False Knock Procharged S550

So, I am still getting quite a bit of false knock on my P1SC-1 stage 2 setup. What I understand to be a fairly common with my application. I have tried to rule everything, including checking all exhaust connections, clearance, motor mounts, headers, fuel, plugs, etc. and knock sensors are still pulling timing in a lot of the logs I've recorded recently. Not always, but a good percentage of the time.

I've been back and forth data logging for several weeks now and at this point the tuner is hesitantly recommending we desensitize KS's a little bit to avoid power loss, though this makes me a bit nervous in the event I get a bad tank of gas. They do recommend I always run an octane booster in this case (using Torco now on track days).

Wondering if I continue to try to determine the root cause of the KS's pulling timing, but not sure I'll see anything I haven't already been looking for and from what I understand, the S550 KS's are extremely touchy. The tuner mentioned that they see this quite a bit on my car.

A couple of logs from yesterday:

Sport Driving Mode

https://www.dropbox.com/s/f2ne3ux0okgbzj7/datalog1%2040%20roll%20sport.csv?dl=0

Normal Driving Mode (usually pulls more timing than Sport Mode)

https://www.dropbox.com/s/79a2xrmrybxl8g0/datalog1 40 roll normal mode.csv?dl=0

When is it pulling the timing? at WOT?

AdrianMAK said:

When is it pulling the timing? at WOT?

Click to expand...

Yes, generally around 5500rpm and higher while in WOT

what kind of headers are you running? Take a look at your top steering shaft bolt and rear header tube clearance "While in the air and move front tires left to right while that bolt and shaft spin". I had to take the shoulder off the bolt and grind it down to where the torx barely grabbed to make it clear with my LTH's.

Also on passenger side I noticed very close clearance between the a/c line junction and a a/c line bracket bolt. Might be another thing to look at. ;)

In your normal mode log it knock before you even went close to full throttle. lower around 3500rpm. From there it was adding timing slowly as it got out of knock fast advance mode. A gear change reset it and you were fine from there.

Fuel looked good, spark was good out of knock. shouldn't be knocking there.

http://datazap.me/u/markmurfe/log-1503686574?log=0&data=2-8-10-13-14&solo=2-8&zoom=769-1879

Jesus another one!!

BigMikeVP said:

what kind of headers are you running? Take a look at your top steering shaft bolt and rear header tube clearance "While in the air and move front tires left to right while that bolt and shaft spin". I had to take the shoulder off the bolt and grind it down to where the torx barely grabbed to make it clear with my LTH's.

Also on passenger side I noticed very close clearance between the a/c line junction and a a/c line bracket bolt. Might be another thing to look at. ;)

Click to expand...

Thanks. I'm running Kooks 1 7/8 catted, soon to be a cat delete. Will check all of this.

OK, so I looked at every log I have recorded while boosted and found a revision that was much better from around a week ago, at least from a false knock perspective. The log is not pulling any timing and actually adding for the most part and worse case 0 knock activity. I had asked for a revision due to quite a bit of low rpm/cruise bucking, which they then changed to enrich sooner and then I had non-stop false knock issues again, similar to the earlier revisions I had uploaded. The false knock would then indicate a tuning issue and not a mechanical issue given that this older revision completely solves it?

See below for a log from today with the older revision. I just did a pretty good drive and this one feels way better, despite some buck and some lean spikes in 4th (pointed out by my tech):

https://www.dropbox.com/s/5vejrkk7m1j6r7e/datalog1%20R5%20WOT%202nd%20to%204th.csv?dl=0

All in and given some hiccups, I still have nothing but good things to say about Lund's responsiveness and willingness to work with you to get things sorted, though this can certainly be a lengthy trial and error process. There are days where I bounce 5-7 emails back and forth with them.

I am going to run this tune at the track tonight to see how it performs vs. last weekend.

I also have some false knock issues. Mostly at part throttle and not at WOT which is why Dakota/Lund think it is false. Also been having some real knock issues with the gas around here lately.

Had a shop look over everything and they found nothing. Stock headers so not sure what the cause could be. They suggested maybe the cats. Theyre coming off next week anyway so we will see after that.

Cats are on my list. Thought about that if they started to die.

venumous said:

Cats are on my list. Thought about that if they started to die.

Click to expand...

Yeah I am getting them off as I don't want to take a chance on them melting and plugging up and blowing the engine. Rare but possible. More likely but still bad is them breaking up and blowing out the tailpipe and then I have no way to pass emissions inspection.

Not worth the risk either way IMO. Plus extra power and maybe it'll fix the knock.

ahl395 said:

Yeah I am getting them off as I don't want to take a chance on them melting and plugging up and blowing the engine. Rare but possible. More likely but still bad is them breaking up and blowing out the tailpipe and then I have no way to pass emissions inspection.

Not worth the risk either way IMO. Plus extra power and maybe it'll fix the knock.

Click to expand...

I too will be removing cats here shortly as a last effort, though they didn't think that was my issue. They were thinking more so along the lines of exhaust connections, trans mount and engine mount connections. All of which have been double checked and seem fine. The only thing that left me thinking was the bushings on my header connections. They rattle at the touch and can only imagine how much more they rattle while under WOT.

I logged some data yesterday and KS activity was pretty good, but did trigger some codes near the end of the night while at the track. P0171 (sytem too lean bank 1) and P0174 (system too lean bank 2), always a bit concerning when a lean code triggers. I'm pretty sure this would be cruise AFR, as WOT seems pretty normal from the tests I've done while monitoring gauges.

This log was captured while the engine code was still on last night. Some light driving, mostly cruise, with a partial/full throttle around 5:30.

https://www.dropbox.com/s/6sirxra9uvse5rj/datalog1%20aug%2026%20rev5.csv?dl=0

With my stock manifold and cats the car ran great, no knock. I've personally only had knock when I changed to the long tubes and mine is only when I change gears hard, so in my case it has to be the engine tourqing over and touching. I just put a couple more pieces of high temp wrap on the passenger frame rail and around the steering shaft. Have to do a couple more datalog and see if that helps.

brettzo007 said:

I too will be removing cats here shortly as a last effort, though they didn't think that was my issue. They were thinking more so along the lines of exhaust connections, trans mount and engine mount connections. All of which have been double checked and seem fine. The only thing that left me thinking was the bushings on my header connections. They rattle at the touch and can only imagine how much more they rattle while under WOT.

I logged some data yesterday and KS activity was pretty good, but did trigger some codes near the end of the night while at the track. P0171 (sytem too lean bank 1) and P0174 (system too lean bank 2), always a bit concerning when a lean code triggers. I'm pretty sure this would be cruise AFR, as WOT seems pretty normal from the tests I've done while monitoring gauges.

This log was captured while the engine code was still on last night. Some light driving, mostly cruise, with a partial/full throttle around 5:30.

https://www.dropbox.com/s/6sirxra9uvse5rj/datalog1%20aug%2026%20rev5.csv?dl=0

Click to expand...

Hey man if your getting lean codes both banks u need to be careful.I would not go wot anymore until u figure out why your running lean.

brettzo007 said:

I too will be removing cats here shortly as a last effort, though they didn't think that was my issue. They were thinking more so along the lines of exhaust connections, trans mount and engine mount connections. All of which have been double checked and seem fine. The only thing that left me thinking was the bushings on my header connections. They rattle at the touch and can only imagine how much more they rattle while under WOT.

I logged some data yesterday and KS activity was pretty good, but did trigger some codes near the end of the night while at the track. P0171 (sytem too lean bank 1) and P0174 (system too lean bank 2), always a bit concerning when a lean code triggers. I'm pretty sure this would be cruise AFR, as WOT seems pretty normal from the tests I've done while monitoring gauges.

This log was captured while the engine code was still on last night. Some light driving, mostly cruise, with a partial/full throttle around 5:30.

https://www.dropbox.com/s/6sirxra9uvse5rj/datalog1%20aug%2026%20rev5.csv?dl=0

Click to expand...

http://www.datazap.me/u/markmurfe/log-1503790620?log=0&data=4-5-8-10-11-12-14-19&solo=4-5-8-11-12-19

At idle you have a bank to bank difference of 4%. At idle you are seeing 10-15% correction for a lean condition. At cruise this difference reduces.

At cruise you are seeing 20%- 45% correction. When you were cruising at 3000rpms it started to effect your measured lambda over 45% correction. Thats not good.

http://www.datazap.me/u/markmurfe/l...o=2-3-4-5-6-7-8-9-11-12-14-19&zoom=9891-19482

Zoomed in and rescaled to the cruise part of the log.

Based on the different throttle angles(MAF follows them which is good), engine RPMs, and load. I would say this is a predictive fuel correction. MAF was changing very little with RPM change, but the more load dropped the more fuel it pulled. Load is based on air mass derived from RPM and MAF values and the airmass that fits the volume of the engine. Something like this would need to be corrected in the speed density, in which the math is very complex. Tuners can and usually disable the compare the ecu does with the MAF to the speed density. If its disabled or the air mass multiplier is maxed out then its unlikely to be fixed in an email tune.