Calling nitrous experts (very technical)

[1sweetGT]

Hello all,
I have the NOS dry kit for the returnless style fuel systems. When I was on the dyno last week my A/F was good up until about 5500 and ended at 12.9 at about 6k. The tuner said my A/F was a little lean. He then programmed the injectors to pulse longer to add more fuel. So on the next run the A/F was the same. Basicly be said I need a bigger fuel pump.

So here is hot the NOS system works. Our fuel pumps keep a constant 50 to 52 psi of pressure. the Fuel enrichment circuit that comes with the NOS kit interfaces with the computer making the computer think that the fuel pressure is only 15 psi while nitrous is engaged. So the car's computer "sees" 15 psi and tells the fuel pump to go full bore to try and bring up the fuel pressure back to 50 psi. And thats how the extra fuel is added.

So my question is what pump do I need and can the tuner make the new fuel pump dump in the right amount while I'm spraying?

Thanks for any help

 

[BlackBadGT]

I'm well aware that a typical "safe a/f" is 12:1-12.5:1 But i don't think a 12.9:1 is horrible.

 

[Bone Racing]

12.9 should be ok

a 190 l/hr should be sufficent
if u get nervous...get a 255

 

[1sweetGT]

Ok so what is my best option for a new pump and can the tuner properly tune for N/A and Nitrous use?

 

[LS2 KLR]

I just had mine dynoed and was also at 12.9. We added fuel and I gained 44rwhp and 76rwtq! I'm not sure what my final a/f was but he told me I still needed more but I was beginning to run rich NA. I'm getting a flip to solve this problem and plan on stopping around 360rwhp on spray. You can't go wrong with an 03 Cobra pump.

What mods do you have to have 278 NA???

 

[1sweetGT]

Comp cams, valve springs, long tubes, o/rx, mass air, home ported upper plenum, thats about it

 

[1sweetGT]

But I want to know what would happen if I just drop in the new pump without a retune

 

[LS2 KLR]

I never had my car tuned, just dropped it in.

 

[1sweetGT]

Ok, so n/a it should work like stock, so what will happen when I hit the juice?
Can I get any other awnsers?

 

[Teen'93stang5.0]

you could always just add an inline fuel pump couldnt you?

 

[sizleen]

ok dude I don't have a dry kit but I have experience with wet nitrous. First and MOST important, bottle temp, what effects bottle preasure is the most critical part of nitrous. If the bottle is too cold you will run "nitrous" rich, If the bottle is hot you will run "nitrous" lean. I would HIGHLY recommend that you get a bottle guage and a bottle heater so you know where you are at at all times. Operating preasure is 1050 psi. The preasure is a very sensitive part of the Air fuel ratio. Being at the right preasure should solve your problem. These nitrous companies will tell you if you need a bigger fuel pump with the system so give them a call if you still have doubts about that.
If that don't do ya, Well, I don't know what jets come with that kit of yours but if you want to richen the fuel system of your car you LEAN the nitrous a hair. Richining the fuel makes you run more lean because the nitrous is a fuel catalyst. Yea you will make more power because leaner=more power. Bottom line, you want a richer fuel system, lean the nitrous. peace out

 

[1sweetGT]

Thanks sizleen.
But I have a pressure gauge and the bottle was heated to 900 psi. If I was at 1100 psi or so I could just drop the bottle pressure to richen up the mixture, but 900 is as low as I want to go. The bottom line is that I need a new pump (I think) but I don't know how the new pump will work with the nitrous fuel enrichment circuit. And what I mean by that is if the fuel enrichment tells the pump to go full bore like it does with the stock pump will the upgraded pump dump in too much fuel?

Also I want to fix the problem with staying with a 100 shot and not going smaller. Thanks

 

[sizleen]

The fuel pump should not affect the amount of fuel that is dumped into the motor because the injectors do that. The job of the fuel pump is to maintain constant fuel preasure. Now you could turn up the fuel preasure, but that would be in the fmu(fuel management unit). Which in my blown mustang case, has been reprogramed.
There are hundreds of nitrous jets and fuel jets. I am not say to go lower then a 100 shot.For example the NX kits that I am familiar with will have a 85nitrous and a 85 fuel jet(fictious #'s). If you go to an 84 or 83 on nitrous you will still have 100hp just leaner on nitrous but tuned better. check out some NOS, NX websites and you will see what I mean. cool man? lates