I got into an argument today about what makes a car “go.” The two schools of thought were:
The explosion (combustion) provides the force, that when applied mechanically, makes the car go.
The force of the exhaust coming out of the pipe was the “net force” of the car acting as a system; ergo the tailpipe emissions make the car go. Without an exhaust, equal and opposite forces would make the car go nowhere.
Which is correct?
Come on now, a little bit of gas flowing out of a pipe is going to push a several thousand pound car? Gimme a break. The gasoline enters the pistons where it is ignited and explodes. The pistons (…) make the wheels go.
The short answer is explanation 1. Sort of.
For the long answer, go to
where you’ll find a dandy explanation for how internal combustion gets the wheels turning. They even have an animated illustration.
I’m bookmarking this site. It looks neat.
How could you drive in reverse if the tailpipe provided the propulsion?
Arjuna34
Even better, if propulsion was provided by the exhaust then what about all the cars, trucks and vans that have a right angle at the end of the tail pipe which makes the exhaust come out of the side of a car. I can see it now, a whole freeway of spinning cars…
-N
Coooool! Jet cars!
Makes me wonder why I just got my gearbox fixed.
Like they said, its #1…BUT. In a car equipped with a turbo, the escaping exhaust gases spine a turbine (turbo, turbine, get it?), which is used to drive additional power through the engine. So its possible to use the power of exhaust gas to provide additional power for the engine.
Umm…all a turbocharger (driven by a turbine in the exhaust) or supercharger (driven by a belt on the crankshaft pulley) does is pump air into the engine. More air = more fuel can burn = more power. There’s no “but” to it. The exhaust doesn’t “drive additional power through the engine”
True, for today’s automobiles, but, there used to be internal combustion radial aircraft engines that harnessed exhaust gas with a turbine that WAS connected in such a way that the power derived helped power to propeller. IIRC they were called “turbo compound engines”. So occ is not too far off.
The taipipe just sucks in enough air to pull the car backwards, do I have to tell you guys everything :rolleyes:
Well, school of thought #2 would argue that the “net force” of the emissions through the tailpipe is given direction by the transmission. If you didn’t have a transmission, the car would could only go in the opposite direction.
School of thought Number 2 is so wrong I do not know where to begin.
But to apply Occam’s razor, without knowing anything about how a car works - it is easily disproven by no other means than observing a large diesel truck with a vertical exhaust pipe.
The transmission example is wrong as well.
the exhaust is not the ‘net force’ but the ‘net wasted energy’. the force leaves the car ‘system’ at the tire/road interface as a propulsive force.
Hypothesis: The gas coming out of the tailpipe pushes the car forward.
Test: Drive to level spot. Put car in neutral. Gun engine. If car propels itself forward, the exhaust made it go.
(Hint, it won’t move.) (Actually, it could move a little, because of torque effects and vibration.)
Yeah, I guess I kinda misread #1 in my haste to mention turbochargers. Ahh well.
Hint: Why do car makers bother with crankshafts, transmissions, drive shafts, differentials, and all that other stuff that connects the engine to the wheels?