Check this thread about intake runner lenght,anwers on a lott of 13B engines and intake runner lenght and

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Le Roux Breytenbach

On 01 Apr 2021, at 19:23, Charlie England ceengland7@gmail.com <flyrotary@lancaironline.net> wrote:

4 port or 6 port? It's been a long time since I had the manifold off the engine, but I *think* my 4 port engine has same size pri & sec ports. I know I used the same size tubing to make the manifold. I believe that the '3rdary' ports on a 6 port are smaller, but I think Steve Boese found that they don't do anything at our more reasonable rpms.

Charlie

On 4/1/2021 12:05 PM, Finn Lassen finn.lassen@verizon.net wrote:
Thanks Ed.

What I meant to say is that Tracy implied that secondary runners should have a larger diameter.

But I made them the same (inside diameter) as the holes in the block (30 mm).

Finn

On 4/1/2021 11:07 AM, eanderson@carolina.rr.com wrote:
Smaller dia may mean that airflow velocity is higher than in the primaries and since the secondary valves open at higher rpms, the higher airflow velocity may help stuff more air into the chamber give the shorter duration the port is open at higher rpm.  Just a WAG.

Ed

------ Original Message ------
From: "Finn Lassen finn.lassen@verizon.net" <flyrotary@lancaironline.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: 4/1/2021 8:48:31 AM
Subject: [FlyRotary] Re: MISTRAL

Tracy remarked on my secondary runners being smaller diameter than primaries and now I see the same here.

If I recall correctly, when I calculated the area of the secondaries vs the area of the primaries (in the engine block) I got smaller secondaries than primaries.

What gives?

Finn

On 3/31/2021 9:44 PM, Kelly Troyer keltro@gmail.com wrote:

Primary Runner length approximately........24 inches
Primary Runner "OD"  approximately.........1.40 inches
Secondary Runner length approximately.....24 inches
Secondary Runner "OD" approximately.......1.66 inches