The way the knock acts is really weird. Sometimes I can mow through gears with zero degrees all the way. Other times I get knock only when I shift. The weird thing is that it will jump up to seven right when I shift and then as the RPM's start going up again the knock goes down to zero and stays there until my next shift. It's like I only get knock with big throttle changes...

What could I tell brian to change in my tuning to make the car run with zero knock? I'm sure i'm not the only one who has this problem.

 

TTT

 

That might be what is called "burst knock". When the MAF sees a certain increase in air flow such as shifting gears it will retard the timing based on value is programmed in.

 

sorry to go off topic but what does TTT mean, i have been trying to figure this out for a while

 

TTT=To the top, it bumps up the thread so people can see it more easily

 

Sounds like "tip in" detonation to me.

 

Can somebody explain "burst knock" or "tip in detonation". Or rather explain what I need to do to get rid of them. What should I tell Brian to mess with in the programming???

So it is real knock or is the PCM just retarding it based on the large throttle change?

 

Tip in is when you first hit the pedal.... the tuner can take that out and pull some timing.

 

Both of those are definite candidates but, just to get back to basics before you retune, did you verify it's knock at all? I had all kinds of weird occasions of knock which remained even with 101 octane. True knock will disappear with 101 octane. The PCM doesn't care if it's true or false knock. It will still retard your timing and you give up HP, so, if it's false knock why worry about it? I finally by-passed my KS and have never had a problem since.

Just my .02, YMMV

 

I'd check your exhaust first.

Sounds like the car is flexing and something is banging.

 

He actually already took away 4* of advance during cruise... Is there some way to richen it up or something to make sure the car has enough fuel for you to nail it and have no knock?

I know nothing is banging my car is sturdy and there is nothing ghetto rigged... I'm sure I would probably hear it too. I do have a small exhaust leak on the driver's side y pipe (not at the head) but that wouldn't explain the erratic knock.

The weird thing is that the knock happens only on some big throttle changes, its not a set thing where if I press the gas a certain way it will knock. Most of the time its zero knock mowing through gears.

To find out if its real knock would I have to use 100+ octane or is octane booster good enough???

 

Octane "booster" is 100% worthless. If the knock goes away quickly like you describe it is probably the programmed burst knock. Even when I run straight race gas I still see some of that ....it is so quick when I hit the record button on my Scanmaster it displays nothing. I have a little bit of true knock when I have 0 retard dialed on my BTM if I'm running pump gas. It gets up there and stays there though. Of course, false knock can stay up there too since the computer doesn't know the difference. One way to tell if it's programmed burst knock is to have "Brian" remove the burst retard from the programming. Then if it's still there you know it's either a spike of true or false knock. Isn't this stuff fun to troubleshoot ....been there/doing that. Some people say the decay rate is programmed in and will be the same whether it's burst, false, or true. In my experience that is not true ....the programmed "burst retard" goes away very quickly (quick decay rate like you describe). Try tuning it out and see if it goes away. Then even if it does ....put it back in just to be safe

 

Thanks for all the advice. I just sent an email to bryan with this newfound knowledge I have about burst knock.

Charlie - Thanks a lot man for all the advice. Honestly, all the stuff you told me about before the car was even running came in really handy tuning it. I have been meaning to shoot you an email for a while now actually

 

So what exactly is this "Burst knock". I know there is no adjustment for it what-so-ever in Tunercat. There is no table that says an x% change in TPS per set amount of time will add X deg's of knock retard. There is no table to set a change in the "accelerator pump" in tunercat either. I know FAST has provisions for this based on the rate of change of the TPS to give a boost in injector pulsewidth so it acts kind of like a accelerator pump on a carb, does LT1 Edit have this? A change to this table may be what your looking to modify. Are the tuners playing with the Fast attack rates, and the Decay rates to help solve this issue? Or is this "Burst Knock" just someone's made up idea and not real?

Bill

 

People confuse "burst knock" with "burst retard" because when explaining either sometimes people refer to one as the other. "Burst retard" is not a made up idea, there is a provision within LT1 Edit to alter it's max values or completely eliminate it. When most people refer to "Burst knock" they are usually talking about a quick spike (burst) of true knock (or false knock). My tuner elected not to eliminate the burst retard as a safeguard. Sometimes I think I'd like to at least temporarily eliminate it just to know for sure what I'm seeing is either true or false. In my case I think it's true knock because the tuner left more timing in than I wanted. No problem though because I can dial it out with the BTM on pump gas or run full timing with a race mix. This way it's tuned for max power and I can still play on the safe side. With pump gas if I dail in ~1.2 or more on the BTM I can't get any knock to appear on the Scanmaster .....otherwise I will see some though. That tells me it's probably real knock.