Should we bring back high compression engines, to save fuel? Definetly more efficient -how much?
In the 70s, EPA rules caused a decrease in compression ratios, for 2 reasons:
1. eliminate lead as “octane improver”
2. reduce nitrogen oxides emissions
BUT:
1. Ethanol as an octane enhancement? – some dragsters use pure ethanol @ 15:1 ratio
-also: more octanes only needed @ wide open throttle – which allows cylinder to be filled more completely. Did car makers switch to 4bbl carbs, to maintain power, by using more air/fuel, less efficiently?
2. If speed limits were reduced, smaller less powerful cars would gain practicality. combined with more efficient combustion, perhaps overall NOX output wouldn’t gain much. slower traffic would also get more people into bicycling.
? efficient high compression engines, as reason for cars used in other countries getting better mileage
– I think high compression is one reason diesels are more efficient.
– high power/weight applications use high comp. – motrocycles, airplanes
– high ratio allows more expansion of hot gases
nigel m – I am talking about a change which took place in the early 70s. horsepower ratings took a big plunge at that time – not the 90s .
at the time, carburetors were common – the change I refer to is that : before, most V-8s had 2bbl carbs, much smaller air flow. after: the 4bbl carb became by far the most common carb., on v-8s.
We’d at least get a higher power/weight out of engines, but I think they were also more efficient – or Why did increase carb size radically
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Filed under Gas Conservation FAQ by on Feb 24th, 2011. Comment. 
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Comments on Should we bring back high compression engines, to save fuel? Definetly more efficient -how much?
Take a look at the current engine specs, we have higher compression ratio engines now than ever before.
The information you site above looks like it is ten or more years out of date.
1. You can not buy a new car or truck with a carburetor – the are all fuel injected.
2. yes
? cars sold in the USA are as efficient on a weight basis as those sold elsewhere, USA cars tend to be heavier causing increased fuel consumption.
- diesel yes
- airplane use very low compression ratios.
- more expansion.
Did you get this from a 1990 publication?
Interesting thought. me thinks back to the 1970′s when Japanese cars became popular. Here comes a car that can gain speed at half the engine size of typical American muscle. How? higher compression in the motors. What the ramifications would be for extremely high compression engines. Not sure. But increasing compression, using turbo to recycle exhaust air, and shrinking the combustion chamber would develop a more fuel efficient car. I’m going to ponder this with my brother who’s an engineer. he has great cooky ideas and theories for this stuff. Thanks, you rattled me brain a bit.
ricardo9505
Japanese car gain speed at half the engine size of typical American muscle. How? ? ? … because they were modern design engines throughout, where american muscle cars were stuck in the 1950′s when any idiot could make a fast car by chucking a riduculously high capacity & very inefficiencient engine in it.