-4 Feedback knock on WOT after tune

been checking datalogs of my engine after getting a dyno Protune tune. I am slightly concerned about the feedback knock during some pulls. the DAM stays at one with the fine knock at 0, but the feedback knock is pulling up to -4 degrees at times. is this something to be worried about? Would this be considered a tuning issue or a physical issue?

 

i also notice occasionally i get 1 count of roughness in cylinder 4, any concern to that? datalogs attached

Redslaya_2rd_Gear.csv

Redslaya_3rd_Gear.csv

Any input?

Moved to tuning forum

I'm not too familiar w/ the roughness observation, so hopefully someone else will chime in about that. Your 3rd gear FBKC appears to occur during throttle mash, w/ the 2nd FBKC hit occuring about 0.8 sec later during spool. Does it usually show up like this, or does it also happen higher up in the RPMs during/after your boost settles in?

 

First suggestion of course would be to run the logs and your observations by your tuner.

 

For some DIY, assuming this is an Accessport-based tune, you could try pulling -2 or -3 deg global timing via the Accessport, to see if the FBKC behavior improves. If it does improve, the tune might be running a little too much timing in the lower RPM/medium load range. If the FBKC doesn't respond to the timing reduction, maybe check underhood for anything that might be rattling. In some cases a rogue rattle will show up as massive FBKC in logs, but in my prev car a loose turbo heatshield would only rattle under load and only in a narrow RPM range, causing small but consistent FBKC.

 

Also, it looks like you're not hitting boost target. Not hitting it in 2nd can happen in warm temps but I'd expect you should be somewhat easily hitting target boost in 3rd. From 2970-3600 rpm you're ~3.5 psi below target. I find it interesting that WGDC in that RPM range remains steady at 30.2%, rather than increasing to try to achieve target boost.

 

To see if your boost is being capped by WGDC, add the Turbodynamics parameters as well as WGDC Max to your logging. If your WGDC and WGDC Max values are the same, it's likely the boost is being capped by WGDC (there are WGDC comp tables that can come into play too). Also see what AF Learning #1A, B, C, D are (to see if perhaps you have a leak that's contributing to the below-target boost).

I'm not too familiar w/ the roughness observation, so hopefully someone else will chime in about that. Your 3rd gear FBKC appears to occur during throttle mash, w/ the 2nd FBKC hit occuring about 0.8 sec later during spool. Does it usually show up like this, or does it also happen higher up in the RPMs during/after your boost settles in?

 

First suggestion of course would be to run the logs and your observations by your tuner.

 

For some DIY, assuming this is an Accessport-based tune, you could try pulling -2 or -3 deg global timing via the Accessport, to see if the FBKC behavior improves. If it does improve, the tune might be running a little too much timing in the lower RPM/medium load range. If the FBKC doesn't respond to the timing reduction, maybe check underhood for anything that might be rattling. In some cases a rogue rattle will show up as massive FBKC in logs, but in my prev car a loose turbo heatshield would only rattle under load and only in a narrow RPM range, causing small but consistent FBKC.

 

Also, it looks like you're not hitting boost target. Not hitting it in 2nd can happen in warm temps but I'd expect you should be somewhat easily hitting target boost in 3rd. From 2970-3600 rpm you're ~3.5 psi below target. I find it interesting that WGDC in that RPM range remains steady at 30.2%, rather than increasing to try to achieve target boost.

 

To see if your boost is being capped by WGDC, add the Turbodynamics parameters as well as WGDC Max to your logging. If your WGDC and WGDC Max values are the same, it's likely the boost is being capped by WGDC (there are WGDC comp tables that can come into play too). Also see what AF Learning #1A, B, C, D are (to see if perhaps you have a leak that's contributing to the below-target boost).

 

this is really the first time ive been logging knock so i dont have much to reference it to.

 

I have been datalogging (car is parked until i get this sorted out now) and have not received much from the tuner other than "bring it in so we can diagnose it"

 

as for the boost in 2nd gear, i know the tuner deliberately has it only hitting 14-15PSI. he went into detail why but i cant quite recall the reason at the moment. however it did make sense.

 

tomorrow i am going to remove the mods i had put on for the tune and go back to the cobb OTS tune. see how the knock goes with that. hopefully that will tell me if its a tune issue or an engine issue

You're logging way to many parameters. Honestly, 2nd gear run is clean. You obviously have FBKC in 3rd, are you a 5EAT? Is everything bolted down? All lines connected? No leaks?

 

You also have no FKLC and DAM is staying at 1...you'll get FBKC occasionally, either from gearbox or something rattling around. The knock sensor is fairly simple and just looks for a sound that resembles a knock. If it was severe, you'd be getting FKLC or worse DAM dropping.

You're logging way to many parameters. Honestly, 2nd gear run is clean. You obviously have FBKC in 3rd, are you a 5EAT? Is everything bolted down? All lines connected? No leaks?

 

You also have no FKLC and DAM is staying at 1...you'll get FBKC occasionally, either from gearbox or something rattling around. The knock sensor is fairly simple and just looks for a sound that resembles a knock. If it was severe, you'd be getting FKLC or worse DAM dropping.

 

yea im a 5EAT. i have a bunch of stuff logging from a previous issue and i forgot to disable those logs. My plan tomorrow is to make sure everything is tight and try to narrow down what could be causing those knocks. my main concern is that i read false knocks are usually only up to -2.8, and the fact that this knock event last for a while makes me think its more than a false knock. Im trying to catch any problem early so i can avoid any further problems down the road

It is not uncommon for the 5EAT to see -4 to -6 correction. As long as it isn't constant and learns its way back to 0, you should be fine.

You're logging way to many parameters. Honestly, 2nd gear run is clean. You obviously have FBKC in 3rd, are you a 5EAT? Is everything bolted down? All lines connected? No leaks?

 

You also have no FKLC and DAM is staying at 1...you'll get FBKC occasionally, either from gearbox or something rattling around. The knock sensor is fairly simple and just looks for a sound that resembles a knock. If it was severe, you'd be getting FKLC or worse DAM dropping.

 

Whether you see FBKC, FLKC or a DAM change depends on which correction mode the ECU happens to be in when the noise is heard. When I had a rogue rattle, I'd often see -8 to -11 deg FBKC with no switch over to FLKC or DAM changes. When I had overboost issues after peak boost in cooler temps, I'd sometimes see FLKC or a DAM change without any FBKC. Merchgod on the Romraider forums listed the specifics for each correction mode and the conditions that are required for the ECU to switch modes here.

 

Empirically I've usually seen FBKC when load is changing quickly, and have seen evidence of the ECU disabling FBK once load stabilizes which is manifested by seeing timing added back in increments that were much smaller than the Feedback Knock Retard Increment (ie: Feedback Knock Retard Increment Conditions Disable -> Ignition Timing Correction Pos). Evidence of this effect is seen in OP's 3rd gear log, it looks exactly like a shift knock issue I had a while back. This appears in the log differently from the 'standard' FBKC decay, where you'd see something like -4 deg FBKC, then decayed to -3 deg, then to -2 deg, then -1 deg, then finally 0 in the log.

 

It is not uncommon for the 5EAT to see -4 to -6 correction. As long as it isn't constant and learns its way back to 0, you should be fine.

 

That much being pulled? That's a bummer. It takes the ECU a couple of sec to decay that much of a timing hit back to 0, so you'd notice sluggish behavior during that period of FBKC decay.

It is not uncommon for the 5EAT to see -4 to -6 correction. As long as it isn't constant and learns its way back to 0, you should be fine.

 

Good ol' phantom knocks. My LV is fairly clean on my 5EAT (after a lot of work). I do see some knock pop up in different cells from time to time, but nothing sticks and IAM is always at 1, so chalk it up to 5EAT. Zip ties on anything loose and an exhaust clamp to crush my UP so it won't move (broken welds).

So what you are saying here is that it is normal to see this kind of data in a log on a 5EAT? this may be a very happy day if thats the case

did some more pulls today before going in to try to find the cause, and now all evidence of knocks are gone

 

datalogs are below. the only thing i did was tighten up the mounting bracket on my CAI. guess that rattling around may have been the cause

Redslaya 1st FIXED.csv

Redslaya 2nd FIXED.csv

Redslaya 3rd FIXED.csv

Good to hear. I wonder if the CAI itself might have been contributing to the problem.

 

It also looks like you're boosting 1 or so psi higher than your originally posted 3rd gear log showed, with same WGDC. Happen to know if it was cooler today vs when you did the original 3rd gear log?

 

You're still not hitting Target Boost and WGDC appears to not be doing anything to try to hit it. Is your protune complete at this point? I know you said your tuner had 2nd gear dialed in for 14-15 psi, and it -is- hitting 15 psi in 2nd, BUT if you look at your logs, Target Boost is 17 psi (not 15), and your Boost Error is showing you're 2 or so psi below Target. That leads me to think your tune might be capping boost via WGDC Max. To confirm, simply add WGDC Max to your logging parameters, and see if WGDC and WGDC Max end up being identical in the logs. If they are, your boost is being capped by WGDC (unncessary approach IMO, with potential downsides as ambient temp changes through the seasons).

 

Was your tuner concerned about overboosting in the taller gears if he set up WGDC/Turbodynamics to try to hit target in the lower gears? I'm running a VF52 and a bunch of supporting upgrades, and have my tune set for 19.7 psi target. It almost hits that in 2nd, and does hit it in 3rd. In 4th-6th (I have a Spec B 6MT swap), it only overshoots by about 0.5-0.75 psi for a brief period of time. It took a fair amt of work getting realistic boost targets defined in the spool region and I had to set WGDC Low to be low enough to avoid overboosting w/ high gear throttle mashes, but it was doable. Not sure about 2006, but 2005 doesn't have per-gear boost tuning capability in the ECU, so there's a slight compromise b/n getting good boost response in the lower gears while not overboosting too much in the taller gears.

Good to hear. I wonder if the CAI itself might have been contributing to the problem.

 

It also looks like you're boosting 1 or so psi higher than your originally posted 3rd gear log showed, with same WGDC. Happen to know if it was cooler today vs when you did the original 3rd gear log?

 

You're still not hitting Target Boost and WGDC appears to not be doing anything to try to hit it. Is your protune complete at this point? I know you said your tuner had 2nd gear dialed in for 14-15 psi, and it -is- hitting 15 psi in 2nd, BUT if you look at your logs, Target Boost is 17 psi (not 15), and your Boost Error is showing you're 2 or so psi below Target. That leads me to think your tune might be capping boost via WGDC Max. To confirm, simply add WGDC Max to your logging parameters, and see if WGDC and WGDC Max end up being identical in the logs. If they are, your boost is being capped by WGDC (unncessary approach IMO, with potential downsides as ambient temp changes through the seasons).

 

Was your tuner concerned about overboosting in the taller gears if he set up WGDC/Turbodynamics to try to hit target in the lower gears? I'm running a VF52 and a bunch of supporting upgrades, and have my tune set for 19.7 psi target. It almost hits that in 2nd, and does hit it in 3rd. In 4th-6th (I have a Spec B 6MT swap), it only overshoots by about 0.5-0.75 psi for a brief period of time. It took a fair amt of work getting realistic boost targets defined in the spool region and I had to set WGDC Low to be low enough to avoid overboosting w/ high gear throttle mashes, but it was doable. Not sure about 2006, but 2005 doesn't have per-gear boost tuning capability in the ECU, so there's a slight compromise b/n getting good boost response in the lower gears while not overboosting too much in the taller gears.

 

it was certainly cooler and less humid today. I do recall the tuner was concerned about overboosting in the higher gears, hence why the lower gears are running less boost. the tune is 'complete' at the moment however i can have revisions done. I can talk to him about his approach to limiting it, however im not sure how much i will find out.

 

right now at the moment im more concerned about having a healthy reliable car over a super fast one. and even on this tune im still at 250whp 307wtq on a 5EAT, so im rather happy with that.

Fair enough. I was mainly curious what the reasoning was for being 'so far' below the 17 psi target. The boost game changes when ambient temps drop back into the 60-70F (and below), so you're probably better off being a bit under in the boost dept while it's hot out. There's a WGDC IAT Compensation table that offsets WGDC as intake temps drop, it just has to be dialed in properly or you can overboost pretty big when it gets cooler outside. I had to make a bunch of changes to my protune from 2 yrs ago to get it to run knock free and consistently b/n the 25F-90+F temps my car sees annually.

im still scared to drive the car in case it comes back, which means there is probably a real problem. but for now it appears to be all set.

 

did have a compression test a month ago with all 4 coming back with great results, however my paranoia may lead me to go get another one with leakdown to be sure

bumping this a bit. have been watching my feedback knock religiously after this whole incident. nothing notable, occasionally it would pull -2 but from what i understand that is normal.

 

but today, as im driving at low speeds through a parking lot, i see it jumps to -10 and then adds the timing back. -10 is not a good thing, i know that. but it wasnt under load or anything, and i havent seen it again since. any explanation? how worried should i be?

 

edit: it also appears that when no feedback knock is present, the DAM is around 0.88 and the fine knock goes to 0.3-0.6

 

edit2: just switched to 91 map and while the DAM and FKL are good now, FBKC went up to -6 at times

So let me restate:

 

you are completely clear of FLKC correct?

your DAM is back to 1.0 correct?

you occasionally see FBKC around -6 correct? If yes, does it occur usually in the same driving conditions (e.g. rpm range/load) ? It could be something loose in the engine bay or exhaust system, which trigger the knock sensor.