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Nitrous for a 6A

Cadstat

Well Known Member
I want to consider adding nitrous to my 6A 320 CS just for take off. I don't want to over boost just gain back some lost horse power. In the summer, density alltitude is often 6500-7000 at our field. What do you think?
 
See Ernie Butcher

Ernie posts on this site and was involved in the "Flyin Tiger" modified RV-4 system. It has been done.

Bob Axsom
 
...What do you think?

I think that by the time you get the system debugged, and also repair the damage done to the O-320 by the early tests, you'll have spent about 1.5 times the money and work that it would take to upgrade to an O-360.

Seriously, it's tricky stuff to use properly; you don't just squirt it in and get a boost. You have to simultaneously increase the fuel flow to match the increased oxygen.
 
One often overlooked side benefit to NO is the cooling of the intake tract, and combustion chamber.

The modern automobile systems are pretty foolproof, just hook them up and go----they are usually set up on the rich side for a safety margin.

IIRC, the air force did a lot of testing of this around WW2.

Good luck
 
I think that by the time you get the system debugged, and also repair the damage done to the O-320 by the early tests, you'll have spent about 1.5 times the money and work that it would take to upgrade to an O-360.

Seriously, it's tricky stuff to use properly; you don't just squirt it in and get a boost. You have to simultaneously increase the fuel flow to match the increased oxygen.


Concur. By the time you've tweaked the fuel system to support it, assuming you're using a dry system and invested the time and money to make everything work (assuming you don't destroy the engine), you'll wish you just bolted up a new 360. Plus you can recoup a lot of the cost selling the 320.
 
I want to consider adding nitrous to my 6A 320 CS just for take off. I don't want to over boost just gain back some lost horse power. In the summer, density alltitude is often 6500-7000 at our field. What do you think?

I think its a great idea.
Make it happen!
Nah sayers are a dime a dozen.
If your motivated, you can do it.
 
Nay sayers... with tons of experience dealing with Nitrous set ups in cars.

The ignition timing, mixture, nitrous window, all need to be timed perfectly. Not hard to do on a carb'd motor with access to a dyno, but then again we didn't build engines to last 2000 hours. And when one failed, it coasted to a stop, we wern't climbing through 300' off the departure end.

For a race setup, looking for straighline speed for racing... sure go for it. For routine use to make up for a lack of power, just put in the appropriate size motor.

That said, you can try anything once. It's your airplane, time and money.
 
Maybe one of the systems made for snowmobiles would work out? Several of them compensate the fuel flow, and are designed for engines with approx. The same horsepower.

Maybe check out snowest.com and search around.

You might need a cruise prop, or a cs to maximize the potential.
 
Rather than try to explain all the reasons why I think nitrous for routine use is a bad idea, I'll just cut and paste.

Read through this and try to think about how you're going to over come the challenges of spark timing, mixture control, fogging, required fuel flow, increased internal pressures and CHT's, etc etc etc.

I'm not saying it's impossible... but as a means of over coming a lack in horsepower for climbout on a routine basis, I think you're playing with fire.

If I was building a single use racer for Reno or something like that, I could justify it. However all you need is one quick detonation with this stuff in your motor on climb out, and it's all over.

__________________________________________________________

In racing applications, nitrous oxide is injected into the intake manifold (or just prior to the intake manifold) to increase power. Even though the gas itself is not flammable, it delivers more oxygen than atmospheric air by breaking down at elevated temperatures, thus allowing the engine to burn more fuel and air. Additionally, since nitrous oxide is stored as a liquid, the evaporation of liquid nitrous oxide in the intake manifold causes a large drop in intake charge air temperature. This results in a smaller, denser charge, and can reduce detonation, as well as increase power available to the engine.

Detail


Nitrous oxide is comprised of two parts nitrogen and one part oxygen. When the nitrous oxide is introduced into the intake tract of an internal combustion engine, it is sucked into the combustion chamber and, on the compression stroke, when the air charge temperature reaches 565 degrees F, a very oxygen-rich mixture results. Nitrous oxide does not burn, it is an oxidizer. If we add extra fuel during nitrous oxide injection, the effect is like a super charger or increasing the compression ratio of the engine. By burning more fuel, higher cylinder pressures are created and this is where most of the additional power is realized. Nitrous oxide has this effect because it has a higher percentage of oxygen content than does the air in the atmosphere. Nitrous has 36% oxygen by weight and the atmosphere has 23%. Additionally, nitrous oxide is 50% more dense than air at the same pressure. Thus, a cubic foot of nitrous oxide contains 2.3 times as much oxygen as a cubic foot of air. Bottom line: nitrous oxide injection is much like a supercharger or a compression ratio increase in that, during combustion, it can dramatically increase the dynamic cylinder pressure in the engine.

Secondly, as pressurized nitrous oxide is injected into the intake manifold, it changes from a liquid to a gas (boils). This boiling affect reduces the temperature of the nitrous to minus 127 Degrees F. This "cooling affect" in turn significantly reduces intake charge temperatures by approximately 55-85 Degrees F. Cooler intake air is denser and contains more oxygen atoms per cubic foot. So cooler air will allow more fuel to be burned and in turn, make more power.

Nitrous oxide boils at -129°F and it will begin to boil as soon as it is injected. This can cause an 80° or so drop in manifold air temperature.

Side Note: For every 10 Degrees F reduction in intake charge temperature, a 1% increase in power will be realized. Example: A 400 HP engine with an intake temperature drop of 70 Degrees F, would gain approximately 30 HP on the cooling affect alone.

Finally, the nitrogen that was also released during the compression stroke performs an important role. Nitrogen acts to "buff or damper" the increased cylinder pressures leading to a controlled combustion process and better slower heat release.

Too Much of a Good Thing?

It should be noted that if the cylinder pressure in the engine is significantly increased, so will there be an increase in potential detonation. The burn rate is increased and requires less timing advance for peak output. Peak cylinder pressure must occur at approximately 20°ATDC to make peak power. If you speed the burn rate, peak cylinder pressure will occur too soon. It is easy to run too much ignition advance with nitrous, but too much will not only hurt power, it can quickly bring a nitrous engine into detonation and destroy it. This is why almost all nitrous motors require retarded spark timing during nitrous oxide operation.

Another challenge with a nitrous oxide system is getting the delivery of nitrous oxide and additional fuel at the correct proportions. The chemically correct nitrous to fuel ratio is 9.649:1. If you feed nitrous to the engine without enough extra fuel, the lean air/nitrous to fuel mixture will make the detonation problem even worse. The oxygen that was left over from burning the limited amount of fuel will result is a lean burn situation raising cylinder temperatures and melting components. If the proportion is such that too much fuel is delivered, the power advantage degrades rapidly.

What About Torque?

Torque is the force that turns the crankshaft and creates acceleration. People are consumed with horsepower (HP) numbers, but HP is not what creates acceleration for winning drag races. HP does create top end speed which is fine for land speed records or long distance endurance racing where acceleration rate / torque is not what determines the winner. To get the best out of nitrous, you need to utilize the massive torque it provides and concentrate on getting the highest torque across the whole rpm range.

Nitrous oxide systems make large amounts of torque by allowing an engine to burn more fuel at a lower rpm range than normal. Burning more fuel this way creates a longer burn period (and slightly higher cylinder pressures, if the timing is not corrected), that will push down on the pistons with greater average force. When the nitrous is injected into an engine and the initial combustion takes place, it creates enough heat to separate the nitrous oxide into its two components, nitrogen and oxygen. Once separated, the additional oxygen is then free to allow combustion of the additional fuel, while the released nitrogen acts as a buffer against detonation and damps mechanical loads.

If Oxygen is so Great, Then Why Not Pure Oxygen?

Air has only 23.6% oxygen by weight, the rest is made up largely of nitrogen. That nitrogen does not aid in combustion at all, but it does absorb and carry heat away. When you add nitrous, it has 36% oxygen with the rest being nitrogen. So the more nitrous oxide you add, the less percentage of nitrogen is available to absorb heat. That is why nitrous increases engine heat very rapidly. If we were to add pure oxygen (which has been tried), the percentage of nitrogen would fall even lower as more oxygen was added. We would not be able to add much oxygen before heat was a problem to control. Also compressed oxygen is in a gaseous form, so adding oxygen takes up more room and reduces normally aspirated power, and the amount of nitrogen from it. To put it simply, using nitrous oxide, we can get more oxygen atoms in the engine and have a lot more nitrogen as well. Nitrous can make much more power before heat is uncontrollable.
 
A pretty good explanation until I got to the part about torque and hp...

Nitrous and Lycomings are not a good mix IMO. Lots of people have fragged stronger engines getting nitrous set up correctly. Bruce Bohannon broke at least one nitrous engine on the Tiger and he had some smart engine guys working on it.

Of course you can make it work if you understand it and are careful. You'd want to use a wet system rather than trying to introduce more fuel through a carb or mechanical injection when the nitrous comes on. Running 100LL and a light 25 shot with standard CR pistons should not require any ignition retard on nitrous activation.

A 360 is probably the way to go.
 
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A pretty good explanation until I got to the part about torque and hp...

Nitrous and Lycomings are not a good mix IMO. Lots of people have fragged stronger engines getting nitrous set up correctly. Bruce Bohannon broke at least one nitrous engine on the Tiger and he had some smart engines guys working on it.

HP is just (torque x rpm)/5252... or something like that. It's been a while and I'm shooting from the hip on the basic math, but if you ever look at a dyno chart it's why HP and torque always intersect right aroud 5200 RPM.

I've seen very strong iron block, girdled motors broken on average nitrous installs, that were setup for it.
 
In the summer, density altitude is often 6500-7000 at our field. What do you think?

Wow...7000'. At my airport it gets up to 10,000' and I do fine with an O-360 and FP prop. Been to Leadville when DA was around 12,000' and did fine.

Count me as another naysayer.
 
Go Big

Why mess around with a mere O-360 when you can "Go Big" with an O-390? :D:rolleyes::cool:

There is no substitute for "cubes".:p
 
Cutting torch

Don't forget an uninterupted secondary flow of fuel (avgas) is mandatory, if you reduce the volume of this fuel it is like hitting the cut lever on a cutting torch (not what you want inside the combustion chamber). Failure will be near instantaneous!! Be careful
 
Do the research

I agree with Mike. ?Nah sayers are a dime a dozen.
If you?re motivated, you can do it.?

Plus I will add is, find people with the correct knowledge on the subject. There?s a lot of what I call ?drag racer mentality? (no offence to the drag racing community) so mis-information abounds about this subject.

I was taught about N2O form a fellow that had his own N2O business in the early 80?s. He taught me the basics of the subject as we too were flailing around blowing up 2 stroke out-board drag engines using our fuel injection system because we listened to the so-called ?experts? at the track. Once we had an understanding of what was going on and applied a little physics to the issues, we built bulletproof N2O systems and engines ran all season without incident. We have built some systems for Lycomings and have seen impressive performance with merely a ?50 hp kit?. Knowing how to apply the N2O correctly, install the correct safety provisions on the N2O, and control the fuel system that goes with it, is key to a safe operating and reliable system. All this does not come without a price, which is usually 3 to 4 times what a comprable N2O system you can get form an automotive after market supplier. But for an aircraft application there are no second chances. The aerobatic performing community has looked at this as a plausible way to do some interesting maneuvers but logistics always gets in the way. It?s hard to lug a N2O refill bottle around to fill the bottle in the plane. And if weight is a concern, which it is in a plane, the bottles get real pricey for a lightweight carbon fiber one.

Don?t get discouraged but get informed by people who are knowledgeable, read up on the subject, then make your own decision if this is for you.

Don
 
HP is just (torque x rpm)/5252... or something like that. It's been a while and I'm shooting from the hip on the basic math, but if you ever look at a dyno chart it's why HP and torque always intersect right aroud 5200 RPM.

I've seen very strong iron block, girdled motors broken on average nitrous installs, that were setup for it.

We'd had this discussion at huge length before here on VAF. Here is a link to one of the lengthy discussions: http://www.vansairforce.com/community/showthread.php?t=46423&highlight=love+torque&page=3

Torque is merely force measured at a distance, hp is work and work is what moves all vehicles- drag cars, airplanes and ocean liners. While hp is a function of torque at a certain rpm, area under the hp curve determines acceleration and peak hp, not peak torque determines top speed on a vehicle with proper gearing. The concepts are misunderstood by many people including some pretty smart dyno operators and engine builders.

Regarding this discussion, nitrous will increase torque and therefore hp right across the operational rpm range. The volume of nitrous and fuel injected will determine the hp gain and how long the bottle will last.
 
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You've received some good advice..

I agree with Mike. ?Nay sayers are a dime a dozen.
If you?re motivated, you can do it.?

........Knowing how to apply the N2O correctly, install the correct safety provisions on the N2O, and control the fuel system that goes with it, is key to a safe operating and reliable system. All this does not come without a price, which is usually 3 to 4 times what a comprable N2O system you can get form an automotive after market supplier. But for an aircraft application there are no second chances.
Don

The last sentence underscores the realities of a BADLY, or amateur designed system.

My late boss raced his Bearcat at Reno with nitrous and ADI (anti-detonation injection...50/50 alcohol and water) and made gobs of horsepower. The weight, cost, research dollars was unbelievable.

Good luck,
 
I wish I could remember the guys name here. He has put nitrous in his float plane to get of the water quicker. Has being using it for 10 or so years now and likes it.
 
Absolutely you can do nitrous successfully if you do your homework. There are tens of thousands of systems operating on cars very reliably. The weight penalty will be 15+ pounds depending on tank size (and you have to refill it once in a while).

I would not expect a 25 shot to reduce TBO measurably if used for 30 seconds during takeoff and initial climb, assuming the AFR is kept in a safe range.
 
It's easy to trash stuff it you go nuts with the nitrous. My guess is that you would probably be reasonably safe if you keep it conservative. The key words here are "guess" and "reasonably".

On big bore fuel injected sports bikes we routinely and safely ran a 40 hp "dry shot" nitrous system. They were called dry shots because no additional fuel was added. Well, that's not quite true. The fuel injection system would fatten up the mixture to compensate for the very cold air that it sensed. On an airplane you can control the mix so as long as you are able to compensate for the amount of nitrous you ought to be fine for short shots, such as takeoffs.

The problem is all of those "oughts." Unless you test in a controlled environment, i.e. a dyno how are you going to know? On a bike or a car if you scatter a motor with any luck you can just pull off the side of the track. Seems to me that the risks are greater in an airplane, especially on a takeoff and climb out.
 
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I think its a great idea.
Make it happen!
Nah sayers are a dime a dozen.
If your motivated, you can do it.

If you are motivated you can do anything. I have lots of nitrous experience in cars, so I feel entitled to make a nitrous opinion. My opinion is to use nitrous only on items that have a small chance of killing you dead when you break crankshafts and things like that. Put a bigger motor, higher compression, bigger cam, etc....if you need more horsepower. Use nitrous on things you take down the quarter mile. For that, I say GAME ON.

I didn't read all the posts but someone mentioned the Flyin Tiger had it. That was done for setting records and stuff and how many times did he return to airport dead stick?
 
I didn't read all the posts but someone mentioned the Flyin Tiger had it. That was done for setting records and stuff and how many times did he return to airport dead stick?

Lots.

They went to turbocharging to break most of the time to climb and altitude records.
 
I didn't read all the posts but someone mentioned the Flyin Tiger had it. That was done for setting records and stuff and how many times did he return to airport dead stick?

he returned to the airport dead stick after almost every time he dropped his wife off (but that was in his cub, not the tiger)....


explanation post
 
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I think they had at least two dead stick landings with the Tiger, one bad engine failure with the nitrous and one where the tanks vents froze at very high altitude. There may have been other egine problems which we didn't read about as those are something the engine sponsors might not want people to see.

A most impressive result with numerous records. Maybe someone who worked on the project could post more details?
 
You could just install a 180 hp Turbine. I think somebody is putting in a turbine in a 8 down in texas so i am told. Anybody know the guy?

ron in Oregon
 
This is what the spirit of our category of airplane is all about: Innovation. I would likely not have a use for it but this is how we all learn and expand our capabilities.

I say go for it!

...remember when people thought it was crazy to put an EFIS in your plane? Who were the ones that drove that? Experimental builders.

- Peter
 
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Hello,

I want to consider adding nitrous to my 6A 320 CS just for take off. I don't want to over boost just gain back some lost horse power. In the summer, density alltitude is often 6500-7000 at our field. What do you think?

...my name is Ernie and I’m a recovering nitrous addict. My addiction wasn’t breathing the good stuff, it was shooting the stinky blend into internal combustion engines. My addiction began in the 70’s with my go-kart, a borrowed bottle, dirty second-hand tubing, and a used needle valve. I blew-up the engine, but I was hooked and wanted more! Over the years I’ve shot-up race cars, inboard and outboard boats, and at my ‘rock bottom’ I was observed shooting-up my lawn mower. Thankfully, my family cared enough to do an intervention and I’ve been clean ever since. Oh yea, forgot to mention that I did have one relapse… I was a crew member on the Exxon Flyin’ Tiger and worked closely on the nitrous system with Gary Hunter, Crew Chief, and Bruce Bohannon. Ok, you have my credentials… following is my opinion.

Short: Bad Idea!

Summary: It’s been an interesting thread with some good information on the use of nitrous. While some have encouraged you to experiment, and I’m all for experimenting, consider that the take-off phase is the most safety critical part of your flight and then ask yourself if you REALLY want to experiment during that phase. Of note, nitrous burning Reno racers don’t use their nitrous during take-off, the Tiger only used nitrous at altitude, and the only aircraft I’m aware of that used nitrous during take-off was Bruce Bohannon’s Pushy Galore… and he melted a rather large stack of pistons and valves. I could write pages citing references from Pushy Galore and the Tiger. Instead, I’ll just ask that you trust me when I say that shooting-up a Lycoming is nothing like charging a land based engine, and further, if you do decide to experiment with a nitrous system on your Lycoming that you WILL experience at least one catastrophic engine failure. In the alternative there have been some great suggestions to gain a few extra horsepower (can’t have too many). A suggestion that may have been mentioned and I missed is that RPM is horsepower for your Lycoming. If you’re not turning your prop at its max rated RPM on take-off, you’re giving up horses you already have.
 
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It's really considerate of you...Ernie...

...to help with your guidance.

I figured that it would only be a matter of time before someone with "REAL" credentials stepped up.

Thanks,
 
Thanks for piping up here Ernie. I knew there had been a few failures on Pushy and Tiger but it sounds a lot worse than what we've read in various articles over the years.

Rare Bear broke a few pistons when fitted with nitrous too. Performance was spectacular until...

The only widespread, seemingly successful use in aircraft was by the Germans on DB and Jumo V12 engines during WW2 with considerable engineering and testing behind them. GM-1 as it was referred to was generally only used at altitude however- above critical altitude, so peak stresses were not greatly increased over SL takeoff and climb power.
 
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