James Cowl and plenum inlet

hydroguy2 · #1 03-13-2012, 05:26 PM

I'm working on smoothing the air in and out of my cowl. The outlet work is coming along slowly and is noted in this Cowl outlet thread. I also am looking at the outlet ramp and clean up of that area. AND I have always had a warmer #2 cylinder(peaks earlier too) so was wondering about the ramp in.
It ramps up nicely BUT has an approximately 1" gap from ramp to cylinder, illustrated by this big Marker slipped between the ramp and the head.

How close should this be and will it benefit from fitting closer?...ie better flow & less turbulence.

Don Jones · #2 03-13-2012, 05:42 PM

Like any other system, it needs no leaks and should fit tight where you illustrate. I used the van's baffle kit and made the forward ramps in front of the cylinder actually screw to the plenum inlet shown in your picture. I have also modified the rear of the plenum along the rear attachment using angle on the baffle and screws throught the top of the plenum instead of that crappy flange sam leaves on the rear. I also modified the plenum around the oil cooler to allow the cooler to be mounted higher. I even redid the plenum in the front of the engine case so it would actually fit.

I will look and see what pictures I have and post them later.

hydroguy2 · #3 03-13-2012, 05:52 PM

Don, I have mine sealed pretty good. The gap is not an opening to below. I have it sealed with the Vans Baffle aluminum piece, the ramp just does not reach the head. Don't think I'm leaking here, just turbulent flow disrupting things as it fills the plenum.

I too reworked the rear of the plenum and cooler area and fit the engine case forward tightly.

Don Jones · #4 03-13-2012, 06:29 PM

I see...... I did cut those down on the plenum so the edge is flush with the aluminum baffle across the front of the cylinder.
Mine isn't flying yet, so we will see if it keeps it's cool. I have a lot of time fitting that plenum, Probably could have built one from scratch faster

gereed75 · #5 03-13-2012, 08:42 PM

I did the same as Don, cut down the fiberglass so that it transitions right into the baffle ramp without the "double overlap" thing you got goin' on there Brian.

If it is sealed to the baffle underneath, dremelize that excess off. It can't help but be better - or maybe slit the duct at 4 and 8 o'clock to create a flap. Heat and fold the flap back to lay on the baffle ramp underneath and then glass in the corners where it was slit.

Always something.

Bruce · #6 03-13-2012, 08:44 PM

Brian,
Mine is 1/4 inch or less. Will confirm Sat.when I see plane.

Rupester · #7 03-13-2012, 10:48 PM

... in that the ramp in front of cyl #2 is straight across, i.e it doesn't slope up to the outside as your pic shows. It's also lower, exposing more of the fins on #2. Maybe mine is a later version where they altered that config? I modified the Vans front lower baffle; have two flathead screws and tinnermans in the plenum throat that hold it tight to the Vans baffle. (or vice versa). Can't tell you how it cools yet cuz I have another couple of months before I'm flying.