost both bolts i never noticed until it started getting false knock

Trans mount is good. Stock replacement from auto store, not the poly HR parts mount though. Bolts are tight.

 

[TurboBuRick]

Are you hearing anything? Does it pull smooth? No hick-ups?

 

[Flyin Brian]

Are you hearing anything? Does it pull smooth? No hick-ups?

It pulls hard until it jerks the timing. Pulls hard and smooth when it is not jerking timing. I don't hear anything but turbo spool. I just hammered it again with the ac on this time and got the same graph on the knock retard. Happens after the 1-2 shift during tire spin.

 

[BEATAV8]

Trans mount?

I should check mine... it's OE and old. Thanks for the idea Rick.

 

[Flyin Brian]

I did about 20 miles of pounding it today with a new set of Delco R42 plugs. I just checked them and they all look the same, brand new. No sign of detonation (silver flakes on the plug means detonation right?) and I can't even find a heat mark. The ground straps look a little discolored around the bend but that's it. Very hard to read. Max EGT recorded on #6 was 1525 F. AFR between 10.2 and 10.6. Boost at 18 psi. Injector duty cycle around 90% near 6000 RPM. Timing at 23 and 21. Still have the big knock after the 1-2 shift. It is very predictable now. Got to look some more.

 

[BEATAV8]

if it runs out nice and clean through 2nd and 3rd gear after the "wheel spin" stuff clears up, and the plugs look good, then you are doing OK.

 

[TurboBuRick]

So many variables it's not easy to cover all the bases.

All indicators suggest false knock but something is there. Is it knocking during wheel spin or when it hooks?

If you can post another log for us. Give us something to do.

RL

 

[Flyin Brian]

So many variables it's not easy to cover all the bases.

All indicators suggest false knock but something is there. Is it knocking during wheel spin or when it hooks?

If you can post another log for us. Give us something to do.

RL

It looks like it is during wheel spin from the log file. Wheels start spinning when I floor it in first of course and the knock hits right after the 1-2 shift. Clears up by the top of second when the wheels stop spinning and is totally gone all through third. Attached is my last log file from yesterday. Fairly hot day and I was running the ac since I just got that working. Thanks.

 

[Flyin Brian]

Well, I may have finally found the source of the false knock. I just posted in the engine tech area on my thread about the mystery metal in the oil filter I had last year. Crank hub key was banged up and the groove in the hub was opened up. Looks like the hub was walking around. I checked the bolt when I was going over the false knock check list. I put over 200 ft lb on it and it did not turn any. It is toast now. Got a BHJ harmonic balancer with my engine freshen up so I should be good now. The BHJ is a press fit and the bolt is torqued to 250 ft lb now. I hope to have it running next month and will see if the false knock goes away. Pistons looked great by the way so it was truly false knock. Thanks for all the comments and suggestions by the way. This forum is great!

 

[KEVINS]

Funny that you brought this back up.

Yesterday I was going through my files and I found some old printouts from this site from 2000. One of those printouts was from Chad Schwartz who always complained about false knock but unexpectedly completely eliminated it after installing a 3.5 LS1 MAF, Translator and Extender chip. Others soon followed and their thoughts were that the stock MAF doesn't react fast enough to sudden changes in airflow when you suddenly nail it.

ks

 

[Turbo6Smackdown]

I have another question on this slow maf fix. Could any of the newer LS1 or Z06 maf's have this problem by chance? And how likely could a bad trans mount cause KR? What is actually happening that would make that mount cause the knock?