Airbox-Trumpet clearance

PostPost by: john.p.clegg » Sat May 09, 2009 5:45 am

Thanks All
Very enlightening,I think I'll aim for a minimum of 1 1/2" on Number 4 with a tapering to approx 3" at Number 1....

John :wink:
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PostPost by: CBUEB1771 » Sun May 10, 2009 1:57 am

Well this one got out of control very quickly but Mr. Clegg has ultimately made a reasonable decision. I sympathize with Mr. Pelly regarding "nonsense", his initial response was the result of an entirely reasonable first order analysis. If the area for flow above the trumpet is not less than the cross sectional area of the trumpet then you should be in decent shape, and this is roughly a 1.6 inch clearance to the airbox for a 40 DCOE. It is possible to create something resembling forced induction if the inlet tract upstream of the throttle plate is sized for flow much greater than the maximum flow rate required by the engine, in other words using the vehicle's forward speed to "stuff" more air into the inlet tract than the engine consumes. This happens when flow entering the inlet tract slows significantly before passing across the throttle and the reduction in velocity head becomes a measurable increase in static pressure at the throttle. But please, let's be serious, how much velocity head due to forward vehicle motion are we dealing with when we are pulling away from a stop light or exiting a roundabout? What Ferrari or McLaren do with their inlet tracts is pedantic for our applications.
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