Engine Tweaks

This plane is nearly ready to go!  I'm just chasing down a few engine quirks.

I spent quite a bit of time adjusting the secondary ignition timing.  I started with the static setting which ran okay, but my RPM drop when I checked the two systems was still a little high.  I tried checking and adjusting the secondary timing with a timing light and a helper, but that didn't make much of an improvement, as didn't really seem all that safe either.  Finally I settled on just running the engine, moving the trigger cap a tiny bit, running it again, and repeating that until it stopped running better and started to run worse.  Then I moved it back to where it seemed the best.  I think that's the best I can do on the ground!

The other thing was an oil leak at the turbo outlet.  I've sealed the oil sump to the turbo at least twice, and it'll stay sealed for a while but it seems to spring a leak if I do a high power runup.  I think it's probably more of a high temperature issue than pressure related.  Sonex sent me a little adapter plate to put between the turbo and the sump, and I also bought the highest temperature sealant I could find, and so far it's been good!  Sonex also asked me to check the ports in the oil pump as some had been setup wrong, but mine was all good.  I guess that could have stopped the pump from scavenging oil correctly and cause oil pressure to increase in that return line, but I don't think that was the problem anyway.

We'll see if it leaks again!

Propeller (2)

 2 hours

Finally, after just over a year since I ordered it, I have my Prince P-Tip propeller!  I think in the long run I will say it was worth the wait; it looks awesome!

I removed the Sterba loaner prop and the 1/2" spacer I had temporarily installed, and bolted the new prop on.  Here's where it got exciting.  As I mentioned a couple posts ago, with the spacer gone and the prop all the way back at the prop flange face, it is MUCH harder to get the cowl on and off.  I found I was able to round off some edges and do some strategic filing to make the lower cowl possible to install without interfering, however the upper cowl appeared to be totally impossible to install with the prop there.  The aft edge of the upper cowl is supposed to go under the front edge of the windshield skirt, and then you rotate the front down until it meets the front of the lower cowl.  But, until it's all the way in position, the front face of the upper cowl protrudes forward 1/4" or 1/2".  With the prop taking up that space, there's no way to get the cowl on!

I scratched my head over this for a while and finally decided it would be worth it to change how the upper cowl mounts.  For now, I left it perched where it was, just sitting on top but not fastened down.  At least now I can do my weight and balance while I ponder how to fix this issue!

Engine Tuning (3)

3 hours

I've done a few engine runs now, just trying to make some adjustments to the AeroInjector, and make sure everything is looking alright.  I have been following the AeroInjector manual, as well as Jeff Schultz's method, explained here:

http://sonex604.com/carb_tuning.html

Anyway, so far I'm using the 2.5 needle and I've adjusted it about 3/4 turn toward lean from the start point, and I think it's in the ballpark.

I also fixed my throttle friction issue from before.  I just bought a rubber fender washer from Home Depot and added it between the throttle lever and the bracket, and now the friction holds it pretty well.

Anyway, as I felt like I was getting the setting close to nearly correct, I tried doing a full throttle run.  I think this is where everything will really start to show up.  Here's what I observed:

(((CAVEAT: I still don't have the correct propeller installed so I will have to re-address all of this later anyway)))

1. I did not get the full 40 in-Hg manifold pressure at full throttle, although the static RPM seemed good.  The Aerovee manual says you should get 3000 RPM static (with the right prop), and the max manifold pressure is 40".  I got about 3150 RPM, which makes sense because the prop is a little too fine.  However I only got up to a max of 34.3" manifold pressure.  I'm not sure if I should expect to get the full 40" static; I will ask Sonex.  I will definitely examine this more once the final prop is installed.

2. EGT's go up fast at full throttle without the plane moving!  I didn't want to spend any more time than I needed to at full throttle because I knew the engine would get hot, but it really does heat up quick.  Looking at the data that the G3X recorded, I spent about 25 seconds at full throttle, and the EGTs quickly rose to about 1200 F, and then gradually climbed to 1300 F.  I did a quick leaning test, pulling the mixture out until the engine stumbled, and in those few seconds the EGTs climbed just to the limit of 1400 F.  That was as far as I wanted to take it anyway, so as soon as the engine stumbled and the EGTs hit the limit I pushed it back to full rich and then pulled the throttle back to idle so everything could cool back down.  The AeroInjector manual says that what you want is an EGT rise of 90-100 from full rich to peak lean at full throttle, so I think I'm pretty close.  Probably close enough to fly with it, but I'll repeat the test again with the correct prop before I call it good!

Here is some data that I recorded.  The graphs, in order, are RPM, manifold pressure, fuel flow, and EGTs.

You can see on the RPM plot where I ran it up to 3150 RPM, and the small dip, rise, and big fall at the end is where it finally was lean enough to stumble, then I pushed it back to rich, and then immediately pulled it back towards idle.

On the manifold pressure chart, you can actually see the boost increase a a little bit as I started leaning, which makes sense as somewhere between full-rich and too lean is probably where the optimal power setting is.

The fuel flow chart shows pretty clearly where I actually started leaning.  At full throttle/full rich it was burning about 7.2 GPH, and then as I gradually leaned it out it made it down to 5.5 GPH which was where the engine finally stumbled.

The EGT chart shows the full throttle/full rich temps around 1200-1300, then a pretty quick rise to 1400 as I did my leaning test.

This data is all pretty useful to have, as I didn't really catch any of this while I actually did it...  I was just trying to not overheat the engine!  The G3X records pretty much everything, once per second, and dumps it into a CSV spreadsheet.  I used the Flight Data Viewer software to view the data, which is a lot easier than just doing it in excel, although that would be possible.  The software is available here:

https://jasflyer.com/

I did find one more issue during all of this too; the G3X is not recording any engine time!  By now I've ran it for at least a few tenths, but the G3X still says 0.0 hours.  I'm pretty sure I know why.  When I switched from the original RPM input to my Honeywell sensor I tried to extract the RPM pin from the connector on the GEA 24, and I messed up that one socket on the connector.  So I just plugged the new RPM sensor into the RPM2 position.  It works fine, but oddly I think the G3X only counts engine time when the RPM1 value is above the minimum.  I'm pretty sure I will need to replace that connector so I can go back to using RPM1!

RPM Sensor Do Over (6)

 6 hours

Alright now that the engine is running I can see that my RPM sensor mounted next to the flywheel does not work very well.  My next best idea was to mount it behind the prop hub to sense the back side of the six prop bolts, so I will try that.

This is the area I'm thinking of:

I think I can fit a bracket there without interfering with the cowl.

Here's my first rough draft pattern:

Something like this:

Attempt number 2:

Next I started making it out of some 0.032" scrap.  I started at the bottom and worked my way toward the top, trimming and bending as I went to try and create what I had in mind.  The bottom mounting point is just an unused tapped M6 hole in the front of the engine case, and the top mounting points will be the forward two bolts on the oil breather plate.

This is pretty close to what I was going for, although I made it a bit too close to the bolts so there's not much room for adjustment!

Next I tested my new setup.  I wanted to sanity check the reading on the G3X, so I bought a $10 lawn mower tachometer and attached its sensor wire to one of the spark plug wires.

Then I just ran the wire through the fuel door and set it on the glareshield.

It works!  Here you can see how much more stable the RPM display is than before, and it matches the lawn mower tach as well.

Now that I know it works, I can improve my bracket.  The original was a little flexible, and too close to the prop bolts anyway.  I made a new one with 0.064" sheet, which is turned out nice and solid.  I made it slightly shorter too, so there's more room for adjustment on the sensor itself.  This is still the temporary prop, so I will have to adjust the sensor later I think.

I put the cowl on to make sure nothing interfered, and it's all good.  You can't even really see the bracket from the front so I definitely don't think it'll block any cooling airflow either.

First Engine Run!

 I finally ran the engine!  Here is a video of the first start:

The engine started right up and seemed to run pretty well, although I didn't take it much higher than idle on the first run.

I only noted a couple of issues:

1. The throttle lever didn't have enough friction even with the friction knob tightened pretty ridiculously tight, so if I took my hand off the throttle it would slide back to idle pretty quickly.

2. The RPM reading on the G3X was super erratic and jumped around like +/-200 RPM constantly.

Here's a video from a later run that shows how the RPM jumped around:

I think the issue is the RPM sensor trying to count the flywheel teeth.  I was afraid it would have trouble since I couldn't get it as close to the flywheel as I wanted to, and I also didn't even consider the huge magnetron trigger magnet that must interfere with the sensor.  I will have to move that RPM sensor somewhere else to get a clean signal!

But, for now at least I'm happy the engine runs without any major disasters.

Temporary Propeller Install (1)

 1 hour

I'm ready to run the engine!  However, I'm still waiting for the Prince P-Tip propeller that I ordered last November!!  In the meantime, I was able to borrow a wooden Sterba prop from a local guy who had used it on another VW engine in the past.  It has the correct bolt pattern, but it lacks the counterbores for the drive lugs on the Aerovee prop hub.  I had a friend waterjet me a quick 1/2" thick spacer to cover up the drive lugs, and then I was able to install this prop.

I would not fly with it like this (the prop is the wrong pitch anyway), but I think this will be good enough for some ground runs so I can start tuning while I wait for my Prince prop.

Miscellaneous Engine Chores (3)

3 hours

Here's some more stuff I should have done on the engine a while ago but finally got around to.

Anyway I had read something somewhere about an engine having some oil troubles due to a blocked pushrod not allowing oil to flow through it.  When I built the engine I hadn't even realized that oil was supposed to travel through the pushrods, so I had no idea if I had checked that there were all clear before I installed them.  So, out of paranoia I removed each one and made sure there was nothing lodged inside that could block oil.  Sure enough, I found one that was totally blocked up, probably with a chunk of the plastic mallet I had used to hammer the tips on.  I couldn't figure out any way to clear it, so I ended up having to buy some more pushrods so I could cut a new one to replace it.  This time I put the tip in the freezer overnight, and that made it a lot easier to install.  Much less hammering required!

While I had the top end apart, I figured out exactly where TDC was and marked it on the prop hub, so now I can easily figure out where TDC for each cylinder is without taking anything apart.  After that I put the valvetrain back together and adjusted all the valves again.

Next, I found after I first cranked the engine that a decent amount of oil leaked between the bottom of the turbo bearing block and the little sump that attaches to it.  I found with the tail raised, no oil sits there, so I could pull the sump off, clean everything, and reinstall it without making much of a mess.  This time I used the Permatex Aviation Form-a-Gasket that I used on the engine case to seal it, instead of the RTV that the plans called for.  We'll see if it leaks this time!

I also re-checked the clearance between the magnatrons and the trigger magnet on the flywheel, since I had loosened one of the mounting nuts on each one, so I wanted to make sure nothing had moved.

Finally, I put the heat shield back on the turbo, and found that I had to cut a little clearance in the upper left edge for the thermostat.  Now I think the engine is ready to go!

Redid magnetron clearance

Turbo heat shield clearance for t-stat & coolant line

Secondary Ignition Static Timing (0.5)

 0.5 hours

I should have done this before I even mounted the engine on the plane but I guess I forgot!

The secondary (coil) ignition has adjustable timing, that you adjust by rotating the little cylinder on the back of the engine.  The cylinder rotates with the flywheel, and it has a magnet embedded on the outside that triggers the upper and lower coils when it passes by.

With the turbo behind the engine, you can't really get a straight look at the trigger to see exactly where it is.  I ended up removing it completely and filing a little mark on the outside edge so I could see where the magnet was pointing from the side.

Here's where the manual says to position the magnet.  Kind of hard to see, but I'm sure it's going to take some adjusting later anyway so whatever.

Here's my best attempt, and the most direct view I could get of the magnet's position by jamming my phone between the turbo and the accessory plate!

RPM Sensor (4)

 4 hours

One of the side effects of switching my voltage regulator to that AVC1 was that pulling an RPM reading directly from the alternator was no longer going to be reliable.  I thought this would be some kind of simple fix but it was a little more complicated than I expected!

After researching around a bit I decided the easiest way to get an RPM reading to the G3X would be with a Hall effect sensor that could sense the teeth on the flywheel.  I found this Honeyweel LCZ260 that seemed like it would work.

This would have been way easier to do before the engine was installed on the plane, but there seemed to be room to mount the sensor on the upper left side of the flange at the back of the engine (where the transmission would mate up in a car), just above the starter.  I tried a few different ideas for how to mount it, and ended up just using a simple little piece of angle I had in the scrap pile.

This is looking at the left side of the engine; you can see the little starter gear below.  I just drilled through the aft baffle fence and the flange to mount my little angle there.

Once I had the bracket location figured out, I adjusted the nuts to set the end of the sensor as close to the flywheel teeth as I could (obviously making sure nothing made contact anywhere).  I used a locknut on the lower nut to ensure it won't ever loosen and fall into the flywheel, and I also put loctite on the upper jam nut too for good measure.

I routed the 3-wire lead from the sensor through the firewall with all the other wires, and connected it to the RPM pins on the GEA24 (+12v, ground, and signal).  Then all I had to do was set up the G3X to understand the sensor output.  To calibrate the sensor, you need to tell the G3X how to convert the signal in hertz into RPM.  The flywheel has 88 teeth, so every 88 pulses equal one revolution.  To convert 88 hertz into revolutions per minute you just divide 88 by 60, and that's pretty much it.  

The G3X let me put 8 data points in to form a calibration curve, but it's linear so I don't really think it matters too much.  Anyway once I got that all set up I tested it by just cranking the starter with the spark plugs removed, and it read 250 RPM, same as before.  So I think it works!

Engine Oil (1)

 1 hour

This is pretty simple, but I'm going to be out of town for a few months and I wanted to get oil into the engine before that.  I followed the AeroVee manual instructions to add the proper amount of oil, mark the minimum line on the dipstick, then add more and mark the max line.  I used the recommended semi-synthetic oil; they sell it on Amazon for like $90 per 12 quarts.

Finally, I cranked the starter for the first time!!  I removed the upper spark plug from each cylinder, gave everything a good looking over, then gave it a spin.  The engine spun up pretty quick with the spark plugs removed, and I only cranked it for a few seconds at a time until oil pressure started registering (also to adhere to the starter motor's duty cycle limits).

After a couple short bursts the oil seemed to be pumping.  It only took a few cumulative seconds total to see the pressure go up.  Here's a video of one of the first cranks, showing the engine spin up to 250 RPM (assuming my tachometer input is set up correctly on the G3X...), and the oil pressure rises to about 14 psi.

Interestingly, you can also see the "IPS LOW VOLT" advisory message pop up on the PFD as soon as the cranking begins.  I set this up to replace the LED light that came with the intelligent power stabilizer, and apparently it works!  What it indicates is that the IPS is seeing a voltage dip and is doing its job of trying to supply a stable 12v to the avionics in order to keep them running during engine start.  You can see the voltage display on the right side of the screen, that shows Voltage #1 (main bus voltage) drop to like 11.2v, and Voltage #2 (the IPS output) managing to provide more like 11.8v.  So that all appears to work as intended.

Anyway, I let the starter cool down a bit, recharged the battery, and came back a while later for a few more cranks to see how the oil pressure looked.  After three or four total ~10 second cranks, the oil made it to 60+ psi.  That actually seems kind of high to me at only 250 rpm, but the oil is sort of cold (60 degrees F), so maybe it's normal.  I will investigate further later, but I'm guessing it means the oil pump finally was able to fully prime itself and that's why the pressure jumped from 14 to 60.  Here's a video of the last crank I did:

For now, I'm satisfied the engine has some oil in it, and the pump does move the oil around!

Spark Plugs Wires (1)

1 hour

Next thing was the spark plug wires.  The four upper plugs are all powered by the magnetos via their built-in wires.  I routed each one through a grommet in the baffle.  The two rear ones go through the baffle all the way in the outboard corners, through pre-drilled holes.  I drilled my own holes for the forward ones.

The lower plugs are powered by the coils, which I haven't installed yet.  I popped the boots over the plugs, but I'm not sure exactly how I'm going to route the wires yet, or where I'll even mount the coils.  So I'll finish them later.

CHT Sensors (0.5)

0.5 hours

I bought 4x CHT thermocouples from Sonex when I ordered the engine.  Installation is pretty simple, you just drill a #32 hole next to each spark plug, and then screw down each ring terminal using the included self-tapping screws.  Here you can see where I installed them, and the other side is the same.  Luckily you can still access this area with the intake installed!

Oil Separator Connections (1)

1 hour

I got some more little hose fittings in the mail so I was able to run the lines to and from the oil separator.  The input is just a hose connected to the breather port on top of the engine.  The output is a braided hose that goes from the bottom of the separator back to the oil sump.  This one is important because if it leaks all the oil will leak out of the engine!