Nitrous Oxide


The first time I heard, or for that matter saw what Nitrous oxide did, was watching a Havoc Movie on a lazy Saturday afternoon maaany moons ago. Well they showed a Drag rail do the Burnout then Stage and launch Hard. A short while later there was a big bang, and the GM type Supercharger bolted on top of the motor, Rocketed Skyward nearly taking a ABC Television Chopper out. We laughed and reached for the next Beer.


Years later I was staying in Denmark and a friend of mine tried building the worlds fastest wreck (or so it seemed at the time). It was a Honda Civic modified to the hilt by yours truly and Pushing out 250 HP at close to 2 Bar boost. Frightening? No way, we decided a 100 Hp Nitrous Fogger system would give us 350 to 400 Horses on the squeeze- now that’ll make any granny shake! OK since I had set up the EFI system we decided to go that way. I read a few books dealing with N2O and phoned suppliers of giggly gas systems- not much help.

So I decided on the following; once the system switch was armed and as of ¼ throttle the Fuel Injectors would remain open completely and the Nitrous Solenoid would get triggered. Once we had Nitrous pressure at the Foggers my Fuel pressure would increase to 60 lbs. (from 40). I would then re map the fuel curve with my laptop in the car. Figuring fully open injectors at 60 lbs. is 50 % more fuel than I needed. Both of us racing Group A at the time made us think we were fit and Quick enough to catch the Fuel Curve.

One cloudy afternoon we got onto one of these narrow country lanes which separates the villages, being round about 7 Km long and reasonably straight. Speed limit was 80 or 90 but we knew that nobody would patrol such a peaceful stretch. We accelerated up to 200 Kph (because N2O would not have such a brutal effect at that Engine load). Got the car to coast, armed the system and accelerated. At first the car Bogged as it overfueled and then the Front tires broke free as PLENTY of horses took their toll. Our conversation is unprintable but we decided that he would try and control the car while I tried mapping the Fuel system. Hey and we picked up power and with a bit more tuning even more power. Imagine me just concentrating on the Motor and Engine management while my Buddy tried to keep the Toad on the Road.

I have no clue on how fast we went, but I know all of a sudden he got of the Gas telling me to shut down systems a Town is coming. We both relaxed. For a fraction of a second, until we realized we did not have all Power left, but still Plenty- the Nitrous Solenoid must have Frozen up.  I did not want to decrease fuel delivery, being scared that the Engine might blow and at the time did not think of Cutting the Spark. I don’t know what the people of the town must have observed, but I know we must have sailed through there at a Hundred and plenty.


So what has nitrous got to do with drug free Namibia- not much except, do not consider it as an option just because you want a bit more power for overtaking.


N2O is 2 Parts nitrogen per part of oxygen (Atmosphere is 21% Oxygen). It is this Oxygen that is released at 572 F that aids Combustion. I find it easier to envisage us injecting too much fuel and we need the Oxygen in the N2O to get the engine to run “Right”. Ideal would be Stoichiometric (9.6:1) but normally far more fuel is added (up to 4:1) to reduce “Lean out” and to cool the motor with raw fuel.


The oxygen accelerates the Combustion process tremendously with associated increased Temperatures. While the remaining Nitrogen slightly retards Flame Travel (Aha Flame Propagation) giving us smoother power. Things like that should trigger a different way of thinking- Cam, head design, timing and Porting for Nitrous vs. Normally Aspirated. Through Better Fuel distribution and Atomizing associated with Nitrous, we have Engines that tend to last longer than their equally powerful non-nitroused motors.


 Nitrous can be pressurized over 1000 Psi at 100 F and when it gets released into the intake it has such a massive pressure drop that it drastically “cools” your Incoming charge (remember your PVI formulas?). Since theoretically your engine picks up 1 % Power for every 10 F drop in temperature (and Nitrous at the nozzle is 128 F below 0 F) this means massive POWER because your charge is denser- remember the turbo intercooler? Power increase is normally a result of the BMEP (Brake mean Effective pressure) increase within the Combustion Chamber. So lock your Head to the Block and remember more Pressure means More Temperature as the Volume inside the head tends to remain the same. Please remember this when building your Motor, so you will not “loose” it within seconds of hitting that switch!


As bottle Temperature rises, its internal pressure rises too, making a massive difference in Nitrous Feed at the Nozzle. Therefore Pro’s normally run at least 2 Bottles in a Controlled Environment. Also remember as you use up N2O the Bottle Pressure Drops, resulting in less Nitrous to emerging at the Nozzles. Finally you have to realize that your Fuel amount Injected in your Motor remains reasonably constant through most of this time- so how are you going to jet?


Nitrous can be injected like Fuel either at a Single point (usually under the carb through a Plate Arrangement) or a Nozzle before each valve. But Nitrous is released through a Solenoid making it a “All or nothing” affair. This Normally means we also add a Fuel Solenoid that then adds All fuel at once at the same time from a separate Fuel supply system. It is Crude, but it works. Sorry if I shattered your cheap dreams of Cruising Indep. Ave. with mum’s Escort and Blow the Mustangs away at the Robot at will. You need at least 6 grand Cash to start of with the Nitrous parts as such. And a whole lot more, if you want to build a real “Ferrari eater”. Power still costs Money. How fast do you want to go?