Exhaust thrust

[rookie]

Here is after the car has passed, his pants don't seem to be off.

Wrong guy, that is the guy that was in front of the car raising the body, the guy that lost his pants is on the passenger side of the car right at the header, it lifts him off the ground and blows his pants off it shows it at least 3 times...you can hear both guys interviews in the video link I posted and he clearly says it, keep in mind this was just a blip of the throttle I can only imagine what its like at full song.

[SchmidtMotorWorks]

Here is after the car has passed, his pants don't seem to be off.

Wrong guy, that is the guy that was in front of the car raising the body, the guy that lost his pants is on the passenger side of the car right at the header, it lifts him off the ground and blows his pants off it shows it at least 3 times...you can hear both guys interviews in the video link I posted and he clearly says it, keep in mind this was just a blip of the throttle I can only imagine what its like at full song.

I see it here:
The way he describes getting the burns I guess it got under the opening and blew them up. If they were synthetic possibly melted them.
That doesn't tell you anything about down-force though.

If you think down force comes from the pipe, maybe it does, do the math, show us how it is possible.

[rookie]

What is the math equation for lifting a 200 pound man and blowing his pants off?...at 1/4 throttle.

[SchmidtMotorWorks]

What is the math equation for lifting a 200 pound man and blowing his pants off?...at 1/4 throttle.

Your way of thinking is a perfect example of how urban legends get started.
Down force depends on the acceleration of gas in the duct.
If you add anything else into it, you are getting further from a correct answer, not closer.

[MadBill]

Besides, the throttle was fully closed again before the car got alongside the crewman, so we're talking thrust at idle.

[SchmidtMotorWorks]

Besides, the throttle was fully closed again before the car got alongside the crewman, so we're talking thrust at idle.

Good eye! The blades are closed.

If the pipes passed right under the openings in his pants that would explain the burns.

It would be interesting to see the pants to see what happened to them, what part did heat play into it?

[rookie]

Jon, if you ever go to a Top Fuel event you should take your calculator and explain to Dickie how what he experienced is mathematically impossible.

[SchmidtMotorWorks]

Jon, if you ever go to a Top Fuel event you should take your calculator and explain to Dickie how what he experienced is mathematically impossible.

The problem is what you think you saw and what happened probably are not the same thing.

I make parts and instruments for a FC team.

[SchmidtMotorWorks]

I asked some people that have a lot of Nitro runs under their belts about what happens when 1 or more cylinders go out on one side of the engine. They did agree that it does cause the car to turn but the reason for the turning was less certain. They had some ideas worth looking into, I'll try to work some of them out to see. One point of interest was noted was that it happens most on engines that burn a lot of fuel after the mixture has exited the exhaust pipe.

[MadBill]

Now that's a good point! It's one thing to develop a little thrust from the exiting mass of normal exhaust gas; quite another to be firing a liquid-fueled rocket in each header tube plus ejecting a far greater mass than just that of the cylinder's combustion products.

[swatson454]

Downforce, thrust or not, that shit blew a man's pants off. Dude!

[SchmidtMotorWorks]

Now that's a good point! It's one thing to develop a little thrust from the exiting mass of normal exhaust gas; quite another to be firing a liquid-fueled rocket in each header tube plus ejecting a far greater mass than just that of the cylinder's combustion products.

The fact that the change happens when the cylinder goes out seems to indicate that the force comes from burning outside the pipe because roughly the same mass is pumped through the pipes whether it is burning or not.

[rookie]

No exhaust thrust...clearly a myth, it doesn't lift a man off the ground, throw him back, blow his pants off or move a big block in the dyno cell...not mathematically possible, any thing you have experienced is all a figment of your imagination. http://www.youtube.com/watch?v=e58-l3IBi0c Please just move along... nothing to see here!

[Kevin Johnson]

Now that's a good point! It's one thing to develop a little thrust from the exiting mass of normal exhaust gas; quite another to be firing a liquid-fueled rocket in each header tube plus ejecting a far greater mass than just that of the cylinder's combustion products.

The fact that the change happens when the cylinder goes out seems to indicate that the force comes from burning outside the pipe because roughly the same mass is pumped through the pipes whether it is burning or not.

Fuel air explosive. Energy dispersed in many directions. Could easily rip the seams of pants by igniting/expanding after being pumped up them (overpressure). That would explain the severe burns as well and the ability to lift the man.

[SchmidtMotorWorks]

No exhaust thrust...clearly a myth, it doesn't lift a man off the ground, throw him back, blow his pants off or move a big block in the dyno cell...not mathematically possible, any thing you have experienced is all a figment of your imagination. http://www.youtube.com/watch?v=e58-l3IBi0c Please just move... nothing to see here!

Rookie, notice the ducting on the headers.

Have you ever noticed a gasoline powered car or motorcycle moving forward from exhaust gasses in neutral by reving the engine? I have not.

In regards to mathematically possible, we still don't know what the force is or where it comes from that turns the car.
The drivers I talked to today said it feels more like a difference in downforce on the tires left to right but you shouldn't jump to a conclusion about what combination of forces are involved.

It could be the acceleration of the gas through the exhaust seat throats, in a Hemi with 45 degree bank angle an 35 degree exhaust valve the seats are nearly horizontal. That region seems most rocket-like but I wouldn't make any conclusion without doing the math 1st.

It might be from fuel burning in the pipes, maybe there is some circumstance that can make burning self oxidising fuel go super sonic in the pipe, never thought about it much so I won't jump to a conclusion until I do the research.

Might be that the fuel burns outside of the pipe when it hits fresh oxygen, that would also cause force.

Didn't the original question relate to a gasoline powered car? If so, these nitromethane examples may have nothing to do with it.