Thread: my 357, questions, estimates, opinions

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Originally Posted by ak99669

when you have a higher compression ratio your combustion area has less air volume ie requires less fuel

Sort of, but not exactly. The smaller volume of the chamber in a high-compression motor means that there is more squeeze on the air/fuel that is drawn into the cylinder and combustion chamber with the intake valve open. More squeeze increases the volumetric efficiency of the motor, allowing more power and more mileage to be produced from the same amount of fuel that might be used in a low-compression motor.

Originally Posted by ak99669

and that all comes into play that's why all the new motors coming out are back up to 10-11:1 compression, and the new v8s are getting respectable mileage AND making more power

Advances in combustion chamber design are mostly responsible for allowing current-day motors to use higher static compression ratios, resulting in fuel-efficient and mileage-friendly operation. Do some reading on Sir Harry Ricardo. Much of the advance in CC design results from his experiments prior to WWII. Please read through this wikipedia article about him......
http://en.wikipedia.org/wiki/Harry_Ricardo

Originally Posted by ak99669

look back to the 80s, an 8:1 350 with a cam that doesn't open the valves long enough to let it clear it's lungs? That's why those motors puked all over themselves lol

Due to pressure from the Feds to get better mileage and cleaner emissions, the car makers were scrambling to find a formula that would satisfy all parties involved, while designing the motors they produced to run on cat pizz fuel mandated by the Feds. That's what finally lead them to electronic fuel injection, roller tappet camshafts and higher static compression ratios, which resulted in higher thermal efficiency, again, due to the tighter squeeze on the mixture.

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