TDC?? Question....
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Pro
Joined: Oct 2000
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TDC?? Question....
What does it mean (mechanically) to have the engine at TDC, in the #1 position?? What should be happening as the engine is turned...does the intake valve begin to open and on and on....?? Or does the exhaust valve begin..etc???
Melting Slicks
Joined: Mar 2002
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From: The cure for the blues is eight cylinders roaring
Re: TDC?? Question.... (72Shark)
TDC=Piston is at the top of its bore.
Compression stroke= I think is what you'r looking for with both valves closed.
hope this helps
Compression stroke= I think is what you'r looking for with both valves closed.
hope this helps
Instructor
Joined: Jul 2002
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From: Raleigh NC
Re: TDC?? Question.... (72Shark)
hmm, I'm not sure about this so someone back me up. At TDC, both valves will be closed because it just finished the compression stroke and is about to ignite the mixture. Then the crank should turn about a half a revolution and then the exhuast valve will begin to open, and will be about closed when the piston returns to the top of it's travel, then the intake valve opens, the piston goes back down, the compression begins again, and you're back at TDC.
Race Director
Joined: Dec 1999
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Re: TDC?? Question.... (72Shark)
During the 4 stroke cycle a piston reaches TDC twice.
It's roughly like this (the valve events are a little more complex but this is the basic idea)
TDC -> intake valve opens, piston travels down -> BDC (bottom dead center) -> intake valve closes -> piston travels up = compression -> TDC, ignition -> expansion, piston travels down -> BDC, exhaust valve opens > piston travels up, exhaust is expelled (pushed out) -> back to beginning.
TDC before intake stroke is when the exh valve closes. You'll see it close, then at TDC the intake will open. (at TDC both valves are actually open a bit)
To set valvelash you'll need TDC after compression (actually it'll be fine anywhere on the base circle, as long as the lifter is not on a lobe), when the ignition occurs. This is when both valves are closed. When you look at the cam, the exh. valve will be the 1st lobe and the intake the 2nd one directly after (turning clockwise)
Marck
[Modified by Twinnie, 7:34 AM 9/30/2002]
[Modified by Twinnie, 7:36 AM 9/30/2002]
It's roughly like this (the valve events are a little more complex but this is the basic idea)
TDC -> intake valve opens, piston travels down -> BDC (bottom dead center) -> intake valve closes -> piston travels up = compression -> TDC, ignition -> expansion, piston travels down -> BDC, exhaust valve opens > piston travels up, exhaust is expelled (pushed out) -> back to beginning.
TDC before intake stroke is when the exh valve closes. You'll see it close, then at TDC the intake will open. (at TDC both valves are actually open a bit)
To set valvelash you'll need TDC after compression (actually it'll be fine anywhere on the base circle, as long as the lifter is not on a lobe), when the ignition occurs. This is when both valves are closed. When you look at the cam, the exh. valve will be the 1st lobe and the intake the 2nd one directly after (turning clockwise)
Marck
[Modified by Twinnie, 7:34 AM 9/30/2002]
[Modified by Twinnie, 7:36 AM 9/30/2002]
Race Director
Joined: Mar 2001
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From: Living in the Hartland
Re: TDC?? Question.... (Twinnie)
During the 4 stroke cycle a piston reaches TDC twice.
It's roughly like this (the valve events are a little more complex but this is the basic idea)
TDC -> intake valve opens, piston travels down -> BDC (bottom dead center) -> intake valve closes -> piston travels up = compression -> TDC, ignition -> expansion, piston travels down -> BDC, exhaust valve opens > piston travels up, exhaust is expelled (pushed out) -> back to beginning.
Marck
It's roughly like this (the valve events are a little more complex but this is the basic idea)
TDC -> intake valve opens, piston travels down -> BDC (bottom dead center) -> intake valve closes -> piston travels up = compression -> TDC, ignition -> expansion, piston travels down -> BDC, exhaust valve opens > piston travels up, exhaust is expelled (pushed out) -> back to beginning.
Marck
