My super charged renesis had a 1” vent. It was too small. Just enough vapor to make a mess. The tube was connected at the oil filler neck so the location may not have been the best choice. I’m planning a 1” vent for the normally aspirated S21 build.

Bobby

Thanks Lynn and Jeff.

Appreciated. My vent is probably only 3/16 inch and It just had me thinking!

Cheers

Steve

> On 1 Nov 2020, at 9:01 pm, lehanover lehanover@aol.com <flyrotary@lancaironline.net> wrote:
>
> Crank case pressure is a function of the volume of combustion gasses escaping past the side seals and through the end gaps at the side seal ends and corner seal fitments.
>
> There will always be some flow even on a new engine. So the trick is to keep the outbound flow speed low so as to keep escaping oil droplets falling back into the engine rather than being expelled. In racing we are required to have a catch bottle with a minimum volume of 1 quart. A well done rotary has a remarkable low flow rate and can get along fine with a small diameter vent tube. Not a big problem on the street.
> In the aircraft the flow will be higher as the engine is usually run at or near full throttle for long periods.
> So run it hard and look into a catch bottle to see how much oil is being lost. A few drops to nothing is ideal.
> Most can be vented into the intake flow but that will not show up any problems. Every landing needs a oil level check. If the breathing is restricted, pressure may push out a seal or turn a seal lip over backwards. Followed by much oil loss. I shorten the seal springs and build seal retainers on each engine. You can also buy double
> lip seals with one lip facing in and out. Keeps dust out of the seal lips.
>
> This is seldom a problem and did not occur on showroom stock Mazda rotaries that were turned up to high RPM. So probably not a factor.
> Lynn E. Hanover
>
> In a message dated 11/1/2020 4:57:53 AM Atlantic Standard Time, flyrotary@lancaironline.net writes:
>
> Hi Lynn EH and all
>
> What size breather from the sump is required?
> Is this the same for all the various models (particularly the Renesis)?
> We have the OEM sump but removed the plastic manifold and put a filler cap with small breather on the top of the steel vertical tube that runs down into the pan.
> What would happen if this breather was too small?
>
> Thanks
>
> Steve Izett
> Perth Western Australia.
>
>
>
>
>
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