Crankpin Location at Top Dead Center

Joined
Jun 11, 2005
Messages
7
Hello to All!

I have a question about crankshaft rotation, specifically the reference point of the crankpin (timing/right side, #1 piston) when the piston is at top dead center.

As the barrel is not directly above the crank/case at 12 o' clock like earlier singles/twins, what is the crankpin location when the piston is at top dead center?

When piston #1 fires what is the location of the crankpin?



:?:
 
Joined
Jun 14, 2003
Messages
747
If the cylinder is canted 10 degrees from vertical, the crank pin will also be at 10 degrees when the piston is at the top of its stroke, or TDC.

Now, when the engine is running, the ignition system triggers the spark plug to fire at 28 degrees before the piston and its crank pin reach TDC. This advanced ignition gives the air/fuel mixture time to burn.

Jason
 
Joined
Jun 3, 2005
Messages
21
Or one could say (applies to any engine with straight connecting rods): When the centerpoint of the crankpin axis lines up with the line formed by the centerpoint of the crankshaft axis and the centerpoint of the wrist pin axis, that is the exact TDC.
 
Joined
Sep 20, 2005
Messages
66
Unless the pistons have offset pins, or the cylinder axis is offset from the crank center, or both.
 
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