Making a snorkel.

[Guest diesel_jim]

There was a similar thread on the D-90.com forum ages back (2000 i think), i managed to find the original text; here goes:

I've been poking around the Machinery's Handbook (INDISPENSABLE reference

source) a little and found a few interesting things (see p.2319 and 2324 of

22nd edition, if you're interested for info on flow of air and water)

1- if you use 3" diameter smooth-wall pipe and keep the right angle bend

radius to at least 3x the pipe diameter, a right angle bend has the same

restriction as 4 feet of pipe (this is listed for water, not for air).

2- if you consider that a 3" pipe has an area of 3.14*1.5^2 or 7 sq.

inches, or 0.05 sq ft, and the engine is drawing 140 CFM, then the air is

moving through that pipe at a speed of 140/0.05 or 2800 feet per minute,

47 ft per second, or about 32 MPH! It's easy to believe that anything

getting in the way of air moving that fast can cause a restriction in a

hurry.

If we assume 50 fps air velocity, and a VERY clean instalation using 6 ft of

straight, smooth pipe, and 3 90 degree bends of 9" radius, then the equation

for pressure loss looks like:

P= 18 * 50^2/(25,000 * 3)= 0.6 ounces per square inch, or 0.07 inches of

mercury (vacuum)

That's just for the (probably over-optimistically clean) piping. I'd

imagine the pre-cleaner itself has more restriction on it's own. We'll see

what Centri says. I wonder what restriction is offered by a paper element

air cleaner? I hear that an oil bath cleaner like the old Series ones is

one of the most effective, lowest restriction, filters for ultra-fine dust

that there is, when it's kept reasonably clean, and that the ideal combo for

engine cleanliness is a pre-cleaner for bigger particles, with an oil bath

for the little stuff......

Oh well, enough musing for today...Time to think about Double Cardon joints

a bit.... :^)

-Dave G.

http://www.egroups.com/group/d90

something for you lot to muse over...