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  16-Jan-12, 14:05   #1
The Definition of Acceleration +1 
mahdrof 

Joined: Nov '09
Location: Canada
Age: 47 (M)
Posts: 2367
Through my teens and twenties I was pretty active in drag racing, mostly legal stuff at a track but a little street racing too. Had a 1967 Firebird which won a couple of events, and a '78 Chevelle "sleeper" car with a turd brown paint job but a modified 6.6L engine which would blow the doors off of Mustangs and such. In 1988 I went to see the NHRA Grandnationals when they used to come to Quebec, and the top fuel dragsters were almost frightening to witness or even imagine driving.

I found this a couple of years ago on the web, and it details what goes on with these awesome bullets on wheels, and hope you find it interesting too.


DEFINITION OF ACCELERATION

One top fuel dragster 500 cubic inch Hemi engine makes more horsepower than the first 4 rows of stock cars at the Daytona 500.

It takes just 15/100ths of a second for all 6,000+ horsepower of an NHRA Top Fuel dragster engine to reach the rear wheels.

Under full throttle, a dragster engine consumes 1-1/2 gallons of nitro methane per second; a fully loaded 747 consumes jet fuel at the same rate with 25% less energy being produced.

A stock Dodge Hemi V8 engine cannot produce enough power to drive the dragster's supercharger.

With 3,000 CFM of air being rammed in by the supercharger on overdrive, the fuel mixture is compressed into a near-solid form before ignition.

Cylinders run on the verge of hydraulic lock at full throttle.

At the stoichiometric (stoichiometry: methodology and technology by which quantities of reactants and products in chemical reactions are determined) 1.7:1 air/fuel mixture of nitro methane, the flame front temperature measures 7,050 deg F.

Nitro methane burns yellow... The spectacular white flame seen above the stacks at night is raw burning hydrogen, dissociated from atmospheric water vapor by the searing exhaust gases.

Dual magnetos supply 44 amps to each spark plug. This is the output of an arc welder in each cylinder.

Spark plug electrodes are totally consumed during a pass. After halfway, the engine is dieseling from compression, plus the glow of exhaust valves at 1,400 deg F. The engine can only be shut down by cutting the fuel flow.

If spark momentarily fails early in the run, unburned nitro builds up in the affected cylinders and then explodes with sufficient force to blow cylinder heads off the block in pieces or split the block in half.

In order to exceed 300 mph in 4. 5 seconds, dragsters must accelerate an average of over 4G's. In order to reach 200 mph (well before half-track), the launch acceleration approaches 8G's.

Dragsters reach over 300 miles per hour before you have completed reading this sentence.

Top fuel engines turn approximately 540 revolutions from light to light! Including the burnout, the engine must only survive 900 revolutions under load.

The redline is actually quite high at 9,500 rpm.

Assuming all the equipment is paid off, the crew worked for free, and for once NOTHING BLOWS UP, each run costs an estimate $1,000.00 per second.

The current top fuel dragster elapsed time record is 4.428 seconds for the quarter mile (11/12/06, Tony Schumacher, at Pomona , CA ). The top speed record is 336.15 mph as measured over the last 66' of the run (05/25/05 Tony Schumacher, at Hebron , OH ).

Putting all of this into perspective:

If you are driving the average $140,000 Lingenfelter 'twin-turbo' powered Corvette Z06. And if up the road, a top fuel dragster is staged and ready to launch down a quarter mile strip as you pass, you have the advantage of a "flying start." You run the 'Vette hard up through the gears and blast across the starting line and pass the dragster at an honest 200 mph. The start-light 'tree' goes green for both of you at that moment. You're doing 200, the dragster just starts the moment you pass him.

The dragster launches and starts after you. You keep your foot down hard, but you hear an incredibly brutal whine that sears your eardrums and within 3 seconds, the dragster will catch - and pass you! He beats you to the finish line, a quarter mile away from where you just passed him.

Think about it, from a standing start, the dragster had spotted you 200 mph and not only caught, but nearly blasted you off the road when he passed you within a mere 1,320 foot long race course.

...... and that my friend, is ACCELERATION!

     
  16-Jan-12, 14:45   #2
  0 
Davoodoo 

Joined: Apr '08
Location: Finland
Age: 27 (M)
Posts: 1612

http://www.youtube.com/watch?v=HldiiDmvTxI&feature=... Filmed in slow mo also gives a hint of the powers involved. Smile

But what do they mean with the "Cylinders run on the verge of hydraulic lock at full throttle." ?



     
  16-Jan-12, 15:29   #3
  0 
arthur72 

Joined: Mar '09
Location: Australia
Age: 44 (M)
Posts: 325
lolol thats a good post Smile Thumbs Up Thumbs Up Thumbs Up

     
  16-Jan-12, 16:14   #4
  0 
mahdrof 

Joined: Nov '09
Location: Canada
Age: 47 (M)
Posts: 2367
Posted by Davoodoo:
But what do they mean with the "Cylinders run on the verge of hydraulic lock at full throttle." ?

Hydraulic lock is when you have too much liquid (which is generally considered to be incompressible) in a cylinder, and the piston has compressed the air/liquid mixture to its maximum but has not reached the end of its stroke. The liquid has nowhere to go and either goes down around the piston rings into the crankcase, or blows the cylinder head off of the block, or both. Smile

     
  16-Jan-12, 17:09   #5
  0 
Davoodoo 

Joined: Apr '08
Location: Finland
Age: 27 (M)
Posts: 1612
Posted by mahdrof:
Posted by Davoodoo:
But what do they mean with the "Cylinders run on the verge of hydraulic lock at full throttle." ?

Hydraulic lock is when you have too much liquid (which is generally considered to be incompressible) in a cylinder, and the piston has compressed the air/liquid mixture to its maximum but has not reached the end of its stroke. The liquid has nowhere to go and either goes down around the piston rings into the crankcase, or blows the cylinder head off of the block, or both. Smile


Nice Big Smile

Im also wondering about the stoichiometric (lambda = 1 , right ?). How come the mixture can only be 1.7:1 ratio air/fuel ?

In a normal car engine running on ordinary gas the mixture is 14.6:1 ratio air/fuel = gives the least emissions, (however if you make the mix a little more fat you will get more power like 13.6:1, i hope im right??).

Has it something to do with the nitro methane that the mix can/shall be so fat as 1.7:1 ?

I doubt a normal car engine with normal gas would run on 1.7:1 air/fuel mix Big Smile

Im just curios because this is EXACTLY what im reading about in school right now !



     
  16-Jan-12, 18:07   #6
  +1 
rbdflyboy 

Joined: Apr '11
Location: Canada
Age: 60 (M)
Posts: 1222


At the stoichiometric (stoichiometry: methodology and technology by which quantities of reactants and products in chemical reactions are determined) 1.7:1 air/fuel mixture of nitro methane, the flame front temperature measures 7,050 deg F.

This fue/air ratio is be avoided in most if not all internal combustion engines because of detonation occuring in the combustion chamber. Prolonged operation in this range produces enough detonation to destroy an engine. For safety, longevity, and cooling purposes engines are set to operate above or slightly below the stoichmetric value. Above this value the combustion chamber is cooled with fuel and slightly below cooled with air. This is why the lead content in fuel is important, its the lead in the fuel that most effectively cools the combustion chamber. Cooling with air is abit tricky as it does cool but is hotter than cooling with fuel and usually requires a fuel delivery system that can be controlled by manual leaning. I understand better now why dragster engines don't last very long.

Dual magnetos supply 44 amps to each spark plug. This is the output of an arc welder in each cylinder.

I'm guessing here, I figure they use low tension systems because that many amps would usually burn up a high tension ignition system.




[/QUOTE]

     
  16-Jan-12, 18:07   #7
  +1 
mahdrof 

Joined: Nov '09
Location: Canada
Age: 47 (M)
Posts: 2367
You can read more about it at

http://en.wikipedia.org/wiki/Top_Fuel

which states that "nitromethane can combust in the absence of atmospheric oxygen, producing hydrogen"

The more fuel you can pack into the combustion chamber AND ignite properly, the more power you will produce. This is also why nitrous oxide allows for so much more power to be produced. With NOS you make the fuel mixture extra rich, and the concentrated oxygen in the NOS gas still allows the gasoline to combust fully. Again, explosions are sometimes the result of this. Smile

     
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