Lowering the compression of engine?

Question

Just curious, how do you lower the compression ratio of the engine? I have seen engines in different compression but with same engines.

Answer 1

You can do it with a different crankshaft, but that will also change the total displacement of the engine.

You can change the connecting rods to something a bit shorter; that will lower compression and keep the overall displacement the same.

You can shim the head with thicker gaskets.

You can use different pistons, ones with less or no crown, or have the wrist pin location higher toward the crown.

You can rebore the wrist pin bores in the pistons and press in off-center bushings (not recommended).

You can use a different camshaft grind that would hold the intake valve open somewhat into the compression cycle, effectively converting the engine to a Miller-cycle engine.

Answer 2

1..differnt head/combustion size

2..thicker head gasget.

3.. "smaller " pistons

Answer 3

Different pistons, different heads, or even thicker head gaskets ( not much there)

Answer 4

"compression ratio" is a design specification -- ratio of the combustion chamber area at TDC to cylinder area.  Not sure why a person would want to lower the ratio of an existing engine, you'd have to compensate with other design changes.

"compression" as measured in PSI is a diagnostic tool for gauging the overall health of a motor.  Best way to lower the compression of an engine is to run it overtemp.............  :D