I am still new to Tunercat. I have a mailorder tune and have yet to modify the tune at all with my laptop and tunercat. I have been datalogging a good ammount, and need to get rid of this knock one way or another by track day (13th) because I am hoping to run some nitrous.

Do I literally go to the chart:Max Knock Retard and make it 0.0 at all RPMs? I haven't looked much at Tunercat, but that is one thing I think would be helpful.

If I run high octane gas, and there is still knock at idle, it is false knock then. Correct?

I am buying some race-gas tonight on my way home to put in the beast and see if it goes away.

 

I dont see a problem with turning off your knock sensor as long as your setup is tuned right. Now, when running on the bottle your going to get others opinions on this as some will leave it on just to make sure. Others will turn it off as long as there a/f is correct and tuned right.

 

Do you get knock retard almost all the time? Have you checked for a code for a faulty knock sensor?

 

using Freescan I see no codes when I go to the "trouble codes" tab. I have knock ONLY at idle and when my foot is on the gas. Makes very little sense to me unless its false.

 

Does Tunercat or "Jet" allow the same amount of datalogging as something like AutoTap? Can you clear codes with it too?

 

Put racegas in it, still knock when I am on the throttle, and 0 when I take my foot off the gas. Stumped. I did see one of my o2's seems to be not bouncing around as much as the other one...

My knock sensor wire is run in the stock location, has anyone had any problems keeping it there? I know there are no spark plug wires near, but there are some big voltage wires from that ground right there. I am about to just tune it out and spray a 125 shot... so any advice would be appreciated. 5-7deg knock while on the throttle, 0 when foot off gas.

 

5-7 degrees is fairly significant. Can you hear the knock?

 

Programmers are not dataloggers or scanners.

 

Nope, it is loud no doubt; but it runs smooth, no audible noises at the track, on the dyno, just a noisy valvetrain that I can't get rid of. I think it is quiet, everyone that hears it that know old SBCs tell me they are loud. I just got new ARP studs and some poly locks to make sure none where backing off and went to the track. It ran great, and there was still 5-7deg knock. here is some typical copy and pastes from freescan:
RPM knock retard
2725 7
2725 7
2825 7
2925 7
2925 6.5
3075 6.5
3075 5.1
3175 5.1
3175 5
3350 5
3350 2.1
2875 2.1
2875 0

As I rev it increases, and the second the foot comes off the gas (throttle position changes) the knock goes away completely until I get down to near idle rpms.

anyone?

 

what do your spark tables look like, if they're wacky and set to 40+ degrees that would explain it.

 

I don't think it is the timing, although I do not know much about what it should be at. I am running 93 octane now, and still the knock care if its 104octane. The max timing im seeing is 38 deg, which is everytime I start decelerating from flooring it. So I am assuming that it should be near 38 while I am at WOT. Since the knock is present at those times, I am seeing around 33 deg timing at WOT after the knock retard is pulling the timing.

I am buying a nozzle setup for a 125 shot, and really need to get this resolved before I start spraying. If tuning out the knock is the best idea, I might just have to do it.

 

38 is a lot for an LT1 (although it really depends on the cam, compression ratio you are running and the elevation where you live). A stock LT1 usually can't take more then 32-33 degrees with high octane fuel. A 160 t-stat may allow a few more degrees. My LT4 HOT motor makes maximum power at 35 degrees advance.

Is this discussion related to the car in your signature? I have tuned a few 383 LT1s also, and I have found they generally like even less timing then a 350 LT1, probably because of the increased intake charge volume. The last 383 LT1 I tuned maxed out at about 31 degrees advance on the dyno before knock set in. Admittedly, it had over 11:1 compression, and a "small cam" for a 383. Combine that with the great air we have here in the Seattle area and you have a receipe for spark knock.

With a 125 shot, you will probably want to remove an additional 4 degrees of timing.

 

FOr whatever reason, mine will register retard without actual knock counts being recorded...but after careful review of literally hundreds of log sessions, I found that no retard was happening until actual knock counts were recorded..then anytime after that when the rpms/tps approached the "area" where the actual knock counts occurred, it would start removing timing without any further knock counts...almost as if it learned where the knock counts were recorded at and anticipated them.
So I started removing timing only at those rps/MAP readings where knock counts were recorded, not paying any attention to just the retard degrees. After doing this repeatedly, and naking sure I did not remove spark from the same locations within the same recording session/reflashing I eventually ended up with no knock counts after hours of driving/logging and therefore, no retard either.
Comparing my timing table to the stock original, I have about 3-5 degrees less in the cruise 1600-2200 rpm and 40-75KPA Map range, but have 3-5 degrees more than stock at WOT 85-100KPA range.

But the cam profile and heads have alot to do with these results. My heads are ported LE2s with a 12.8 SCR setup.

 

Hmm really? I have not changed the spark advance since I got the tune from PCMforless. I have over 11:1 compression myself, and ****ty gas out here. I think I will turn down the spark advance like you are saying to 31 or 32... that is the spark I am getting AFTER the knock pulls out the timing, so maybe that is a good place to start. I have yet to use tunercat, looks like this weekend is learn time.

 

Ideally you want the spark advance to the point where you are seeing 0-1 degrees of KR (knock retard). The PCM doesn't remove timing "gracefully" via knock retard, and out here in Seattle, we actually see power gains by removing timing from factory maps which are causing KR (due to our low elevation, and s**tty gas).

In other words, if your timing is set to 36, and it's KRing to 32, you might actually find more power if you just set it to 32 (or even less if there is still KR at 32).