I've read about some cars using mechanical fuel pumps with nitrous. I didn't think that it was a good idea but it sure would be easier than running wires and relays and stuff. Would a good aftermarket mechanical one that gives more fuel pressure work? I don't plan on using over 150 hp on the bottle.

 

anyone?

 

It kind of depends on the pump, and what sort of power the engine is already making. Regardless of whether you use nitrous, SC, or N/A, the bottom line is HP = GPH; so as long as the pump can support the overall flow it should be OK. A good pump like the Carter or Holley should be able to feed enoough fuel for about 550 HP or so total.

------------------
"So many Mustangs, so little time..."

 

Finding a mechanical fuel pump that will have enough pressure for fuel injection is no easy task. I've seen them, but they usually cost a small fortune. I think you'd be better off just using your stock electric pump, or upgrading to a better electric one, like the Walbro 255 lph pump.




------------------
89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

 

I'm not using fuel injection and my car doesn't have an electric fuel pump. The car is old. What I need to know is which mechanical fuel pump that can be used.

 

If it is any sort of answer... I am using a Carter Street pump and a Holley 750vac and plan on a 150HP shot.

------------------
1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane...

-=ICON Motorsports=-

 

N2O in short is the addition of liquid oxygen under pressure into the combustion process. If a proportional amount of fuel is not increased with the spray, an extremely lean condition will result and pistons will melt. I would not advise using a mechanical pump with N2O. You need a constant supply of high pressure fuel with N2O regardless of the hp shot.

If your set on sticking with a mech. pump, you will have to run a dual regulator system of the discharge side of the pump that can feed the demand with the shot. One for normal driving to the carb around 12 psi and one for the N2O which will be set around 40 psi. The kit will come with a solenoid operated valve that will open the N2O fuel supply when the N2O switch is closed. The pump should have enough capacity for the total engine hp with the shot plus 30% to be on the safe side. You will also need an electronic timing control to retard the total ignition as cylinder pressure is dramatically increased and pre-detonation will result without spark retard.

You will also need a free flowing exhaust and preferably a N2O cam that will open the exhaust valve sooner to expel the additional spent gasses generated from the shot. If you don’t want to spring for a new cam, then you should advance the cam 4-6 degrees. This will help, but is not the optimum fix.

I’d recommend you pick up one of David Vizard’s books. He’s an N2O advocate and covers it in detail.


Mike

 

I'm sorry, but what are you talking about? 12psi for normal driving? You will run WAY too rich... that is if you don't blow the needles off their seats when you crank up the engine. Carbs run best around 5psi.

Maybe if you are running a 2-stage nitrous setup with a 300HP shot, then you may need to run an additional pump to a separate solenoid. My suggestion along with the book would be to post on the power adder and carb boards about this too...

 

Thanks everyone for the reply's. I just got an e-mail from NOS and they say to use no less than the Holley "blue pump" which flows 110 gph free flow and 70 gph at 9 psi. It is preset at 14 psi and I will need a regulator for my carb. They also recommend between 5 1/2 and 6 psi and do not use the red pump.

 

I think the Carter mech pump is rated at 120gph. Mine was putting out 7psi, but I regulated it back down to 5 1/2psi.

Certainly listen to the NOS people, they are the experts and it is their reputation on the line if what they say is wrong...

Good luck.

 

94-6spd: I use a mechanical pump on my Malibu driving a 400ci small block and a 150 HP plate system (high 11s). I use a Carter street pump- but not by itself.

It is NOT adequate to feed the setup by itself, but not becuase of the pump's capacity!). In fact I started seeing dipping fuel pressure running as slow as 13.7! It's not a matter of how much fuel the pump can deliver (plenty) as it is of how long the draw is from the tank to the pump. On top of that throw in the strong first gear acceleration working AGAINST the pump and you can imagine why I ran out of fuel so quickly.

My solution was to put a Carter electric street pump back by the tank to give the juice a "shove" up to the mechanical pump which then did the final pressure regulation (6PSI) and shoved the fuel up to the carb.

Pressure now never wiggles off of 6 PSI under any and all conditions.

 

What am I talking about? Sorry, I should have phrased that, "no more than 12 psi to the carb". Sorry for the error....

I have a 355 running somewhere around 375-400 hp with a 650 performer and the regulator is set at 9 psi. That's where it likes to run and it is not rich or floods. I also have a 406 at 520 hp running at 12 psi with a 4150 850 cfm. It has 81/83's in it with the power valves blocked. It also likes to run at 12 psi and the f/a ratio is 12-13.

5-7 psi is where "stock" engines seem to run best, but not "all" performance built engines depending on their fuel requirements.

I did not recommend a "dual pump" system. I recommended a "dual feed with dual regulator" system for the N2O.

Thanks for pointing out my mistake in such a mannor that I now feel like a dumbass. I'll try to be more acurate when I give someone free advise from now on...

 

if you advance the timing for nitrous, you will blow something up in a hurry. that must have been a typo. the NOS people will have a formula to determine how many degrees to back timing off. so many degrees per 100 horsepower of the nitrous i think.

------------------
88 S10
Dropped 3/4
Dart equipped 406
12.20 @ 115.25 mph