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January 24, 2007

Acceleration Vs Speed


Many people think that speed and acceleration are the same thing, but that's only true in the sense that I and a newborn child are the same.

While I have reached a measure of stability in life, the newborn is just starting on its journey.
Speed is the goal. Acceleration is the journey.

I like speed. Fast music, fast cars. Things like that I like fast but the thing about cars I like the most is acceleration.
When I put my foot about 1/4 inch down on the gas pedal my mighty Mopar answers by pushing me gently back into the leather seat. When I push my foot down about half way I feel like I don't really need seatbelts due to the force gripping me to the seat.

I bring this up because of Top Fuel Dragsters. I absolutely love 'em. I get almost orgasmic just watching a race.

I'm not talking about some namby/pamby Daytona or Indy racer, no. I'm talking about some serious horsepower.

To give you an idea of what I mean:

Under full throttle, a Top Fuel dragster engine consumes 11.2 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 426 Hemi V8 engine cannot produce enough power to drive the dragster's supercharger.

With 3000 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 1.7:1 air/fuel mixture for nitro methane the flame front temperature measures 7050 degrees F ( 3900 degrees C ).

Nitromethane burns yellow. The spectacular white flame seen above the stacks at night is raw burning hydrogen, dissociated from atmospheric water vapour 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 1/2 way, the engine is dieseling from compression plus the glow of exhaust valves at 1400 degrees 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 at 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 RPM's from light to light! but stop & ponder the fact that the engine is only used for apx 4 to 5 seconds.

Including the burnout the engine must only survive 900 revolutions under load.

The red-line is actually quite high at 9500 rpm.

The Bottom Line; Assuming all the equipment is paid off, the crew worked for free, and for once NOTHING BLOWS UP, each run costs an estimated $1,000.00 per second. The current Top Fuel dragster elapsed time record is 4.441 seconds for the quarter mile 10/05/03, (Tony Shumacher). The top speed record is 333.00 mph (533 km/h) as measured over the last 66' of the run (09/28/03 Doug Kalitta).
Putting all of this into perspective: You are riding the average $25,000 Honda MotoGP bike. Over a mile 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 RC211V hard up through the gears and blast across the starting line and past the dragster at an honest 200 mph (293 ft/sec). The tree' goes green for both of you at that moment. The dragster launches and starts after you. You keep your wrist cranked hard, but you hear an incredibly brutal whine that sears your eardrums and within 3 seconds the dragster catches and passes 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 1320 foot long race course.

Melanie Troxel (right, with engine on fire) beat Bob Vandergriff in the first round of the 2006 NHRA POWERade Drag Racing Series.

All that from a car that must weigh at least 2150 lbs. and have an engine no larger than 500 cubic inches.
One Top Fuel Dragster 500 c.i. engine makes more horsepower than the first four rows at the Daytona 500.
I'll take acceleration over speed any day. Speed is the destination but acceleration is the journey!

- Joatmoaf -

January 24, 2007 at 07:45 PM | Permalink


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Those are some fun facts.

I think you've got a typo in the average RPM for a run. Maybe it should be 5400?

Posted by: Foobert at Feb 1, 2007 3:56:45 PM

9500 is redline. Remember, it only turns about 540 times under load, so 9500 is about right.

Posted by: Joatmoaf at Feb 5, 2007 12:08:21 PM

9500 revolutions per minute. 4.5 seconds elapsed time. 9500/60*4.5=712. 540 is a little low, particularly if the engine isn't running at redline all the way, but 5400 is way high.

Speed Age magazine, in the issue announcing the impending arrival of the Edsel, had an article in which some professor asserted that drag racing was nearing its limit, based on the presumption that 1G was the maximum attainable acceleration for a wheel-driven vehicle. It occurs to me on reading this that he was already proven wrong, in that acceleration off the line would have been greater than that.

Posted by: triticale at Feb 26, 2007 10:05:37 PM

*claps hands*

Pretty flames and shiny things!

Seriously, that is some awesome power. I have always wondered why they were called 'drag racers.' Isn't that an oxymoron?

Can nitromethane added to gasoline improve
mileage and performance? Can it even be had by non racers?

Posted by: Cricket at Apr 11, 2007 9:31:02 AM