I am working on getting an NXL setup up and going right now and having some issues...

This is the setup here; complete intake and rails:


The accumulator is a band aid, so we setup a proper fuel system from the get-go and now we can't get the AFR anywhere near sane. The car has 2 walbro pumps that Y together (-6 output lines) into a Y block that has the 2 -6 inputs and they feed a -8 line that runs to the rails. On the exit side of the rails, they feed a Kirban race regulator and it's return goes back to the tank. The car is setup with 58.5psi on it's single pump. When the nitrous is armed, the second pump turns on and pressure sits at about 60psi. The AFR is 12.7-12.8:1 off the jug.

All tests done between 950-1000psi bottle pressure.
On the hit, at the 120hp jetting, there is a tiny brief lean spike (less than the 150 wet kits that are rail fed and running aftermarket pumps) and then the AFR plummets to the LOW 9s.

NX recommends the following jetting:

80hp - N20=18 Fuel=9
120hp - N20=20 Fuel=10
180hp - N20=26 Fuel=12
250hp - N20=38 Fuel=14

So then we tried the 180 N20 jets with the 120 fuel jets (10s)... Got the tiny lean spike, felt the gas, but then the AFR went right to 9.6-9.8:1 AFR so we let right back out of it.

Calling NX tech support... the guy was nice, but I knew I wouldn't get any help after a few minutes of hearing things like LS1s have a dead headed fuel system (already told him our setup) and then he went on to tell me that the PCM would crank up the pump voltage when the spray came in (!!?!) So.... we have a tech support guy who has no idea how the platform works, yet they have built and sold this entire LS1 intake and system.... He told me it was designed around a stock fuel system.

Basically I need some jet sizes that will work; not a guess. This custoemr is not interested in buy 3 sets of 8 jets to get where we need to be,

 

One thing that sticks out to me is you went up on the nitrous jet by 6 but had little effect on the A/F ratio. First thing I would check is to make sure there isn't a nitrous delivery issue. This could either be solenoids not opening or a restriction in the lines.

A quick nitrous consumption test would determine if there is a restriction somewhere. This can be done by dry flowing the nitrous for 10 seconds, then turning the motor over with the coils unplugged to evacuate the nitrous from the motor. You should use 1# of nitrous for every 100 HP you are jetted for.

If the consumption is fine you would need to continue to decrease either the fuel jetting or the fuel pressure. One issue we have seen with the NXL kits is that they will pull vacuum on the injector which will increase the amount of fuel supplied with each injector pulse. This issue will become more pronounced as shot size increases and you are all ready using one of the smallest jets available.

 

Whats the Fp at? and are the plugs reading rich(are you sure the a/f is correct)

 

Last year on stock pressure we ran 28n 16f jets and it was rich enough to hurt 2 pistons.
Went to 30n 16f @ 48psi and it was alot closer.

Can you take fuel pressure out? I know you will have to retune the motor but its that or buy some jets and try it.

Turn the fuel pressure down until you get the AF right on the spray then tune the motor at that pressure.

 

Ray - we went from 9.2-9.3 on the first pull and the second try, using the 180 jets got us 9.6-9.8. We will give the consumption test a shot to see what is being used. We are getting enough that when he hit it at the top of first, it blew through the 1-2 gear change with the tired 4l60 that's in the car.


Fp is rock solid with the two pumps, heavy harnesses, and front mount regulator at 60psi with both pumps on. We will be pulling and inspecting the plugs this weekend, as we are moving to TR8s from 6s as we go up on the shot size. So no, we haven't seen the plugs right after a pull, but going by everything else (the rest of the data at cruise, WOT, warmup, etc) the wideband is working fine and it is a new sensor and calibration.

Thanks for the input.

 

That thought had definitely crossed my mind. It hurts though; I have a lot of time (plus the owner's dyno time) into that SD tune.

The motor will have to be retuned before each retry though. If we pull out X% fuel, we will have to get the car back to it's 12.8ish off the bottle (gets raced on the street NA a LOT) and then re-try the shot. I wouldn't want to have to do that too many times if it could be helped, though I'm sure it can be sorted out in this manner.

Thanks.

 

If the consumption test comes out ok then you have ruled out a restriction on the nitrous side.

One thing you may check is to make sure the solenoids are opening when fired. Make sure you have a good connection and are using a large enough wire to carry the amp load.

If all the above is ok.

Odds are the nozzles are pulling the fuel from the injectors. I see in the picture you have bigger injectors in the intake. We have found that combo to not work so great in many cases. The under the injector nozzles are bad about pulling about a 3lb vacumme on the injector which pulls the fuel from the injector.

When these nozzles first came out we put a set on Tonys car. We had that adjusted to a very small fuel pill at 6psi and It was still pig rich. This is when we starting noticing these nozzles were not the best option when using large high flowing injectors. We pulled them off and put real nozzles in the intake and the problem was gone.

Vinny also Ran into the same issue on his car and he is the one that did the test and relized it pulls a 3lb vacumme.

Dave

 

Summit Racing has an excellent return policy. You'd only end up paying their $11 handling fee + whatever it costs you to ship the unused jets back.

 

BINGO!!!
Those nozzles cost me 2 sets of forged pistons, from going way too rich. Its the weirdest thing, but it goes fat even when jetted 'traditionally lean'. Its even worse with big injectors, I'm convinced they are impossible to tune with larger shots.

Try this, put a vac gauge on the fuel jet holder and test fire some n20 while the manifold is on a bench, and look to see how much vac it pulls. You will be suprised.

This is the set-up I had:

 

Wouldn't a fuel pressure change just be a matter of adjusting the Injector Control tables (more specifically, the Flow Rate table, since the injectors are the same) and just a dyno double check instead of a "retune"?

 

If all of the offset data were available and accurate for non OE injectors it'd be that easy. In practice though, sometimes it's simple and sometimes there's a lot involved. This car has been most difficult from the beginning, so I'm not surprised

The car has 42lb injectors and we had planned to move 250 through this intake and up to 100 more through an upline fogger.

 

I would put the smallest jet you can in there and see what it does. to get from 9.0 to 11.8 on a 175 shot with a 12 fuel in it now your going to be neer a blank fuel jet.

 

gonna end up unhooking the fuel noid and doing it up dry

seriously though, we will try the #9F with the 180-hit over the weekend and see which way it goes.

 

Thats whats up !

 

The #9 jet from a number 10 jet will not make enough of a change. The orfice size of the fuel jet is getting dangerously small.

Did you do the flow consumption test? Did you varify the nitrous solenoid is hitting? Also what size wire are you using from the battery to the relay and the chassis ground to the solenoid? How long are those wires?
Dave

 

I remember that! Was back in 2003ish. Cost me some melted pistons as well.

Tony

 

Hey Dave, thanks for the response.

The nitrous noid is hitting. I won't be back in front of the car until the weekend though; it's out of town. The wiring is solid; I came from an 8 year sentence as a controls engineer before this But to be more specific; it's been a good while that it was wired up, but the triggering relay is under the hood and between the battery and the intake, so it's a short run. The wire feeding it is one size larger than the noid wiring (14ga I believe or it may be 12ga; I forget whether the noids are 14 or 16, but at a glance they appear to be 16).

I see talk of nozzle replacement, but can that be done with this intake? Are we getting screwed because we *don't* have a half-assed fuel system?

 

The issue is not with the fuel system...its the location of the nitrous discharge...by placing it under the injector, the nitrous discharge is pulling more fuel from the injector.

 

Frost,

Sounds good. Those are common questions I ask everyone. Sometimes its something so simple you take for granted. There have been many cases that the gauge of the wire was the issue and only one solenoid was not operating. Not everyone understands amp draw. Or they do not know how many amps the solenoids draw. Some nitrous solenoids pull as much as 27amps a piece.

On that set up the nitrous solenoids pull 11 amps each and the fuel pull 3 amps each.
So technically a 14 gauge wire would be only good for about 3 feet and a 12 gauge wire good for about 5 feet.


Anyways sounds like the wiring is good then. So do the flow consuption test and if that comes out ok. The nozzles are the issue..

I talked to Abney from NX over the phone a few minutes ago. He said to tell you that if Everything checks out and the nozzles are the issue he will trade you our for traditional directport systyle nozzles.

Dave

 

Ray just pointed out to me you have the actual NX intake with the discharges made in. This entire time I did not look at the pic well enough to notice that. I was thinking you had the under the injector nozzles.

I guess you can not trade that in as easy.lol
Dave