Cam and compression ratio compatibility
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===Cam phasing=== | ===Cam phasing=== | ||
You can fine tune a particular cam by advancing or retarding it. This procedure does nothing to alter the lift, duration, lobe separation, etc. of the cam. What does happen is the phase of the camshaft is advanced or retarded in relation to the crankshaft position. Advancing the cam closes the intake valve sooner. This will build more pressure in the cylinder and shift the power band lower. Retarding the cam will cause the intake valve to close later, this will build less pressure in the cylinder and shifts the power band higher. | You can fine tune a particular cam by advancing or retarding it. This procedure does nothing to alter the lift, duration, lobe separation, etc. of the cam. What does happen is the phase of the camshaft is advanced or retarded in relation to the crankshaft position. Advancing the cam closes the intake valve sooner. This will build more pressure in the cylinder and shift the power band lower. Retarding the cam will cause the intake valve to close later, this will build less pressure in the cylinder and shifts the power band higher. | ||
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| + | Modern engines with '''variable valve timing''' are able to phase the cam while the engine is running. This represents the best of both worlds because the same cam is able to optimize valve events based on engine RPM's. This means the VVT engine is capable of: | ||
| + | *advancing the cam (early IVC) at lower RPM's to produce more torque, less intake reversion, and less lope at idle | ||
| + | *retarding the cam (late IVC) at higher RPM's to produce more horsepower | ||
| + | Of course the SCR remains constant despite cam phasing. The DCR will vary based on RPM since this effects intake charge velocity. | ||
==Resources== | ==Resources== | ||
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