Looking back from the firewall. The mechanical fuel pump is on the right. Oil filter is on the left. I put a fuel fitting on to see if there was enough room just for the fitting.

The same view from a little farther away and higher.

Looking down from above. You can see the firewall and fuel filter on the right. The oil filter is on the bottom. And you can see the (out of focus) fuel supply line on the right.

So the question is, do I leave it as it and route the fuel line up between the oil filter and fuel pump? Or do I try to rotate the fitting at the fuel pump so I can route the line forward of the engine?

The aluminum oil lines from the nose oil cooler have been in for a while. But I couldn’t install the flex lines to the engine because I needed to install the sandwich plate on the engine which provides the inlet and outlet for the oil to the secondary (nose) cooler.

So I drained the oil, removed the filter and installed the sandwich plate.

Then I got the 1/2″ braided, stainless steel flex lines and cut them to length. We figured that straight fittings were not going to provide good routing for the oil lines so I bought four 45-degree fittings. I installed one on each flex line, slide the firesleeve over the line and then installed the fittings on the other ends. I finished up by clamping the firesleeve to the fittings.

At Malcolm’s insistence, I purchased 4 “Del Seals”. These are little washer than go inside flare fittings. They insure a good seal between aluminum and steel fittings. So I then attached the oil lines to the firewall fitting.

Attached at the sandwich plate.

Then the new (shorter) oil filter was installed.

Cooling a rear mounted engine is a bit trickier than a front mounted engine. With the traditional front mounted engine, you put a couple of openings at the front of the cowling and let the propeller push the air into the engine compartment. Then the air is forced down through the cylinders and exits out the bottom of the cowling through cowl flaps.

The Velocity uses a pair NACA Submerged Inlets (or ducts) on the top of the fuselage to provide airflow into the engine compartment.  Unfortunately, the ducts supplied by the factory aren’t true NACA’s. They have some minor deviations which reduce their efficiency. But they should be good enough. If I had to do it again, I would take the Andy Millin approach and build them myself from scratch.

The air from the NACA’s is ducted into a plenum. This plenum is basically a fiberglass box that is fitted to the engine.

This is a picture of Rich Guerra’s finished plenum and ducts. Rich is running a different engine, but you get the idea.

I have four problems with this: 1) Every other piston airplane I’ve seen doesn’t have a plenum. They use the engine cowling to create the plenum. 2) When you have to service the engine, you have to remove this plenum. 3) With the plenum so close to the engine, it will be very difficult to distribute the airflow evenly over all the cylinders and 4) I’ve already had to modify the cowling to give the engine enough clearance in three places. This means that I’ll now have to modify the plenum too.

So after a lot of discussion with Malcolm and Lynn, I decided to wander way out into left field (or come in from left field) and go a more traditional route and use the cowling to create the plenum.This will require a sheet metal baffle that will seal against the cowl.

I looked into buying a set of baffles from Cirrus or Lancair (both use the same engine I have) and then modify it for the Velocity. But that was WAY too expensive. So I bought a couple of sheets of aluminum and some construction paper and got to work.

Here’s after building up the copilot side out of construction paper. The box with the “X” is the approximate location that the duct will penetrate the forward baffle.

The area below the oil cooler was a real challenge (not much room).

The pilot side was more of the same. snip a little, position, snip, position, snip, position, etc.Once I had all the paper templates, I transferred them to the aluminum and cut it out. After they were cut, Lynn let me use his brake so I could bend them where necessary.

Here’s the piece that goes between the oil cooler and the #1 cylinder.

The right front.

Right shelf.

Right rear.

Then I started putting all pieces in position (and trim some more) until they fit together and to the engine. Once I had everything fitting nicely, I began drilling and preparing to install the nutplates.

Here’s the final result. I don’t have all the attachment holes drilled just yet.

Next comes the brackets that attach the whole thing to the engine.

The cooling plenum parts are fitting together quite well. So now I’ve got to get the whole thing attached to the engine. Each cylinder has a location to attach the side “decks”. First is to cutout and drill the pieces.

Then they have to be bent.

Then riveted to the decks and bolted to the engine.

Next are fore and aft brackets and a stiffener near the alternator.

Now that the plenum is (mostly) complete, I need to get the cooling air into the plenum. In the normal installation, this is accomplished with NACA duct extensions.

I could use these extensions, but they would restrict access to the area between the engine and the firewall. So I decided (big surprise) to go a more traditional route. I created a pair of extensions that would permanently attach to the inside of the cowling. To build these I started with some foam that use formed to the desired dimensions. Then I covered them with a release agent (duct tape). Placed the forms on the inside of the cowling and covered them with a few layers of BID and a layer of Triax.

When they had cured, I trimmed them and created a lap joint where they would meet the rear of the NACA duct. Then I trimmed the forward wall of the plenum.

When it’s time, they will be bonded to the inside of the cowling.

While I was working on the baffling, I heard from another builder who mentioned that he had a problem with his oil cooler hitting the engine mount. He said that when the engine is starting and stopping that it moves a bit and had removed some of the paint from the engine mount. He caught it before is wore a hole in the oil cooler.

He had just less than 1/2″ clearance.

I decided to check mine and here’s what I found.

Not good. 🙁

I checked with the factory and they modified the engine mount a while back (before mine was made) to provide more clearance. They couldn’t figure out why I don’t have the proper clearance. They told me I could send back the mount and they would modify it but that would require removing the engine. I don’t have an engine hoist and doing it solo wouldn’t be fun. Plus, I didn’t know what other changes that modification would create.

So I came up with plan B. I removed the oil cooler and sent it to Pacific Oil Cooler Services. Here’s the result:

There are three pressure sensors that have to be installed. Fuel pressure, oil pressure and manifold air pressure (MAP). There’s also an oil temperature sensor but that’s installed on the oil cooler.

The rule is that you don’t install sensors directly on the engine. The vibration can cause them to crack or break and then you’ve got fuel or oil running all over the place.

There are a few different approaches to how the sensors are mounted.

One way is to mount the sensors to the firewall individually. Like this:

One of those is the fuel pressure sensor and the other is the oil pressure sensor. (I don’t have a picture that shows the MAP sensor.

But my buddy Brooke has his sensors consolidated.

On the left is the fuel pressure sensor, the right is the oil pressure and the center line connects to the MAP on the inside of the firewall.

This manifold was made from a piece of 3/4″ x 1″ x 5″ solid aluminum. I couldn’t find any 3/4″ x 1″ but I did find some 1″ x 1″  at McMaster-Carr (I love that place!).

Here’s my plan.

Here’s the 1 foot piece of aluminum that I bought.

I marked the location of the five holes on one edge (three for pressure and two for mounting).

I made a decision to move the fuel and oil feed lines from the side to the bottom. Here’s it is with the holes drilled.

And the finished product with cut down to 5 inches long with the holes taped and fittings & sensors installed.

Looking at it now, I should have put the MAP feed line on the bottom too. Since I’ve got enough stock left, I may make another with the three feed lines on the bottom.

Update…

I decided to see where I would mount this masterpiece. The three lines will all be coming from the right (co-pilot) side so that seems to be the logical location. But once I placed it on the firewall I noticed something.

This thing sticks WAY out. Which means that when I change the oil filter, it’s going to be in the way and in danger of getting bumped into.

I could try a vertical orientation. With the sensors on the top and feed lines on the bottom. But then I’ll still have to run the long feed lines all the way to the firewall.

Another method that I saw which I’m now giving serious consideration to is mounting the sensors to brackets that then mount on the engine with a short feed line. That way, instead of a couple 1/4″ feed lines going all the way to the firewall, I’ll only have four wires. Here’s an example that I found on a Cessna 350:

Still not sure how I’m going to resolve this.

After much thought and discussion, I’ve decided how I’m going to handle the pressure lines from the engine. Rather than have all of them go to a single manifold on the firewall, I’m going to route each of the three lines (fuel, oil & manifold air) independently.

For the Manifold Air Pressure, I’m going to simply use bulkhead fittings on the plenum and firewall and terminate it at the sensor inside the cabin. The oil pressure will be mounted on the fire near the oil cooler where the pressure line originates.

Oil pressure sensor mounted to firewall.

View from above.

For the fuel pressure sensor, I decided to mount the sensor inside the plenum. This will allow for a shorter pressure line and not require penetrating the plenum.

Because the manifold air pressure sensor is plastic, it has to go inside the cabin. So I’ll penetrate the plenum and firewall with bulkhead fittings.

Prior to mounting the NACA duct extensions to the inside of the cowling, I placed the extensions in position between the NACA’s and the plenum. Then I installed the upper cowling and marked where the flanges of the extensions would be. I also drilled three holes through the cowling into the extension flanges. Then I removed the cowling and painted the inside of the cowl where the extensions would be along with the extensions.

Once the paint (actually, primer) was dry, I sanded the mating surface of the cowl and the flanges of the extensions. Then I applied structural adhesive to the flanges and mounted taped them to the NACA’s. The upper cowling was then mounted and cleco’s were used to hold the extensions to the cowling.

Once the adhesive had cured, I cleaned the inside of the extended duct and applied a radius of epoxy.

Finally, I used flush head pop-rivets and 1″ square titanium tabs as a mechanical fastener.

Looking back down the right NACA.