knock vs False Knock & Engine Noise?
10-08-2023, 02:18 PM
#1
knock vs False Knock & Engine Noise? so I've just finished an engine build for my truck (2005 sierra 2500HD)
Specs - LQ4 3rd oversize, Forged flattop pistons, Ported & Softened 799 Heads (final comp is 10.6), lightened forged rods, Sum Stage 2 Hi-Lift Truck cam - 218/227 112+2 0.600 lift, TBSS intake & 90mm TB, and oem 60lb injectors. I have yet to install a set of 1 3/4 long tube headers. Valve springs are BTR platinum 0.660 springs, hardened 7.4" pushrods, ls7 lifters with the preload I was recommended to run by TSP
Tune is getting there, MAF is fully tunned, VE is tunned near perfect everywhere but idle. Idle needs a tad bit of work, transient fuel isn't bad but will need work, and timing needs work.
I was getting some strange KR even on 93 with octane booster up to about 97ron. It would pull 4-8* of timing in the lower rpm and it was the worst while getting going from a stop. It was pulling so much it would fall flat on its face. So I pulled 4-8* from those regions just to see it still pulling 4-8*. I assumed this was false knock and desensitized the knock table 25%. Still, see timing pulled in 1st although nowhere near as much. I was messing around with spark advance control in Hp tuners with the motor held against the convertor. It desperately needs more spark advance. Burst knock table is set to 0 so it's not burst KR
While I was doing this I had set up a DIY knock headphone system filtering 5000hz - 6000hz audio through my laptop. It works, but there is a ton of valvetrain noise. basically, all I hear is the LS sewing machine noise.
how do I figure out if it's just false knock? there's so much engine noise I can't hear anything other than valvetrain noise. Should I just dump octane booster in so that I've got 98 and then desensitize more if I'm seeing knock that won't go away when I pull timing?
Also, I had originally just removed 5* of timing from the stock truck table. Later I downloaded a tune file from a mild cam 6L and coppied the timing into my tune then removed 5*. The difference was crazy especially on the top end (sorta expected). Stock timing curve shifting at 5800rpm was too late, it had already signed off, but now it's happy to hit 6k rpm. And I'm not getting any KR at WOT (AFRs are around 12.4 - 11.9 WOT). There is the occasional degree or 2 but it averages out to basically nothing.
once again, Just wondering what I should be doing. Knock sensors are in the factory location in the valley cover.
Specs - LQ4 3rd oversize, Forged flattop pistons, Ported & Softened 799 Heads (final comp is 10.6), lightened forged rods, Sum Stage 2 Hi-Lift Truck cam - 218/227 112+2 0.600 lift, TBSS intake & 90mm TB, and oem 60lb injectors. I have yet to install a set of 1 3/4 long tube headers. Valve springs are BTR platinum 0.660 springs, hardened 7.4" pushrods, ls7 lifters with the preload I was recommended to run by TSP
Tune is getting there, MAF is fully tunned, VE is tunned near perfect everywhere but idle. Idle needs a tad bit of work, transient fuel isn't bad but will need work, and timing needs work.
I was getting some strange KR even on 93 with octane booster up to about 97ron. It would pull 4-8* of timing in the lower rpm and it was the worst while getting going from a stop. It was pulling so much it would fall flat on its face. So I pulled 4-8* from those regions just to see it still pulling 4-8*. I assumed this was false knock and desensitized the knock table 25%. Still, see timing pulled in 1st although nowhere near as much. I was messing around with spark advance control in Hp tuners with the motor held against the convertor. It desperately needs more spark advance. Burst knock table is set to 0 so it's not burst KR
While I was doing this I had set up a DIY knock headphone system filtering 5000hz - 6000hz audio through my laptop. It works, but there is a ton of valvetrain noise. basically, all I hear is the LS sewing machine noise.
how do I figure out if it's just false knock? there's so much engine noise I can't hear anything other than valvetrain noise. Should I just dump octane booster in so that I've got 98 and then desensitize more if I'm seeing knock that won't go away when I pull timing?
Also, I had originally just removed 5* of timing from the stock truck table. Later I downloaded a tune file from a mild cam 6L and coppied the timing into my tune then removed 5*. The difference was crazy especially on the top end (sorta expected). Stock timing curve shifting at 5800rpm was too late, it had already signed off, but now it's happy to hit 6k rpm. And I'm not getting any KR at WOT (AFRs are around 12.4 - 11.9 WOT). There is the occasional degree or 2 but it averages out to basically nothing.
once again, Just wondering what I should be doing. Knock sensors are in the factory location in the valley cover.
