Need Quick Answer: Nitrous Question

[MN6WS6]

Yes, I did buy a resistor pack from MSD when I got my 6AL. They come in evens and odds, 5 per pack, within the 1,000 RPM range. Like 5100, 5300, 5500, etc. However, if you do a google search, you can find the cheat sheet and make your own, which is what I do now. Basically it's a resistor that costs about $.02, and a pack of connectors (usually 20 to the pack) that sell for about $4 around here. So, pretty much, you can do the same thing MSD does, without the pretty plastic piece with the sticker on top, for about $.50 a piece. Instead of $3 or $4 that MSD charges. I have one of these in my 6AL, and one in my window switch. I used a standard MSD pill that I already had for the other side of my window switch.

[jerrysta]

So, which one do you recommend that I use? I want it before the fuel cutoff, which is 6k. So do I go 1 or 3 hundred less than that? I was thinking 5700 for the pill.

Let me know if that's OK.

[MN6WS6]

5700 should be fine, but there are those who run them 100 away from the fuel cutoff. I just don't trust it that much, because if you are approaching the limit quickly, you could technically break that barrier before the ignition would truly cut off. I run mine in 200 RPM increments. What you ought to think about doing is running a 6AL if you don't already have one, cut ignition 200 before the factory cutoff, and the nitrous 200 before that on your window switch.

[jerrysta]

I don't have a window switch. I have an arming switch which is run to a WOT switch.

I have the MSD6AL it just is not installed in the car yet. It sounds like I will set the limiter at 5800 in the MSD. I also have to get the fuel pressure safety switch set. Other than that, it's all installed.

Can't wait to see how the extra 100 horses affects my ETA's..

[Formulaboy95]

Start slow... try the 50 shot jets and work your way up. Also might want to add a bottle heater to that list.

[MN6WS6]

You really need a window switch. There's no sense in not having one. You don't want to ride on the limiter for very long, even if it is a soft touch one like the MSD. They're fairly cheap, and if you get an MSD one, you've already got the RPM pills for it.

[jerrysta]

The window switch hooks up to the MSD box or the CPU in some way?

What do you have your window set at? Like 2400-5700 or so, and then using the soft touch limiter above the 5700 rpm?

[jerrysta]

Do you have the MSD window switch or the NOS window switch?

[MN6WS6]

I have the MSD window switch. It gets a tach signal from the MSD, but the rest of it's wiring goes to power, ground, etc. My system is setup in stages. The switch has to be on, the car has to be at WOT, there has to be sufficient fuel pressure, it has to be within the settings on the window switch. Stages of protection like that save your engine.

[Formulaboy95]

I went with the NX window switch. 3k-5400. I didn't want to spray through the shifts.

[jerrysta]

Okay. For seventy bucks I guess one more layer of protection is a good thing.

I looked at the wiring diagram on their site and it looks pretty easy to put in too.

BTW, while reading the description of the part, I wondered how does the system know when the car is shifting? My car is an auto. It's not as if you are hooked right to the CPU. Very curious about that. The idea of not spraying during shifting sounds good, though.

[Injuneer]

It doesn't know when you're shifting. You set the upper limit to cut the nitrous off before the shift points that you normally see.

[jerrysta]

Ok, I prove my idiocy yet again!!!

On a serious note, I want to thank you guys for all of your help. I know that this could have been very difficult and expensive without your help.

Formula boy: do you find that stopping the spray at 5400 is Okay?

Lastly, Guys tell me if you think this would be OK.

I have an arming switch that needs to be switched on--

I have to open the valve on the bottle--

Only at WOT when the RPM's reach 3k window switch activates--

At 5600 window switch deactivates--

At 5800 The MSD soft touch limiter activates--

At 6000 The CPU rev limiter activates--

Anytime the fuel pressure dips below 35 psi the FPSS shuts down system--

Does this sound like everything I need to run the system properly and safely?

[MN6WS6]

That will cover it. Eventually you're going to want to get a bottle heater, so you can keep the bottle at a constant temperature for more consistent passes. On wet kits, this thing ought to be required, because nitrous pressure is directly related to what jets you need to run for a given fuel pressure. If the nitrous pressure is real low, and you spray with jetting for nitrous pressure to be at it's normal range, then you could flood the engine and wash the cylinder walls down. It's not as vital for the LT1 dry kit, but I have one anyway. I won't spray unless my pressure is above 900, usually 950-1000. Being that I'm in the south, I typically only have to use the heater in the winter time, but it's still nice to have it for safety reasons.

[Injuneer]

Maybe it sort of late to raise this issue again, because you seem to have worked your way gradually to what you plan to do...... but....

Where are your shift points right now? I would push everything up a couple 100 rpm, if it won't put you into the shifts with the spray.

Just a thought... why not:

-up the PCM rev limiter to 6,200
-set your MSD rev limiter at 6,000
-cut the nitrous at 5,800 (or 5,600 if it shifts below 5,900)

It just seems like by cutting the nitrous at 5,400 you're leaving a lot of HP on the table. The higher the RPM, the less stress the nitrous puts on the engine.