What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Reliability and complexity of alternative engines.

akschu

akschu

Well Known Member
Patron
Forum,

I've been doing a lot of research and reading about using a subaru engine in my project and one thing that I'm struggling with is the complexity of alternative engines. Face it, there is just a lot more to fail when your dealing with EFI controller, Ignition system, electric fuel pumps, alternator, battery, cooling system, turbos, etc.

I do agree that the basic subaru engine is far more reliable than a lycoming, but I'm not sure it is when you include all of the other systems it depends on. A gravity fed carburated lycoming is so simple that there isn't really anything to fail shy of catastrophic failure like dropping a valve or breaking a crank, where the NTSB is riddled with cases where a subaru engine lost power because of wiring or a fuse or some small dependency that doesn't exist in the lycoming.

At this point I'm trying to determine which poison I want:

Lycoming and the noise, vibration, pain in the neck cold weather operation, expense, and risk involved with using a 50 year old case and crank.

or

Subaru and the complexity of the installation and massive amount of dependencies.

I'll summarize my concerns with an example: Bud Warren. An A&P who makes a great gear drive, that has shown to be reliable, and uses a chevy engine which is also shown to be reliable, still lost his plane because of a failure in the system. Granted, the fuel line could have failed on the lycoming too, however, it goes to show you that the installation of the system could compromise it, and generally speaking, the system required to run a lycoming is MUCH simpler.

Anyone have some thoughts on this? I really really want to run a subaru since I live in Alaska and having heat in the cab would be wonderful, but this place isn't at all tolerant of failure and I'm concerned about the complexity of running a subaru engine.

Thanks,
schu
 
Not as much difference as you think.

It all comes down to your comfort level, and how much you are going to make vs. buy on an alternative powerplant.
I went with an Eggenfeller FWF package that was quite simple to install. If you are planning to 'roll your own' then it is a lot more work and complexity in the design and installation.
As far as the 'massive dependencies' for the Subaru, it's really only the externally supplied electrons vs magnetos.
Both engines have alternators, and turbo systems if you're going that route, and even a carburated Lyco needs fuel pumps on our low wing planes, so that's a wash from a dependency viewpoint.
Cooling is different, but the difference is in the installation. Engine failure due to cooling failure doesn't seem to be a big issue. Getting your cooling system to work well is a bigger issue. In Alaska you'll have fewer problems than most :cool:
So you need a robust electrical system. It is a dependency the Lyco doesn't have, so you have to decide if the benefits outweigh the risks. You have to be comfortable that you can design and implement a reliable, failure tolerant system. Don't forget immediate notification of alternator failure! Designs (and support) are available on the AeroElectric Connection.
When you say the NTSB database is 'riddled' with cases where a Subaru lost power due to a dependency that doesn't exist in the Lyco - exactly how many are we talking about? (I've never bothered to look - I hope it's not many :eek:)
Oh, and I doubt your Lyco will have a 50 year old case and crank. The design may be that old, but the parts will probably be a bit newer :rolleyes:
 
I've got twin batteries and twin alternators on my EG33.

With your gravity feed to the HP pumps (two) you should never have a fuel feed or VL situation.

The controllers are bulletproof if they don't get wet.

Follow current best practices on the cooling system and I would not expect any problems there in your climate.

More unknowns exist with the PSRU as each installation is unique and untested.

All supporting system must be well designed as you correctly point out, this is where most problems have occurred to bring down alternative engined aircraft.
 
STOP!

The Subaru basic engine is not more reliable that a Lycoming. (as stated in the second paragraph of the first post)
Be honest with yourself. You can have your own point of view, but you can't have your own facts.
There are no alternate engines that are demonstrably more reliable in aircraft than 'aircraft engines'.
Now that I have that off my chest......proceed with caution, I am.
I'm having a blast building my power plant, and redoing so many parts is just going to happen. Not only are there very few pre-made parts, most parts you make will be redesigned, refabricated, or repositioned. Plan on it and enjoy it. Once you get the engine running, you must evaluate all the systems you created. On a Lyc system you can pretty well count on the basic systems to integrate with minor problems. Not your combination, they never knew each other before this moment.
Most Lyc parts have been developed to go the distance and the estimated life is already known. The same for the accessories like mags.
All your custom designed brackets, pulleys, hoses, tubes, filters, mounts etc. etc. are one off articles that will require vigilant evaluation over their entire lifespan, which is unknown, because no historical data has been available on your unique arrangement.
If you are up for that, then go for it. Don't fool yourself, go forth with clear mind and eye, build the engine of your dreams.
 
Here we go - sit back and watch !!!!

I think I'll pop up some microwave popcorn for the show to come...gets more interesting and a little bit crazier every time!
 
Something better

SteinAir said:
I think I'll pop up some microwave popcorn for the show to come...gets more interesting and a little bit crazier every time!
Click to expand...


Hey Stein,

I'll bet some Kettle Korn would be even better. Shhhh..... Quiet the previews are starting. This is going to be good.
 
Here we go again.........


The endless engine debate. I think it would be helpful to have 2 tables side by side. The first would have all the parts to a disassembled Lyc the second all the parts to a disassembled Sub. The builder/pilot would peruse pick up and handle the parts from each table. After careful observation the builder pilot would make his/her selection. Nothing written online or in print would have the impact of such an exercise. The lightbulb would come on. The choice would be clear.
 
I will pass on this one for sure....

Mathew, there's a guy out at Homer with a EGG Subaru. I can't remember his name off hand but I've exchanged e-mails with him. Get in touch and see how he is doing. If you call the Homer airport operator they should know who he is.

(I just remembered his name, it's Vince Tillian)
 
SHIPCHIEF said:
The Subaru basic engine is not more reliable that a Lycoming. (as stated in the second paragraph of the first post)
Be honest with yourself. You can have your own point of view, but you can't have your own facts.
There are no alternate engines that are demonstrably more reliable in aircraft than 'aircraft engines'.
Now that I have that off my chest......proceed with caution, I am.
I'm having a blast building my power plant, and redoing so many parts is just going to happen. Not only are there very few pre-made parts, most parts you make will be redesigned, refabricated, or repositioned. Plan on it and enjoy it. Once you get the engine running, you must evaluate all the systems you created. On a Lyc system you can pretty well count on the basic systems to integrate with minor problems. Not your combination, they never knew each other before this moment.
Most Lyc parts have been developed to go the distance and the estimated life is already known. The same for the accessories like mags.
All your custom designed brackets, pulleys, hoses, tubes, filters, mounts etc. etc. are one off articles that will require vigilant evaluation over their entire lifespan, which is unknown, because no historical data has been available on your unique arrangement.
If you are up for that, then go for it. Don't fool yourself, go forth with clear mind and eye, build the engine of your dreams.
Click to expand...

I think the original poster was talking about the core engine, not the entire powerplant assembly of which he is well aware is a one off, unproven collection of parts. I've worked on both engines. There is nothing inferior in the Subaru design to the Lycoming. This has been proven in BILLIONS of hours of use, hundreds of thousands of flight hours, millions of engines in service and validation exceeding certified engine requirements.

If you are not mechanically inclined, patient and willing to do a lot of fab work and testing, don't go down this path- bite the bullet and get a well built 540 from Barrett or Aerosport. You will get into the air sooner and likely have less headaches in the long run.
 
Last edited:
asav8tor said:
Here we go again.........


The endless engine debate. I think it would be helpful to have 2 tables side by side. The first would have all the parts to a disassembled Lyc the second all the parts to a disassembled Sub. The builder/pilot would peruse pick up and handle the parts from each table. After careful observation the builder pilot would make his/her selection. Nothing written online or in print would have the impact of such an exercise. The lightbulb would come on. The choice would be clear.
Click to expand...

I guess you mean Subaru here.;)
 
SHIPCHIEF said:
The Subaru basic engine is not more reliable that a Lycoming. (as stated in the second paragraph of the first post)
Be honest with yourself. You can have your own point of view, but you can't have your own facts. There are no alternate engines that are demonstrably more reliable in aircraft than 'aircraft engines'.
Click to expand...

I am being honest. In cold weather operation -20F some days, a liquid cooled engine will always be more reliable. Unless your airplane is hangared and not flown in winter NONE of the engines around here go TBO, where there are zillions of subaru cars left out in the cold that start every morning. Subaru cold starts their engine thousands of times and brings it up to operating temp as fast as they can during the testing period, there isn't a lycoming that would live through that.

So if your talking about a lycoming in Texas or Arizona, sure they work great, but around here you can expect a buy a top end before TBO.

schu
 
Made my choice

When I first started looking, I wanted a subaru for my 8. I changed my mind after reading up and talking to a lot of people. The deciding factors for me were weight and complexity of installation. I don't know what you are building, but this is truly an individual decision and what is important for me might not be important for you, and vice versa.

I suggest you find out as much as you can, and then go with what you like with your eyes open. In your harsh environment, you might have some reliability issues with either choice.
 
Ross,

I am able to do the engineering and fab work and enjoy it, which is why I would rather have the subaru, I'm just trying to make sure I make the right decision. On one hand I really don't want an air cooled engine, on the other hand I can't ignore the fact that the lycoming is a very simple setup that doesn't depend on an electrical system.

At this point I'm very much leaning toward the subaru since the complete package will be worth the extra time and effort. Having heat is a pretty big deal, and I would be much more comfortable taking off in -10F when I can see the temp gage showing a warmed up engine. It's kinda scary to start an aircraft engine in that amount of cold, kinda sorta warm it up on the ground, then pour the coal to it and expect it to make rated HP, while trusting your life to it. I know what is going on inside that engine, and it doesn't give me a warm fuzzy when I do it.

Other posters,

It's interesting how you guys see this as a debate, I don't view it that way, I'm just trying to nail down the dependencies, and their pros and cons. I'm not asking which one is better, I can make up my own mind about what works for me, just looking for feedback to make sure my dependency concern is reasonable.

DGlaeser points out that the major difference is mags vs electronics, which means that the majority of my concerns can be resolved by a well thought out and designed electrical system. So let me ask a few questions about that:

1. Do the subaru guys run a redundant fuse block? I suspect the ECU is fused which means a faulty fuse could cause engine failure, do you guys live with this or do you have a primary and secondary engine systems fuse block and have a switch?

2. How much redundancy in the wiring is reasonable? More connections always add more points of failure, but some redundancy is good. I was thinking about running two alternators with two batteries, each with it's own fuse block which then put a switch between the fuse block and master switch. This would effectively allow me to switch between electrical system A and electrical system B.

When you say the NTSB database is 'riddled' with cases where a Subaru lost power due to a dependency that doesn't exist in the Lyco - exactly how many are we talking about? (I've never bothered to look - I hope it's not many :eek:)
Click to expand...

The NTSB has almost 40 incidents with subaru engines, but none of them are block failure, they are almost always electrical problems or fuel issues, usually followed with bad decisions in the cockpit. I wouldn't say that is that many, but it does cause me to understand that the sum of the parts make an otherwise bulletproof subaru engine much more prone to failure.

Anyway, I'll contact that guy in Seward and talk to him, there is still more to learn before I make the decision.

Thanks,
schu
 
mikegraycmg said:
When I first started looking, I wanted a subaru for my 8. I changed my mind after reading up and talking to a lot of people. The deciding factors for me were weight and complexity of installation. I don't know what you are building, but this is truly an individual decision and what is important for me might not be important for you, and vice versa.

I suggest you find out as much as you can, and then go with what you like with your eyes open. In your harsh environment, you might have some reliability issues with either choice.
Click to expand...

I'm building a bearhawk which flys fine with either a o-360 up to a o-540. So I can install a EG33 and not have any CG problems, and the 230 stock HP is plenty for my setup. I do want to run a small turbo so that I can run just a little boost, but then again thats making things even more complex.

If I do decide to go without a turbo then it will be much less expensive since I won't have to mess with pistons and such, but on the flip side I think a turbo will work much better because we recover some of the losses and we have much more performance at altitude.

Anyway, lots to think about....

schu
 
You bring up good points for cold weather operation. Subes won't need preheat and with an oil thermostat in place, the oil warms up as fast as the coolant on my engine.

My post about going in with eyes wide open was directed more at others viewing the thread, not you, as I can tell you are a pretty savvy guy, with skills and a questioning mind.

Not sure if you've seen Wardstrom's Rover V8 powered Bearhawk on our website. They really like it and it has worked very well from day one. Maybe another engine to look at. http://www.sdsefi.com/air38.htm
 
Last edited:
Electrical diagram

akschu said:
[snip]
DGlaeser points out that the major difference is mags vs electronics, which means that the majority of my concerns can be resolved by a well thought out and designed electrical system. So let me ask a few questions about that:

1. Do the subaru guys run a redundant fuse block? I suspect the ECU is fused which means a faulty fuse could cause engine failure, do you guys live with this or do you have a primary and secondary engine systems fuse block and have a switch?

2. How much redundancy in the wiring is reasonable? More connections always add more points of failure, but some redundancy is good. I was thinking about running two alternators with two batteries, each with it's own fuse block which then put a switch between the fuse block and master switch. This would effectively allow me to switch between electrical system A and electrical system B.
[snip]
Thanks,
schu
Click to expand...
Here is a link to my electrical diagrams:
http://www.wideopenwest.com/~glaesers/electrical_plan.htm
See page 7 for the engine electrical system. It's based on Bob Nuckoll's Z-19 architecture. I only have one alternator, and 2 batteries. If you want to run dual alternators and batteries, Nuckolls has an architecture for that as well (don't remember the number).
My goal was redundancy with no single point of failure for the systems providing fuel and electrons to the engine (with the ECU considered part of the enginie). The engine will run from either battery if the alternator fails.
 
Dennis,

Thanks for the wiring diagrams, I'll be looking at them over the next few days.

Ross,

Is the turbo worth the cost and trouble? I can get a JDM engine for less than $1k, where buying turbo pistons and having the machine work done is going to get pretty expensive. I figure a turbo is going to add $4k to the engine, having ran both do you think it's worth it?

schu
 
akschu said:
I am being honest. In cold weather operation -20F some days, a liquid cooled engine will always be more reliable. Unless your airplane is hangared and not flown in winter NONE of the engines around here go TBO, where there are zillions of subaru cars left out in the cold that start every morning. Subaru cold starts their engine thousands of times and brings it up to operating temp as fast as they can during the testing period, there isn't a lycoming that would live through that.

So if your talking about a lycoming in Texas or Arizona, sure they work great, but around here you can expect a buy a top end before TBO.

schu
Click to expand...

Starting any engine in -20F is the equivalent of approximately 6 to 10hours, or more, continuous run at operating temperature regarding TBO (if there is a set TBO). A tight tollerance Subaru engine is certainly not better than a loose Lycoming in this respect.

I don't see any logic in designing redundant electrical systems, and at the same time plan to regularly start the engine below 0C without a pre heater. A pre heater is simple, cheap and light weight, even the ones that runs on fuel. In cold weather, a pre-heater is the single most important item for a long lasting trouble free engine.
 
SvingenB said:
Starting any engine in -20F is the equivalent of approximately 6 to 10hours, or more, continuous run at operating temperature regarding TBO (if there is a set TBO). A tight tollerance Subaru engine is certainly not better than a loose Lycoming in this respect.
Click to expand...

Absolutely it is. The loose lycoming is designed to have proper piston/bore clearances when it is hot, therefore when it is cold it has very tight piston/bore clearances. The subaru engine also has tight piston/bore clearances, but not nearly as much because it has a much smaller bore and because it's not designed to operate over 250*. The bore size and temp delta force the lycoming to run much larger tolerances.

I don't see any logic in designing redundant electrical systems, and at the same time plan to regularly start the engine below 0C without a pre heater. A pre heater is simple, cheap and light weight, even the ones that runs on fuel. In cold weather, a pre-heater is the single most important item for a long lasting trouble free engine.
Click to expand...

A pre heater is somewhat effective at getting the engine warm, but as soon as you start it the cold air will take the heat way pretty quick and the engine doesn't generate enough heat at idle to really warm it up. Any which way you look at it, you are expecting a cold air cooled engine to make rated HP at take-off even though the cylinders haven't grown enough to have the piston/bore clearances of running temps. The subaru on the other hand can be warmed up by a freeze plug and pan heater which is a simple plug in, then when you start it, it will come up to operating temp before take-off regardless of outside temp.

Perhaps you have never flown in -10F before, air cooled engines are a totally different animal, while a liquid cooled engine will act exactly the same except for the freeze plug heater to warm it up, not to mention the cab will break 30F.

schu
 
The big differences are in the oils available today for auto engines- 0W-20/30 and 5W50. These give you awesome cold cranking capability and full protection on the top end. The much closer tolerances and faster warmup in auto engines exhibit far lower wear rates during a cold start and warmup cycle.

Lots of car engines go 300,000+ km here in Canada with half the year below 0C and winter months at -20 to -30C or even colder. They last just fine. Most people don't plug in block heaters here until it dips below -20C. My record starting an engine here without being plugged in is -38C. I don't think a Lycoming would do that.

A typical 550 watt block heater will raise coolant temps from -20C to +10C in about 1 hour- pretty efficient.

Cabin heat via a heater core is far more effective than muffs and dispenses with that hot metal smell usually associated with exhaust muffs.
 
Last edited:
Speaking of lubrication quality--------

How about the fact that one common thing for use in really cold climates is an oil dilution setup, where you add gasoline to the oil pan at shutdown, to lessen the drag for cold starting.

A buddy who lives in Alaska has this on his C185.
 
Mike S said:
Speaking of lubrication quality--------

How about the fact that one common thing for use in really cold climates is an oil dilution setup, where you add gasoline to the oil pan at shutdown, to lessen the drag for cold starting.

A buddy who lives in Alaska has this on his C185.
Click to expand...

I think it was Elmer Fudd who said "very carefully".

All the big radials had provisions for oil dilution and charts for amounts of fuel to add and boil off times. In cold weather, boil off times are considerable. Big advantage here to liquid cooled engines with 0W or 5W oils.

This is where modern technology offers a huge leap in real world useage. Just start it up with no preheat, get your oil temps in the green (thermostat) and take off.
 
akschu said:
Absolutely it is. The loose lycoming is designed to have proper piston/bore clearances when it is hot, therefore when it is cold it has very tight piston/bore clearances. The subaru engine also has tight piston/bore clearances, but not nearly as much because it has a much smaller bore and because it's not designed to operate over 250*. The bore size and temp delta force the lycoming to run much larger tolerances.



A pre heater is somewhat effective at getting the engine warm, but as soon as you start it the cold air will take the heat way pretty quick and the engine doesn't generate enough heat at idle to really warm it up. Any which way you look at it, you are expecting a cold air cooled engine to make rated HP at take-off even though the cylinders haven't grown enough to have the piston/bore clearances of running temps. The subaru on the other hand can be warmed up by a freeze plug and pan heater which is a simple plug in, then when you start it, it will come up to operating temp before take-off regardless of outside temp.

Perhaps you have never flown in -10F before, air cooled engines are a totally different animal, while a liquid cooled engine will act exactly the same except for the freeze plug heater to warm it up, not to mention the cab will break 30F.

schu
Click to expand...
Interesting. I flew a Commanche 260 with Lycoming IO-540 for many years. Originally it had no Tanis and we rarely used pre-heat due to availability and cost issues. The engine was started many many times below zero F. We didn't fly until we had an oil temp indication. Our engine was overhauled at 2200 hours. Everything in the engine met field overhaul tolerances except for the crank and cam bearing shells. If cold starts are that terrible how did our engine do so well? Bill
 
rv6ejguy said:
My record starting an engine here without being plugged in is -38C. I don't think a Lycoming would do that.

A typical 550 watt block heater will raise coolant temps from -20C to +10C in about 1 hour- pretty efficient.
Click to expand...

I have never run my car in -38C, but I remember once it was -32 or something. The main problem at those temps is that the engine will not heat up properly unless air to the radiator(s) and engine is blocked off (usually done in the middle of nowhere with cardboard, aluminum foil or whatever you can find while freezing your fingers off :) ) The heating of the cabin air alone, is more than enough cooling at those temps.

The problem is much more severe for modern diesel engines, especially the larger ones. If it gets just below 0C, the engine will start to cool down. Here (in Norway), diesel cars from 2L displacements or thereabout usually have mounted an additional heater (Webasto), that burns diesel and heat the cooling water during the whole ride if needed.

You can purchase kits consisting of baffles that block off some of the air flow at the intake for Cessnas. I think Cessna makes the kits themselves.
 
We had nearly 2 weeks here where the OAT was never over -20C and was down to -36C for a day or two at night. I was driving my trusty 1984 Toyota Supra winter beater with our SDS engine management system on it.

Brutal on the the wheel bearings. You let the clutch out at idle and the engine almost stops due to the congealed trans oil. The shocks and rubber bushings are virtually solid and it rides like a horse buggy. But start it does. Takes about 5km of slow driving to get coolant up to 50C to get a bit of heat and a full 10-12 km to get the thermostat to open at 80C and full cabin heat. Didn't need cardboard over the rad but in the old days when I drove 1200 Corollas with the heater on full blast, the coolant temp would fall to about 60C at idle.
 
Bill Dicus said:
Interesting. I flew a Commanche 260 with Lycoming IO-540 for many years. Originally it had no Tanis and we rarely used pre-heat due to availability and cost issues. The engine was started many many times below zero F. We didn't fly until we had an oil temp indication. Our engine was overhauled at 2200 hours. Everything in the engine met field overhaul tolerances except for the crank and cam bearing shells. If cold starts are that terrible how did our engine do so well? Bill
Click to expand...

I'm not sure about your conditions, but I suspect you didn't regularly fly in below 0 F weather. In my current ride (C-150) I only see a small oil temp indication even after a 5 minute climb.

I'm happy to hear that your engine went that long, that is great.

My record for starting my diesel truck without the block heater was -38F (-39C) and no it never warmed up.

My wifes van has been started in that cold, and if you wait 10 minutes it's at operating temp, something I have yet to see with my aircraft engine at -10F even after hours of use.

schu
 
And the difference is---------

akschu said:
My wifes van has been started in that cold, and if you wait 10 minutes it's at operating temp, something I have yet to see with my aircraft engine at -10F even after hours of use.

schu
Click to expand...

One of these cooling systems has a thermostat controlling the flow of the primary cooling medium.

Anybody care to guess which one????

P.S., pass the popcorn.
 
P.S. said:
I doubt this thread will be that exciting. I think he now realizes that if he posts anything that is less than constructive he will be permanently banned from the forums. So save the popcorn.
Click to expand...
 
Last edited:
You must log in or register to reply here.
Back
Top