False Knock Issues driving me nuts...

J

Justa6MB

Member
Joined
Nov 14, 2011
Hi, I've been chasing false knock and I'm looking for ideas. I've checked all clearances, new HR mounts all around, new flex plate, tight converter bolts, new knock sensor, reset valves, ran 110 fuel through it at low boost, add and subtracted alky. I have a 210/215 Comp roller cam & lifters with Scorpion Rockers. I've got the valves all set individually at 3/4 of a turn past 0 preload. New Plugs set to .035". The knock retard happens at around 5600 rpm. More Powerlogger files available. Lots of fuel psi, and fat rich. Is that too high of rpm? I have one source that reads shift around 5,200? I have a few remaining ideas. Check crank end thrust? Could my timing be out?? chip default to 23* in 1/2 and 21* in 3/4. It happens in all gears over above rpm. Does Fast XFI use the stock knock sensor? Any suggestions would be appreciated.
Oh btw, 6.0 TurboTweak Chip.
Thanks
 

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What gear where u in? It looks like this was from a stop? Also how is it shifting? Are u shifting it or is that the point it shifts off on its own? Have you tried doing a roll on in thrid gear and see what happens?
 
When did this start? After you put the engine in? After the poly mounts?
" new knock sensor"....Torqued to?? Should be 14#, AIRC.
 
It could be way rich I was relooking at the log and it is from 7.36 to 9.15 during the knock.. Thats if the wideband is reading correct
 
^ might not have the correct WB selected to see the correct a/f. to the OP what WB setup do you have?

i doubt its that rich
 
Hi guys, sorry for the lag... Yes that log was in 1st gear rolling into it - just holding it in 1st. It will do it in any gear and typically I let it shift itself. When I rebuilt the engine I basically changed the entire combination. I did fight an over boost condition at the start due to a crappy down pipe. Unfortunately it took some testing to find out the problem, so could I have hurt something? See photo of what I found when I cut off the wastegate pipe where it joins the downpipe :( Otherwise it's running tip top, quiet idle, smooth etc. Changing the knock sensor was hunting for a solution. Tried different torques, teflon tape etc, no change. Solid mounts installed same time as rebuild. Engine had new Champion GN1's with springs that were to work with cam and combo - I'm assuming. Wideband is a PLX system. Thanks for the replies.
 

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Here's my suggestions:

1) Clear chip to go back to default settings.
2) Adjust FP to 43#'s line off
3) Get tank full of fresh 93 fuel
4) Set boost at 16#'s.
5) Turn off alky
6) Drive around until memory is learned and accelerate quickly W/O wheelspin a few times to see if knock occurs.

Eric has built many chips for these cars and the default settings are determined by years of experience that he has been programming chips. I'd start with his settings and branch out from there as you feel comfortable.

BTW, I wouldn't turn on the alky unless the car performs well without it and you are ready to bump up the boost to a much higher level than 16#'s.

Best of luck, I know how frustrating this can be.
 
Similar combo here, except I'm running E85. 215/220 cam and GN1 heads. Stock stroke.
I was having persistent false knock issues as well. I tried retarding timing all the way to 13 degrees and the same 2 deg knock retard would still show up. Did not matter what the A/F was. Did not matter if alky was on or off. Did not matter if timing was 21 deg or 13 deg.

Switching to a different spark plug made a huge improvement. Went from Autolite 103 to NGK TR6 and then to an Autolite AR472. The cold non projected tip with the cut back strap and a tight gap is the way to go. You can pretty much only get that with a "racing plug". With gasoline you may need a hotter plug than the AR472, but with E85 I'm looking to go even colder with a Champion S53C and see how that one works out.

All the plugs mentioned here are 14mm .70" reach tappered seat compatible with a GN1 head.
 
That massive false knock you are seeing right after to roll into it might require some knock ignore in the chip. But if it is always "massive" like that through any gear all the time, it probably has to be something mechanical like the exhaust or the trans mount banging around, or maybe an electrical gremlin in the knock sensor circuit.
 
I had false knock for 2 years. Chased it forever. I changed out every part I could relate to trace it to a source. I found it INSIDE my lock up convertor. Ordered a new one from Dusty and not a peep on the knock gauge since. It was at a consistent RPM too, but closer to 3000.
 
Ok thanks again... So I have the chip in default settings, fuel pressure is 42# line off, fresh 94 fuel, boost is at 15#, I do have alky set at 3 on the last test session so I can turn it right off and I'll run it tonight. How does one check the valve springs? I would get Eric to set the chip to ignore the knock till a certian speed - but that won't help in the top of 3rd - and that's where I want to see it. I'm contemplating just running race fuel and unplugging it till I find it or it becomes apparent. I know there are likely some bad stories about doing that??
 
Justa6MB said:
Ok thanks again... So I have the chip in default settings, fuel pressure is 42# line off, fresh 94 fuel, boost is at 15#, I do have alky set at 3 on the last test session so I can turn it right off and I'll run it tonight. How does one check the valve springs? I would get Eric to set the chip to ignore the knock till a certian speed - but that won't help in the top of 3rd - and that's where I want to see it. I'm contemplating just running race fuel and unplugging it till I find it or it becomes apparent. I know there are likely some bad stories about doing that??
Click to expand...

I have Eric's, speed density chip set up to ignore knock up to 30mph, I don't think he would set the parameter to ignore knock much above that. To check the valve springs you need to take them out, go to the local auto machine shop, they can test them.... at that point, might as well replace them while there out.

Reviewing the power log file notice frame #274, the wide band is max out at 10.0 and the O2 sensor is .874 I'm wondering if it's not to much fuel and pig rich knock.
I know this can cause knock 1st hand, although I'm not 100% sure what the threshold is that will cause the knock. I shoot for 11.0 with alky flowing, and I believe that should be in the area of 750 with the O2 sensor.

I would post this up at Turbo Tweaks Forum http://www.turbotweak.com/forum/forum.php I bet Eric could help you out.

Chuck
 
Justa6MB said:
Ok thanks again... So I have the chip in default settings, fuel pressure is 42# line off, fresh 94 fuel, boost is at 15#, I do have alky set at 3 on the last test session so I can turn it right off and I'll run it tonight. How does one check the valve springs? I would get Eric to set the chip to ignore the knock till a certian speed - but that won't help in the top of 3rd - and that's where I want to see it. I'm contemplating just running race fuel and unplugging it till I find it or it becomes apparent. I know there are likely some bad stories about doing that??
Click to expand...

How did you do at the track last night? A good PL file would be helpful in determining what is causing your problems.

You shouldn't use alky until the car is mechanically sound and then only when the boost is high enough to take it. Too much fuel and alky at low boost can give you huge knock readings and they are real. I had some 29* KR readings before I learned that lesson. I don't like any knock but I can live with short and low readings when the tires are being blown away but that's really more knock than I want. Running your pump at a setting of less than 6 will cause it to "get lazy" according to Julio. Suggest you look at his sticky about tuning with alky.

Good suggestion to post problem on TT forum. I would provide Eric with the chip number so he can look up how he programmed your chip.

It's hotter than hell in Oklahoma today and my car is showing some some knock with minimal boost. I run AR23 Autolite platinum race plugs and they looked "okay" but I started researching plugs and came across a article about plugs and they had concluded that platinum plugs ran hotter than same heat rated conventional plugs and would be more prone to cause detonation. I'm going to install some Autolite 23's tomorrow and see if that gets rid the knock readings. Let you know if it works.
 
check the downpipe, loosen and retorque with something in between where it maybe hitting. lastly turn boost to 10# and start up. GL.
 
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