Nitrous: Anyone experience false knock?

[higdominator]

Like the title states, I'm looking to brainstorm to help track down a potential false knock issue.

-Brisk RR14S @ .030
-NX plate kit- 100 shot for testing
-Maximizer 4 controller running each solenoid independently - currently set to spray at 3500, off at 7k.
-E85 (quality E85) w/ BAP & 47's
-Lund nitrous tune, don't suspect issue with the tune, looking for mechanical possibilities.
-It does this on both the stock and Holley Sniper intake.

-Car has JLT, MAK cat deletes, Holley Sniper

Car runs great on the nitrous tune NA, absolutely no KR.

As soon as the nitrous is sprayed I get instant KR 1,2,3,5,10*.

It does this no matter what shot. I've tried the 50 (35N23F), 100 (52N32F), and 150 (62N38F), all using NX's recommended jets for E85.

AFR's appear to be within reason, it was a bit rich but has since been right about where it needs to be.



I have triple checked the system. Everything is working, I've sprayed out the plate/lines/solenoids with compressed air. No leaks, solenoids are mounted to the TB and not contacting anything but the bracket.

I'm just at a loss for what could be causing such fast and large KR corrections. The plugs looked great, slight/light tan coloration, no peppering. The car doesn't buck or feel "dull" at WOT. I can't readily hear any audible knock.

Has anyone experienced KR like this running a NX plate kit? Just making sure to check everything I can before resorting to desensitizing the knock sensors.

Again, I don't feel this has anything to do with the tune, just my car being a real prick.

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[Jay-rod427]

Are you sure its false? I would triple check the tune to verify lowered timing from standard e85 tune. Do you get knock retard without the giggle juice WOT?

You say AFR is a bit rich. What is it?

 

[higdominator]

Are you sure its false? I would triple check the tune to verify lowered timing from standard e85 tune. Do you get knock retard without the giggle juice WOT?

You say AFR is a bit rich. What is it?

Timing is reduced. I get -5 on the Nitrous tune NA. I've even placed only the nitrous tune on the NG to make sure it's the only thing to load. I know Jon has had his eyes on it numerous times to verify timing retard.

AFR has varied previously from .780-.820 target is .82. There were issues running rich before, but I had 1 jet size too large in the fuel side .036 vs .035.

Even with fluctuations between solid AFR and a bit rich I get the same results as soon as the nitrous solenoid opens.

 

[Terminator2]

What's commanded timing with the nitrous?

 

[kcc0521]

This might not help but I had a hell of a time chasing down an issue on my old fox body nitrous kit and it turned out to be a faulty nitrous filter. The filter was not letting enough nitrous in the car.

 

[Jay-rod427]

What's commanded timing with the nitrous?

This. Not the knock retard, what is the commanded timing?

 

[higdominator]

That I am not certain of.

 

[Need4Speed15]

Don't assume its false knock. I had spray on my 2012, put prob 100 bottles through it over 2 years and ran awesome. All of the sudden out of the blue I was getting bad knock and I assumed it was false. I checked everything, exhaust, etc and couldn't find anything so stupid me sprayed it again. Well, it wasn't false and I ended up taking a nice chunk out of one of the pistons of the Aluminator that I installed.

Never did figure out what caused it. Ended up putting the car back to stock and eventually got rid of it.

All I'm saying is be careful and don't continue to spray it untill you figure it out.

 

[higdominator]

That's why I'm here asking if people have actually experienced it;)

I'm trying to find potential causations to investigate so I can eliminate them from the equation.

 

[Terminator2]

Don't assume its false knock. I had spray on my 2012, put prob 100 bottles through it over 2 years and ran awesome. All of the sudden out of the blue I was getting bad knock and I assumed it was false. I checked everything, exhaust, etc and couldn't find anything so stupid me sprayed it again. Well, it wasn't false and I ended up taking a nice chunk out of one of the pistons of the Aluminator that I installed.

Never did figure out what caused it. Ended up putting the car back to stock and eventually got rid of it.

All I'm saying is be careful and don't continue to spray it untill you figure it out.

This. Don't assume it's false. Pull out 5* from the tune and see if it stops.

 

[higdominator]

RPM SAFOT PED AFR1 AFR2 KR
3892.8 17 100 0.861 0.81 -3.484
3894.5 17.3 100 0.861 0.81 -3.484
3905.8 17.3 100 0.861 0.81 -3.484
3912 17. 100 0.849 0.794 -2.859
3928 17.5 100 0.849 0.794 -2.859
3986.5 17 100 0.849 0.794 -1.766
4020.3 16.5 100 0.724 0.69 -0.266
4005.5 13 100 0.724 0.69 2.016
3982.3 12 100 0.724 0.69 4.078
3991.5 10 100 0.699 0.678 4.641



I got home and got a clean log with good bottle pressure and 62N/38F jets in per NX. I got about less that one second into the hit before I aborted.

I believe I maybe have figured out one part of the puzzle. My fuel pump voltage (BAP running full time) jumps at WOT. While the injectors don't seem to have issue adjusting, the extra pressure may be making typical jetting way too rich and causing fuel to go way rich. It doesn't seem to be too bad until cylinder pressure rises with the nitrous coming in.

In this quick 1s snap shot the fuel is ramped slightly ahead of the nitrous to prevent a lean spike. Instead the extra fuel pressure creates the ugly rich spike.

The next step down in jetting is essentially the gas jetting (.036). Going to try that. Target AFR is .82, so it looks like the kit just needs some attention.

Why can't I think of this stuff when I'm staring at a data log quietly while everyone is sleeping in the house? Only after I beg for help, lol.

Please feel free to poke holes in my theory, I'm still half brain dead from work today.

 

[Jay-rod427]

Your data logger should have a pid for commanded spark, total spark advance.

 

[higdominator]

Pulled some fuel jet out. Went from recommended .038 to .036- improvement. Went from .036 to .035 (gas jetting- I'm on E85)- Much more improved. All I have now is a slight rich spike when it hits, probably because I had built the fuel side to help kill any lean spike. Going to pull some fuel with the controller and see how it goes!

On the .035 jet it initially, but slowly, pulled 1,2,3 then started adding timing back in slowly after about .4s. Seems the rich hit is the cause, timing, as I mentioned, is OK at the moment.

 

[Rhamlinii]

This. Don't assume it's false. Pull out 5* from the tune and see if it stops.

I agree. I would also up the fuel jet by one aswell. Lo, and see tbe results.

 

[dubster99]

AFR1 is a bit on the lean side until it pulls all that timing out. Timing doesn't seem too high to me with E85 in the tank. But it's not liking something that is going on. What kind of timing and afr's are you seeing without the spray?

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