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top fuel dragster facts

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Rog02:

--- Quote from: AdeV on December 13, 2009, 07:55:45 PM ---
--- Quote from: chuck foster on December 13, 2009, 07:25:46 PM ---what do YOU think is BS about these fact's????

chuck  :wave:

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--- Quote ---* Even with nearly 3000 CFM of air being rammed in by the supercharger on overdrive, the fuel mixture is compressed into nearly-solid form before ignition. Cylinders run on the verge of hydraulic lock.
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If Wikipedia is to be believed, the compression ratio is 6.5:1; if you'd injected enough fuel to come close to hydraulic lock, almost all of the burn would take place after the exhaust valve was opened.
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The static compression ratio measured at piston to deck height may approximate the 6.5/1 level but add on a 10% to 25% overdrive on the blower and see what happens to the dynamic compression. 


--- Quote ---* 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 off its fuel flow.
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--- Quote from: AdeV on December 13, 2009, 07:55:45 PM ---This also seems unlikely. These engines will run very advanced ignition to try to maximise power; dieseling can only be controlled by the fuel injection timing. Since top fuel racers allow both fuel and air in through the intake valve, dieseling would cause immediate and massive backfiring and engine failure.
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NHRA rules are very specific!  The timing curves can be altered through electronic means but the fuel curve is set by pneumatic actuators, spool valve and pills.  Ever watch the crew chief open the "toy box" and tweak a few things after watching another car make a pass?  May be the timing, may be the fuel, only the crew chief knows for sure.   The timing may advance for part of the run, retard for the mid range and advance again after the clutch comes in.  Just depends on the data and how the crew chief feels about how much the track will hold.

The current ignition systems are dual MSD (Multiple Spark Discharge) boxes and distributors firing 2 spark plugs per cylinder.  While some electrode erosion is considered normal, the loss of an electrode will put the "hole out" and the hydraulicking of the unburned fuel will wreak all sorts of havoc.  Definitely finding the weakest parts first be it an intake valve (huffing the blower) or ventilating the block by breaking the connecting rod and forcefully ejecting it through the side of your last Kieth Black (Donavon, John Force Racing, Dart, insert your favorite supplier here) block.

The engines are shut down with the fuel to eliminate an explosive situation where liquid fuel is left in the cylinder and the cylinder heat soaks on the return road and explodes.  This happened with dire consequences in the 50s when it killed a couple of racers bringing about a ban of nitro for several years.  Ain't you glad Garlits never got that Hydrazine stuff past the tech guys?


--- Quote ---* Dragsters twist the crank (torsionally) so far (20 degrees in the big end of the track) that sometimes cam lobes are ground offset from front to rear to re-phase the valve timing somewhere closer to synchronization with the pistons.
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--- Quote from: AdeV on December 13, 2009, 07:55:45 PM ---Erm, competition crankshafts are hardened. They'd shatter before twisting.
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The journals are surfaced hardened while the core and journal webs are left in an annealed state.  A "through hardened" crank would shatter as it could not handle the torsional stresses and harmonics acting upon it. 

Ed Iskaderian, Chet Herbert and several other cam grinders have experimented with the "torsional grind" cam concept through out the years.  Mostly on motors of the BBChevy design as the drag caused by the distributor and oil pump drive has a noticeable effect on the rear cylinders.  Most folks seem to prefer a large base diameter design and call that good but there is still some serious discussions held in the wee hours of the morning in dyno rooms all over the country.  With the advent of crank triggered ignitions on about every thing except Fuel and Alcohol cars the discussion is pretty much mute at this time.  The engines used in AA Fuel Coupe and AA Top Fuel cars use a front crank driven ignition drive and crank driven dry sump oil systems so the cam is not as loaded as in the BBC design.


--- Quote from: AdeV on December 13, 2009, 07:55:45 PM ---The sad thing is, Top Fuel dragsters really are works of engineering art - but someone has seen fit to massively conflate their actual achievements far above reality. Unnecessary IMHO.

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This is stuff spewed forth from an over ambitious track announcer.  Many of the "facts and figures" quoted are out of date.  The onboard data is clearly indicating the engines are making upwards of 8,000 HP these days.

Oh, Yeah I would like to know where I can buy some of that $30 a gallon Nitro Methane.  Last barrel I bought was $54 a gallon and that was 3 years ago.  I'll take about 2,000 gallons.  Nitro is in short supply.  Don Schumaker Racing is setting on a horde of the stuff and I am told there is a line at his door from industry bidding to get it.  The Texas refinery (only one in the states still perc'ing nitro) blew up again, so it isn't producing.  The Chinese stuff is inconsistent so "suspect". 

"Speed costs money kid.  How fast can you spend?"

Roger

Come on down.  Spend a weekend with the rednecks.  It might prove very entertaining.

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