Knock Reduction - Keeping it Real

[FunkedOut]

I have attached a log from a short drive where nothing major happened (except maybe one good stretching of the legs).
I see scattered bits of KR here and there and they are from varying cylinders.
I have stock timing tables and use 93 pump gas from Shell that very, very consistently measures 10-10.5% ethanol, as measured by my 2004 Flex-Fuel Tahoe.
I do have headers and a 3" exhaust that is louder than OEM.

My gut tells me this is not knock, but the noise setting the sensors past their threshold.
But I don't want to desensitize the sensors if the knock is real.
Before I go trying to adjust the timing tables any (I was hoping to advance them some to gain some power), I want to rule out this knock.
Race fuel source is about an hour away.
How about some octane boos additive? Will that definitively help me rule out if the knock is real?

(I need to make T-Shirts, "The Knock is Real")

I would greatly appreciate suggestions on how to proceed, safely, on my path to spark adjustment.

Thanks in advance.

[cc-rider]

Get a can of Torco and put it in with a tank of 93. That should put you up around 97-98 octane. If the KR is gone...then you know its true knock at the pump gas levels. If you still get KR...then you can probably assume its your knock sensors being too sensitive but you should probably slowly creep in and test/retest on this. There's a good thread here of a guy going through exactly what you are and tried this procedure. Search and you'll find some good reading.

[cc-rider]

Looking at your log... You've got a few spots with KR there. But no wideband data??? The KR I see is always when your climbing in RPM but haven't entered PE mode. It's commanding stoich but your on the throttle a little bit and rpms are increasing. I bet if you lowered your PE/MAF OL trigger down you'd see this go away. So it may not be false knock. The stock ECU puts it into MAF only mode at 4000 rpm. Below that its using the complex MAF/VE/dynamic mode. I see you have headers as well. Did you ever tune your MAF or VE for this?

I'd say kick dynamic mode out at a lower RPM and see what happens. You may need to get into PE quicker.

[FunkedOut]

apologies on providing a log with no wideband data. I collected this one for another purpose.
I'll log my drive tomorrow and look at what you noted about getting on the throttle out of PE.

MAF and VVE got addressed after header install, and again after intake install.
I need to retouch them after a ports TB and 3" exhaust install.

I think I'll prefer to kick in PE sooner and adjust the PE curve down low.
While tuning MAF and VVE, I always felt the car behaved with a more consistent respone in VVE mode.
I'd rather keep that around as much as possible.

Thanks for the help. I'll search for that thread you're talking about.

So Torco is as good as race gas for this purpose?
The Octane boost is real? (I gotta stop)

[FunkedOut]

Good stuff here:
http://www.hptuners.com/forum/showth...ighlight=Knock

[jtrosky]

I keep seeing Torco mentioned in order to test to see if KR is real or not. Is Torco available at any national chain stores (Advance Auto, AutoZone, etc)? If not, were do you get it? What about the regular "octane booster" that you do see at the chain stores - does it bring octane levels up high enough to use for determining if KR is real knock or not?

Thanks!

[schpenxel]

I've always bought it off of Amazon. I haven't seen it in auto stores but haven't really looked for it either

[FunkedOut]

pulled this off the Torco website:
accelerator-ratio-93.gif

1 can for a tank full of 93 only get you up to 98-99 octane.
2 cans get you up to 103-104 octane.
3 cans, 105-106.
4 cans, 107.

Is 1 can per tank full of 93 enough to prove a point?
Or is 2 the safe bet?

[schpenxel]

Pure methanol is like 99 octane. Most people quote the wrong AKI (octane value that we are used to in the US) for methanol and E85 for that matter.

98-99 should be enough IMO

[cc-rider]

pulled this off the Torco website:
accelerator-ratio-93.gif

1 can for a tank full of 93 only get you up to 98-99 octane.
2 cans get you up to 103-104 octane.
3 cans, 105-106.
4 cans, 107.

Is 1 can per tank full of 93 enough to prove a point?
Or is 2 the safe bet?

I just now noticed that I mistyped my post above about Torco. I said it would get you to 107-108 octane and I meant 97-98. My mistake. I'm going to go edit that post in case someone else comes across this thread via a search in the future.

[FunkedOut]

What does it mean if KR is registering (1* or so) and none of the individual cylinders claim responsibility for it?
Is there a source other than the 8 cylinder PIDs that feed into the KR PID?

[schpenxel]

I just ignore those little < 1* blips that make no sense. I always assumed it had something to do with knock learn thresholds or something like that