Need help on Sam James Plenum - builders needed!
 

I posted this in the SJ cowl Plenum thread, and got no response, so I will try the direct approach.

So, I have fitted the cowl with SB fasteners and glassed the inlet rings. SJ builders, please read below and tell me what you would do or did differently. After rebuilding the back flange, I will cut off the front inlets, make some from styrofoam, and re-glass them to fit properly against the forward heads. Also allow for a gradual expansion of inlet air. I really need some experienced opinions here.

Not addressed yet is the fact that 1/3 of the oil cooler is blocked with the rear at this plenum cover level and I have not formulated the details of how to fix that yet.

The baffles have been trial fitted on side and back, but before getting into the fitting at the front of the engine I searched and studied and even cut out the SJ templates. In order to understand the baffles, I got the Lycoming engine installation drawing and used it to overlay the baffles and understand what the exact dimensions are for the Vans baffles.

To begin - the SJ plenum is a "universal fit", it does not fit anything. I have an early one, but Sam says the new ones are the same. I am not going to argue with him.

Here is a box built with the exact dimensions expected to fit the engine. It is parallel, spark plug locations provide a good datum for fore/aft locations. Inserted is the SJ plenum. There are a couple of dimensions on the plenum that are good, the side span is perfect and parallel, the forward contour fit to the case is pretty good. The back is bad, are the air inlets are bad. Not shown is that the height above the heads is the same as measured at the center of each head (inline with plug 2" above valve covers).

I used the contour and the plug locations to affix the engine. The contour is tight against the from of the case and down as low as it can go. The inside flow area is 2 inches above the top of the valve covers. Meaning, it can not go lower or I runout of cooler flow area and risk possible air flow throttling at the inlet over the front head/cylinders.



Here is the back - and how the original glass does not follow the baffles. it is off in every way. I will cut off the flange and re-glass that.




Here is the left and right view of where the inlet snouts "match" to the forward baffles. There is a significant gap on both sides. The left side inlet is centered with the cowl, the right is 1/2" low. it can not be moved anyway with the other constraints.

Right side -



Left:


EDIT - I did look at HydroGuy's, RonDuren, and Mike Bullocks pictures. Rupsters posts had some good pictures too, but he has a 320. All of these contributed immensely to my understanding. I also looked at ALL pictures on the yahoo SJ group. These are just ill fitting parts, and I would suggest making your own.

Well if you seen my photos, you know I had to hack my James Plenum up too. I made it work but took many hours doing pretty much just as you are doing. I glassed in the front to fit better and the sides of the inlets to ramp gaps.

For the cooler area I raised it up back there about 1/2-3/4 inch and left the baffles taller back there. I also built a angle mount for the cooler, this makes a small plenum in front of the oil cooler. I find it cools pretty well.

Your description of the plenum is similar to mine. I did some variations on the theme. For the oil cooler, I have an angled fitting goes on the back at the left hand side of the rear baffle and the fitting is for a 4 inch scat tube. The tube goes to the oil cooler which is mounted on the firewall lower left. It has been tried before and has advantages that the cooler is not blocked, the cooler is not mounted on the baffles, I could put a butterfly valve to control the air flow to the cooler. If you need more details send me a message.
With respect to the plenum, I rebuilt the back along the entire baffle line. The worst misfit was behind cylinder 4. It all came together well using the baffle as a "form". The front required some addition shaping but everything aligned. Sealing the areas around the front ramp took the greatest thought. I screwed the plenum to the vans ramp which I used with small modifications.
It takes time, but not magic. I guess somewhere the work patience might also appear. In the end, I am quite happy with the product.

Update
 

With all the PM/email responses I have done a couple of things. One was to raise the plenum cover as high as possible. That meant close to the cowling. Actually, the front did not move, but the rear was raised 1 inch. The positioning is done at the spark plug locations. The picture is below. Funny, the earlier post with the "unchangeable" front, got revised. By tilting the back up, the lower ramps of the inlets came nearly exactly inlace to mate to the lower baffle ramps. I will won't use them, as the inlets now are severely pointed down relative to the cowl inlet rings. I used small clay points to determine the clearance and found a couple of things. The plenum cover contour is poorly matched to the cowl. Also this restricts the ability to raise the front and get more flow area to the front heads. Since air has to get past the front to be distributed, then it is a possible "restriction". Are others seeing the same opening? See pict for dimensions.

Note the cardboard template of the cowl profile in the upper left. Sorry for the crummy photo, I need a new camera. Color rendition and contrast on this iPhone are poor.

If the SJ plenum pilots can say that 100kt climb on a hot day (90-100F) yields CHT's in the acceptable range, then it is probably ok. Remember this is a IO360 180hp, no jets, & slick mags.

EDIT: If you look close the 5" dimension is to the left of the ruler. The correct dimension is 3.8" at the right arrow.


Here is how I positioned the cover. A tab is mounted on a long bolt at each spark plug location. THe back is 3" above the valve cover flat and the front is 2".



Musings:
Negatives:
Smooth finish is on the inside. More work to make it pretty.
The contour is bad limiting the air flow area at the front of the heads.
The back match to the baffles has to be reworked.
Each inlet has to be reworked to make a good transition (good pressure recovery).

I wonder if it wouldn't be easier at this point to custom make a cover using the upper cowl to begin making a mold. That would solve all the above issues except the inlets, and styrofoam bucks are well along for that for either path.

plenum
 

Bill, I will be at Whiteside co. (SQI) at Rockfalls from 7:30 till about 11:00 tomorrow morning (weather permitting- morning fog). I have a James plenum adapted to Vans rectangular inlets. I can take the top cowl off for you to look at if you stop in. Ron 815 291 8864

I talked to them and i was told that the plenum fits without any mods. I told them all the problems i was having and was told that i was the first person to report it to them. I told them that many folks have issues. At the end of the day I ended up cutting every flange off and the plenum down the middle. It was alot of work. You can see the work i did if you click on the links in my signature below.

James Plenum
 

Mine was "racked" from corner to corner--had to cut off the rear flange and re glass it, remake the front flange, and realign the inlet areas. It would have been easier for me to have made my own----but this was back in 2005--I assumed that they had fixed these problems!!! It was, however, smooth on the inside! BTW, the cowl fit fine!

Cheers,

db

New Direction - - - Progress
 

Well, with the SJPlenum - - it just was not going to fit well without cutting into many pieces and reassembling. So I decided to make a plenum cover using the inside of the cowl as a mold. (like Paul K)

The air inlet restriction over the #1 and #2 would be eliminated if more of the clearance to the cowl was utilized. I drew up some flow paths ( yes i draw not CAD) and was satisfied that much more flow area was possible and that pressure recovery expansion was possible in the length available.

The inlet ducts will be made separately from the plenum cover. This allows easier installation with screws around the inlet perimeter and removal of the cover (with inlets left in place) for inspection.

Here are some pictures of the pink bucks in place with clearances checked with clay balls on the top.


I had trouble ensuring the bucks were accurately placed and could be repeatedly installed in the same place, so I glued on some aluminum strips for a hard mount. Now they are quite rigid. Any misalignment with the cowl will me made later in the process.



The center section was made from cardboard (many interactions) and then formed in .032. I was concerned about the pressure behind that center wall pushing out the baffle bracket into the prop oil line, so a foot was added to prevent movement should that attempt to happen. Better now than to repair later. The perimeter needs to be sanded to match and more clearance made for the tube, but this is it so far.


When stacking the pink blocks for gluing (DanH micro method) I found that ensuring the stagger was a pain, so i matched each layer and screwed the layers together with 1 3/4" drywall screws to hold in position to ensure it matched the engine/cowl. Then marked the parts and added glue while still using the screws to keep all in position until set.

More later as progress is made.

Keep going Bill. I should have done the same during initial building, but did what I thought was fine at the time. Now I look at mine and want to redo do it for ease of removal. Mine works great and looks ok, but could be better. I keep saying it'll be a winter project to build a new plenum....problem is the winter has been great and I keep flying. Heck I can't even find time to do the Condition Inspection that's due this month.

Good job!

You have that retirement home to finish! I keep this updated to report how it works out, and probably (definitely) ask for help along the way.