The nitromethane only partially combusts, as it carries it's own oxygen, and you get the most power (and some cooling) by mass flow of the fuel and partial combustion...then when it hits the air, the second stage of combustion happens.
I go to dirt races occasionally and you can tell when someone has spiked their fuel with nitromethane when the flame out the exhaust is much more prominent. Plus the smell is also very obvious.
Something interesting about nitro, my mom lost her sense of smell after having a brain tumor. When we went to the NHRA finals in Pomona last year she could smell the nitro and is looking forward to us going to the Winternationals in a couple weeks.
I had also read at one time that part of the flames is burning hydrogen. From one of those 'check this out' lists.
"-Nitro methane burns yellow. The spectacular white flame seen above the stacks at night is raw burning hydrogen, disassociated from atmospheric water vapour by the searing exhaust gases."
True or not, makes a good story.
It's funny. You spend years *knowing* how much fuel these things use, and yet when I watch that video I'm still astonished. Sometimes quantities can be abstracted away until it's right there in all its firehose glory.
A bit like the helitack I watched on the weekend sucking up water at about ~65L/s. Seems obvious enough until you see 65L/s come out the end of a pipe.
I scanned an article ages ago and posted it on my personal website. I don't think I've touched that site in 10 years, but the article is still there. From a publication in 1991: (Uploaded to Google Photos since that old website is massively insecure)
State of the art Top Fuel in 1991.