Nitrous on 2.5 Drag

[CI STV]

Michael Dixon ran nO2 on some of his drag STVs and won a lot of races. He was an innovator at the time and used a progressive system that injected it in stages, as opposed to all at once. But, i don't think he ever ran a slide. If I'm not mistaken he injected it into the horn. If you could get a chance to talk to him you could get a lot of questions answered on the tech side. He's out of racing now but hasn't forgotten much.

Yep, he certainly is a very knowledgeable fellow and his accomplishments attest to that. Very nice guy too. He actually sent me a PM on this forum and gave me advice on setting up the boat (setback, gearcase height, etc.) back when I was putting it all together. There’s some very savvy guys on here, which is why I started this thread.
I honestly wish I had used a progressive controller instead of just a window switch, because that would also be easier on the motor and gearcase, and the newer controllers have a built-in window switch function anyway. I was trying to keep it as simple as possible and a window switch is a bare necessity on any setup, IMV. Same goes for a WOT switch.
I have used a number of different progressive controllers before on cars, and I currently have a NOS mini progressive on my race car and it’s an amazing little gadget.
NX also builds the simplest progressive of all, which simply replaces the relay and has a very simple single dial that allows you to set the time you want it to pulse the solenoids. I have one of those on my Vette along with a window switch, and it works great. I might just buy one of those and plug it in, since I wouldn’t have to change any of the wiring.

[25two.stroke]

The spray bars do not carry jets, they have drilled offices in the bars themselves. No solenoids. If I remember to take pictures I will post them. They are long...the whole height of the slide. If I use it ever I would mount it with a 1" spacer to get it away from the reeds. I assume the less you spray the more consistent it will be across all the cylinders on a non adjustable system like I have? Is that correct?

[CI STV]

The spray bars do not carry jets, they have drilled offices in the bars themselves. No solenoids. If I remember to take pictures I will post them. They are long...the whole height of the slide. If I use it ever I would mount it with a 1" spacer to get it away from the reeds. I assume the less you spray the more consistent it will be across all the cylinders on a non adjustable system like I have? Is that correct?

I’m thinking the if the nitrous volume is regulated by the orifices in the spray bar, then the smaller those holes are the better distribution you should get across the length of the bar. In any event, I think the distribution problem primarily occurs when you activate the nitrous and then once the bars fill with nitrous and fuel, the flow evens out.

[tlwjkw]

here's what ya lookin' for... we used basically same thing on 7 petal 2.4 carb motors...

Nitrox nitrous system

[CI STV]

here's what ya lookin' for... we used basically same thing on 7 petal 2.4 carb motors...

Nitrox nitrous system

Yeah, a friend of mine has one of those old Nitrox spraybar systems, but it looks pretty damn old. I much prefer the nozzles to spray bars. On a horn motor you could do one nozzle in the side of the plenum for every pair of intake slots, since each nozzle can flow enough for 150-200 hp.

Here’s another nice option option which I was first contemplating using, which should work and is a very reasonable price too:

https://inductionsolutions.com/shop/...oat-plumb-kit/

BTW: IS/Steve Johnson is one of the baddest nitrous kit builders and tuners in the world and he makes quality parts. I have a Holey Moley plate system on my race car from him that can flow up to 640hp with a single pair of jets. The jets are special wide body jets, the largest one having a .173” orifice, IIRC. The “Trashcan” nitrous solenoid that came with the kit is about the size round of a beer can.

[tlwjkw]

lotta improvements over tha years.... you can make 'em live long nowadays as ta what we had ta deal with 20 + years ago..

[CI STV]

lotta improvements over tha years.... you can make 'em live long nowadays as ta what we had ta deal with 20 + years ago..

Yep, and one of the biggest changes is the jetting. Back when I started messing with Nitrous back in the late 80s, the jetting on a NOS Cheater kit called for bigger fuel jets than nitrous jets at every hp level. Nowadays it’s the opposite and the spread between the N2O and fuel jets is pretty big, even on the carbed kits.
That’s because guys like Monte Smith and Steve Johnson figured out that we were using way too much fuel augmentation, and that the key to making power safely wasn’t running rich, it was pulling enough timing on the juice. A nitrous motor doesn’t need nowhere near the amount of timing a N/A motor needs, as the fuel mixture burns much faster when you introduce nitrous in it.
And it’s not just the nitrous system that they figured out, it’s how to build an engine to run on big amount of nitrous. Things like combustion chamber shape come into play. And cam/valve timing, which we can’t change on a two stroke without changing port timing. Makes me wonder if any of those boys that ran really big nitrous on their 2.5s experimented with that…

[rjdubiel]

The spray bars do not carry jets, they have drilled offices in the bars themselves. No solenoids. If I remember to take pictures I will post them. They are long...the whole height of the slide. If I use it ever I would mount it with a 1" spacer to get it away from the reeds. I assume the less you spray the more consistent it will be across all the cylinders on a non adjustable system like I have? Is that correct?

[CI STV]

Thanks for posting these pics. You can see from those photos that the holes in each the two spray bars, one of which is for the fuel and the other is for the nitrous, are angled towards each other.
but it’s a pretty wide angle and the two spray bars are about 1.5” apart, so the intersection point of the nitrous and fuel would be somewhere in the area of the reed cage.
To me, that’s part of the problem with that design as you want the nitrous and fuel to mix, although bearing in mind it’s going into a crankcase with a swinging crank that’s going to mix everything anyhow.
Still, I much prefer using the nozzles which mixes the fuel and nitrous at the discharge point.

[rjdubiel]

I also ran this on an old OMC with the foggers. But basically the tubes are the easy way! different size holes for different HP and all that. Nitrous is fun!

[Chaz]

So much to cover ... LOL
Lets start at the discharge point and work backwards. Since the cylinders are stacked vertical you must first fill the tubes / lines before anything comes out. The larger the diameter , the longer it takes to fill. Spray bars tend to pulse / phase change between the last hole and the end. thats why you see a solenoid at each end of modern plenum systems. They also have hardware to jet them. The worst thing about them is when you stop spraying ... it's like a straw you take your finger off of. Everything runs to / out the bottom. So less length, smaller ID is always gonna be better.

Lack of ring gap and too much timing are where I have gotten in trouble before.

Excessive oil in the hole is not your friend either. Kills octane and promotes detonation

I ran the numbers mentioned .. I targeted 6 / 1 N / F ratio @ 55 psi (top line is base it spit out)

.009 fuel



.012 fuel

[Stoker boy]

Nitrox systems products always work great for me. Have run them for at least 20+years.

[CI STV]

Nitrox systems products always work great for me. Have run them for at least 20+years.

Do they still exist? I read on here a while back that Chuck Goodman had passed away. I can’t seem to find anything that indicates that the company still exists?

[CI STV]

So much to cover ... LOL
Lets start at the discharge point and work backwards. Since the cylinders are stacked vertical you must first fill the tubes / lines before anything comes out. The larger the diameter , the longer it takes to fill. Spray bars tend to pulse / phase change between the last hole and the end. thats why you see a solenoid at each end of modern plenum systems. They also have hardware to jet them. The worst thing about them is when you stop spraying ... it's like a straw you take your finger off of. Everything runs to / out the bottom. So less length, smaller ID is always gonna be better.

Lack of ring gap and too much timing are where I have gotten in trouble before.

Excessive oil in the hole is not your friend either. Kills octane and promotes detonation

I ran the numbers mentioned .. I targeted 6 / 1 N / F ratio @ 55 psi (top line is base it spit out)

Thanks Chaz.

That looks like a much more complicated nitrous calculator than I’m used to…

I agree that spray bars are the less ideal way to do it, but a lot of us guys that run superchargers and nitrous (a particularly dangerous combination) make it work. I’m not so sure that siphoning is a real concern when the solenoids slam shut at the end of a run. I certainly don’t see (on datalogs) or feel anything like a rich surge at the end of a run.

Why do I say this? This is admittedly only based on my very limited personal experience: The spray bars on the kit on my Vette are very long, and there’s a lot of additional tubing between the solenoid (where it’s jetted) and the spray bars themselves, and I can attest to the fact that it works fine.

Here’s a few pics to help explain what I’m talking about:

As you can see from those photos, the spray bars are about 16” long, and with the additional stainless tubing and another 12” of hose, once the nitrous is activated the nitrous and fuel has to travel probably 18-24” to get to the first set of holes and another 12-14” to get to the end of the spray bars.

But, somehow, this thing works flawlessly, without any sign of uneven distribution or surging, etc. And I’m using small jetting (~75-100hp) on it, simply because it’s a stock LS3 bottom end and it already has 13psi of boost (and its breaking loose up to 95mph anyway, according to my datalogs). Of course, good fuel (VP X85) helps as well as low timing (14-16*) depending on weather conditions.

Would a set of 8 nozzles in the side of the manifold be better? Absolutely. It might get that one day too, whenever the track here reopens.

But based on this, I wouldn’t have hesitated to use a spray bar system. Truth is I’m only using the fogger nozzles and nylon/showerhead distribution system because it was easier for me to do myself.

I wholeheartedly agree that too-tight ring gaps are a real problem, and that has ripped many a ring-land off a piston. I learnt that years ago with some 225hp jetting on a cheater kit I had on a 1989 305 in my Camaro. That was my first nitrous motor kill. It lasted surprisingly long, to be honest. Shamed a lot of fast guys with that old 305.

The second one was the replacement ZZ3 crate 350 I bought from Chevy a few months later, with some of those new-fangled hyperuetectic pistons. A stuck fuel pressure reg and too much timing reduced those pistons to dust. It even stuck a wrist pin through the block and folded the con rod over the crank and locked it tight. That was my second and last failure on a nitrous motor. It was spectacular though. Never knew a metal hood could flex like that one did when it belched a sheet of flame out the cowl.

After that, I stopped listening to what the local gurus recommended and read everything I could find on nitrous, and eventually joined Yellowbullet forums and I learned a ton more from the guys on there like the aforementioned Monte Smith and Steve Johnson, who have along with a bunch of others, revolutionized nitrous.

But this 2 stroke thing is new to me. Hence this thread.

Big thanks again to everyone who’s chimed in. My head is now spinning with all kinds of ideas. Probably some bad ones too.

Like: how can I a shifter solenoid to reduce my timing when the nitrous is activated…?

[scott reierson]

Me too they worked great.

Nitrox systems products always work great for me. Have run them for at least 20+years.