Baffles & Exhaust Heat Sink

I've been bouncing around between little tasks as I wait for additional stuff to arrive (like more electrical stuff to finish up the FWF wiring). That makes it a little tough to document in a way that would make any sense to someone not seeing the big picture, but I'll give it a shot.

One of the weaknesses I've read about is the cabin heat.  Apparently a lot of people find that they just can't get enough warm air from a single muff setup like I have.  My Vetterman exhaust has one heat muff - basically an 8 or 9"ish cylinder that goes over part of the tail pipe and has an inlet and exit.  The inlet gets fresh air from the front of the engine just as it comes into the air inlets behind the prop, and the exit takes the heated air from the muff and sends it via scat tubing to the cabin heat valve.  In order to get more hot air, I basically need to increase the surface area of hot metal.  After seeing some different ideas on VAF, I figured the best approach was to bolt metal heat sinks around the tailpipe so the incoming air had more hot metal to move around. I took some measurements and made a design in CAD and sent it off to sendcutsend.com to have it cut out of 1/16" stainless.  It's pretty amazing that I can design something at home and a week later have custom parts in hand for $30.  My design essentially has a strap that will bolt around the tailpipe and tabs that I will bend 90 degrees up into the airflow.

The gotcha with this design is that the heat muff isn't centered on the tailpipe - it sets very close on one side and has about a half inch of space on the opposite site (to make a better path for the air).  To account for that, I designed my parts so that the tabs are smaller on one side.  Here's what the raw parts look like:

My first attempt showed me the error in my design - when I did the math to figure out the length of the part, I neglected to take into account the 1/16" thickness.  That means the overall length is a little short and the tabs stick up a little further than I anticipated.  It's all fixable though. I'll just bend the tabs for the bolts a little closer to the bolt holes and I'll start the bend for the tabs so that they are a tiny bit shorter.  Bending the tabs is rough on hands, so I only did a couple of rings today.  I'll just do a few here or there each day until I finish up.

I also received my alternator this week.  Van's sells a Plane Power alternator with their kits, but they are  known for having terrible reliability.  B&C alternators have a stellar reputation, so that's what I went with.  I went with a very different style of alternator than is typical though.  The most common B&C alternators use a remote box for the electrical brains.  That's fine, but requires you to run quite a few more wires from the engine back to the boxes aft of the firewall, especially if you have a backup alternator as well.  Last year, B&C came out with a new style of alternator though - one that has all of the electrical brains in the alternator itself, including overvoltage protection.  So in essence, it mimics an automotive alternator with the addition of the overvoltage protection.  There are some cons to these units vs the old style, but for what I need, the pros far outweigh the cons (including the fact that they're about 1/2 the cost!).  If it were any other company, I probably wouldn't roll the dice on an unproven alternator, but B&C is as good of a company as you can find, so I'm fine being an early adopter of their new units.  They are getting ready to release the spline drive alternator for this line as well, so that's what I'll use once I decide I'm ready for a backup alternator.

It was a little shocking to see how little the alternator was!  I mounted it to the engine case, but won't tighten the tension bolts until the prop is on.

I've been doing baffle work a little here and a little there.  I do a little bit, then have to run a wire to see where it goes, then a little more baffle work...and on and on.  I received a chunk of 1x1x1/8" angle that I ordered to help stiffen up the aft left baffle corner where the oil cooler attaches.  There are no plans for this, but it's a common spot for cracks to form due to the weight of the oil cooler and engine vibration.  I fit the angle, then also had to cut a 1/8" thick spacer to go under the baffle stiffener that extends forward above the cylinder.  I can't finalize the piece of angle until the oil cooler is ready to mount, but it's already far stiffer.

Fuel Pump & Baffles

The engine driven fuel pump came with a couple of straight fittings already in place, but they don't match up with what I need.  I swapped out the exit fitting for a T fitting that allows the fuel pressure line to come off of it as well.  The smaller fitting that goes into the T for the fuel pressure line has a restrictor in it - my understanding is it not only helps even out the pressure readings, but it also serves to limit fuel loss if for some reason the line comes off.

I'm waiting on a number of electrical items to arrive, so I decided to jump over to the baffles to see how all of that goes together.  I wasn't really planning on working on them, but got sucked in.  The baffles are cut to the outline of a Lycoming 320.  While the Titan has a slightly different shape in a few areas, the bulk of the baffles fit very well. The oil cooler hangs off of the baffle behind the #4 cylinder, and a common issue is for the baffle to crack over time due to the weight of the cooler and the vibration of the engine.  There are a number of solutions I've tracked down, the most common being adding a 1" aluminum angle to the junction of the rear and side baffle (which the oil cooler bolts to) as well as a piece of rod that ties the other side of the cooler to the case or the cylinder.  It's hard to describe, but it'll make sense once it's laid out.  I don't have any 1" angle, so as is the norm, now I hurry up and wait for it to arrive.

These baffle sections fit quite well (minus the rear baffle on the right - the shape of the Titan was significantly different, so I had to do about 100 trips back and forth to the sander to get it right).  Where I'll really have to make some changes is on the baffles that wrap around the inner portion of the cylinders.  A typical Lycoming has cylinders that are a consistent size, but the Titan has cylinder fins that taper.  

Air Vents

I checked off a random task today - I bolted the air vents in place and connected them to the naca duct in the side skin with scat tubing.  There have been reports of the scat tubing sliding off of the vent adapters, so I put a couple of dabs of RTV on each end (not shown in the pic) to try to keep it from vibrating off.

Engine Sensors & Wiring

I need to get caught up - I've gotten a fair bit done on the FWF, but recently it's been in 10 minute increments, which aren't as easy to document in a meaningful way.  There is so little information provided about the install of the engine and FWF systems that it can sometimes take me an hour or two to research something that takes me 10 minutes to actually do.  So I'll get one thing accomplished, then have to spend the evening trying to sort out the next 10 minute task.

The manifold air pressure line goes from a fitting in the outer aft corner of cylinder 3, through the firewall and to the sensor.  The engine came with a plug in the sensor port, which is fairly normal I suppose, since not everyone measures MAP.  After my experience getting the oil pressure plug out, I was a little nervous about doing it again.  Turns out, I had reason to be.  You wouldn't think that threads would be seized on such a new engine that's barely been run, but between whatever thread sealer they use and the paint over the top of it, this one didn't budge!  I tried very gingerly for an hour with nothing to show for it except a slowly rounding off hex head (I tried hammers, heat, you name it).  The hex was getting rounded off enough that I knew I was running out of time to break the plug loose.  I put an allen socket in my impact driver and crossed my fingers that the impact  would break the plug free at least a little.  Nope.  After that attempt, the hex head was completely rounded off.  I'd read that this wasn't an entirely unusual situation, but that didn't make me feel much better!  Since I had no other choice at this point, I drilled the head of the plug slightly larger and deeper (making sure not to break through the back) and used a bolt extractor.  Finally, after tons of heat and hammering, I was able to break the plug free.  It only took me a few hours!

The MAP line that Van's sent is much longer than I need it to be, but it sets in a pretty natural curve against one of the engine mount arms, so I'll just use the length to my advantage and clamp it to the mount.

The name of the game for mounting items FWF is using multiple adel clamps - one to hold the wire/hose and one to hold the first clamp to the mount.

There is a fitting high up on the engine just in front of the oil filter that is for the oil breather line.  Van's provides a piece of rubber hose as well as a big aluminum tube for the breather line.  Unfortunately, the angle adapter I have for the oil filter puts the filter in the way and doesn't allow as straight of a shot as the plans show.  I cut the rubber hose down to essentially just have the 90 degree elbow, which I clamped to the engine fitting.  I did a bunch of bending of the aluminum tube to get it to fit into the rubber hose and then run down the firewall (it'll have an adel clamp to hold it to the firewall), but can't finish it up yet until I have the tailpipes on.  The opening of the breather is supposed to be just above the tailpipe, so any oil blown out just drips on the hot tailpipe and burns up.  I won't know exactly where to put the tailpipes until I've done a basic fitting of the lower cowl.  So as usual, this is a task that has to stay partially done for now.

If you look on the other side of the filter, you can see the aluminum portion of the breather line.  It has a flared portion at the top to fit into the rubber hose, then curves down to the firewall.

One other partially completed area was the amp shunt and ANL fuse holders.  I probably could have just finished up by using large gauge wire, but I didn't have the few inches of wire that I needed, let alone the various ring connectors.  I had a chunk of 1/16" copper left over, so I decided to go with that instead.  The copper bar from the shunt to the primary 60A ANL fuse was straight forward.  I THINK I could have just taken a second short bar from the 60A fuse holder to the second fuse holder, but the advice I got from the alternator manufacturer (B&C) was to fork off at the shunt to go to the second fuse.  I'm pretty sure the electricity doesn't care (and the alternators have diodes in them. so there's no way for current from one alternator to flow into the other one), but I didn't care enough to spend another 2 hours trying to find an answer.  I decided to just cut out a chunk of copper to go from the shunt to the second (40A) fuse holder.  This 40A fuse will be the spot for a future backup alternator.  With this work done ahead of time, adding a backup will be as easy as installing the alternator and wiring it to the ANL fuse.  I didn't have any heat shrink large enough for this copper bar, so I dunked it in Plasti Dip.  That stuff is kind of addicting.  After seeing it work, I wanted to wander around the garage and find other things to rubberize.  I snapped the covers onto the fuse holders.  This is all done now and ready for an alternator, which I still need to order.

Next up, the cylinder heat temperature sensors.  It took me an embarrassingly long time to figure out where the ports were for these!  They go underneath each cylinder head, but you can't actually see the  holes unless your under the engine looking up.  The sensors have a threaded adapter that screws into the engine, then the sensor slides up through that adapter.  The first 5" or so of the sensor are covered in a spring, and the twist on connector uses that spring to provide some pressure against the sensor to ensure it bottoms out against the cylinder wall.

Here you can see one of the CHT sensors in place.  It is directly behind and underneath where the lower spark plug will be.  I haven't figured out how I'm going to route the wires yet.  I need to get everything in place before I start committing to wire routing.

The exhaust gas temperature probes insert into the exhaust a few inches below the attachment flange.  The AFS manual says they need to be at least 1 1/2" below the flange and ideally no more than 3", with the location being consistent from one exhaust to the next.  Each exhaust has a curve to it in a slightly different location, so I just had to go for the best compromise, which ended up being 2 1/2" inches below the flange.  I measured about 50 times and then drilled a #30 hole into each exhaust stack.  The probes on the left side of the engine point out and back, but the probes on the right side of the engine actually have to point forward and out in order to not be in the way of the lower spark plugs.  I checked a number of pictures online, including of a few of Van's demo planes, and they all have these right side probes facing forward.  Once the probes are inserted into the exhaust, a hose clamp snugs them up (there's a little flange on the probe that the hose clamp pulls against the exhaust).

Here I thought I was done with the rat nest of wiring, but time to do it again!  I pulled the EGT/CHT wires (the brown ones) through the firewall from the EMS module, and started laying out the wiring for the rest of the FWF stuff (the rainbow harness).

I went through the wire harness and labeled each wire so I could start to figure out where it goes, and ultimately what path they all have to take.  It turned out that there were about a dozen wires in the harness that I won't use - some because I'm using the ACM, and some that are simply for other types of engines, like carbureted.  I thought about just looping up the wires and leaving them in the harness, but I decided it would be a lot cleaner if I just took all of the wires that I don't need out of the Dsub.  So I spent some time unpinning the wires, then also adding in a few additional wires, like for the fuel take senders.

The EMS module has two big Dsubs that go into it - one is the EGT/CHT wiring and the other is for everything else.