Blackthunder50

I recently picked up a Zex LT1 nitrous kit #82018 and have been researching all of the necessary supporting parts I will need to run this safely. I plan on starting out with the lowest jet (75hp) and seeing what happens in the 1/4.

In addition to the kit I plan on adding:
-NGK TR6 plugs gap @ .035
-Mallory 685
-FPSS (don't know if this comes with the Mallory box or which one I should get)
-Inline Walbro GSL392 (255lph)
-nitrous pressure guage and fuel pressure guage
-Stock injectors, will they be sufficient?
-Purge kit
-93 octane

1. I need to know if I can setup the Mallory Box to retard the timing when I arm the system. From my research and the instruction manual I assume 4 degrees should be plenty (2 degrees/50hp). In conjunction with the FPSS does it shut down the nitrous if the fuel pressure reaches a dangerous level?

2. Can I set the nitrous to never activate below a certain RPM and shut off before the rev limiter?

3. Does the inline fuel pump only activate when the system is armed or is this always on?

As far as the engine, it's in great mechanical condition. I have about 5000 miles on the new cc503 cam and all of the supporting mods for that.

I would appreciate any suggestions to the questions above or any other feedback on helping me get this setup. Thanks in advance!

MTL_Z28

I will try to answer some of your questions even though I'm not an expert on dry nitrous kits...

The mallory box has functions to retard timing when spraying your nitrous system (2 deg. per 50 hp is a good rule of thumb as you've said) and also your can set the RPM window at which you want the nitrous to activate and turn off at. You can for example set it to come on at 3k RPM and shut off at 6k RPM or maybe just before your shift point. another feature it has is a rev limiter... Alot of ppl when they get an aftermarket ignition box raise the rev limiter in the PCM (with lt1 edit or tunerCATS) and set the true rev limiter in the Mallory box, since stock PCM will cut fuel but the box cuts spark instead which is better.

The FPSS is just a hobbs switch that comes pre-set at a certain Psi... It shuts off the nitrous system when fuel pressure drops below this set point. You can get one from anyone who sells nitrous systems. Mine is set at 35 psi I will test it out and see how it works (you adjust it via a screw in the switch). The stock LT1 fuel system is rated at 43.5 psi IIRC but sometimes when you stomp the gas it can temporarily drop so it may cut the nitrous activation if it drops below 35. I guess I'll test it out and see what works best.

Injuneer

The LT1 fuel system only runs at 43.5psi WITHOUT vacuum compensation. When you attach the vacuum compensation line, the pressure will drop proportional to intake manifold vacuum, meaning with a stock cam its going to idle at 36-38psi. When you "stomp on the gas" vacuum disappears and the fuel pressure INCREASES closer to 43.5psi. Additionally, if this dry kit is anything like the NOS 5176 dry kit, it uses reduced nitrous pressure on the vacuum compensation line to boost fuel pressure when you spray, and increase fuel flow through the injectors. IF it works like that, the FPSS has to be set to the elevated pressure required to supply the extra flow through the stock injectors.

As far as the inline pump that builds pressure for the dry nitrous kit, it has to run all the time. If you shut is down, it becomes a major flow blockage for the intank pump.

Blackthunder50

Great responses! I'm going to set everything up in the car and double check to make sure each component is functioning properly. When everything is set, I'll come back and post up the parameters that I set for each component. Any suggestions at that point would be helpful, then I'll see it it works