Subaru 3.0r Six cylinder with Turbo

Installation details.



My goal is to provide all the details you need to install this engine into your aircraft. I started this process 12/6/2005. On that day I received the 2005 EZ 3.0 engine in a crate. Brand new p/n 10100BM500 from the Subaru factory. You can purchase this item for $8k direct from Subaru. Gross weight of that container was 300#.


Now, there are some very important… and unexpected...circumstances here. Subaru enthusiast Joel Hall has donated this engine and all of the other components. He arranged this when I expressed interest in developing this engine package. The terms of this deal? So far, it’s just “publish the install details”. Wow! I think I can handle that!



           Engine features:

This Horizontally opposed 6 cylinder engine is rated to produce 220 hp at 6000 rpm. That will jump to around 290 hp with 10” of boost from the turbo. Flight testing will determine my net hp output. Looks like I’ll finally get to use that O2 system for pilot……


Unusual items:

· Plastic intake. This is relatively new development. My other engine had a 15 lb cast aluminum intake. This one is only 6 lbs.


· Oil pan is cast aluminum. The only steel is the end cap. I’m told this improves rigidity of engine, enhances heat transfer.


· No throttle cable. This is a “drive by wire” throttle body. I will replace that with traditional throttle body.


· Variable valve timing and variable valve lift.

   for more info. It changes the cam timing            and lift depending on rpm.


· Independent coils for each spark plug.


· Water / oil heat transfer system. Coolant is way more efficient at extracting and releasing heat. This engine takes advantage of that by using coolant system to remove excess oil heat.


1)      Put engine details into 3d cad so you can determine mounting and fit to your aircraft.    Completed 1/12/06

2)     Remove unneeded components. Completed 1/14/06

3)    Record and publish install details.

4)    Make any engine mods needed for flight.

5)    Arrive at baseline weight of engine.

Engine flywheel end viewEngine top viewEngine components removed

I have the engine in 3d wireframe cad. Here is 2d image of where the engine, psru fit the Cozy.  

Cad plot of engine in aircraft

Intake manifoldCoolant tube before

Initial measurements found the intake manifold was too tall to fit my Cozy engine covers. However, the intake is designed to allow you to flip it 180 degrees. I’ve done this. Now the throttle body faces away from the bell housing. I had to saw off one boss on the manifold to make it fit. Some simple plumbing changes needed too.

Coolant tube after changes


After tubing changes

Original alternator brktalternator brkt after mod




Bracket has been

Reduced using


Two ECU’s with vibration isolation added.

They are stacked on top of each other. I really like the Vi-Pec design. They are one of the few ECU’s that can handle the OEM crank trigger signal. Same with the variable cam timing. An abundance of sensors and outputs available for ECU connection. I’ve installed Haltec ECU’s to this plane. Also Megasquirt Pro’s. Vi-Pec seem least on the surface.

Want to be guaranteed to fail? Just don’t measure the parameters. Here’s an important asset Joel found. Turbo speed sensor by Owen Developments. Converts the high freq pulse to one my plc can measure. No more speculating….just the facts! We’ll use this to optimize turbo selections. The glass cockpit will warn me if on edge of overspeed.


In any endeavor, there are a handful of things that really make a difference. Key items. Sensors are one of those items. Most failures have “lack of measurements” as a cause. The more things you measure, the better your understanding. But it’s the details that make a difference. They have to be calibrated sensors, they have to have the accuracy and precision we need. The measurements must be logged and displayed in easy to interpret manner. If you have a bunch of round gages on your panel, you are a total bozo. That’s history. Grossly inadequate way to display info. They are dumb as can be. See Glass cockpit for optimum solution.


Temperature sensors:


Most of the oil and coolant sensors have inadequate range. Here is link to the best price I could find with the best sensor. It’s range is –40 to +275F. Perfect. Temperature sensor

Pressure sensors:

Here is the best source I could find for pressure sensors: Omega pressure sensors. Model px309-100g5v, also px309-50g5v. Chrissi suggested these:  Pressure sensors  They just took forever to ship. M5100 model with specs: 0-5vdc output, 24” jacketed cable, 1/8”-27 npt male, 0-50 psig range.  All of these sensors have built in voltage regulator, so you don’t need to worry about variation in supply voltage. Makes for simple wiring, attractive, small, and accurate.

wire harness before modsWire harness modified

New injector connectors.

Connectors removed

Surprisingly few changes were needed to the engine wire harness above.  I’m eliminating a few of the connectors and direct soldering the ECU wires to the engine harness. This is a safety advantage, yet the engine will still be able to be easily removed. Connectors are historically a leading cause for electrical issues.

I was particularly cautious in soldering the new injector connectors. I added strain relief rubber isolators to each pin to improve fatigue resistance. I used magnifying glass to inspect each solder joint. Keeping in mind that changes are my highest risk aspect of this conversion.

Engine wire harness before mods


Click for full size image

Throttle body from 3.3 liter engine

This throttle body is from 2000 2.5 liter Subaru. I’m using it instead of the  “drive by wire” on the newer throttle body.

3/8” aluminum adapter. The bright notch allows idle air bypass to function properly.

Press fit plastic spacer.

Steel plate locates on thin idle stop rod

Steel plate, tapped for two fasteners

Separate steel shaft welded to (3)     8mm nuts

All of these mods allow adding second TPS sensor (throttle position sensor). This provides huge safety margin, as each ECU has it’s own sensors. (2nd TPS not shown)

Speaking of redundancy. I use two throttle cables. The backup cable assy always has a little slack. If my throttle cable breaks, I will experience a slight rpm drop, and then the backup cable takes over control. This approach allows me to use the oem spring loaded throttle controls with very little risk.

Enlarged holes to fit intake manifold hole pattern

Steel plug modified

This is a steel plug found in the heads, flywheel end. It caps off a large bore in the cooling system. I drilled and tapped the center. I also welded a steel tube to the end of it. This allows me to use the plug as an attach point, yet have no risk coolant leaks. I found this a convenient engine attach point.

New light weight flywheel. The notches on perimeter are for crank timing signal sensor.

Fuel delivery

I made this fuel header out of 1/8” aluminum. That’s needlessly thick….but it was easy to weld. It holds 3 gallons. I leak tested it with water prior to drilling.


Submerged, “wet” fuel pumps are very safe. All car manufacturers use this approach now. It completely eliminates the risk of vapor lock. The pump lasts longer, as it’s always cooled by fuel. Reportedly this has greatly reduced warranty issues related to heat...thrown armature windings.


This design, with two reservoirs, means that the main pump will always run out of fuel before the aux pump. So if you run tank dry, switching pumps yields immediate flow.

Aux reservoir will trap all water, main reservoir will be free of water. This is because aux reservoir is at the inlet.


Recommended improvement: My fuel inlet should be relocated. It should be at bottom of the aux reservoir. This would maximize head if I ran out of fuel, it would rapidly

re-prime. Self priming fuel system is important design characteristic.


I’m using Permatex #2, forma gasket to seal the two halves. I drilled and tapped all of the bottom flanges, except one… the one near the firewall. Those screws are installed from under the plane. So the top half of tank is drilled and tapped 1/4-28.


The fuel pump is Walbro # Gss 342

Tiny little thing. Love it. High flow at high pressure. It only comes with pump, rubber isolator, and filter bag. So I had to adapt it to a Honda prelude fuel pump bracket kit from Airtex.


Originally I was going to use the Airtex pumps, but found numerous design flaws, so abandoned them. Poor packaging caused pump inlet fracture on both pumps. Found one wire rubbing bracket. Wire leads designed to allow them to short against bracket. Both pumps were not vibration isolated from mounting bracket. Just shoddy design.


Recommended improvement: My fuel filter is not close enough to the bottom of the reservoirs. I should have designed it with pumps rotated 180 degrees to get that white bag at bottom.


The white bag on the pump inlets strains out debris, yet does not add a significant pressure drop. The bag serves to retain fuel when pilot flies uncoordinated on low fuel. It’s also self cleaning. Hugely superior to traditional in-line filters. Once again, the bag  is standard on all cars.

Bottom fuel tank installedFuel pump


Filter bag






Vibration isolator



Fuel return


Walbro #342


Light weight flywheel

Muffler Construction:

Here’s a muffler with some excellent safety

features. It’s not welded to the exhaust headers,

it sort of floats between the two headers.

This prevents weld fatigue due to expansion

and contraction of exhaust and engine.


1) Cut up a long tube of  3” diameter x .05” thick stainless steel. I used 321 ss. You need 2 pieces 6” long, 1 piece 5” long. I did this all with my band saw. It took less than 2 hours to make all of the muffler components.


2) Cut one of your 6” long pieces full length. Making a “C” shape. Then flatten the sides of the “C” to make it “U” shaped.  This is the main body of the muffler.                                

3) Now cut your other 6” long piece to make a “C” shape. Make it just big enough to mate with the piece you formed in step 2 above. This completes the main body of the muffler.                                                                                                

4) Flatten the remnant from step 3 to create your baffle. Trim baffle to 6”x3” rectangle shape.                                                

5) Cut your 5” piece in half lengthwise. Resulting in two “C” shaped pieces. Flatten them, then roughly cut them to shape. These are your two oval shaped end caps for your muffler body.                                                                                   

6) Make your two slip joints by cutting a short piece of tubing. The outlet from your exhaust header will slide inside these pieces. They need to have around .02 to .04” clearance for slip fit. I ended up cutting a slice in a piece of tubing that was too large, then welding the seam to achieve that slip fit.                                                                                 

7) Drill 22 holes, size .275 into your baffle. 25 holes size .230, and 22 holes size .17”. This totals 2.85 sq. in. of holes. That happens to be 1.6 times more area than your exhaust pipe. Yielding quiet exhaust that doesn’t restrict flow.                                                                                               

8) Weld it all together. You have to remove 1 exhaust header, fit muffler in place, then reinstall the header. One simple brace holds it all in place.


9)              Please note: This version of muffler is much shorter than original well proven design. Until I test this, I recommend you build your muffler 8-10” long, instead of this 6” version. The longer version is still very light, will certainly last longer than 240 hours.  I measured engine power output . Compared muffler to straight pipes built to tuned lengths. No measureable power difference. It just so happens,  a friend did sound measurements of various aircraft flying overhead at 1000 ft, two different speeds. Mine was the second most quiet out of around 10 aircraft.



Muffler componentsMuffler main body

Step 2

Main body of muffler

Vi-Pec 88 ECUAl and Cozy with 3.0R engine installed

Al, Engine installed… close to first start………….

Exploded view of muffler componentsBaffle drilled and welded in place

Perfect place for O2 sensor if you need one

Red text to left describe components removed to save weight. Total weight reduction so far is 24.4 lbs. Surprise heavy items were the black steel covers shown in the photo. They have steel ribbing. It’s pretty clear they serve to protect the fuel rail from external heat… insulated on the underside. I’m going to replace them with fiberglass copies. I’m sure they are not needed in aircraft, but cosmetically they really clean up the installation. The fiberglass replacements also have significant insulating value.

Below are before and after pics of coolant tube. This provides warm water to throttle body. Prevents icing. I cut off portion, welded on hose nipple, to allow it to fit intake manifold that has been rotated 180 degrees.


Before and after alternator bracket. I used my band saw to cut up the bracket. The wood blade handled it fine. This provides the clearance for alternator to fit. Much less room available for the alternator now that the intake manifold has been rotated 180 degrees.