Looking for a little help with a issue I'm having with my recently installed nitrous setup.

Just a little history on the car. Its a 2008 a6 ls3 with stock fueling. Nitrous is set up on a window switch. I previously had a 5th gen ls3 integrated solenoid plate system on my car and it ran great. Ran it at the track on a 150 and made some good passes but when it got dyno'd on the 150 it only made an extra 102whp/72wtq. I threw a 200 in it and tested it out and that too ran perfect but no dyno/track time.

So I ordered a 90mm plate kit from NX to try and get some more power out of it. I got it all hooked up today and decided to start out with the 200 pills. On the hit the car stuttered/bucked super hard so I immediately let out of it. I figured it was just too much nitrous and thankfully nothing got hurt that I know of. Stepped it down to a 150 and it did the exact same thing. At this point I checked to make sure both solenoids were firing and they both did. So I put a 50 shot in it and again on the hit it stuttered/bucked and let out. I tried it one more time but this time stayed in it and after bucking/stuttering a couple times it pulled fine. I decided to try throwing a shorter fuel line (7in vs 23in) on the solenoid to plate. My guess was that the nitrous was getting to the plate faster than the fuel. Went for a test hit and there was no longer a buck but just a very small stutter on the hit. I tried adding a foot of line to the nitrous line (2ft line now 3ft) but it didnt make a difference.

So Im thinking if I make the nitrous line even longer say 5ft total would that fix my problem? I really couldnt think of anything else so any input would be great. Thanks!

Heres some pics of the line lengths.

 

Pull the fitting out of the inlet of the nitrous solenoid. Check it for debris in the screen. I bet it has something in it causing a flow restriction.

 

What jets do you have in it?

 

I always wonder if using a progressive controller even set to a short time frame would help that pressure differential issue with nitrous vs. fuel. maybe something to consider

 

Sure enough it did have some gunk in there. Cleaned it out and put the long fuel line back on and the stutter was just as bad. Going to put the short line back on to see how it does.

 

Its a 50 shot. 35 nitrous and 20 fuel till I can figure out the issue.

 

Ya its just wierd how it is doing it at every level Ive tried. There was no difference on the hit with a 200 vs a 50. It stuttered just as bad. With my old plate setup with a 200 it worked perfect.

 

After the initial hit it pulls perfectly fine through the gears.

 

Glad to hear I'd clean that filter one more time. Maybe even blow out the lines don't want any debris in there.

 

I checked it again after a few pulls and it was still clean along with the lines. I'll chime back in later tonight to see if its a clean hit now that the short fuel line is back on.

 

Put the short nitrous line back on and it has just one stutter on the hit. It only does it on the first hit after opening the bottle up and purging it. I did 3 pulls after the first one and it didnt stutter on those 3. I closed the bottle. Waited about 5 minutes. Opened it back up. Purged it. And it stuttered on the hit again. I may be just being picky about it but it never did this before on the old plate system. I also rechecked the filter after all the pulls and it was clean.

 

Check your plugs. What gap are you running? What plugs? I transitioned to copper plugs once I went over a 150 shot.

 

That short fuel line / long nitrous line trick has been around for a long time and does work. But, from my personal experience, that always done to soften the "lean hit" that comes from nitrous being injected slightly before the fuel, due to the pressure differential. Normally it just hits real hard with equal length lines. So, I don't think it's stumbling from the nitrous hitting early - normally with a medium shot like that, it just hits real hard when the nitrous system is switched on. You would probably have to dump a ton of nitrous in it to cause it to stall or stutter.
Dumb question, but you've checked to make sure that the jets are the right way round, correct? Don't ask, but that has happened before...
I'm not sure whether you're experiencing a stutter or a rich stumble from the mixture being rich on the initial hit. The fact that you had a lot of gunk in the N2O inlet screen at first would seem to indicate that the buck you were initially getting was from the mixture being too rich?
Are you using a controller? If so, does it have a fuel offset feature? If so, try adjusting that. If not, I would invest in a good controller anyhow.
Also, I've seen this sort of thing happening before on an LS1 car where the plate was mounted backwards and the nitrous was being sprayed forward towards the MAF. I'm not sure how the NX plate works, but you can check that as well. NX makes top notch stuff, from what I've seen, and I've used them all over the years.
Good luck and I hope that you get it sorted soon.
Happy foggin!

 

Plugs looked normal. .032 for the plugs and they are the non projected br7ef.

 

The jets are the correct spot. I always second guess myself and end up checking 3-4 times before i actually put them in. I dont use a controller.

 

Well good news. I made in a a dyno tonight to see whats what and it didnt stumble at all. I didnt care for the number too much since my car always dynos low. But the afr is what i was after and with a 200 in it the stock pump had enough in it all the way out.

Going to the track tomorrow to see if my trans will be happy with it or not.

 

What jetting does that kit use for a 150 and 200 shot, respectively?
You certainly have a cold enough plug and the gap is tight enoug for sure. I know a lot of people will advise that you should run the non-projected plugs, but I don't like them for street use.
I've run up to a ~200 shot (.082" jet IIRC) on my 6.2 A6 AWD Sierra Denali with 7IX Iridium plugs on 93 Octane pump gas with no issues.
BTW: I just re-read your original post and was reminded that you're using a window switch. Depending on how that's activated and working, it may be that could also cause a stutter on activation of the system. Just a possibility, stranger things have happened...
As far as the transmission is concerned, one thing you might experience with the bigger shot is that the transmission will not shift fast enough and this will cause the engine to bang up against the limiter instead of shifting. This can be taken care of by tweaking the low gears shift speed (mph) tables in the TCM tune. These transmissions are torque input sensitive and the more power you put in them, the more you will have to compensate by telling the transmission to shift early. You also want to tweak the shift times to shorten the time it takes to complete each shift, because you want to limit the amount of time that the clutches slip on the shift. Tuning is critical with these transmissions, especially with FI/N2O on these cars.
Good luck and keep us posted.

 

Awesome let us know what you run.

 

Will do 10.49@131 is the time to beat.

 

Well it made more power and went slower dead hooking. 10.6@130 is all it has.