Landracing Forum
Bonneville Salt Flats Discussion => SCTA Rule Questions => Topic started by: Flyboy on November 30, 2006, 05:42:02 PM
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Can you have a nitro bottle and plumbing on your bike and still run in the P/P category? The bottle would be hidden out of site and would be empty to be verified by inspectors prior to running. This would obviously enable a person to run in other categories and the bike would appear stock.
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Nitro?
Or nitrous?
Nitro requires a whole different fuel system.
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Yes, I guess I'm speaking of nitrous. "spray"
But on the other hand could someone please explain the difference and at which times both are utilized. Want to learn. Thanks.
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7.B.21 Nitrous Oxide Systems, states that "The nitrous oxide bottle(s) must be removed when competing in gasoline classes."
7.J.1 Production Engine Class, states that "All Production engines run in gas class."
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Nitrous Oxide is an oxidizing agent -- doesn't burn unto itself, but adds more available oxygen to the system -- so that more fuel can be burned. You're supposed to turn up the fuel injection simultaneously with turning on the nitrous, and the increased combustion of fuel results in more hp. (Note I say "supposed to" -- witness all the burnt pistons too many of us have to prove that nitrous without additional fuel results in a WAY lean mixture real quickly!).
Nitromethane is a fuel -- it'll burn, can be run up to 100% -- no gasoline or other fuel is REQUIRED for combustion, although some/many/most use a mixture of nitro and gas/alcohol/bug juice.
I'm just a puppy about this stuff -- I'm sure others will have far better explanations, but this is a start.
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Wow, thanks for that explaination Jon. That was simple & to the point. Even "I" understood it! hehehe
:mrgreen: <- big hair!
Deb
(we need a ponytail girl smiley!)
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Why is one used over the other? I always here about nitrous but never about nitro except in the explosive nitroglycerin. Do you guys use nitro at the salt flats? If so,in what senario?
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I use nitro. The scenario is "trying to go real fast".
No seriously, both nitro and nitrous are widely used.
Nitrous can be easily fitted to most gasoline powered vehicles, without major changes, so it's popular for that reason. But the nature of a nitrous burn is such that peak cylinder pressures will be higher, for a given power level, than say a nitro or boosted motor.
Nitro is a whole new ball game from the point of view of the fuel system, and introduces other issues as well. You have to deliver a whole lot more fuel to the motor. To give some perspective, my bike uses a -12 fitting on the bottom of the tank, that gets split into a pair of -8's before going to the special nitro carb that has two fuel inlets. Only one of the fuel inlets is regulated by the float, the other is controlled by a cam attached to the throttle. Since fuel flows in unregulated when the throttle is open, I have to take it out the carb overflow and pump it back to the tank (else I'll run out before I can finish a pass!). The main jet I run has an orifice that's more than a quarter inch in diameter. You could stick a number 2 pencil through it. You also need the mother of all ignition systems to light the stuff at mid to high concentration levels. It doesn't mix with gas so you run it mixed with methanol. At higher concentrations, you have to start the motor on methanol before applying the nitro-methanol mix, or you'll take off a cylinder head. Likewise it's not advisable to run a rev limiter at high levels because it'll take off a head. The stuff is very unforgiving of any kind of a mistake in tuning or procedures. Think of it as riding a two-wheeled bomb and you're pretty close.
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When you look at all of the work we do to go fast, it's all about getting more air in the engine. We deal with an air limited sport. You can dump fuel in with a fire hose.
The SCTA splits the world into three parts.
1. Gasoline.
2. Every other approved liquid fuel; alcohol, hydrogen, nitromethane, and unapproved gasoline. Nitrous Oxide also, but it is a special case. There are thousands of combustible compounds, these are the approved ones.
3. Supercharger or turbocharger. (Gas or fuel)
With gasoline you are limited to the amount of air you can stuff into the engine. Physics dictates that a 14.7:1 ratio of gasoline to air is the stochiometric ratio where all of the fuel will combine with all of the oxygen. That's 14.7 pounds of air to 1 pound fuel. The air we breathe is 21% oxygen, 78% nitrogen and other trace gases. The oxygen is the only thing that matters. Above or below that ratio and you will be rich or lean and produce less heat to expand and drive the piston down. Because it is a dynamic event, and not in a laboratory, a ratio of 12.5:1 to 12.8:1 is the rough ratio for maximum power depending on the blend of gasoline used. At 14.7:1 you will produce roughly 18,400 btus of heat per pound of fuel.
Switching to the fuel class and running methanol results in 9,500 btus per pound of fuel. Far less! If you burn methanol in a coffee can in the sun light you can't see the flames. So why is it a better fuel? Because it combines better with oxygen. At 5:1 ratio you can stuff twice as much in the cylinder and achive 20% more power. Methanol has a higher heat of vaporization than gasoline, so that as the liquid fuel changes to a vapor, it cools the engine more than gasoline.
Putting in nitromethane results in only 5000 btus per pound of fuel. Even less! The chemical formula is CH3NO2. Notice the two oxygen molecules? Nitromethane is a monopropellent by itself. You can pour a massive amount of nitromethane through an engine due to the 1.7:1 fuel/air ratio. The result is 135% more power than on gasoline. IF the engine will take it. It's no wonder the top fuel guys use it. The higher heat of vaporization combined with the higher fuel flow results in a lot of engine cooling.
Which brings us to nitrous oxide. SCTA classifies it as a fuel, although it is an oxidizer, not a fuel. When you squirt nitrous into an engine you displace the 21% oxygen air with 33% oxygen nitrous. Everything noted above for the fuels increases because you can dump more fuel because of the increased oxygen. The breakdown of the liquid nitrous oxide into N2 gas during combustion releases heat separate from the oxygen benefits, adding more power. Can you run 100% nitrous oxide with no outside air? It would depend on the size of the engine and how many bottles you can carry. It's more to the point to ask the question "At what point will it grenade?"
A supercharger or turbocharger allows you to stuff more air in the same volume, allowing you to put more fuel in for a bigger bang. Can you use nitrous oxide with a supercharger or turbocharger? Sure!
Can you achieve a supercharging effect with nitrous oxide alone? With a direct port injection you certainly can! Nitrous oxide is popular because it's easy. Nitromethane is looked at as only something an "expert" would use. The true answer is in the fuel class there is no end to the power you can generate, probably far more than the engine will take. In the supercharger or turbocharger classes destroying an engine is not hard. So, crank up the boost or tip the can until it blows, then back off a little. :-D
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Dean
I've run a fair number of methanol fueled engines and had a very little experience with nitro. I've understood the basic requirements but have never seen it so clearly explained. Thanks!
Pete
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Dean,
Excellent discourse. Now let's finish that bike and get 'er done!
DW
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Dean,
Thank you for an excellent write-up.
A couple questions for you--
1) Can you corrolate BTU's to horsepower?
2) How much more horsepower does nitrous oxide add to an engine when it is being sprayed?
3) In aviation we suck on 100% oyxgen when up on altitudes. Would setting up a 100% oxygen bottle to your bike make any difference to mixture power if pure O2 was released into air intake just before the "big mile"?
4) From your write-up it appears there are only a handful of people in each state that know about and that can safely work with nitromethane. Can I assume that to be correct?
5) Can I also assume that once you set up your bike for nitro-- you can just about forget riding it around town?
Thanks
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Flyboy: with all that was said-NO
Dean: A nitrous engine will NEVER "smell" good. A nitro engine will ALWAYS "smell" good. :-D
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My oh my has this thread go into the land of silly and impossible..LOL..
I won't wear anyone out including myself but....
Flyboy do you own or have used or watch someone use a cutting torch??? If you had the use of 100% oxygen would explain itself real quick.. No you can't do it, it does not work period. All heat and nothing to expand just melts things. Nitrogen is the operative gas in a engine. You heat the working fluid and it expands, no it does not explode, the rise in pressure makes something move depending on what type of engine, sorry it is not a motor either go look up the definitions sometime.. :-o
Dean.. sorry you can not make 'boost' with nitrous How did you plan on doing that?? Close the wide open throttle blades??? :? Even worse anything much greater than 50% of what an engine makes without nitrous is a really good trick. It has been done for very short periods of time but it gets back to charge air cooling the amount of working fluid to expnad, and the vapor pressure of the fuel that needs to partially evaporate in order to start combustion.. As Forest Gump would say nitrous is like tequila, a little is a lot of fun too much and you have a problem... Buy a chemistry book and a few books on fluid dynamics and thermal dynamics and it will all make sense.
Nitro burns very very slowwwww so if a high rpm bike figure it out.. They have a NHRA gear run made to buzz them and slow them down..
Dave
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Sorry to question all the wisdom that has been in this thread, but "nitrogen is the working gas....." is not a correct statement for these IC engines. The chemistry of the air, the chemistry of the fuel, and the chemistry of the combustion process would strongly refute such an statement. The EXPANSION of burning gas is what pushes on the piston. In the vernacular, nitrogen ain't it. The BURNING of fuel provides the heat for the expansion to occur. Nitrogen has a bit of a problem in accomplishing that work.
Even though I might normally be interested in anything that might even come close to violating the second law of thermo, nitrogen can't even be propped up enough to take the heat for an expansion phase.
BTW - an O2 rich environment would be of some interest if sprayed in the normal atmospheric inlet to the engine. That has been done with some success before.
All puns intended.
OK, now I will go back to piddling in the shop space on a snowy day in the high country.
Regards to All,
HB2
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1) Can you corrolate BTU's to horsepower?
Relating heat to horsepower requires resolving all of the variables; compression ratio, valve timing, ignition timing, etc. Brake Mean Effective Pressure (BMEP) is another very effective yardstick for comparing the performance of one engine to another. Comparing a 300 cubic inch engine to a 400 inch engine is difficult. Using BMEP allows you to compare how much pressure is being developed. The definition of BMEP is: the average (mean) pressure which, if imposed on the pistons uniformly from the top to the bottom of each power stroke, would produce the measured (brake) power output. The absolute answer is that until you put it on the dyno, you don't know, and until you take it down the course in real race conditions, you'll never figure it out.
2) How much more horsepower does nitrous oxide add to an engine when it is being sprayed?
Horsepower is the answer we are most familiar with, but unless you have dyno readings for a particular setup it is mostly advertising. Nitrous is frequently advertised as "75 horsepower" when what they really mean is there is the possible, maybe, kinda sorta, if you play your cards right possiblity of having that kind of power increase. Since most of their customers don't have access to a dyno, no one really knows if that is close or not. Unless you match the fuel to get the correct ratio you can't get maximum effiency. The difficulty lies in figuring out where on earth to start. The seat-of-the-pants method is to always start on the rich side and work back to the correct ratio, determined by checking the plug color. If you have a mass air flow sensor your life gets a little easier, but this is why the guys with little experience have it so hard. "I really want maximum horsepower, but don't want to blow it up."
3) In aviation we suck on 100% oyxgen when up on altitudes. Would setting up a 100% oxygen bottle to your bike make any difference to mixture power if pure O2 was released into air intake just before the "big mile"?
It sure would, if you could keep it from torching a hole in the piston. Nitrous oxide has the advantage of releasing oxygen in the heat of combustion, where pure O2 produces lots of heat NOW. Not that it couldn't be used, but control is difficult. O2 is easily available in compressed form, not liquid. Nitrous is a liquid, and the difference is the amount of power you can put in a compressed bottle.
4) From your write-up it appears there are only a handful of people in each state that know about and that can safely work with nitromethane. Can I assume that to be correct?
Only from the stand point that not that many people ever run nitromethane. Most racing is gasoline oriented. Drag racing and land speed racing are the two biggest forms of racing that use it. RC cars run 20% nitromethane all the time.
5) Can I also assume that once you set up your bike for nitro-- you can just about forget riding it around town?
You haven't priced nitromethane, have you? :evil: At $40-50 a gallon, and using 5 times as much . . .
Did I say something about the smell of nitrous oxide? I didn't think I did. Nitromethane on the other hand . . well I'm addicted to the smell. It's no doubt poison, but when you smell a top fuel engine light off . . . AHHHHHHH.
I worked with a fuel genius in the late 60's. Have you ever tried oil of wintergreen? The smell when burned is pretty exotic. Makes a good buffer for methanol/nitromethane too.
Should we discuss hydrazine? Also was popular in the late 60's. Still popular as rocket fuel. With nitromethane it produced tons of power. If you let it sit for a few days it went from a pretty decent fuel to a Class A explosive. I wonder why they banned it????
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Dean and others... thanks for your input.
Three more questions:
1) When an motorcycle engine is rebuilt is it true that you must have special pistons to handle the nitrous so they won't melt?
2) Can you spray nitrous on fuel? Wouldn't you get more power than spraying gasoline?
3) The C numbers on the cans. At BUB I saw mostly C19 or C16? on the cans of fuel. I personally brought C12 as recommended by a dragster. What does the numbers represent? And how does one determine which fuel is best for their engine? Thanks.
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1) When an motorcycle engine is rebuilt is it true that you must have special pistons to handle the nitrous so they won't melt?
Depends on what the stock piston is made of. Cast pistons aren't as good as forged pistons. One of the fastest guys on the planet, John Noonan works for JE Pistons. Use his stuff. "Won't melt" is a dream come true. The truth is that aluminum melts at 1200 F (depending on alloy). You can melt any piston. The more fuel, nitrous, compression, boost, rpm you add to the mix puts more stress on the piston. It only has to last 5 feet past the finish line.
2) Can you spray nitrous on fuel? Wouldn't you get more power than spraying gasoline?
Nitrous oxide adds more oxygen to the mix, doesn't care what it gets sprayed on. SCTA doesn't allow nitrous with gasoline. SCTA rules class nitrous as a fuel.
3) The C numbers on the cans. At BUB I saw mostly C19 or C16? on the cans of fuel. I personally brought C12 as recommended by a dragster. What does the numbers represent? And how does one determine which fuel is best for their engine? Thanks.
VP Racing Fuels:
http://www.vpracingfuels.com/vp_01_fuels.html (http://www.vpracingfuels.com/vp_01_fuels.html)
C16
Used in turbocharged engines, blown engines and nitrous applications with CRs up to 17:1. Recommended by the top nitrous oxide companies. Spec Fuel for NHRA Comp Eliminator.
? Color: Blue
? Motor Octane: 117
? Specific gravity: .735 at 60? F
C19
Used in high RPM, normally aspirated drag race applications with CRs up to 17:1. Spec fuel for NHRA Comp Eliminator classes.
? Color: Yellow
? Motor Octane: 116
? Specific Gravity: .695 at 60? F
C12
The best all around racing fuel made. Recommended for CRs below 15:1, satisfying the needs of 75% of today's race engines. One of the winningest fuels in racing history, including Modified Tour, GNN, D.I.R.T., Indy Lights, NHRA, AMA as well as other local and national championships across the U.S. and around the world.
? Color: Green
? Motor Octane: 108
? Specific gravity: .717 at 60? F
Check out their web site, it lists tons of different blends. The designation doesn't mean anything. Which one is right for your application? Gooooood question. Higher octane numbers allow higher compression without detonation. Color and specific gravity don't tell you anything.
ERC Racing Fuel is the supplier for speedweek.
http://www.ercracingfuels.com/default.htm (http://www.ercracingfuels.com/default.htm)
Their web site gives more information, including BTU's. More BTU's more heat, more heat more power.
Check here for the chemical properties of just about everything combustible in an engine.
http://www.me.mtu.edu/~slpost/CLASS/hcprop.html (http://www.me.mtu.edu/~slpost/CLASS/hcprop.html)
You may notice gasoline isn't listed. Gasoline is a blend of hydrocarbons from several of the base stocks listed on that page. If you buy gasoline for your car from the same gas station every time, you probably don't get the same blend everytime. Which fuels won't pass the SCTA requirement of 2.025 Dielectric Constant as read by the SCTA fuel check meter? I don't think anybody knows.
Also, gasoline is pretty much like buying a bike. Everybody has their opinion as to what works best. Me, I would just run what the record holder uses!
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"You can't spray Nitrous on gas."
I know what you meant to say but what you did say was a funny.
You may try again. LOL
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Dean,
What do you do for a living? Work for JPL? I hope you're teaching young ones. This country needs more educated people like you.
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. No you can't do it, it does not work period. All heat and nothing to expand just melts things.
[/quote]not quite true. in 5o's barny navarow was injecting pure o2 in his flathead ford, he did melt a lot of pistons, and found it real hard to regulate,hence laughing gas much easier, with todays tec maybe o2 could be feasible???
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I have been wondering ---with todays faster chip ECUs on a system that has a fast O2 sensor system it "might" just be possible to introduce enough O2 upstream to "knock" the D alt. back toward sea level, and below lol. As more gas engines begin to use muiltble pulse direct injection like diesels do now--- I will bet that we find we can do lots of things we couldn't in the past..
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Aswracing - I take it that you carburate nitro, would be interested to know what % you run and some details about your fuel system.
I run a " mud drag truck" with a 532ci Enderle top hat injection and run 33% load of nitro. I wanted an alternative to using a 500 shot of nitrous like most the other competitors. I work as a crew member on several friends NHRA nostalgic T/A dragsters.
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Aswracing - I take it that you carburate nitro, would be interested to know what % you run and some details about your fuel system.
for carb- 850 holly dbl pump-- enlarge all psgs: including discharge tubes -big steel needle& seat- open up jets poeportional to % nitro - big fuel pump & lines from tank to carb- one street 340 plymouth ran 25 % load with this setup- { oh ya colder plugs-- carful here} stock car stayed @ 5 % load due to cost .mini rod stayed @ 10 % as about all heads {215 buick} could take w/ 30 lb boost,1 puller trk got by w 30% load : but short run time so no heat problems- think he was a bit ritch as starter had tears in his eyes & don't think it was cus he was happy or sad. To get nitro to mix w/ gas requires toluene or zylene as a blending agent- bonus- they are octane bosters.