Dry shot NOS

[ert01]

Hi guys, I have a friend who is selling a 20lb tank and all the associated bits/pieces for dirt cheap and I was thinking it may be fun to throw in my Jeep for when I'm playing in the mud.

I am a complete newb to NOS however and I have no idea what it would take to install a dry system. I have the Rusty's air tube/K&N setup right now so I would assume I just need to put a port in it somewhere...

Any info/tips/install ideas would be great... time to figure out if this is a worthwhile project or not.

 

[seanyb505]

I seem to recall someone who put a nitrous system on their jeep. Ran like a 13 something, then blew up a little while later. I would google it, theres probly a crap load of info on how to set up nitrous systems, but be careful if you like your engine.

 

[j99xj]

How are you planning on adding fuel to go with that shot of nitrous?

 

[dennisgrimm]

It is a dry system. He doesn't add any additional fuel. If he was running a wet system it would add additional fuel when hitting the nitrous.

Right now you are thinking "what the hell good is additional oxidizing agent (NOS) without additional fuel?!?!". Hopefully your computer will realize you are running lean and compensate with fuel. Or you can choose to run a bit rich all of the time so there is fuel available when you need it. Hence the risk of a dry system, easy to run too lean and detonate.

Good write up:

http://www.barrygrant.com/nitrous/default.aspx?page=115b

 

[JJacobs]

It's risky. I'd feel a lot better about doing this with a carb system that was up-jetted first. The PCM can be a little slow about adding fuel with the short term fuel trim- a lot slower than your engine will decide if it doesn't like it. 75 shot's probably not enough to really worry about timing, either, but it's something to be aware of.

I run a 200 shot wet system(not on a 4.0!!!) , but this is with two step colder plugs, 5 degrees of timing backed out and a wideband to monitor the air/fuel ratio and turn the nitrous off if it leans out. Even with all this I still pull all plugs after every 1/4 mile pass and look for peppering.

It's your motor, do what you want, just be careful!

 

[ert01]

I wasn't thinking anything big, maybe a 40 or 50 shot max.

What are my options for adding more fuel to the mix? Would the stock computer handle it well enough with a small shot and compensate or should I look into something else?

 

[FoMoCo]

FWIW I saw a blower for the 4.0 that used a 7th injector for the extra fuel needs, it piggybacked off the fuel rail and was mounted in the intake tube pointed directly down the TB. I think it only opened at WOT but I'm not positive...it probably wouldn't be too tough to rig it to open when you hit the juice button

that said, I don't think the 4.0 would have any trouble with a 40 or 50 dry shot, but it basically boils down to what you are comfortable with, do the research and follow your best judgement

 

[ert01]

FWIW I saw a blower for the 4.0 that used a 7th injector for the extra fuel needs, it piggybacked off the fuel rail and was mounted in the intake tube pointed directly down the TB. I think it only opened at WOT but I'm not positive...it probably wouldn't be too tough to rig it to open when you hit the juice button

that said, I don't think the 4.0 would have any trouble with a 40 or 50 dry shot, but it basically boils down to what you are comfortable with, do the research and follow your best judgement

I really like the idea of another injector that hits at WOT with the NOS... But would it work well? Too much fuel maybe? I'm assuming I could just wire it up to the same switch that triggers my nitrous shot...

I'm pretty comfortable just running it as is... but a simple solution like adding an extra injector could be just the ticket I'm looking for to give just that little bit of insurance to the system.

 

[MudDawg]

The ole Dawg likes wet systems....sufficient fuel pressure, stable bottle pressure and a Hobbs switch set at 4 psi to shut it all down if the fuel pressure tries to falter....I have a 75 hp kit on the mighty 2.5...O-ringed head and block...all N.O.S stuff, fogger 2 nozzles....timing controller, etc, etc...but I don't recommend kicking it in low range....it will break parts....and if you break your driveline under full boost, no rev limiter is quick enough to stop the motor from spinning up to deadly rpm. Oh and also....there is no such thing as too much octane with nitrous....and with the poor quench in a jeep engine....well you need as much as you can get...I wouldn't even consider less than 116 octane....seperate small fuel cell.

The road to the best tuneup is paved with broken parts...Shannon Jenkins.

 

[Stumpalump]

Dry shot is for diesel. If you use it without extra fuel think small or tiny nozzle.

 

[Israel]

Dry shot is for diesel. If you use it without extra fuel think small or tiny nozzle.

I wouldn't say it's just for diesel motors, but they do respond to a dry shot very well.

Depending on who you talk to, wet systems can be safer since your not relying on the computer to hurry and compensate for a sudden increase in oxygen. But then others say a dry system is safer since you don't have a mix of fuel and oxygen sitting in your intake manifold waiting for a backfire.

So many opinions out there. I say read up on it and do whatever the hell you want.

 

[MudDawg]

Wet system owners make it a habit of cranking the motor over with the ignition off before actually cranking the engine....this eliminates the chance of a backfire...and NEVER operate a system under 3k rpm and/or at less than wide open throttle.

 

[badron]

Yes, you may start with a 40 or 50 shot. But the need for speed has taken over a many a brain. Out the window goes reason and soon you have a 650 pound door stop. It happens all the time with go fasters not just nos people.
On the 4.0 the stock injectors are at there limits as is. Many 4.5+ need larger injectors at just 3500 RPMs. So larger injectors or higher fuel presser may be called for.
On the dry shot I know of no way to shut down the NOS if you go bad lean. Please post if that has changed!
This is ONE big drawback to dry. But it's your air pump luck to you.

 

[JJacobs]

There's at least two ways to shut down nitrous if it leans out. One's the Prologger wideband, the other is sold by Nitrous Express. Neither is cheap.