Quote:
Originally Posted by rdruss
If my math is right it appears that a 4 liter at 2000 rpm would be 282 cfm.
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I'm not sure what formula you're using... but this is how I got there:
CFM = (CID x RPM x VE)/3456
4.0 liters comes out to ~244.1 cubic inches. The 4Runner's engine max RPM is 6,000. And I'll make a guess and peg Volumetric Efficiency at around 85%. So let's do the math...
(244.1 x 6000 x .85)/3456 = 360 CFM
So you'd need 360 CFM at wide open throttle at 85% VE. At 2,000 RPM you'd only need about 120 CFM. So the 275 CFM unit the OP was talking about would cruise around OK, but starve the engine at higher RPMs. Running around with an air filter that can't flow sufficient CFM... produces nearly identical symptoms to a clogged air filter.