I have a bit of a technical question about dynamic compression ratios and turbo's (and cam's).
This article:
cochise.uia.net/pkelley2/DynamicCR.html
suggests that the optimum dynamic compression ratio for an engine is usually 7.5 - 8.5:1. Now I understand everything written in the article but am wondering what the situation is when a turbo is added to the engine.
For example, I have deduced that my engine, with a static compression ratio of 8.5:1, will have a dynamic compression ratio of 6.01:1 with the standard cam that closes the inlet 78 degrees ABDC.
If I change the cam to one which closes at 63 degrees ABDC, the dynamic compression becomes 6.85:1. This is the mildest cam I can fit without having one ground.
The question is will I gain performance by switching to the milder cam? I know that the dynamic stroke will be greater and therefore less of the air/fuel mix will be pushed out of the (still open) inlet valve. Also, since my cylinders will be more than 100% full (due to the turbo), there will be less (or no) ramming effect with the longer duration cam than there would be with natural aspiration.
Therefore, it is my opinion that I'd be better changing to the milder cam. Does anyone with experience in this area agree/disagree?
Cheers
(Random picture to ease boredom)
This article:
cochise.uia.net/pkelley2/DynamicCR.html
suggests that the optimum dynamic compression ratio for an engine is usually 7.5 - 8.5:1. Now I understand everything written in the article but am wondering what the situation is when a turbo is added to the engine.
For example, I have deduced that my engine, with a static compression ratio of 8.5:1, will have a dynamic compression ratio of 6.01:1 with the standard cam that closes the inlet 78 degrees ABDC.
If I change the cam to one which closes at 63 degrees ABDC, the dynamic compression becomes 6.85:1. This is the mildest cam I can fit without having one ground.
The question is will I gain performance by switching to the milder cam? I know that the dynamic stroke will be greater and therefore less of the air/fuel mix will be pushed out of the (still open) inlet valve. Also, since my cylinders will be more than 100% full (due to the turbo), there will be less (or no) ramming effect with the longer duration cam than there would be with natural aspiration.
Therefore, it is my opinion that I'd be better changing to the milder cam. Does anyone with experience in this area agree/disagree?
Cheers
(Random picture to ease boredom)