In almost every form of motorsport, fuel management is crucial. Get the perfect blend of fuel and air, get the most power and efficiency from the engine. But watching Top Fuel dragsters run, especially at night, it seems apparent that a whole lot of fuel is not burned in the engine, yielding great flames from the headers. My question is- Why? Is there some great thing I don't understand? Great minds want to know, so do I.
because watching drag racing would be even more boring without flames shooting out of the pipes......
As I understand it with drag racing, the top fuel cars have so much fuel in the cylinders that if they lose spark or back off the throttle too quickly it liquid locks and that's usually why they blow the heads off.
They are not fueled by gasoline or alcohol, they burn an industrial explosive. Mixture is not so important as quantity- more dymanite makes a bigger bnag.
Stoich is 2:1 for nitromethane. They run around 1:1 for in-cylinder cooling. The rest just looks awesome :) (I guess a lot of it is the heat disassociating water, and it re-associates after it leaves the header)
The heads leaving the block thing isn't due to hydraulic locking so much as if you get a hang-fire, you don't have as big of a blowdown, and you may still have burning fuel in the chamber when the intake valve opens.
Those drag engines have the fuel injectors under the valve covers, BTW.
The main reason you see flames is that the header pipes are so short. Shorten them up enough on any car and you'll see flames out the exhaust.
I had a beetle that would shoot flames out of it's (legal) exhaust while accelerating at WOT.
maybe not the most efficent, but was fun to watch people back off
You want flames out the exhaust . . .
A bud had a Honda CL100 with a high pipe. You could always tell when the points were closing up, he'd back off the throttle and it would spit fire about 6" out of the pipe often accompanied by a rather loud bang. 
We would roll to a stop and set the points with a matchbook cover. 
It's not that crazy if you consider the scale. If you take the headers off of a sanely-sized, regular car engine you'll see at least a small cone of flame at the exhaust ports...
From that Fun Top Fuel Facts email that makes the rounds like Cicadas, I believe those flames aren't coming out of the headers, but the heat of the exhaust gas is igniting hydrogen in the atmosphere.
EDIT: Yep, at least according to this un-vetted email:
Nitromethane 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.
alex wrote: EDIT: Yep, at least according to this un-vetted email:Nitromethane 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.
Day.
Um.
No, its for down force. If I remember correct, the zoomies produce 800 lbs of down force at full throttle.
Hey Kia Racer- The Green Mamba jet car's garage was in my warehouse complex when I had my metal shop in Tampa. I didn't know it until he pushed it out into the entry road and fired it up. Considering that we were less than half a mile to Tampa International airport, it was "Interesting" He told some wild stories, and I seriously doubt that he is still alive. That was about ten years ago.
Appleseed wrote: No, its for down force. If I remember correct, the zoomies produce 800 lbs of down force at full throttle.
Much more than that... but the downforce is why they point them up and not back.
They USED to point them back, to "blow the tires clean". Then someone discovered that they had more traction with them pointed up. This was in the very early days, when a high powered digger motor made about what one cylinders' worth makes today.
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