I am also a BIT CONFUSED , not that that isn't a state that i
haven't gotten used to in the last 50 years. Shouldn't the V.I. reflect
boost if your motor is supercharged, ie Boost divided by 14.7 +1. Kvach
----- Original Message -----
From: Lawrence E. & Cathy R. Mayfield <lemay@hiwaay.net>
To: Thomas E. Bryant <saltracer@awwwsome.com>; Land Speed
<land-speed@autox.team.net>
Sent: Friday, February 11, 2000 4:40 AM
Subject: Re: Air Scoop Formula
> Hey Tom, good job on the formula! I had went about it a little differently
> though but with the same, I hope, results!
>
> I developed the following:
>
> Inlet Area (in sq) = (Disp * RPM *VE) / (MPH * 2112)
>
> Where: Disp is engine displacement
> RPM is RPM at which you want to run
> VE is volumetric efficiency of engine (1 if you don't know)
> MPH is the at which you want to run in MPH
> 2112 is a combination of conversion factors)
>
> So, an example... my car, 306 CID, 200 MPH, 6250 RPM, .8 VE
>
> Inlet area = (306 * 6250 * 0.8) / (200 * 2112) = 3.622 in sq.
>
> This provides for an exact balance of the engine needs. I would use a
> volumetric efficiency of 110% to account for some ram air effects,
however.
> This is an interesting equation because the slower you go the larger the
> scoop. I think this means that when testing on the dyno that you need a
> large plenum and inlet. Tom, does your equation do this also?
> Unfortunately, adding a scoop or the inlet adds some drag to the car, but
> if confined within the frontal area envelope, shouldn't add much, if any.
>
> Neat stuff, this!
>
> mayf
>
>
> At 10:50 AM 2/11/00 -0800, Thomas E. Bryant wrote:
> >Group,
> >
> >I hope that I can explain the formula where it makes sense and is useful
> >to you.
> >
> >The idea is to calculate how much air the engine requires while covering
> >a mile. The cubic inches of air is then converted to square inches by
> >dividing by 1 mile. This gives you the size of the opening in the scoop.
> >Naturally this is not absolutely accurate because of the variables,
> >volumetric
> >efficiency, wheel slippage, etc.
> >
> >The size of the column of air 1 mile long can be found by working
> >backwards from the distance covered (mile) divided by tire
> >circumference, equals the number of revolutions the wheel makes
> >multiplied by the gear ratio to calculate the revolutions the engine
> >makes while covering the distance, divided by 2 (since it takes 2
> >complete revolutions of the engine to complete the firing cycle for all
> >cylinders) multiplied by the cubic inches of the engine equals the cubic
> >inches of air pumped. Now divide this by the distance (mile) and you
> >have the size of the opening.
> >
> >Here is the formula for my engine geared for the Lakes:
> >
> >Mile (63,360") / tire circumference (86") x gear ratio (3.18) / 2 =
> >1,171.41 x engine size in cubic inches (304) = 356,108.64 cu. in. / mile
> >(63360") = 5.62 sq in.
> >
> >I have put this formula in the computer so I can plug in gear ratios and
> >cubic inches and get instant results.
> >
> >The higher the gear the smaller the size of the opening needed.
> >According to Tom Burkland, if the size is right for the engine, baffles
> >are not needed inside the scoop because the pressure is equalized to all
> >cylinders. He also said that it is wise to oversize a bit, to allow for
> >going through the gears, since the calculation is for top gear.
> >
> >Tom, Redding CA, #216 D/CC
> >
> >
>
>
>
> L.E. Mayfield
> 124 Maximillion Drive
> Madison, Al. 35758-8171
> ph: 1-256-837-1051
>
> http://home.hiwaay.net/~lemayf
>
> lemay@hiwaay.net
>
> Sunbeam Tiger, B9471136
> Sunbeam Alpine Bonneville Land Speed Racer,
> '66 Hydroplane Drag Boat (390 FE)
>
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