I just received my safety switch, the instructions are showing a fuel pressure gauge, do I need to get a gauge that wold mount in the car or under the hood or what? What is the right way to go in terms of the safety switch. I have a dry kit and am not sure what pressure to adjust the switch to? My NOS Kit is supppose to operate at 80 to 85 psi when the nitrous is activated. I don't think I can set this switch to cut off the nitrous solenoids if the pressure drops below, say 75 psi? Also the instrution are only showing one nitrous solenoid in what is a wet kit setup, but I have two nitrous solenoids on my LT1 setup, do I only hook it up to the first solenoid? Please help?

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Lalo
95 TA
"It will never be fast enough."

[This message has been edited by rpm4lalo (edited June 09, 2002).]

 

A fuel pressure gauge isn't mandatory, but its a very good idea. You can mount a fuel pressure gauge inside the car only if it is electrical, or with a high pressure isolator if it is mechanical. Electric gauges are very expensive... ~$180. (AutoMeter just recalled their $80 fuel pressure gauge because of leaking pressure sensors). But a high pressure isolator, braided S/S lines and a mechanical gauge will cost you as much, and IMHO are still a PITA to keep filled and very risky (I had an AutoMeter high pressure isolator fail).

I think the upper pressure limit for the high pressure Hobbs switch is only about 70psi or so, so that is where you need to set it.

You wire the nitrous solenoid ground circuit through the fuel pressure safety switch, so that if fuel pressure falls below the switch set pressure, the ground to the nitrous solenoid is interupted and closes the nitrous solenoid.

It sounds from your description like you have an NOS 5176 dry kit, with the 2 nitrous solenoids in series, and the blue regulator mounted in between. As a result, you can not interupt the ground circuit on the first nitrous solenoid (the first one the nitrous comes to after the line from the bottle). That solenoid has to open when fuel pressure is at the stock setting, to send a small pressure regulated stream of nitrous to the vacuum connection on the fuel pressure regulator. When that nitrous applies pressure to the stock FPR, it boosts the rail pressure. Then the fuel pressure switch should sense the correct pressure, and close the ground circuit to the SECOND solenoid.... the one closest to the spray nozzle.

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Fred
94 Formula A3: 381/TH400/N2O
Detailed Mod's List
11.513@115.59 on motor; 11.162@127.67, 1.643 60' on a 125-shot. Going with a 275-shot this year

[This message has been edited by Injuneer 94FormM6 (edited June 10, 2002).]

 

Thanks for the expert info. I was curious, can I run an in-line MSD high pressure pump with the 5176 Kit or do I have to purchase the one from NOS.(I bought the kit used and it is missing the electric pump) Ideally, I would prefer to buy a Holley 255 lph intank fuel pump to avoid noise, but all the pumps I read about talk about how much fuel they flow at 40 psi and such. Which pump, besides the one from NOS can handle the 80-85 psi my NOS kit says it needs? Once again I appreciate the great info.

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Lalo
95 TA
"It will never be fast enough."

 

You can run the 5176 kit without a in line fuel pump. I just use my stock one. I also bought my kit used without the pump. Been running it for 3 years without it. Just have to be alittle more careful without the extra fuel.

 

My kit is jetted to about 125 to 130 horsepower. I already have some bolt on's and I'm already weary of the injectors not being able to support the shot. I am just curious if you guys think I should go with the Holley 255 LPH in tank or the MSD in line? I need a decisive answer that explains why your choice is the better one. I appreciate the great help thus far guys.
Peace.

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Lalo
95 TA
"It will never be fast enough."

 

Get the Walbro 340 high pressure fuel pump. It will just barely provide the lb per hr of fuel you need for 500 hp at 80 psi. If you go with a wet kit later it will have enough output for almost double that HP.
Mike B

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Mike Bambic A.K.A. "The Bambinator"
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Here's what I have found out. Called up MSD and they said max PSi is 80 and can support 500 Horsepower(can buy from summit for $76.) Called NOS and it holds 700 horsepower and has a max psi of 100($200 from summit). I want to get the MSD and add an intank later if necessary. What do you guys think?