The other pistons in the engine are at different points in their cycle; when one piston is at BDC and about to go up to TDC, another piston is at TDC going down to BDC

The inertia of the engine components keeps things moving, particularly the flywheel.

RVA's scenario is true for multi cylinder engines

Cpro's response is also in effect and particularly true for single cylinder engines

There is no vacuum on the exhaust stroke. The piston has to do work to push the exhaust out.

The other responders are correct about where the energy for that work has to come from.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

dgallup,
For multi cylinder engines, does the exhaust manifold provide any substantial suction on the cylinder in question?

Exhaust manifold design as well as the entire exhaust system design certainly have an effect on getting some of the exhaust gases out via the pressure waves that bounce back in forth in the exhaust system. The majority of the gases though are simply pushed out the cylinder by the rising piston.

Hi folks,
Thanks a ton for your useful replies.What i understand is that the force of the pistons downward motion raises it again to the TDC.Please correct me if i am wrong.Thank you.

The work put into the system by the explosion provides momentum. The inertia associated with this movement keeps it going and brings it back to TDC for the second explosion. A flywheel is a big chunk of rotational mass designed to help this. Additionally the other cylinders in a multi piston engine are firing at different times, so more work is being put into the system and the crankshaft keeps revolving.

Hi Rvamache,
You hit the bull's eye.The flywheel you have mentioned is the one which gives me a greater understanding of this concept.Thanks a ton to everyone.

P.S.: I am not getting notifications on my inbox on my threads although i didnt turn it off.Any suggestions would be highly appreciated.

There are old single cylinder engines that regulate their speed by firing only when the speed drops (hit and miss engines). The flywheel inertia can keep the engine turning for several revolutions between combustion events.

Watch a few youtoob examples and perhaps you will become more comfortable with the idea of flywheel inertia sustaining crankshaft rotation: https://www.youtube.com/watch?v=MtrEUecw2Uk

Thank you Ehudson.It was very useful.

An old friend of mine worked in a bush mill over 50 years ago. The head saw was driven by an enormous single cylinder "hit and miss" engine. The flywheel was about 7 feet or 2 meters in diameter.
Friend said that the crew would turn off the fuel when they went for their 1/2 hour lunch break. When they returned 30 minutes later, the engine would be still turning.
They would turn the fuel back on and go back to work.
They don't make them like that anymore!

Bill
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"Why not the best?"
Jimmy Carter

Quote (An old friend of mine worked in a bush mill over 50 years ago. The head saw was driven by an enormous single cylinder "hit and miss" engine. The flywheel was about 7 feet or 2 meters in diameter.)

How'd you like to be the whistle punk who had to crank it on a cold morning?

jack vines