Nitrous Oxide Info

Last updated: December 2, 1997

Date: Wed, 05 Apr 2000 14:07:21 -0500
From: "Rick S." (
Subject: (rx7) (3) Zex Nitrous Experience

I wanted to pass on to anyone interested an update on how the Zex Nitrous System is working out on my 3rd Gen. It has been about 6 months since the installation was completed.

It is currently jetted for a 55hp shot. I have not tried any of the other settings yet. I have gone through about 6 bottles of N0S so far. I am finding that a refill runs about $25. Zex claims approximately 3 minutes of use on a full bottle. I find that I rarely get into N0S for more than 3 seconds at a time. Typically I will not spray in 1st or 2nd gear. I can't keep from spinning the 275/40/17 A032Rs at anything but 3rd on. The system is activated by 4.6vdc at the TPS. This roughly equates to about 90% throttle.

I am closely monitoring fuel pressure and AFM for any signs of going lean. I usually run at 12psi w/N0S, but have had it up to 15 psi. At no point have I ever seen anything but full green and plenty of fuel even up to 15 psi. The system has run flawlessly and I am quite happy with its performance.

I would not recommend using this system without some fuel, ignition, and computer upgrades. I think the key to having plenty of fuel was the addition of the RP fuel pump. I am not sure if others are seeing the same pressures as I am, but at idle I see 38 psi and then at 0 psi of boost it jumps to 41 psi and then 1 psi of additional pressure for every lb of boost thereafter. The Zex adds approximately 15-20 psi additional fuel. I have seen the fuel pressure rise up to 74 psi at 15 lbs. of boost.

On the dyno the car made 371 rwp at 12 psi. I have not dynoed at 15 psi, but it feels real strong at that level.

I have not heard from anyone else that has installed the Zex. I would be interested in others experience with the system. I spoke with Zex and they will have the Relief Valve Kit available this month.

Install instructions from Rick.


Got this as a humor article, but there is good tech info on nitrous. I cut that out and pasted it below. I also included the humor below that. --Steve

A Really Short Course on N20 (Nitrous Oxide)
by Mark Grubelich

Editors note: We met Mark Grubelich, a rocket scientist for Sandia National Labs. (no kidding) during the One Lap of America, where we competed against his 440 Challenger. Recognizing a similarly sick mind at once, we promptly struck up a friendship. The result? Mark has crossed that invisible line that delineates the boring white-shirt-and - -tie guys at High Performance Mopar to the "we'll try anything -- once!" Mopar Action mavens. In other words, welcome to our team, Mark! - -- R.E.

All internal combustion engines require air to operate. More specifically, they require oxygen (O2). Air is composed of approximately 20% oxygen and 80% nitrogen by weight. Simply put, the nitrogen in the air does not take part in the combustion process, but is merely heated by the combustion of O2 with a hydrocarbon fuel such as gasoline (C8H18, iso-octane). Steam, hot CO2, and hot N2 then expand to push the piston down. Therefore, if we could replace or add additional O2 to the engine and burn that O2 with more fuel, we can make more power. In theory, if we replace all the air with pure O2, we could get 5 times the power out of an engine by being able to burn 5 times as much fuel per power stroke. In practice, we would blow up the motor at startup.=20

Nitrous Oxide allows us to significantly increase the output of an engine without blowing up the motor, up to a point. Past that point, it's like trying to put 6 pounds of sand in a five pound bag: the bottom falls out. Over-nitroused motors cause piston crowns, ring lands, pin bosses, and rods to collapse. Don't over-nitrous! N20 primarily increases engine power by supplying more O2 to the engine. N20 is 36% O2 by weight, whereas air is 20%. A motor running on pure gaseous N20 could make 1.8 times more power than if it ran on air.

If we inject liquid N20 into the engine, we can make substantially more power than this because the liquid nitrous is many times denser than air. Inject liquid N20 into the engine displaces only a small percentage of the air. The liquid N20 rapidly evaporates upon reaching the cylinders during the compression stroke. With the valves closed and the cylinder sealed, the initial cylinder pressure is increased before the combustion process starts. (This is similar to the process of supercharging an engine.) All we have done is cram in more N2 and O2. We must add more fuel to burn with the additional O2. If we don't. the additional O2 will react with the piston crown or exhaust valve like a cutting torch.

So there you have it: you put more fuel, oxygen, and nitrogen into the cylinder and you make more power by raising the cylinder pressure. Supercharging in a bottle. But wait -- there's more. With the increased oxygen percentage in the cylinder (remember N20 is 36% O2 whereas air is 20% O2 by weight), the combustion temperature and flame propagation rate can increase dramatically. In order to compensate, we must provide excess fuel as coolant and retard the timing or use a slower burning fuel.=20

The theoretical stoichiometric nitrous to fuel ratio is 9.75 lb or N20 to 1.0 lb of C8H18 (gasoline) of 4.13lb N20 to 1.0 lb of CH3OH (methanol). This will result in maximum power but will also produce unacceptably high combustion chamber temperatures. As mentioned above, we must run additional fuel to cool the combustion process. How much?=20 A reasonable starting point is 100% excess fuel (twice as much fuel as the combustion process requires). In other words we would run 4.82 lb of N20 to 1.0 lb of gasoline, or 2.07 lb of N20 to 1 lb of methanol. The reversed ratios are 0.21lb of gasoline or 0.47 pound of methanol to 1lb of N20. Using less excess fuel will result in more power but higher cylinder pressure and temperature.=20

How much horsepower can we make? A rough rule of thumb is that if we inject 5lb/min of nitrous into the engine with the appropriate additional fuel, we will make an additional 100HP. Another rule of thumb is to not drop below 50% excess fuel unless you know exactly what you are doing. Don't add more than 0.3HP/cu inch of engine displacement to a stock (cast piston) motor. For example, for a 120 cu inch motor, 120 cu in X 0.3HP/cu in =3D 36 HP. For a 440 cu in motor, 440 cu in X 0.3HP/cu in =3D 132 HP. Retard the timing 3 to 4 degrees per 0.3HP/cu in. Don't use a slower-burning fuel such as alcohol unless you know what you are doing. Don't engage the system below 3000 RPM. Always flow-test your nitrous system and fuel system to insure proper fuel and N20 flow. Don't ever run a nitrous system into the engine rev limiter. With ignition cut outs, dangerous levels of N20 and fuel will build up in the exhaust system, and with modern computer-controlled fuel shut offs, the motor will run excessively lean. Back off before you hit the engine rev limiter or install a safety switch switch turns the nitrous system off before the rev limiter engages.

But, most of all, have fun!


From: Buras, Keith
Sent: Tuesday, August 11, 1998 5:21 PM

Well, I might be installing a Nitrous Express kit on my 93 Touring, partly because it is an automatic and partly because I don't want to do too much to the car that would make it hard for my warranty company to fix anything. I figure if the engine goes out then I'll be able to get it fixed right next time. They allow me to go anywhere I want.

I would run a fuel pressure safety switch that would cut the nitrous off at a preset pressure 30-35psi. A little safety net in case the fuel system malfunctions.

I've talked to NX people about 10 times and NOS people about 10 times. Very little info on using these kits on 3rd Gen RX7. I even talked to a NOS distributor, St. Andres, they recommend only using the NOS brand 50 hp kit with a boost switch to cut of nitrous after the car reaches about 7 lbs of turbo boost.

There was one other person on the list that had a NOS Sportman Fogger 80hp, but decided to trade it in for a ECU upgrade. He apparently did not like spending $70 for a bottle refill (not sure where he lived, it's only $30 here) and the bottle was always empty when he needed/wanted it.

I think I will stick with a 50 hp kit and move up to 75 later. IF I decide to go this way then I'll keep you posted of my results.

I do know that Nitrous Express did a test with their kit and the NOS brand kit. They tested both 75hp brands on a 95 non-turbo Eclipse. The NOS brand made an additional 48 rear wheel hp, while the NX kit made an additional 74 rear wheel hp, with less nitrous and fuel. NX rates their kits at rear wheel versus everyone else's at the flywheel. They also did the same test at 100hp on a late model Mustang and found even better results. All this info can be found at their web site.


The humor:

See: the full story and pictures.

Mopar Action, April '98, pp 21-23

Say 'Bye to Neon

Story by: Richard Ehrenberg

Ever want to nitrous your ride, but were afraid you'd grenade your mega-dollar motor into smithereens, or trash your daily driver? Well, fear no more. For the measly sum of $19.95, we can absolutely guarantee that you won't blow YOUR motor. How? Heh heh heh. Just rent a car from your local, smiling Thrifty agent (we highly recommend the sunny Phoenix locations.) His motor + your nitrous system =3D no problem. Experience the thrill of nitrous, totally uninhibited. No longer will you feel the urge to back off because you're afraid of scattering YOUR dollars along the side of the road or at the strip. It's like hot fudge sundaes without the guilt. Mopar Action's staff, the same people who brought you the Rental Car Nats and the famous "push-o-war" (nose-to-nose burnouts), are out on a brief furlough from Nurse Ratchet's psycho ward, and will outdo themselves again by showing you how to knock over 3 seconds off a bone stock Neon. Yeah, you got it! 16.90 @ 81MPH to a zero-traction 13.82 @ 102. Have we got chrome-moly spheres, or what?

We slammed together a supersimple N2O system for our bone stock 3-speed automatic rent-a-Neon (with 13-inch wheels!!) The setup consisted of readily available parts from the NOS nitrous catalog and the local NAPA parts store. Our goal was to make no engine mods and unbolt nothing from the car during installation. In other words, we wanted to be smarter than O.J., and leave no incriminating evidence behind (is America a great country, or what?)

The system consisted of an N20 tank held in the back seat by the lap and shoulder belt, a length of braided hose laying on the carpet, and routed through the unused clutch-cable firewall hole, the cheapest electric fuel pump we could find, nitrous and fuel solenoids and two simple injectors. The injectors consisted of nothing more than two short lengths of 3/16" brake line tubing with the solenoids attached at one end and 2 NOS-modified "AN" fittings that accept NOS nitrous and fuel-metering jets on the other end. A painless incision into the soft plastic air box hose allowed N2O and fuel to be injected directly above the throttle body. The whole deal was held in place by duct tape and cable ties. Replaceable jets allowed precision tuning of the system to any level of insanity desired.=20

Auxiliary fuel (alcohol "drygas") was stored in the windshield washer reservoir and the small electric pump was added to supply fuel (the windshield wiper fluid pump will not supply enough fuel) to a solenoid. This setup was rigged into the horn wiring to open the solenoids when you punch the horn button (we did disconnect the horn button).

So how did it work? Awesome. Simply awesome. We started out with a 50HP nitrous jet with 100% excess fuel. Hitting the horn at 4000RPM in 2nd gear felt like 15 lbs of boost. Were we happy? Nope! Onward to the 75HP jet and only 50% excess fuel. The Neon was amazing. We worked up the guts for 1800 RPM launches in first gear. Oops=97out of nitrous, before you can say: "Thrifty." Luckily, we had brought a second bottle.=20

The entire Mopar Action staff flogged the Neon mercilessly, but we couldn't break it (yet). They high (low?) point came when "Crazy" Eddie Yeznaian, intrepid rally racer and wildebeest extraordinaire, actually power-braked the car to the floor, cut the wheel to the left, and hit the nitrous in reverse. Nothin' like nitrous doughnuts after a hard day at the office! (Since this was done in the rain, does that make it Dunkin' Donuts?) If you can imagine what it must be like to be trapped in a spinning top at 200 RPM, you get the idea. Where are the air-sickness bags for this ride? H-E-L-L-L-P!

After the second full 10 pound bottle of nitrous had been greedily half-guzzled by the motor, we decided to go for broke before it was empty. We slipped in the killer 150HP jets. Is this sick, or what? We more than doubled the stock HP output! Jeeez! 13.82 @ 102mph. The motor took first gear launches at 2000RPM with cylinder pressures that should have shot the plugs through the hood, and exhaust gas temps that were slightly hotter than the surface of the sun.

Could the Neon go faster? And, mainly, would the converter stay in the transaxle, or launch like a Saturn rocket and slice our legs off at the knees? (And, do they rent hand-control Neons?) For our last runs of the day, we leaned out the fuel jet for only 5% excess fuel and stuck our guinea pig editor, Cliff "Pleeeeease don't blow the motor, guys!" Gromer behind the wheel. For his first duel, Cliff matched himself up with an automatic Mustang GT at the track. The pony car came out of the shoot even with the Neon, and pulled ahead by the 300-ft mark. The Neon, now in second, gets juiced by Gromer. Result? Like taking candy from a baby. Cliff's little rent-a-PL was so far out on the 'Stang that he was able to back off in third, turning a 14.15 at 96.7.

Later, in an impromptu street run from a 10mph roll-on, Cliff, the sick puppy that he is, hit the horn button in first gear, right on the "3" count, the 2-liter Twinkie motor screamed for mercy, the tires spun all the way through first gear. We were fender to fender with a fast 440-6 Challenger R/T. He ripped his piston-grip to second, but we pulled ahead. Clifford boiled the tires big-time into second gear, allowing the R/T to pull alongside. The Neon mini-motor wound tight-right to the rev limiter. Did Cliff lift? Did he back off? No chance! Ka-boom! A glowing three-foot fireball barked out of each side of the hood, and rolled back over the windshield. Cheeez! This actually caused the R/T driver to lift, but not Cliff! Wow. Say goodbye to Neon.

We pulled over, fully expecting to see rods hanging out of the block. Surprise. Only the airbox is blown apart. With the leaned out fuel system and the motor running so far into the rev limiter that the stock injectors were shut completely off, we musta floated the valves and backfired through the intake system. The motor was running a little rough (a slight understatement) and we're sure we bent at least one valve, or, more likely, blew the head off of a couple. Guess we should have followed Mark's rules (see sidebar). Needless to say it was the best $19.95 we ever spent. We gassed the Neon back up and limped back to the ever-smiling counterperson.

Thanks, Thrifty.

By the way, if you're interested in renting a Neon for $19.95 a day to go mustang hunting, Performance Resource is currently looking into marketing a complete nitrous kit (minus the bottle) that is jetted and flowed, and that you can bolt onto your rental Neon (or your own Neon for that matter) in less than an hour. Just so there's no misunderstanding, the kits are not available at this time, but they can be whipped together if there's sufficient interest out there in Neonland.

Contact: Performance Resource
12 Barbara Drive, Fairfield, NJ 07004


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