The LeMans had the intake pretty much straight with only one 30·

(?)

bend.

If you start to do more bends like Jerry's Russel application the

efficiency

must go down for the more work the air needs to go around the

bends.

When

you have to do different bends for for/aft rotor you will also

have

different flows even if the tubes are same length. How do you

compensate for

different intake tube shapes due to bends in the tubes.

Thomas J.

OK I have no idea. I guess the larger the bend radius the better.
I agree but we don't have the room for 16 to 18 inch straight

runners.

Perhaps in a helicopter.

Paul Lamar

Thomas,
Practical experience has shown that smooth curves have very little

effect

on flow. There is probably a slightly higher effect in a rotary due

to a

higher

average flow than a piston engine but not much. The manifolds that

have

worked for Mazda are very similar to piston manifolds with a

slightly

larger diameter. Many of the tuned intakes on new engines are very
curved. There is some loss of course, but usually the manifold can

flow

more than the engine can take anyway. For absolutely maximum flow
straight intakes are best but only if they fit in your cowl!
Bill Jepson

So I take it if you have different shaped runners it doesn't do any

damage?

Generally (at least with piston intakes) it seems that designers go out

of

their way to make all runners flow the same, that seemed to be the

message

when I read aftermarket-intake comparisson reports in the 5.0 Mustang

mag,

some long time ago. Pictures showed quite obviously different cross

sections

for different runners, but the flowbench results (when flowed through

the

intake bolted to the heads...) showed rather even flow distribution...

I thought we might have the same deal here.
Paul Yaw also seems adamant about flowbench testing when modifying

systems

and parts: http://www.yawpower.com/Flow%20Testing.html

I know we run fairly low speeds compared to racers, but everything

counts, I

guess.....

Bill, you say that manifolds usually flow more than the engine can take,

but

what about fuel/air ratio?
Airmass is normally measured only in one spot, before you split the air

into

individual runners. If the flow is not absolutely the same in every

runner

you never get the same ratio for each rotor. Unless you start to measure
airmass in every runner - too big an installation.

Any ideas for a cheap flowbench? Not necessarly for the finest

differences

for porting or so, just to match intake runners....

Thomas J.

Thomas,
I haven't tride it yet but a 'Cheap Flowbench' is using a shop Vacuum with
the same plastic tube Paul uses to measure pressure drop on his Radiator
set-up.
I believe the Vacuum tube is located just past the butterfly, with the shop
vac sucking on the inlet ( rotor housing entrance end).

I figure that should be cheap enough.
George ( down under)

 
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