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

Oh, also why does it stay so damn lean until the 3200 rpm mark?!?!

Are you running port injection or a plate

I am sorry?

It's a HSW Wet kit, nozzle behind the maf.

First of all you need to upgrade your injectors if they are maxing out. Since you are running a wet kit the injector duty shouldn't change much between n/a and spray. Are they maxing out when you run n/a? I'm just trying to make sure you're not adjusting your a/f while on spray with your injectors, it should be done only with the fuel jet.


Did you have it hooked to a scanner to see if its knocking and pulling timing? I very well might be false, it was for my car. I find it hard to believe that its real knock with only 15* timing. Assuming fueling is correct.

I'd like to see how much timing is being pulled. Think about it, if you're commanding 20* and getting 4* or KR, then commanding 15* and still getting the same 4* KR then the answer is obvious.

By obvious, you mean its false?

It was pulling 4 degrees when we commanded 20. And 4 degrees when we commanded 18.

The injectors are maxed NA, we tuned the nitrous AFR with the fuel jet. Started with a 35 and ended up with a 38 on the fuel jet side.

I really don't want to hurt this motor...
:bang:

You should get some bigger injectors first off.

try pulling a 2 or 3 more degrees timing, run a little fatter fuel jet like a 43 ish and put some high octane in there. If you still get KR then it might just be false.

My car use to have KR no matter what I did. I ended up pulling like 10* timing during real time scanning and it would still have random KR but always at the same rpm. So I put some high octane in there and desensitized the sensor till it went away then I just put my timing back up, car runs like an ape now.

BTW, what changes were made between those 2 nitrous runs? I'd really like to see a copy of your bin and scan file if you have one.

First nitrous run was a 100 shot. Second was a 175.

I will ask for the bin file.

Is the red line the motor dyno? If so its rich between 5000-6000. Get the motor right by the wideband then check the plugs. If the wideband matches what the plugs are telling you, then pull at least 6 degrees of timing and run a good cold plug. If you're still seeing KR try some race fuel to make sure its false. If you still get it then just lessen the amount of timing that gets pulled by KR. Then get the fuel tuned in right on the gas and again check the plugs. Then hit the track and check the plugs again.

Sometimes you only get one chance to fuck up a nitrous motor, better to be safe and take extra time than hurry it and be sorry.

Isnt that the truth!