low load/part throttle -1.4 knock & FKL, protuned, what next?

6521 Views 8 Replies 7 Participants Last post by enoxard, Jun 27, 2018

coyotesfan

Discussion Starter · Sep 29, 2013

Ok, so I have been seeing an occasion -1.4 knock correction at part load/light throttle, that has manifested itself into some FKL. The knock correction is typically in the range of

calc load = 0.8~1.5
boost = -3 psi ~ 5 psi
RPM = 2500~4000 rpm
throttle post = 10~30%

Here is a typical log, although this one doesn't show any knock, only the fine knock learning is showing up.

https://docs.google.com/file/d/0B6NCz2qBnK7aS1E4Q1p0QlFzcHc/edit?usp=sharing

I discussed this with my tuner quite a bit, his opinion is that since it's so light load it's not a real risk. I'm throwing this out there for some experienced folks to offer some insight into my data.

Here are my mods:

* Protuned by local tuner, for crappy AZ 91 octane gas
* Built short block including Outfront Motorsports rods, CP pistons, ARP head studs, killer b oil pickup
* TGV deletes
* phenolic intake spacers
* stock airbox
* invidia catless DP, maddad CB exh
* 750cc injectors
* Walbro 255 pump
* Crawford AOS v2

Any advice is greatly appreciated. I am thinking of going E85 since our gas out here is so crappy. I get my gas from a station that has high volume FWIW.

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hutch959

· #2 · Sep 30, 2013

i think this is normal...
i watch mine all the time... i have a v3 so i even watch the knock count and typically, low load, low rpm, these cars knock.

im assuming that the ignition is so advanced at low load, for emissions, that its the nature of the beast.

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Madcow

· #3 · Sep 30, 2013 (Edited)

I wouldn't worry about it. I think you're experiencing 'phantom' knock. The way the knock sensors work is if they pick up any noise that's more than a certain value over what the factory motor makes its determined as knock and will pull a bit of timing. The opposite will happen if the computer determines the motor is too quiet for a given RPM, load, and throttle (it will add timing). Built motors, especially with forged pistons, are known for being noisier than stock. Your sensors are probably picking up on this added noise and determining it as knock. Since you aren't getting knock under 100% throttle you have nothing to worry about as I doubt you are getting actual 'knock'.

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8cd03gro

· #4 · Sep 30, 2013

It's noise at throttle tip-in. Completely normal.

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El Guapo

· #5 · Sep 30, 2013

How do you know it is real knock? Do you see ignition being pulled when you see the FKL values? As mentioned before, built engines do make more noise and ignition timing around those loads are fairly aggressive for fuel economy and emission purposes, so the ECU does make some mistakes and you might see some knock here and there. If you aren't seeing any timing being pulled then I'm sure you're ok with seeing some small values in FKL, at least in low load, low rpm situations. If you're seeing knock in higher rpms, higher load and WOT then you should be worried and lay off the throttle.

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endrswrd

· #6 · Sep 30, 2013 (Edited)

If your on the stock fuel line / FPR / Damper, then you need to do this and the accompanied tuning that goes with it.

http://www.iwsti.com/forums/how-install/254372-fuel-line-extension-stumble-fix-mod.html

It'll smooth things out for ya. Both driving feel wise and less low load knock counts.

Tip-in knock can be bad, but usually the way to tell that its tip in knock(two types, one is pre-emptive, the other can be real / noise) is if the knock occurs on the first line for 100% throttle.

If you only getting it on partial throttle though, then it could be a few things, the most likely being either its GR stumbles related which is a fueling water hammer effect that causes a cylinder to go lean, or your tip in injector tuning could use some more work.

If it occurs a few cells after WOT, then its not tip in knock its more then likely spool up knock which is bad mkay.

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coyotesfan

Discussion Starter · #7 · Sep 30, 2013

I was hoping you'd chime in Ceir. I forgot to put in my mod list the stumble fix... I did that a few months ago. It did help reduce stumble in this rpm range, but you can still feel it a little bit. I did change the cruise and accel load compensation tables as indicated in the stumble fix thread.

From what I can tell it's not tip in knock, I have done some pulls and don't see it there ever. I'm not familiar with "spool up" knock, could you explain a little more. I often see the knock show up just puttering around the neighborhood at almost constant part throttle 3rd gear, or the same on city streets 4th gear. Very little throttle position change.

endrswrd said:
If your on the stock fuel line / FPR / Damper, then you need to do this and the accompanied tuning that goes with it.

http://www.iwsti.com/forums/how-install/254372-fuel-line-extension-stumble-fix-mod.html

It'll smooth things out for ya. Both driving feel wise and less low load knock counts.

Tip-in knock can be bad, but usually the way to tell that its tip in knock(two types, one is pre-emptive, the other can be real / noise) is if the knock occurs on the first line for 100% throttle.

If you only getting it on partial throttle though, then it could be a few things, the most likely being either its GR stumbles related which is a fueling water hammer effect that causes a cylinder to go lean, or your tip in injector tuning could use some more work.

If it occurs a few cells after WOT, then its not tip in knock its more then likely spool up knock which is bad mkay.

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endrswrd

· #8 · Sep 30, 2013 (Edited)

Alright, then what your probably seeing is what Heide264 (or w.e it is), posted about in the fuel line mod thread.

Basically, some tuners / car combos required basically a dip/hump in the timing in that area to compensate for the stock fueling setup / ignition timing.

You may need to talk to your tuner about smoothing that area out and removing any large bumps in it.

Basically, the dip is there on cars because of trying to find MBT in that general area (lower load, partial throttle, transition to light boost), fine tuning ignition down there can cause pretty random but reproducible knocks in that area, and alot of tuners compensate with this by bumping the base timing tables up, to counteract, what the actual load compensation tables do. (basically the load compensation tables inflate the LOAD up, which when timing is graphed is shown as a dip down in timing) [WARNING: this may be confusing to some, so consult with your tuner / send them this way to see what I am talking about, it is referenced in the fuel line thread as well, or pm me! Either way dont just increase timing in your lower load / cruise area thinking it will help with knock! You must first make sure the hump exist by consulting your tuner and or looking at your timing tables graphed out in 2d & 3d graphs and have the fuel line mod INSTALLED!]

If you smooth this bump in timing because you have reduced the load compensation tables(effectively reducing how much load is inflated, and thus not reducing timing as much), it should get you what you are looking for.

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enoxard

· #9 · Jun 27, 2018

subscribed to this dusty old thread because its relevant.

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