What's causing this spark knock on the N20?
 

http://i41.tinypic.com/nlvqc5.jpg


As you can see on the 175 shot.. I have a HUGE gap of spark knock. The AFR was reasonable around this area.....

It also did it on the 100 shot but at a higher RPM.


The injectors are maxed out, and we upped the fuel jet to combat that and it still was running semi lean around the 4000-5000 RPM areas.

We were only running 20 degrees of peak timing. Is it possible that it was sucking the rails dry? I have a walbro 255. It seems like if it was sucking them dry at 4500 rpm it would do the same thing.. even worse at 5500+ rpm.

I did replace my fuel filter after the dyno, and a lot of black looking fuel and small chunks came out of the old one.

Also, is it possible this is fake knock? Possibly caused by the open headers I was running or something else? It knocked even when we put max timing to 15 degrees.

Thank you,
Brandon

Also, why in the hell does it stay so lean until the 3100 rpm mark or so?!?!

We always tuned them off (knock sensors), they wont save the motor but they will slow it down.

Lean til 3100 is in the tune.... the N20 doesnt hit until 38-3900.

Do you think its REAL knock... and do I look too lean on the juice? What are your suggestions for fixing the issue.

If you are going too lean pulling timing isn't going to fix you. Fuel upgrade?

I've got a racetronix kit. I only have the 26lb injectors... and they are maxed out. I think that is whats killing it. Does it look too lean from the graph?

it looks like to me that you are introducing too much fuel into the system and the injectors cant keep up... that is why you are still getting knock at 5100 because you have timing low to add fuel but it cant add that fuel because the injectors wont allow it....

my opinion ofcourse and could be entirley wrong.

So by your theory, injectors would fix my problems?

I agree, I saw something similiar, on the dyno, the TQ/HP decreased when the Wet opened up and then the fuel pump recovered the HP/TQ picked back up.

I would start with a set of 42's. I am 417 NA and my duty cycle w/ 42s NA is about 65% without the spray.

I have a Racetronics and then added a BAP.

Was the Knock audible and did you capture KR in a EFI/HPT log?

The knock was not audible... we couldn't tell anything was wrong until we looked at the graph. It was logged in HPT.
Whats a good, cheap set of 42's for my car?