Reliability and complexity of alternative engines.

[rv6ejguy]

Originally Posted by asav8tor

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 guess you mean Subaru here.

[akschu]

Originally Posted by SHIPCHIEF

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'.

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

[mikegraycmg]

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.

[akschu]

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 )

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

[akschu]

Originally Posted by mikegraycmg

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.

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

[flytoboat]

Schu,
The EGG site has the installation manuals available. Should answer your questions on electrical issues.
http://www.eggenfellneraircraft.com/iindex.htm
good luck

[rv6ejguy]

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

[DGlaeser]

Originally Posted by akschu

[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

Here is a link to my electrical diagrams:
http://www.wideopenwest.com/~glaeser...rical_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.

[akschu]

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

[SvingenB]

Originally Posted by akschu

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

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.