So I have this part throttle knock that moves around depending on where i engage the PE. I started chasing it when i showed up in the 1600-3200RPM with 90kpa range just getting the turbo starting to spool and make noise. It is a 5.3l with a 78/75 turbo, decapped injectors, 400walbro, factory pcm. Moved the kpa the PE engages at down in 5kpa increments and the TPS min to engage. When you move either one, the knock retard shows up where ever you move the PE engagement to. Keep it at 90 and the knock retard happens at 85-90, drop it to 60 and it shows up at 55-60, etc... Lowered the timing to next to nothing, its seeing 8-10 degrees mostly out of boost and it still does it. Changed the commanded fuel numbers around trying to get it richer, didnt work. The min engagement rpm, nothing.

You roll into the throttle going 55 on the highway in 3rd gear(th400) about 2500 rpm and boom, knock retard at sub 40%tps at whatever the kps for PE is set to.

I searched a ton, have someone from the site here I paid to build the tune to get me going, they're still assisting me but this kinda has us both stumped a bit. I have a wide band hooked in and logging, afr err and timing retard logging. No real lean spots showing at the knock area. The one thing i did come across that my tune might be conflicting with is i have a vacuum/boost referenced aeromotive fuel pressure regulator and my IFR table is not a flat line, its scaled. I was starting to think it was a false knock, the plugs didnt show a lean engine or pitting or aluminum deposits.

For the three scans i just did a tiny bit of VE adjustment between, same thing comes back every time. The kicker for me is that right after flashing the VCM i can get on the road and rolling to it hard with super hot IAT after its been sitting while flashing and it never engages the knock retard on that first pull...but after i get into a cruise and roll back into it, comes back. Looking at the IAT i would swear it starts doing it once the temps fall below about 115-120" once the intercooler gets them back to 90 or less the problem stick around. water/meth isnt getting the knock retard to stop either after it kicks in. The knock retard sticks on once its one untill you come off it no matter the psi i have it capped at or the psi i turn the meth on.

Stumped.
I'm posting a scan or two and my current tune with the spark lowered a lot and a picture of one plug. They all showed about like this one.

 

Right about now, if it was mine, I'd be heading down and picking up some race gas to test the sensors. It shouldn't knock on 110 at all. If it does, then you can assume that it is indeed false knock. The plug doesn't look terrible, as in no pitting and it looks like it's on the richer side. The ground strap is showing the timing mark. This also depends on how long it ran after any pulls.

 

Going by your logs, your timing is only 4 degrees before knock shows up. AFR is showing plenty of fuel as well. The knock it's showing doesn't look like the typical "stair step" pattern where it registers a little, then gets worse on the next cycle, as the PCM is usually a little too slow to correct it immediately. Is it audible? Can you actually hear it occurring?

This just might be a case of overly sensitive knock sensors. I could be wrong though. Like I said, best way to sort it out for sure is get some race gas and run that. While you have the race fuel in there, adjust the knock sensors accordingly (a little at a time) until it stops registering.

 

No, I can’t hear it. I can get some race fuel, which I’ll probably be doing tomorrow. Or at least 5 gallons of 110 and 2-3 bottles if VP booster stuff since it has some 90 in it. Unfortunately 90 is the best it gets here at the pump, 110 is $26/gal. I even debated making a knock listening tool from plastic earmuffs and some hose and copper pipe and running that badboy through the fire wall. But I cannot even hear a slight tick in the engine when it knock retards and it does it at a fairly mellow exhaust note so the engine isn’t hard to hear.

False knock is what I started thinking today. But when it moved with the kpa changes almost exactly i started thinking it had to be some event happening there maybe not a detonation but something abnormal. Ill head to my old race shop in the morning and see what i can get.

 

Damn that's a pretty steep price for 110. Last time I picked some up it was under $10/gal down in Newport News. It was for a very similar issue as you are having.

Other considerations are checking for anything mechanical that could be causing the sensors to be tripped, like exhaust too close to the wiring, or the pipes resonating. All it takes is a metal on metal sound in the 6400 hz range and the sensors will register it as knock.

I've also thought about building some knock phones like that lol. Just never got around to it. One of these days I will though haha.

 

Try disabling burst knock?

 

Saw something similar tuning a truck. Part throttle knock. Wouldn't occur after a flash but would show up after 2 or 3 key cycles and engine being warm. Turned out to be a damaged knock sensor from over torquing during installation. Check the resistance of the knock sensors (dont recall off the top of my head what the value is supposed to be but can search on the forum here for how to do). Good luck.

 

It has been disabled from the start.

 

well i got some VP booster stuff but unfortunately race gas with no lead is impossible to find here. I have to make a 100mile round trip to get any sunaco and i think they only have 100 in no lead. The booster treats 10 gallons at +8 point. My tank has about 15 gallons in it, so i put in 2.5 bottles and hoped for 98-100octane.

Knock retard still showed up.

 

I cant open the file as the hpt version is too new but what does your power enrichment rate value say? I hope it's maxed out

 

rate of 3
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However i discovered a spot where the down pipe is touching the passenger side manifold. I cna hear no audible knock anywhere, it has about 100 octane in it and the sensitivity of the sensors is set to 4 in the area it is happening. I think the pipe has to be it, its one small spot i can probably whack with a rounded rod and hammer to make it clear. The factory heat shield is on there too in that same spot so ill cut it off there.

Its stock bottom end, no cam or anything. The only thing i did was add pac springs. The cross overs are 2". I cant imagine it being back pressure, 2" is nothing crazy.

 

Sorry I didn't mean the eq ratio but the "ramp in rate."
Determines how quickly your power enrichment fueling comes in, check what it says is the limit on that table (2 or 4 most likely) and try that high value.
If you're a gen 4 ecu, then disable desoot mode but it sounds like you're gen 3.

 

Sorry, i caught what you meant right after i hit reply and went back and edited it. It is a ramp in rate of 3

 

Is that the max value it can take? (Says in the description when you hover your cursor over it)

 

Nope, but 4 is and after you mentioned it i tried it at 4. The knock retard is still right at the PE transition and starts occuring after the the min requirements of KPA and TPS are met.

Something i just noticed in the fueling though is that my graph is showing rich in a call when the WB clearly shows it leaner than commanded

 

Is your graph set to + , - , or Average?
Set to average if it isn't.
When you say wideband shows leaner than commanded, do you mean the wideband itself or the wideband pid in the scanner?

 

two more scans and the tune here.

The Channel for the WB AFR here shows 16 and the commanded is 14.89. It's graphing an average there on the zoomed in data that shows rich

in the last scan i spotted a point when im rolling into the throttle 80ishkpa range, 1900-2000rpm range. As the throttle is slowly opening it is leaning out, just mere tenths of a second. its commanded is 14.89 but the WB has it at 15-16. The knock retard starts coming in right then and the PE engages a little bit later. It's just going lean while climbing under load up to the kpa the PE is set to, but it doesnt matter what KPA that is, could be 40, could be 90 it leans out until it hits it.
Just richen everyting 10% over in that spot? I think i tried that and it did nothing.
transient fuel issue?

 

It sounds like a transient issue as you tried moving PE activation around. Try confirming with a known source that your injector data is accurate first. Then experiment with transient settings.

 

what about this, I have my FPR referenced to vacuum and boost. Some of the info i saw said that in my type of setup that this table should all be set to the 0kpa value?

 

Yup, all should be the same value and offset tables are in need of adjustment from a returnless fuel system tune to a return style with a vacuum/boost reference. That may help your issues out.