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What kind of wot timing are you guys running? Stock ls3 besides headers, ls9 cam. I know it varies with rpm and load but just a general wot range.
I am currently tuning my Vortech t trim setup on 93 and am getting lots of knock with only 8psi and very low timing (7-8degrees). I keep pulling timing but still getting alot of knock. I am almost thinking I am getting false knock but it seems to be fairly consistent so I'm not sure. I am thinking of adding a couple cans of torco to see if it clears it up any.
Here is a log from the other day. I was running it a little leaner up top to see if it would help but still same.
Any insight would be helpful, I am ready to put it on the corn but want to get the 93 tune 100% first.
Difficult to follow BC you have too many whites in the second graph. The cursor is stopped at 5* and serious steady knock. When knock increases you're losing even more timing. Those timing steps are being pulled BC of the knock but it would be helpful to see what else is going on when knock spikes to estimated 6/7* and timing is almost flat lining. Something happened there and timing doesn't register enough to cause that much real knock. What is fuel pressure doing at that spike? How are you measuring fuel? AFR?
On a healthy pull you should be at about 12/13* timing at that point, that RPM. Hard to believe you're pulling 8 lbs @ 99% throttle and only 5* or less timing. Not nearly enough info here to begin to tell where. Are the headers making contact on the frame somewhere?
If you have good known 93 fuel, you won't be experiencing real knock at only 5* advanced @ WOT, w/o something else being terribly off.
The chart you have isn't helping you diagnose much. IATs would be one of a couple of open questions.
Difficult to follow BC you have too many whites in the second graph. I think I can see timing. The cursor is stopped at 5* and serious steady knock. When knock increases you're losing even more timing. Those timing steps are being pulled BC of the knock. When knock increases to estimated 6/7* timing is almost flat lining. On a healthy pull you should be at about 12/13* timing at that point, that RPM. Besides the timing pulled BC of the knock, something else has timing flatlined as well. Not nearly enough info here to begin to tell where.
Are the headers making contact on the frame somewhere? If you have good known 93 fuel, you won't be experiencing real knock at only 5* advanced, w/o something else being terribly off. How are you measuring fuel? AFR? and what is the fuel pressure at this point?
The chart you have isn't helping you diagnose much.
Yes, I have a wideband afr is logged in the second graph, sorry its kinda hard to read with just a snapshot. I was mainly wondering what was the norm for timing in those area as i felt i was having to pull too much timing and you seem to confirm that as well. I have filled up multiple times with different 93 stations so I doubt it is a bad fuel issue. I have looked at the headers and dont see any rubbing, I am going to change plugs to the tr7ix and add some torco and see if it helps any.
What’s your IAT at? Unless it’s really high >150*(in which case your tune would probably be pulling timing) you shouldn’t be getting any knock with that level of boost and such low timing on 93 octane pump.
What kind of plugs are you running? TR7IXs are a bit of overkill for that boost level, but it wouldn’t hurt to try them, I guess. Have you pulled the plugs to look at them?
I’ve run 8.5 psi w/ 14* @ ~130* IAT and ~11.5 AFR with just 93 pump in 95*+ weather (@sea level) with stock ZR1 iridium plugs without ever seeing any KR. That was with the stock LS3 cam, BTW.
Something is definitely wrong. There’s no way that thing should knock with that low timing. I also about wonder about cam phasing or maybe an injector is fouled or something and that cylinder is knocking?
Check the basic stuff first:
Inspect the plugs to see if one or more looks lean, check injector harness connections, check carefully to see whether headers are touching the chassis somewhere, or something else rattling and causing false knock, etc.
The knock, as recorded, is abnormal. Knock, when present, is immediately met with a timing adjustment which corrects the knock. In this case, it comes on steadily, holds, and increases even with a timing reduction, so this knock is something else. Maybe even a bad knock sensor, but the normal remedies such as fuel, cold plugs, etc, are not the answer here.
Ok to answer some of your questions, Iat was 102 at the end of that pull posted above. I haven't had time to pull the plugs but I will do it tommorrow hopefully and see how they look. The cam was installed dot to dot with the stock ls9 gear. I'm fairly confident their aren't any issues with the cam as it was installed back when I was running nitrous and I didn't have any issues with KR then.
I went ahead and ordered a knock sensor and will try that since they are cheap.
Yea burst knock has been disabled. I was getting some weird timing swings with it enabled so that was one of the first things I did.
I have pulled the plugs and they all look good. I went ahead with the tr7IX's.
I also went ahead and installed my flex fuel system and secondary fuel pump. Running on E75 I still get random knock as before. So now I am pretty confident the knock is false. I haven't installed the knock sensor I ordered yet as my wife put it somewhere and now it's MIA
I feel like I'm getting some belt slip as well as I'm only making 11psi max with the restrictor plate removed and a 3.25 pulley. Looks like I'll be ordering a laser belt tool soon.
I attached a log file if anyone cares to take a look. Thanks for everyones help.
11-10-2017, 07:09 PM
Timing on Supercharged Ls3
but want to get the 93 tune 100% first.
