Dynamic compression ratio calculator

[michael hurd]

http://www.chevytalk.org/fusionbb/showtopic.php?tid/92966/
http://www.chevytalk.org/fusionbb/showtopic.php?tid/92966/
Like the link says, the only compression ratio the engine 'actually sees' is when both valves are closed, and this is dependent on the valve timing events.

Too low a dynamic compression ratio will lead to a 'lazy' engine, compared to one that has a wide powerband. Keep in mind that this is also RPM dependent. If you want a peaky, one hit wonder, shoot for a low dynamic compression ratio engine.

 

[slowburb]

DCR is kind of like voodoo. It's theoretical at best, and OK to use for comparative purposes. It may help determine the snappiness of an engine, and generally aids in determining octane requirements. It's more straightforward in old school engines with carbs and distributors than it is with EFI because of the dynamics of fuel and spark control through the computer systems.

The last set of figures I used comparing DCR of stock L31 cam timing and "395" cam timing showed a hair less DCR from the "395" cam, yet the engine had way more power with the "395"', all else constant.

The best read for understanding and the best calculator for DCR that I've came across is here:

http://cochise.uia.net/pkelley2/DynamicCR.html