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Old 03-29-2005, 02:30 AM   #31
srober32
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Quote:
Originally Posted by vwhobo
Newsflash for you, Twinkie. You were the one bitching about it and now you have two posts in this thread that didn't answer the question. Wanna go for three?
Yup, pole puffer, fun ain't it?
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Old 03-29-2005, 02:35 AM   #32
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Quote:
Originally Posted by srober32
Yup, pole puffer, fun ain't it?
What, puffing poles? That would be your department. As a matter of fact you should start a thread about it and you won't have to worry about getting any input from me because that is your area of expertise.

Are you going to go for four? Hypocrite.
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Old 03-29-2005, 02:37 AM   #33
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Quote:
Originally Posted by vwhobo
What, puffing poles? That would be your department. As a matter of fact you should start a thread about it and you won't have to worry about getting any input from me because that is your area of expertise.

Are you going to go for four? Hypocrite.
Congradulations! You found your calling in life! Typing with one hand!
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Old 03-29-2005, 02:46 AM   #34
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Originally Posted by srober32
Congradulations! You found your calling in life! Typing with one hand!
I don't even know what that's supposed to mean. You might want to think about hiring a put down writer.

Five anyone?
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Old 03-29-2005, 03:15 AM   #35
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Quote:
Originally Posted by CarEXPERT
A 6cyn engine fires/powerstroke every 120 degrees of crank rotation. a 4 cyn 180 degrees, an 8cyn 90 degrees.


errr. you sure that this is right? because I believe the subaru legacy's 6 piston engine is a flat-plane crankshaft. Same thing goes for the f430.

is there a flaw in my understanding?
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Old 03-29-2005, 03:21 AM   #36
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depends on cylinder arrangement (ie straight 6, V6, horizontally opposed etc)

the crank angles are determined to balance the engine. Everytime a piston hits the bottom of its stroke, it's applying a force downwards, similarly an upward force at the top. By changing crank angles and crankshaft counterweights, you can stop these forces from shaking the engine to bits.

A straight 4 cyl is easy because its symmetry means that the two in the middle are on the same part of the crank, and the two outside ones are exactly opposite. They fire on consecutive strokes though, not together.
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Old 03-29-2005, 09:57 PM   #37
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Quote:
Originally Posted by windsonian
depends on cylinder arrangement (ie straight 6, V6, horizontally opposed etc)

the crank angles are determined to balance the engine. Everytime a piston hits the bottom of its stroke, it's applying a force downwards, similarly an upward force at the top. By changing crank angles and crankshaft counterweights, you can stop these forces from shaking the engine to bits.

A straight 4 cyl is easy because its symmetry means that the two in the middle are on the same part of the crank, and the two outside ones are exactly opposite. They fire on consecutive strokes though, not together.

Crank angles determine balance of engine?? I thought the couterweights and the flywheel balances out the power strokes.
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Old 03-29-2005, 11:59 PM   #38
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Quote:
Originally Posted by CarEXPERT
Crank angles determine balance of engine?? I thought the couterweights and the flywheel balances out the power strokes.

They are used to balance out the forces created by the pistons.

Think about it this way ... (btw everyone, i know this is a dodgy example)
If you've got a ball on a piece of rope. Tie the end of the rope around your wrist and throw the ball. When the ball hits the extent of the rope and starts coming back you will feel it tugging on your wrist. This force is why an engine needs to be balanced.

Imagine that all the pistons went up and down together. Everytime they hit the top of the stroke (all at the same time), they would all try and pull the crankshaft upwards. Then at the bottom of the stroke, they would all try to push it downwards. This makes for a whole lot of shaking in the engine.

The counterweights effectively apply a similar force to the pistons, so between the force of the pistons and the force of the counterweights, there should (in theory), be no overall force trying to shake the engine.

In theory (if I remember correctly), a straight 6 cylinder engine can be balanced without counterweights at all.

Balancing comes in 2 parts, static and dynamic ... but that might be a bit complex for this thread.
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