flyrotary@lancaironline.net Mailing List Archive

Ed,

I am using 1 ¾ secondary and 1 ½ primary tubes. That is what matched the port size on the engine (when deformed to the oval shape of the port). The lengths of the runners are eight inches from the side of the engine. The runners terminate into a 4" manifold log and a 65 or 70 mm T/B. My plan is to build a new manifold log with velocity stacks and then experiment with different length radiator hose for runners. I know this is not optimal for flow but it should get me in the ballpark quickly. Any suggestions are appreciated.

Thanks,

Jason

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson
Sent: Sunday, July 30, 2006 8:04 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Back in the saddle again!

From the opening of the intake port (inside the engine) to the center of my throttle body my intake length is 22". It appears that a length between 17-24" is workable and gives good results. Tracy use a similar approach (from which I stole a lot of ideas) and also got excellent results when he was flying a 13B.

Since I use the stock cast lower and part of the upper cast (which I cut the cast tubes off and install my own light weight tubes) the actually length of my tubes is 7-11 inches (adjustable - tubes inside tubes) . That is the length between my cut-off upper manifold (the one with the 90 deg bend and cast tubes) and bottom of my throttle body plate. However, The crucial distance of course is from intake port to throttle body - not how long the tube portion itself it. I use 1 1/4" dia tubes for the primary and 1 1/2" dia tubes for the secondary. To make an adjustable one I have a 1 3/8" dia tube over the 1 1/4 and a 1 5/8" tube over the 1 1/2" - but of course you don't need to do that.

Too large an intake tube appears to diminish the mixture velocity and inertia and decrease the amount of mixture stuffed into the combustion chamber, so while large intake diameters are fine for the 9000+ rpm racers, they don't appear to offer what we need at the rpm we operate at.

Here is a photo of my most recent intake and one I have flow with for 3 years. The blue throttle body mount is make out of a two part polyurethane casting resin and I use a 65mm Mustang TB. Here is a photo.

----- Original Message -----

From: Hutchison, Jason

To: Rotary motors in aircraft

Sent: Sunday, July 30, 2006 7:52 AM

Subject: [FlyRotary] Re: Back in the saddle again!

Ed,

You are correct! I have the 2.85 drive. I scraped the tangential muffler and now using spintech muffler. I received my velocity stacks last week, so it on to rev "B" intake. By the way how long are your runners?

Thanks,

Jason

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson
Sent: Saturday, July 29, 2006 4:56 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Back in the saddle again!

Jason, if I recall correctly you do have the 2.85 gear box. You should be seeing 5800-6000 rpm static (perhaps a bit less in that heat). I however do not recall your prop set up but if it is close to the 74x88 prop Tracy and I both fly with our 2.85 then it would appear your are not getting adequate airflow into( or out of) the engine.

Ed

----- Original Message -----

From: Hutchison, Jason

To: Rotary motors in aircraft

Sent: Saturday, July 29, 2006 9:13 AM

Subject: [FlyRotary] Back in the saddle again!

Update on my airplane, I now have four flights on my engine after replacing the seals. Last night I was up for an hour. At 5000msl it was 28C temps stabilized at 197(water) and 188 oil. I still need more power. I am only getting 5000rpm static which makes for very shallow climb outs. In the air, I'm getting between 5500 and 6000 rpm at about 140mph (no wheel pants or fairings).

I did an experiment with a 12" fan mounted behind the radiator. The fan keeps the water temp under 190 on the ground, but caused about a 10-15 degree increase in the air. So now I'm thinking about mounting a small radiator with a fan under the engine.

My next project is to rework the intake for more static rpm.

Jason (waiting for winter or at least temps below 90 degrees)