Nitrous Limits...

[RedEnuf93]

I did dyno my old -93 Gen 1 last weekend and with 150 jets and 93 pump gas I got: 500HP/633TQ. The old (no NOS) numbers were 410/477.
Not bad, but with 150 jets I was expecting a bit more.

Where are the limitations with the NX Express system and Gen 1 motor?

Who has used the 250HP jets or 300HP jets without problems? I have no modifications to the fuel system, is it capable of feeding the 250-300 jets?

I am going to dyno this Saturday with the LS-1 guys and I would like to try atleast the 200 jets. I filled up the NX tanks (since they were half empty and resulted a pressure drop in last dyno pull)and got 5 gallons of VP 12 to be on the safe side.

Now I know why they call it Laughing Gas.... It puts a smile on your face!

Lauri

 

[Jack B]

You can definitely do a 200 shot (flywheel). The cars are all a little different. If your fuel and nitrous has no restrictions a 200 shot should be close to .050-.053 on the nitrous and .033-.035 on the fuel. You want to keep the a/f at 11.5:1. This is safe with some margin for error. Always keep the bottle at 900-1000 psi so you are consistent. Start with .050 and .035 to verify the a/f. This is all predicated on a base fuel pressure of 55 psi. Even safer is to start with the .035 fuel and work up from .045 nitrous. You will find the power rises quickly with small jet changes up to .053, after that the power goes up slowly if at all.

A little hint, if you do not have headers and exhaust the torque will rise fast and fall off quickly. With headers and exhausts the torque will rise fast and then fall off slowly.

 

[RedEnuf93]

3500- 14.0
4000- 12.5
4500- 11.8
5000- 11.7
5500- 11,3
These were done on NX 41 and Fuel 22.
According to the card from NX the 200 shot seems to be NX 52 and Fuel 33.

I have 2002 "headers", in other words the stock 2002 exhaust on a gen one, jetcoated. It is mated with 3" exhaust with Dynomax Bullit mufflers, no cats.

3000-225HP-350TQ
3500-380HP-580TQ
4000-460HP-610TQ Topped at 3800rpm at 633TQ
4500-480HP-560TQ HP the same 500 between 4700-5200
5000-500Hp-525TQ
5500-480HP-460TQ

 

[PRVT JET]

I don't know if the jets are different on the nx than nos, I run a 46/30 on my car for 145rwhp shot. My a/f is at 10.5

 

[dansauto]

Laurie your a crazy man. I think 200 shot is the limit to be safe. I have heard some guys using 250's, but I wouldn't chance it without a fuel upgrade. I can help you with a fuel upgrade if your thinking about that next.

 

[VIPER D]

use propane and be really safe.


nitrous d
take a look
http://visionsofspeed.net/custpics/04viper/

 

[RedEnuf93]

Dan, I'll do the 200 shot tomorrow on dyno and I'll call you later what the numbers were.
Maybe it's time to do the fuelpump upgrade?

Lauri

 

[Jack B]

The NX and NOS brand jets are close, however, the feed to the jets can cause different a/f's. 52/33 is the stated, however, start richer or use less nitrous and work up to the stated.

 

[PRVT JET]

I agree jack, I started with a 40/30 which was way too rich below 10.

 

[RedEnuf93]

Well, here is the latest:

I dynoed today 562HP and 714TQ.
Nice numbers, but something is not quite right.
This was the NX 200 shot (52-33 jets) and everything went well, until the nitorus was engaged. The Nitrous hits hard and after a second, it has a hesitation. Then it comes back on, but this time really rich. The plugs are the NGK's and gapped for 0.35. I will pull them out tomorrow to verify the condition and gap for 0.33.

Here's some numbers, if someone can help me with reading the actual dyno charts, I would appriciate it! I can e-mail the charts if you want to see them.

Air/Fuel problems:
2500- 15.5
3000- 14.5 - Nitrous engaged
3250- 10
4000- Below 10
4500- Below 10
5000- Below 10
5500- Below 10

These were done on NX 52 and Fuel 33.
According to the card from NX the 200 shot seems to be NX 52 and Fuel 33.
I quess I could go with 31 jets for fuel (or larger NX jets?), but before doing that I just want to see that everything else seems to be OK....

Here are the dyno numbers:

3000-340HP-580TQ
3500-425HP-650TQ
4000-520HP-695TQ Topped at 3750rpm at 714TQ
4500-560HP-650TQ Topped at 4750 at 562HP
5000-550Hp-580TQ
5500-510HP-490TQ

Is it the fuel management system messing with my Gen 1, and Nitrous (oxygen) fooling it to belive it is WAY too rich

Thanks!
Lauri

 

[Jack B]

Either post your curve or sent me the file and I will post it. A lot depends on which sprayers you are using. Two things are obvious, your nitrous is restricted. Most of the dual nozzles will flow up to a .063. My gusess is you have to go down on the fuel and up on the nitrous.

Another item is the hp is peaking too early, this could be due to the over rich mixture. Some O2 sensors have a hard time giving an accurate reading in the over rich state, maybe you are even lower then indicated. Don't tune for the hp, tune to get an a/f of 11:1, that's not max hp, but, its is safe.

 

[RedEnuf93]

 

[RedEnuf93]

This was without the NX.

 

[RedEnuf93]

This one is with 150 shot.

Jets were following: 100 shot NX #35 Fuel #18
150 shot NX #41 Fuel #22
200 shot NX #52 Fuel #33

 

[Jack B]

The curves show two problems:

1. The headers/exhaust are not allowing you to get full power from the nitrous.

2. The car is so rich it could be skewing the whole curve down. You have to start adding nitrous and substracting fuel till you get 11:1.

 

[Alternative]

The Nitrous hits hard and after a second, it has a hesitation.

Do you have a Fuel Pressure Safety Switch (FPSS)? I've heard that this could cause intermittent issues. According to the NX installation instructions, an FPSS should not be installed between the fuel solenoid and fuel pressure regulator.

 

[RedEnuf93]

I do not run the FPSS switches.

My buddy Ed dynoed his -95 and check his results... They are almost identical. His air/fuel ratio is going downhill as soon as he opens the solenoids, just like mine.
I think I will try to run the 200NX shot with 150HP fuel jet, on the dyno, so that we can monitor the air/fuel ratio's.

 

[PRVT JET]

Jack, last question I promise. Since you said to try 48's, can I use NX jets with my NOS set up?

 

[RedEnuf93]

I was advised that NX jet and NOS jet numbers do not match.
I wanted to buy an assortment from NX and their idea of an assortment was 10 pieces of each size! I am still trying to find something inbetween 22 and 33 fuel jets.
If I dont get them, I will measure and modify them myself, being a watchmaker I am used to much smaller tolerances than NX jets...

 

[VIPER D]

I made 674.2 hp and 904.7 tq on my stock srt with just k&n, stock headers,bullets mufflers and no cats. (btr's nx and propane set up)

The Afr #'s were good all the way thru. Do you guys think that I should go for even more?


vd..

 

[PRVT JET]

Viper d, to take full advantage of the nitrous you need a nice full exhaust system.