Okay. I knew that there were several recent(ish) engines that had outrageously high compression ratios, but I’m having trouble believing what I’m seeing. A European-spec Mazda2 with a normally-aspirated 15:1 compression ratio! FIFTEEN TO ONE! And to add to the insanity, Mazda claims that it runs on regular gas! For those of us in the USA, we’re limited to a 14:1 compression ratio.
From Wikipedia.org regarding a related Mazda technology:
Skyactiv-X is the first commercial petrol engine to use homogeneous charge compression ignition (HCCI), in which the fuel-air mixture ignites spontaneously when compressed by a smaller, separately ignited charge of fuel. This allows it to reach a compression ratio of 16:1 instead of 14.0:1 of previous generation and operate much leaner than a spark ignition engine, reducing fuel consumption and emissions.
I’ve honestly never been really taken by Mazda vehicles, but I’ve admired them as a company that marches to their own drummer, and I did know they had some cool technology. Frankly, the details are far more interesting than I would have imagined.
This got me thinking about how today’s compression ratios for new vehicles compare to the classic muscle car period. The following graph tells the story, with the 1964 – 1974 period highlighted in green.
The 1971 – 1974 drop in compression ratios is clearly displayed, followed by an almost linear forty-year rise in compression ratios. The last year with values is 2015, with ratios well above 10:1. Remember that these are averages, not the highest values. The 2015 average is a full point higher than the peak of 1970!
I, for one, didn’t think I would ever see average compression ratios exceed those of the classic muscle car period! But, I would be wrong, wouldn’t I?
