DIY: Nitrous oxide setup for ~$100

[Daox]

I've been thinking of power adders for the Mirage lately. If you haven't seen it, the thread on compressed air supercharging is pretty interesting, and not very expensive to make up. I think stuff like a header and intake are great. I would personally love to fabricate my own header for the Mirage, and I'd also love to mess around with intake design. However, the cost per horsepower are pretty high, and the time required to do things correctly is pretty high as well. If you want a significant power increase, turbocharging or supercharging are also a great way to go. But, they cost a lot more. I believe I've found a cheaper way to eek some good power out of the Mirage. If you read the thread title you already know I'm talking about nitrous oxide.

What is nitrous oxide and how does it work? I'm sure a lot of us already kind of know, but here is a good link that describes a nitrous oxide system. I'll quote a snippet for the speed readers:

Nitrous oxide, or N2O, is made up of two nitrogen atoms and one oxygen atom. When heated to around 570 degrees Fahrenheit (gas heats up during compression and, of course, combustion), the chemical bonds holding the oxygen to the nitrogen will break, thus increasing the amount of oxygen present in the combustion chamber. With more oxygen available, you also need to inject more fuel to keep the air-to-fuel ratio optimal, which yields a more powerful explosion, which means more torque to the wheels and thus faster acceleration times. Yay!

Alternatively, you can watch a young Engineer Explained video which covers things pretty thoroughly.





So, the system is pretty simple, you got a tank of liquid N2O, some high pressure line, a solenoid and a jet. Doesn't sound too complicated right? Well, it really isn't. That is why nitrous kits start off at around $375. That doesn't seem too bad to me for a big power adder. Granted, that kit probably won't include everything you need, but thats not too bad. You can adjust how much you want to inject to get the right amount of power increase. Sounds great. But, I bet we can DIY for a lot less than $375... This is what I'll be looking into.

I think I'll end it here for now. I know its a short first post, but the next steps really get into it. I will add some additional info soon.


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Quick links:

1. Wet vs dry nitrous system
2. System overview
3. Selecting a tank
4. From the valve to the solenoid
5. Selecting solenoid valves
6. Solenoid to the intake
7. Where to inject nitrous
8. Modifying the solenoid valve - Part 1
9. Modifying the solenoid valve - Part 2
10. Making the jets

[Eggman]

Dude, that's crazy.

A Mirage on the bottle. This ought to be fun.

[stevedmc]

[Daox]

Alright, so the first step we need to look at is weather we want to go with a dry or a wet nitrous setup. All this really means is are you going to shoot just nitrous into your intake (dry), or are you going to shoot nitrous and fuel into the intake (wet).

Lets start by talking about a dry system. With a dry system, it is expected that when you activate the nitrous, your O2 sensor will see a lean condition once you jam the engine full of oxygen, and the fuel injectors will start blasting in more fuel to compensate and maintain a correct air fuel ratio. Seems nice and simple, no extra complication of having to deal with a whole additional injection system for fuel. This also makes things cheaper and easier to setup. The downside is that your fuel system has to be capable of compensating for as much fuel as is needed to maintain the correct air fuel ratio. If it can not keep up, your air fuel mixture will lean out and bad things can happen. In the case of the Mirage, we have no idea how much power the stock injector and fuel pump setup can handle. Can it handle 10% more power? 40%? We have no idea because we don't know the flow rate of the injectors or the fuel pump. If anyone does have this info, I'd be really interested to hear it. I am somewhat tempted just to buy an injector off ebay and send it in to Witchhunter Performance to have it flow tested. Alas, I doubt I'll do that.

Now, lets look at a wet system. In a wet system, when you activate the nitrous, you spray both nitrous and fuel into the intake at the same time. The jets or nozzles for the nitrous and fuel are sized in such a way that maintains the correct air fuel ratio. Your fuel injectors just do minor tweaking as the ECU sees fit. In this case, your engine never goes lean at all which I kind of like. It also bypasses the injectors as a possible bottleneck in the fuel system. As long as your fuel pump can supply the fuel necessary, you can keep bumping up the amount of nitrous/fuel and thus power along with it. So, this setup has the possibility of much higher power output than a dry setup. Of course, it is also more complicated and expensive with more parts.

As of right now, I think I would lean toward a wet system. I wouldn't want to be restricted by the flow rate of the fuel injectors. I'm also guessing, but I imagine that the stock fuel pump is probably oversized. I know that is the case for some other small cars. So, the probability of getting a good amount more power is much more likely with this setup. Worst case the fuel pump has to be upgraded, and that isn't too hard or expensive. Also, since it won't be asking the fuel injector to blast fuel in, there is less chance of of some weird effects there with fuel trims and tuning stuff.

[Loren]

I still go by the "20%" theory. There should be 20% of headroom in the stock fuel system. And the rest of the drivetrain should also be able to handle 20% more power without issue.

I'd keep things simple and go with a dry setup first. Something that will peak at 20% more power, but is adjustable, so that you can start with a nice safe 10%, and then dial it up as you watch or log your AFR.

If you get 20%, you'd be at 89 hp. I think that's a difference you'd readily feel, and for a minimal investment.

Then, if that's not enough, you can look at switching to a wet system.

[Daox]

Thats not a bad idea. Its a good and easy place to start.

[Daox]

I think we need to go over the whole system in a bit more detail to see what we’re looking at. The first post went over the brief overview, but there is obviously a bit more to it when you are building your own system vs just buying a kit. Lets start with the tank and work our way towards the engine’s intake system because that just makes sense to me. Also, I’ve gotten most of this information from Nitrous.info. The site is full of very helpful information on DIY nitrous oxide systems for motorcycles and cars.

The tank is well, a high pressure tank. The tank has to handle a bit over 1000 psi of pressure. Nitrous oxide tanks are basically the same thing as CO2 tanks, but with a different valve. However, CO2 are much more prevalent (and thus cheaper). CO2 tanks are pressure tested to 3000 psi, so they’ll easily handle the job. Also, all CO2 tanks have a burst valve which is rated for something less than 3000 psi. If the tank pressure gets too high, this valve literally bursts and vents the contents of the tank to keep things safe.

Next up we have any adapters that will be needed to convert the tank fitting (whatever it may be) to the high pressure tubing fitting. The adapter(s) also need to be rated at very high pressures since they will also handle that ~1000 psi between the bottle and the solenoid valve.

That leads us to the high pressure tubing. This is braided stainless tubing. It also is a tubing that has to be rated at 1000+ psi since it is handling the full pressure of the bottle. Not the cheapest stuff at ~$5 per foot from mcmaster-carr (I’m sure there are cheaper places).

Next up we need adapters again to convert from the braided tubing to the solenoid valve. Again, the fittings must hold up to 1000 psi and convert from the stainless tubing fittings to whatever the solenoid valve has.

The key ingredient that we need now is a nitrous solenoid valve. This valve has to be able to switch that 1000 psi on and off which is no simple task. That is a lot of pressure to open against. Typically, these are a bit pricey, but I’ll show you how we’re going to find one for under $20. We’ll go over this one in a lot more detail as we get to it.

Next on our parts list is a jet. This item will regulate how much nitrous flow we get, and thus how much horsepower we’re going to make. Nitrous.info has a beautiful chart showing how much power you make for different nozzle sizes. It shows what size nozzle for nitrous and for fuel if doing a wet system. We will be making our own nozzles as its much cheaper. So, we can select whatever amount of power we want by swapping out this one part (or two parts if its a wet system).

Next we need more fittings to hold the jet, and also to convert from the solenoid and jet to the lower pressure tubing that will go to the intake of the car. This of course means we’ll need lower pressure tubing, and also some fittings to connect the tubing to the intake.

Last up, we’ll need to wire things up. At the least, we need 12V power, an arming switch to confirm we want to use the system, and an activation switch to open up the solenoid valve.

Here is an example diagram I threw together to roughly illustrate what we're looking at.





These are the parts required for a dry system. If we want a wet system we will also need these parts.

A tee or tap of some form to get fuel from the fuel line to our fuel solenoid valve. The fuel pressure in our cars is a normal ~45psi. So, we aren’t dealing with any crazy pressures. Just about any ‘ol fitting will work here as long as we use clamps to hold it in place. I imagine a brass barbed fitting will be suitable.

Tubing will be needed next to bring the fuel from the tee to the fuel solenoid valve. Again, anything rated for 60 psi and that will hold up to gasoline will be fine. Rubber fuel line is a good inexpensive choice, but plastic line is fine too.

We need fittings to convert the rubber or plastic line to whatever fitting the solenoid uses. I imagine again brass barbed fittings.

Now, we need the fuel solenoid valve. Again, since we’re dealing with only ~60 psi, this isn’t nearly as hard as finding a solenoid valve that handles 1000 psi. We just have to find one that has seals that can handle gasoline.

Next up is more fittings to convert to low pressure tubing like we did on the nitrous side. And, we’ll also need fittings to convert the tubing to the intake system.


Phew, that is a lot of parts! Next up, we will start going over how to select each component of the system.

[Loren]

I'm gonna mostly stay out of this topic. Nobody allows NO2 to be used in autocross, so I have no interest in it.

But, I will throw out the safety reminder that NO2 is pretty hazardous stuff! Besides the fact that you can easily damage your engine if you're not careful, any problems with the system can result in fires, and anytime you're dealing with high-pressure, there is potential for things to blow up.

For that reason, as a noob to the world of NO2, I wouldn't dream of building my own system. Just pony up and buy a small kit and be done with it. You'll get everything you need, it will be a properly engineered and tested system.

This stuff can kill you!

[Fummins]

Yup, I'd just buy a kit. Zex makes a cheap simple one. I've installed a few a long time ago. I had a friend who rigged up a dry shot with a big nozzle that was just on a momentary switch. It lasted a few months til a whoops happened and it started knocking. Then the rush was on to remove the evidence so the dealer would warranty an ls2 lol

[Daox]

Awww, thats no fun. Gotta figure out all the fun bits and learn how it works. Well, thats how I like to do it at least.

BTW, this is being done. I've already ordered parts. The total cost for the system is going to be about $100. For that price, I couldn't not do it...