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post #1 of 3 (permalink) Old 10-07-2013, 01:26 AM Thread Starter
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cfm of stock HO

hi there, does anyone know what the air flow of an `88, stock everything 5.0 HO (mustang) engine is, whatever the limiting factor is (throttle body i suppose).

I`m shopping for air filters and am thinking of doing something custom,.. but i`d like to not limit the flow.

cheers,

Mark
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post #2 of 3 (permalink) Old 10-07-2013, 07:15 AM
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Re: cfm of stock HO

The rule-of-thumb for "average" efficiency engines at .5 lb/hr BSFC is 140 CFM per 100 hp. The formula is:
Quote:
CFM = 140 * HP / 100
So, for a 220hp engine:
140 * 220 / 100 = 308 CFM

Sound small? It does compared to sales ads. But, even Holley recommends a 350 CFM carburetor as a "performance upgrade" for a 220hp engine. Yes, the CFM is generally less than most folks think, though any restriction from the filtering is bad. I try to keep it less than 4kPa or 0.5" Hg restriction for a daily driver. Too big is not a problem of course. Attach a vacuum gauge between the filter and throttle to directly test for losses -or- read manifold vacuum and run the engine no filter/with filter to compare added restriction.

David

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post #3 of 3 (permalink) Old 10-07-2013, 07:52 AM Thread Starter
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Re: cfm of stock HO

cheers! thats really helpful..

thanks,

Mark
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