Burst knock....B6212

[hquick]

Well......
after alot of reading...again I decided to try '0'ing all the values in table B6212 to see what effect it would have on the amount of KR I have been seeing.
Surprisingly..it made a huge difference.
Previously I have been getting KR of 8.0 or so for no apparent reason.
VE was good, out of boost, no serious changes in rpm.
Once B6212 was '0'd most of my KR disappeared and now I have a new feature....'KR on command' .
Basically...if I stab the throttle I can generate KR....so atleast I know where to start looking now.
On that note...would adding more fuel via B3647 be the way to go?

From this:



To this:

[cmitchell17]

I would also get knock with the stock tune with burst knock.

I zeroed it and now I can't even try to get knock. Maybe its becuase my truck never warms up to temperature (I think thermostat).

With burst knock on it would give me random 2-3degrees knock and then shifting into second it would pull like 4-7degrees for no reason.

And anytime I hear audible knock in the knock region(4000-5000rpm) it never shows up on the scanner?

[hquick]

That's exactly what was happening with mine.
Here you can see I was getting KR with no apparent reason behind it.

[SV8346]

i was getting a very similar knock with mine untill i started playing around with commanded fuel vs RPM. I found that getting the fuel mixtures correct for the given load was the trick to it. Also what might help you a little is to set your lean cruise all to 0 then create lean cruise within your commanded fuel vs RPM map.

What i have is from 20kpa-65kpa in the 1600rpm-2400rpm range I'm running 15.8AFR. That way when your just light throttle cruising it isn't dumping a bucket load of fuel into it. Excess fuel can create knock for no apparent reason.

[Tordne]

In your last image you will see that the KR line comes in high, then decays, and then spikes up again. This generally indicates that the knock is real, as the timing is increased the knock sensors trigger again.

I used to get a lot of KR on throttle transition. Initially the few things I did were:
- 0 out the Burst Knock table(s).
- Installed a PCV catch can. This stops the oil from the crack case venting back into the throttle body and diluting the charge.
- Change to a spark plug one heat range colder.

As SV8346 says, I also believe that too much fuel can induce KR, as can too little fuel.

[hquick]

Thanks for the suggestions guys.
I'm already running a temp colder on the plugs (as recommended by most running a supercharger...and new installed a few weeks ago).
I was unaware I was running lean cruise. As my truck uses the US PCM I didn't think it was possible?
Here's my current tune and the resultant log. If anyone can please have a look for me and tell me what they think..that'd be greatly appreciated.
So far I've run more than 100 logs in the past few months trying to sort this out.

Thanks

[SV8346]

ok, no your not running lean cruise but you have got it set to closed loop for while your cruising. You also running very rich in the top end of the B3647 map, AFR's at some points are going to 11.1 on your plx while on small amounts of throttle and has a maximum of 10.0 AFR, that is way to rich. Also a few other things i have noticed, what injectors are you running and what fuel pressure reg are you running. I dont think your injector flow rate table should be flat like it is, it should be referenced to manifold vac/boost.

i have create a quick edit of you tune, give it a go and tell me what its like.

[hquick]

Thanks for that....I'll try it.
I'm running Bosch 42lb green top injectors in the mercruiser marine manifold.
I'm running the stock reg...so..58lb fuel pressure.
I was of the understanding that as the reg is manifold ref'd it should be a straight line?

[Tordne]

I was of the understanding that as the reg is manifold ref'd it should be a straight line?

Correct. That opened my eyes the first time I saw it

[SV8346]

yeah as tordne said, that is correct. As the reg is manifold ref'd it should be stright lined.