Quote:
Originally Posted by brn12345
The sound of ball bearings on a marble floor is hard to miss. For me i have ZERO full throttle knock, but upon shifting during normal driving as soon as i let go of the clutch and put my foot back on the accelerator it knocks (heard/logged). I am not too concerned about it but what bugs me is that it drives the IAM down. By the end of an afternoon driving the IAM is at 0.25 today. If i go out and find a nice stretch of road and floor it for a while it goes back up quickly to 0.6-0.8.
So regardless if its real knock or not, the impact on IAM is real (unless something else is making the changes to IAM). To confuse a bit more check this post of mine, I am still baffled by why IAM dropped like it dropped there. Nice to see you in this post 
http://www.ft86club.com/forums/showp...2&postcount=56 |
I know you're not the OP but I'm going to address your posts because it is still relevant. I downloaded your logs and made some plots.
Top chart shows engine rpm in blue, knock retard events in red. Bottom chart shows vehicle speed kph in black and IAM scaled up where 100=1.0
I'm going to throw something out there. I think in some cases you're getting LSPI. Considering the nature of LSPI it's not going to happen on every detected knock event, but the fact that you are hearing "ball bearings on a marble floor" sometimes is a big sign that this isn't always false events.
What the heck is LSPI? It stands for
Low Speed Pre Ignition also known as
Super Knock or
Mega Knock. It's not very well known in the aftermarket. It sounds scary, and it kind of is. It's what can happen when a turbo engine spools up at low rpm, especially turbo DI engines. It usually happens at 2500rpm or less, especially under 2000rpm. You don't commonly hear about it because DI engines with factory turbos are tuned to stay out of the "no man's land."
Usually an LSPI event will hit peak cylinder pressures of 140-190bar, similar to a diesel. Your pressure rate of gets very very high. That's where the noise comes from. It's different from regular old knock or preignition from hot spark plugs and such. There's basically no simple solution for it, and it's somewhat random. Pulling timing often doesn't solve it, although a richer mixture can help sometimes. Theories for its causes abound and I won't dive into them here.
So basically, if you're actually hearing a loud "marbles in a can" sound at low speed tip-in, and some simple spark retard is not working, you have limited options to solve it... there are guys with PhD's who have been trying to figure it out for years. I'm not trying to sensationalize anything--you probably make it go away with enough fuel and spark retard. It's important to recognize though that this problem exists and if you really do have it there isn't an easy solution.