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What is a "REAL" light sport aircraft engine?
What is a "REAL" light sport aircraft engine?
I was surprised to learn that many believe a "real" aircraft engine should not contain "unreliable" automotive parts, but rather "aircraft" parts. One individual just spent good money on what he considered to be a worthwhile since the engine supposedly did not contain any of these "automotive" parts.
First off, for an engine manufacturer NOT to use an abundance of mass produced, over the shelf, aftermarket or OEM auto parts, would not make any sense. Whom would want to fly behind any engine where the designer not only had to design the architecture of the engine itself, but also the composition of the piston rings.
Since the exact list of what parts are from what source, we will just go by what would be the norm
Cast parts such as:
The crank case, cylinder heads, intake manifold would normally be sourced from an aluminum casting house.
The Cylinders themselves could be automotive parts, parts made by someone that make / made OEM or aftermarket cylinders.
The oil filter, oil cooler, oil hoses, spark plugs, pistons, piston pins, piston pin cir-clips, all bearings, cylinder liners (if used), valves, valve seats, valve springs, valve hold down hardware, push-rods, any hydraulic tappets, rockers, oil pump gears, starter, gaskets, air filter, intake rubber couplings and clamps, fuel injectors, fuel regulator, spark plug wires, coils, the mighty ECU controller that actually runs the entire works, the electrical connections, the generator parts, the voltage regulator and the more are likely automotive or from some lawn tractor.
So, what is the point of all this? Well, just because it is direct drive and air cooled does not mean it is everything your brain think it is. Not good or bad, just not the "from the ground" up, all made for your aircraft, thing.
We just had a 2018 Honda Accord 1.5L GDI Turbo engine arrive today. All Honda tested. Not made for aircraft but a marvel of closely tested parts, ready to fly any light aircraft around.
Replies to This Discussion
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Permalink Reply by Jon Humberd on
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After seeing Jan’s post/comments on at least 2 different forums, I feel the need to make some validations and corrections to this engine debate.
Yes, I chose to put a rather expensive air-cooled engine that was specifically designed for “aviation” on my airplane. With that being said, very few people would argue against the fact that Honda makes fabulous engines. If that is what suits you, then please go for it. I am going to stick with what I think will work best for me. I will give my reasoning after I address some mis-communications.
First off, almost all engines have parts sourced from reputable suppliers, casting/forging houses, CNC machinists, etc. The new engine designs would be crazy to not consider and utilize the metallurgy that took decades to prove reliable for the composition of rings, pistons, rods, cylinders, valves, shafts, etc.
Second, I never said that automotive parts were “unreliable”. In fact, at first glance, the Honda “conversion” seemed like a great idea for my airplane. However, the more I consider what it really is, the more I realize an “auto conversion” is not the set-up I want in my airplane.
Dependable? In cars, absolutely yes! In airplanes, maybe (time will tell).
So let’s look at the details:
I would surely hope that all the “donor” Honda engines use the i-DSI ignition (2 spark plugs per cylinder). If not, this would be the first no-brainer as to why I would not even consider it for aviation. All pilots should already know about the lead fouling problems with using 100LL Avgas (think back to leaning out that Lycoming which caused an extra step at run-up to help burn off lead deposits so it would run smoother). If the engine had only 1 plug per cylinder, it would take just one fouled plug to loose well over 25% power on a 4-cylinder engine.
Next up is the additional components required for operation, which are also added potential points of failure.
An airplane engine’s main goal is to “move” air and it is simply inefficient to not utilize some of this for “air-cooling”. Why should we carry around “potential failure points” in the form of water pumps, coolant, hoses, radiator, extra sensors/thermostat, and several pounds of extra material that is required to form water jackets, ports, and ducts just to carry liquid heat away from the engine so the liquid can then be air-cooled? Our engines are already pulling a fan (prop) that is plenty capable of air-cooling a properly designed aircraft engine.
A gearbox is another added weight, power drag, and un-necessary evil that is required because the engine has to turn 5,000+rpm to produce enough power to even be considered for our aviation operations. Again, introducing another whole set of potential failure points including extra bearings, seals, oil, gears, etc.
Now let’s move on to the advertised new “advanced technology” in these automotive engines that “have made all other engines fall behind.”
- Fractured rods: Actually, fractured rods have been around for decades. They were developed in the 1960’s by McCulloch for use in their high speed chain saws and then quickly became utilized in go-karts. However, this technology is only better when based on cost of production. Honda uses the fractured rods to decrease their cost. Any other argument of fractured rods being better is an opinion and nearly invalid when you consider that almost all NHRA, Nascar, and race engine builders are using high quality “machined” rods instead of fractured rods.
- Variable valve timing: This is valuable in the automotive world because it allows an engine to be more efficient and reach better power across a broader rpm range when compared to engines without variable valve timing. This is great for vehicles because they can produce more power at a low (idle) speed and still maintain good power at higher engine rpm’s. In airplanes, which generally fly within a comparatively close rpm range, this technology is practically useless if the engine is designed to operate in this range. It is also additional weight and several additional potential failure points.
- Offset Crankshaft: Another excellent idea that has been around almost as long as the internal combustion engine. There are advantages here, however, these advantages are “offset” by disadvantages including higher vibration which brings up another whole set of issues.
It is basically impossible to perfectly balance a I-4 engine and with a little research, you will find that most of these engines have a counter-balance shaft which is just another drag-producing weight with plenty of other downfalls including, extra bearings, shafts, belts, etc.
The horizontally opposed “boxer” engines are much better balanced and generally do not need the extra counter-balancers to reduce all the vibration.
So, let’s get back to the “simple” reasons for my engine choice.
I picked…
Air-cooled: It has essentially worked flawlessly when properly designed for aviation and implemented correctly.
Direct-drive: the good far outnumbers the bad. Just forget about all the extra “stuff” involved here.
Fuel-injected: efficiency, smoother operation and response, no carb icing/carb heat
Boxer design: horizontally opposed=less vibration, period.
In conclusion: “Simpler” does not necessarily mean you are giving up high-quality designs, modern technology, and engineering. Do your own research. Research the company, technology, parts availability, problems, and even the people who sell the engines for “aviation”. As pilots, many of our lives are depending on a marvelous invention called the internal combustion engine.
P.S. No one ever said flying was cheap. If you want a cheap hobby, you better keep researching your options and pick something besides aviation. Happy flying and I’ll see you in the sky!
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Permalink Reply by Ken Ryan on
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["...
It is basically impossible to perfectly balance a I-4 engine ... The horizontally opposed “boxer” engines are much better balanced..."]
I haven't heard of any complaints about the Honda vibrating a lot. I have, however, heard Viking owners say that their Honda was by far the smoothest engine they had ever flown behind.
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Permalink Reply by Jan Eggenfellner on
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I assume the smoothness is due to a counter-balance shaft. If so, this adds another layer of complexities including additional bearings, an extra driven shaft with a counterweight (creating vibrations to counteract vibrations is never a good thing), and an additional belt that works like a timing belt.
I hope that I am wrong on this, because if this is true, the engine damage caused by a counter-balance shaft failure can be pretty dramatic to the internals of an engine. I have seen the aftermath of this first-hand more than once with being around performance engine builders and machinist for more than 30 yrs. It can get quite ugly.
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You are filling up this thread with negativity and loose facts.
I thought you would have known that a 1.5L 4 does not need / make it worthwhile to add a balance shaft.
Also, let’s not get into if a Honda engine is reliable. It is.
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Jan, thanks for clarifying the balance shaft concern. That should partially ease the minds of everyone who reads this forum and is considering a honda engine.
A forum is a place to discuss thoughts, opinions, and discover facts (good and bad). My intent was not to throw around any "loose facts". In the whole balancing concern, I did said "I assume".
(As a side note, I will admit that I am not as familiar with the Honda Fit engines and I assumed this because honda has used balance shafts for decades in most of their I-4 engines. Some using timing chains and others using belts to drive the counterweights.)
I have to say that the use of only one spark ignition system (plug) per cylinder still concerns me, especially when utilizing AvGas continuously. (Just my opinion)
However, you are correct, Honda makes very reliable engines that are an attractive engine option for the experimental homebuilt aircraft.
I apologize for seeming to be only negative and I hope these concerns will be far outweighed by the positives as we move forward.
Parts availability and lower costs are two huge positive benefits with these engines!
I absolutely wish you and all the people flying with the Honda/Viking engines the best! If/when the fleet gets more age and they prove reliable, it will be a big benefit to all of us involved in experimental aviation. Happy Flying!
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Thank you
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Permalink Reply by Loren Warner on
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After weighing many different factors, I chose the Viking 130 for the Zenith 750 STOL. That does not mean I think any less of the other engines, because I don’t. What I really enjoy about experimental aircraft, is our ability to make choices. Perhaps I may clear up some misconceptions you may have.
As for fouling spark plugs when using 100LL, its much less likely with the Viking engine than a Continental or Lycoming. To burn-off lead, the combustion temps must be kept higher which is generally by increasing rpm to say around 1,000 – 1,200 rpm, and lean to best power. To achieve the same 1,100 propeller rpm with the Viking’s 2:33 reduction gear, the engine will be turning around 2,600 rpm, which will burn-off lead deposits even more, and recharge the battery quicker.
There is no way the fuel/air mixture of a carburetor or fuel injected Continental/Lycoming could be as well tuned or efficient as that controlled by Honda’s ECU with GDI, therefore plug fouling is less likely. With all being equal, having an ECU also reduces a pilots work load.
By your reasoning, if we lost one cylinder (25% power) because of a fouled plug, our Viking 130 would still have more power than a Continental 200. In other words, I can reduce power and continue running on three cylinders long enough to find a safe place to land. We also intend to change spark plugs frequently when running 100LL to establish just how often spark plug changes is really necessary. We are also free to add a slightly hotter plug if necessary.
You list many differences of the Viking engine compared to a “boxer type” engine as negative and evil, but avoid any mention of the negative design characteristics of boxer engines. While the Viking 130 has water jackets and a few hoses for a radiator and maybe a cabin heater, it does not have a ram air box, baffling, cooling fins, abundance of external oil lines, oil coolers, cabin heat with potential carbon monoxide issues, full time attention needed to track CHT, control fuel mixture, and more. What Viking does offer is an additional 30hp and a lot more torque at the same weight as a Continental 200. You must also view Rotax as having many unnecessary evils.
Bottom line, Viking 130 engines weigh about the same as a Continental 200, has 30hp more, considerably more torque, and runs much smoother than any Continental or Lycoming 4-cylinder. Time will tell as to the Viking 130 engines long term reliability, but if properly installed, maintained, and operated, we hope get many hours of enjoyment.
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Maybe you can clarify something for me. Does your Viking have 1 or 2 sparkplugs per cylinder?
I agree, as builders and pilots I hope we can all see many enjoyable hours of flying!
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1 spark plug per cylinder.
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Permalink Reply by christopher fryatt on
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my O-200D has never yet had fouled plug problem,
no issues on airport available 100LL
Ill go up against any other 4 cyl in a smoothness competition, with composite catto and factory balanced engine.
Only fault so far, no engine driven fuel pump makes me "mr. sparky dependent for electric fuel pump"
I had a car conversion previously (one less complex ((corvair)) ) , the Viking and ul both share a highly electronic dependent powerplant. I like having engine that just needs air and gas to rotate a prop ( ok ...I know installed magnetos are old fashioned tractor tech)
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I think the O-200 and Corvair are fine engines, and wish you many years of safe trouble free flying. We also have 100LL available all around Alaska, as well as mogas along the road systems. At any given time our gas will be a mix of avgas and mogas, depending on where we happen to be.
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