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*HEI451* · 06-09-2011, 11:51 AM

The whole mileage game is linked to air/fuel ratios, and engine performance packages.

That said, with a cruise air/fuel ratio of say, 14.5:1, 60 mph would use LESS air/fuel flow than 75 mph. Any engine that uses less air to run, such as those with smaller displacements and air flow passages in the head, such as Honda, will get better mileage than other engines that are larger and have larger air flow passages, such as the old 153 Nova inline 4 cylinder.

One deviation to this rule is carburetor vs EFI systems. A carburetor relies on air flow past set orifii to pull the fuel into the engine, and that fuel is in the form of somewhat large rain droplets. EFI, on the other hand, uses pressure technology, which injects a more precise volume of fuel, doesn't rely on vacuum as the carb does, and the fuel is injected as a very fine "London fog" of a vapor.

So, smaller displacement, lower total air flow, more finite handing of the fuel/air mixture and fuel in a vapor form, over a giant rain drop = better volumetric efficiency, better mileage.

06-09-2011, 11:51 AM	#52
HEI451 Account Suspended Join Date: Mar 2011 Location: Yerington, Nevada Posts: 864	Re: what are you guys getting for mpg? The whole mileage game is linked to air/fuel ratios, and engine performance packages. That said, with a cruise air/fuel ratio of say, 14.5:1, 60 mph would use LESS air/fuel flow than 75 mph. Any engine that uses less air to run, such as those with smaller displacements and air flow passages in the head, such as Honda, will get better mileage than other engines that are larger and have larger air flow passages, such as the old 153 Nova inline 4 cylinder. One deviation to this rule is carburetor vs EFI systems. A carburetor relies on air flow past set orifii to pull the fuel into the engine, and that fuel is in the form of somewhat large rain droplets. EFI, on the other hand, uses pressure technology, which injects a more precise volume of fuel, doesn't rely on vacuum as the carb does, and the fuel is injected as a very fine "London fog" of a vapor. So, smaller displacement, lower total air flow, more finite handing of the fuel/air mixture and fuel in a vapor form, over a giant rain drop = better volumetric efficiency, better mileage.