Low load spark knock!!!

millhouse · Post by **millhouse** » Tue Jun 13, 2006 3:56 pm

I am running msns-e 029q with megatune v2.25 on a v3 main board.

The car…my 5.0l twin turbo mustang with mods as seen in my sig below.

Alright, I am having low load spark knock issues which wont go away. The sound is your typical paint can rattle sound....and it happens between ~ 1500-3000 rmp and ~ 40-65 kpa. I have checked to verify my base timing, and it is indeed correct. My ve tables in that area are a bit on the rich side (in my attempt to try to overcorrect). I have reduced the timing in those areas down to 18 but it does not seem to help.

Any and all help would be appreciated!

millhouse · Post by **millhouse** » Sun Jul 02, 2006 8:21 pm

Post by **jsmcortina** » Mon Jul 03, 2006 5:11 am

Your spark table seems very conservative in those regions so it seems unlikely that it would be the problem. The fuel table looks odd with jumps up and down around 100kpa. I presume this is where you have been richening up certain bins.

Have you double checked you timing with a light? Are you getting any tach spikes?

James

millhouse · Post by **millhouse** » Mon Jul 03, 2006 5:23 pm

jsmcortina wrote:Your spark table seems very conservative in those regions so it seems unlikely that it would be the problem. The fuel table looks odd with jumps up and down around 100kpa. I presume this is where you have been richening up certain bins.

Have you double checked you timing with a light? Are you getting any tach spikes?

James

Yep, I was still getting the ve table tuned in...but it's much better now. The AFR Across the board however is still what I'd consider "safe".

Hmmm...tach spikes you say. I'm not 100% sure about that one. I just reset my timing (blew a head gasket....long story) and did not notice it jumping....I think. I'll have to double check to be 100% sure though.

-nick · Post by **-nick** » Wed Jul 05, 2006 8:10 pm

I'm having the same trouble - and with a _very_ conservative advance map. When I hit between 20-40kpa at around 2000rpm I can hear a rattle. I'm also running very rich still in that area ~11:1 AFR's. I'm wondering if leaning it out will actually get rid of the knock?? Since lean mixtures burn more slowly?

Is it imperitive that vacuum advance and leaner AFR's go hand in hand?

ps- this is on a 10psi boost 2.0L, MS-II & EDIS

cheers
nick

edit: just found this interesting article:
http://www.bridgestonemotorcycle.com/do ... ssion6.pdf

It uses 2-stroke engines as an example, but the curves in figure 17 are pretty interesting!