Quote:
Originally Posted by Daox
It has 14:1 compression ratio, the lowest of any passenger car diesel engine. It says that the lower compression ratio allows for better air/fuel mixing and optimized combustion timing.
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I don't think whoever wrote this article knows what they're talking about.
For one thing, they actually report the compression ratio as "
14:1.1". Aside from being a completely unorthodox way of defining compression ratio, that equates to only 12.7:1.
Secondly, I've tested various compression ratios in detail for years (with engines on a dyno) and have never seen a scenario where lowering the compression ratio increased the efficiency. Efficiency of the diesel cycle is fundamentally tied to the compression ratio, and is probably the biggest reason why diesels typically have higher efficiencies than gassers. See here:
The Diesel Engine
The drawback of higher compression ratios are that the max power output drops becuase the cylinder pressures go up and, therefore, components sometimes need to get heavier and more expensive. It's also not uncommon for smoke to increase some.