flyrotary@lancaironline.net Mailing List Archive

I can detect a flow reduction with a wall as close as 3". Much more reduced when closer. In the Mazda the complex tuned pipes are used to assist the sad low end torque. In the LeMans racer it was used at about

7,500 RPM tops. Even then they built a set of complex trombone style adjustable runner lengths. Because if you are limited to the number of gears in the transmission, you will need some low end torque in several locations where low RPM first gear corners live.

I favor large bells on short tapered runners. So the highest flow velocity is right at the port face in the iron.

A Drummond built 12-A uses a nearly stock intake manifold gasket to produce 244.4 HP.

Tracy's race winning engine had short runners. This engine tunes like a dirt bike engine. Even more so in a Periphery ported engine.

Lynn E. Hanover

n a message dated 9/19/2019 12:54:02 PM Eastern Standard Time, flyrotary@lancaironline.net writes:

So you think it's more important to have a 1.18" (pipe/runner ID) spacing between bell mouth and plenum wall than maximizing runner length?

I guess I should put a plexiglass lid on top of the plenum, put a vacuum cleaner on the pipe and have a source of smoke for the plenum inlet and have a look at the flow pattern around the bell mouth as I move it towards/from the plenum wall.

Finn
(Printing it with bell mouth up now, hoping it won't collapse or sag).

On 9/19/2019 11:40 AM, lehanover lehanover@aol.com wrote:

I think runner length is less important than bell shape