Engine/propeller Decision for a SUBARU engine FWD package
Since starting my GLASTAR project in 2001, I wanted a new innovative solution regarding Engine & Propeller rather than the technology of the 50’s/60’s from Lycoming or Continental.
Rotax engines that already existed at that time were too weak in power for the Glastar with 890 kg (1960 lbs) MTOW, the first diesel engines (such as Continental Diesel, Centurion, etc.) were very heavy and far too expensive. But the Boxer engine from Subaru with 170 hp (2.2 Liters) or 205 hp (2.5 Liters) are in terms of design, weight and performance ideal for aircraft like my GLASTAR. Fortunately, at that time there were 3-4 engine manufacturers (Eggenfellner, NSI, MPS, etc.) who built complete engine-forward packages based on these Boxer-Subaru engines, thereby becoming serious alternatives to the Lycomings 320 or 360.
During my Glastar construction phase, I calmly observed the entire engine scene and began to weigh up the advantages and disadvantages of these Subaru packages compared to the Lycomings. The Lycomings have of course been proven aircraft engines for many decades, but are associated with high fuel consumption, usually still linked to the very expensive aviation fuel AVGAS, high fuel consumption values and, associated with this, greatly reduced ranges. Of course, all of this results in very high operating costs per flight hour.
The new-technology of Subaru Engines fly with car gasoline from 87 octane, with a consumption of 16-22 liters/hour (approx. 4-6 US gallons) at 115 to 120 kt travel power (and approx. 60% power).
Of course, I use the Super cargasoline (usually 98 octane) that is offered at our airfields for Rotax engines. Of course, MOGAS and AVGAS can also be refueled at any time, but AVGAS will be avoided as much as possible due to the higher costs.
In 2004 my GLASTAR project was already so advanced that I had to make an engine decision. In the meantime, many aircraft (Glastar’s, RV’s, etc.) were already flying with Subaru Engine packages, and especially the NSI package appealed to me best because it was overcomplete and very well coordinated. A complete ready-to-plug engine forward package including matching cowling and engine mount for the Glastar, including a beautiful AVIONIC panel including all engine-relevant displays and equipment and a complete electrical wiring diagram for wiring all remaining flight instruments and components.
After I was at Glastar Aviation in Arlington (WA) in 1999 before purchasing the Glastar kit to attend a 2-week practical Glastar assembly workshop, I decided to fly to Arlington again in 2005, at its airport (and only a few hangars apart) happened to be based by both the kit manufacturer GLASTAR-AVIATION and the engine manufacturer NSI/MPS. So I had the opportunity to do test flights in 4 different Glastars with 4 different engines, namely a Lycoming 320, Lycoming 360, a Subaru 2.2 liter with 165 hp and the most powerful Subaru 2.5 liter with 205 hp.
After extensive test flights over several days, after inspecting the assembly operation and the engine test stand and after many discussions with the boss and his technicians at NSI/MPS, I made my decision on site and ordered the powerful Subaru Engine Package with the 2.5 liter engine with 205 hp, with a powerful A40 PSRU (Propeller Speed Reduction Unit) newly developed specifically for this powerful engine, an electrically adjustable 74 inch Whirlwind 2 blade propeller, new engine mount and cowling for the Glastar, and an overcomplete avionic panel including 2 PC545 Odyssey batteries. The delivery of all parts arrived in Austria undamaged and on time.
In addition to the 205 hp, this more powerful 2.5 liter Subaru engine is also more powerful in terms of internal engine parts such as camshafts, valves, etc., which in turn leads to more longevity and smooth running of the engine.
This engine package is designed to be dual (redundant) as far as possible in terms of fuel system, electrical system and ignition system. E.g. 2 batteries, 2 ignition systems, 2 electric engine controls (ECU’s), 2 LOW and 2 HIGH pressure fuel pumps, etc. etc.
During my completion phase of the Glastar and installation of this engine package, some experimental colleagues suddenly complained with these engines about startup problems in colder winter temperatures. These incidents made me think a bit about whether I had made the right engine decision, as it can get very cold here in Austria in winter.
Fortunately, while I was still in Arlington, I met the technology genius Paul Messinger, who was also involved in the development of the HUBBLE telescope at the time and was also very knowledgeable about tuning engines. He also knew the NSI engine manufacturer very well personally, also knew this Subaru Engine Package, but was not involved in the fine-tuning of this engine until then. It’s a shame, because these starting problems would probably never have occurred in cold temperatures. Paul gave me his contact details and offered to help me if I had any questions or problems.
Due to these incidents, I made personal contact with Paul Messinger weeks before my first engine start and described to him the startup problems I had heard from other colleagues. He asked me to send him the engine’s current tuning data. These 2 electric ECUs can be connected to a laptop at any time, retrieve the existing settings and change them if necessary. I printed out all the engine parameters and submitted them to Paul Messinger. Paul lived not far away from Arlington, drove to the engine plant with this data and at the engine test stand they found out, that especially in cold temperatures, the included PC 545 Odyssey batteries were a little too weak. As a result, starter speeds were too low in cold temperatures, which meant that the powerful 2.5 liter Subaru engine in particular started poorly. This could lead to hard kickbacks (misfires) when starting, which ultimately weren’t good for the PSRU either. It was then generally recommended to switch to the more powerful Odyssey PC645 and the problems were resolved. After consulting Paul Messinger again, I decided to install the even more powerful Odyssey PC928 straight away. Since these larger and heavier batteries weren’t a problem for my Glastar in terms of weight, I was on the safest side and the starting problems shouldn’t occur to me at all.
My first engine start was completely problem-free, and regardless of whether it was winter or summer, I haven’t had any startup problems with this setup to date. Paul Messinger told me afterwards that it was hardly below zero centigrades in Arlington and generally on the Pacific Coast, and that the engines were therefore good to start, even with the weaker batteries. These starting problems especially occurred in colder regions. With the more powerful batteries, you can immediately achieve a higher starter speed, even at cold temperatures, which is very important for a safe engine start.
During cold winter days I also plugged in a „battery monitor” to ensure that these 2 batteries are always sufficiently charged.
In conclusion, I can say that I have not had any problems with this Subaru Engine Package since my first engine start in 2006 until today and I have always been very safe and reliable with my Glastar since then. Today – and 19 years later – I can say that I did made the right engine decision in 2005.
