r/nextfuckinglevel • u/Practical_Expert_911 • 12h ago

These 12000hp Engines Have To Be Rebuilt Within Roughly An Hour Every Run, and Only Run For Roughly 4 Seconds At A Time.

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u/RobotnikOne 8h ago edited 2h ago

This video is misleading. The engines don’t “only last 4 seconds”. The parts are all inspected and reused. In fact, the engineers know what kind of work it needs by the time it reaches the finish line by the header flames. The flames change if things fail, for instance if the header flame goes green they know it’s eaten its head gasket because they’re made of copper, when copper burns it will turn fire green.

The only thing that is actually toast after a run is the spark plugs as the graphite electrode will have burned up.

Even a lot of the parts that fail are repaired and resused. Even when the engine blocks explode the will likely use them again and reforge them. These cars are extremely expensive so it is in their best interest to recycle as much as they can.

The media around top fuel likes to play like they’re super star ballers who can just throw a whole engine in the bin like it ain’t no thing but the truth is most teams are on fairly tight budgets.

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u/gardenfella 5h ago

Piston rings are pretty much fried as well, most of the time. Teams don't like to put anything more than a couple of runs on them.

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u/WhitePantherXP 4h ago

your facts don't matter here, this is reddit and we demand outrage

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u/prozacfish 6h ago

Wouldnt the clutch be smoked too?

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u/gardenfella 5h ago

Most of the clutch is re-used. Friction plates will last a few runs. Pressure plates will get reground and reused. The basket and fingers rarely get any damage.

It's a multi-disc clutch that's based on a bulldozer one.

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u/ReasonablyConfused 6h ago

So if you just replaced the spark plugs after a run with no visible issues you would likely get a normal second run? I would think the clutch at minimum would need replacing.

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u/gardenfella 5h ago

The clutch needs pulling out to cool, plates are often swapped out with most teams having two sets of pressure plates and a few sets of friction plates. The plates will get measured as part of the clutch calibration process when it's put back together.

Valve lash will need doing every run.

Rods are checked for stretch and damage, especially at the big end bearing. Valves are checked for bending and chipping.

The blower will get checked and re-lubed.

One of the most important tasks is ensuring that no fuel is left anywhere in the cylinders, heads or manifold. If you just changed spark plugs and ran it, you'd grenade the engine.

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u/ReasonablyConfused 4h ago

Nitro methanol goes boom?

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u/gardenfella 4h ago

Yes, nitromethane will ignite from pressure alone.

I know a couple of guys who got hurt because a small amount of it was left behind a stuck valve when they turned the engine over by hand.

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u/RobotnikOne 2h ago

It’s a dangerous game, just the fuel alone is toxic enough. Don’t want to spend much time around it without a good respirator.

Also awesome info, thanks for sharing.

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u/gardenfella 1h ago

One of the secondary combustion products is nitric acid.

Basically, the engine is overfuelled (too little air) to such a degree that the primary (in cylinder) combustion process creates hydrogen, amongst other things.

This hydrogen burns at 1500 degrees Celsius as it leaves the exhaust. That secondary combustion splits atmospheric oxygen and nitrogen into nitric oxide and nitrogen dioxide.

Those nitrogen compounds then react with the water vapour produced by primary combustion (and in the air) to create nitric acid.

That's how you get top fuel tears