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2004 Forester XTi
1,005 Posts
Discussion Starter #1 (Edited)
Ok, so you have fuel that get's mixed with the air that get's sucked into the combustion chamber. The piston compresses that amount of air into it's compression ratio. The spark plug ignites the air:fuel ratio and that explosion pushes the piston down the block. That force pushes the rod (between the piston and crank) to force the crank to spin about 1/2 rotation until another chamber gets another explosion force to finish the full rotation of the crank.

Now, that force spinning the crank (that has the crank pulley at one end) spins the power steering and alternator via belts. I'm guessing the other end of the crank is connected to the flywheel. That spins freely until the clutch disk is applied against(?) the flywheel. The clutch is attached to the selected gear of the driver, spinning the wheels depending of the size of the gear selected.

The exhaust that results from the timed explosion in the combustion chamber (after the piston is fully forced down from the explosion) gets pushed out through two exhaust valves via the piston. The exhaust is pushed out the exhaust manifold, cleaned through the catalytic converters, neutralizes the sound/vibrations of the force of the exhaust, and out the tailpipe into the ozone.

I would like to be corrected on how a car get it's power down to the wheels from the engine?

There are other factors that are of my concern that I don't fully understand. Ex's:
1. Too light of a flywheel and pulley may allow the flywheel to spin too much for daily driving... resulting in jerky acceleration?
2. Detonation is force from an early explosion pushing against the piston during compression, causing in engine destruction?
3. Too strong of a clutch plate (unnessary clutch upgrade) does something bad to the drivability... I don't know
4. I don't fully understand the concept of N/A cars needing some type of backpressure (not too big of an exhaust diameter) while turbos don't. They use the same engine, don't they?
5. When/where does the timing belt come in to play?

Premium Member
Two Mini Coopers!
10,629 Posts
1. Yes, overly light flywheels and pullies can allow the engine to rev up, but since they don't weigh anything, they don't help it slow down either. So what you get is an engine that revs very quickly, and has a tendancy to keep going at the speed rather than that controlled slow down.

2. Yes, detonation is caused by bad gas exploding before the spark plug goes off (basically, spontaneous combustion due to higher temperatures) and if that happens while the piston is still moving upwards, you may as well be hitting the piston with a sledgehammer. it does not take much detonation (pinging, pre-ignotion, all the same) to destroy your pistons and rings.

3. Clutch plate? Probably just the fact that it's hella hard to push down with your leg - that gets tiring.

4. A N/A engine needs backpressure, because as the exhaust comes out of the engine (heads) the backpressure can help suck the exhaust out. Too open of an exhaust and you lose that "scavenging" effect, and lose power. A turbo charged engine is different in that the air is being forced through the engine at high pressure. You don't need back-pressure at this point, you need to open things up to allow more air to go through the system. Therefore, a turbo will always want a bigger (or none at all) exhaust, where a N/A engine will need a properly sized exhaust. Too big on N/A and you just lose power.

5. Timing belt is used to open and close the valves as the engine spins. Sometimes cars have timing chains, and older cars have pushrods and a central cam shaft which operate the valves. Kinda complex to explain briefly, though

Try and you can get details about all this stuff as well, or look for a book by Corkey Bell called Maximum Boost. Excellent book. Here's the link:
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