Viking Aircraft Engines, thoughts? (Honda piston AE?)

[DGlaeser]

The question is not how many built using a car engine but how many are flying regulary with one. Likely none to few.

Mine has been flying regularly for over 9 years (6 cylinder Subaru). I'm not the only one at my airport flying a car engine regularly. All it takes is proper engineering...

 

[GRG55]

That is somewhat disconcerting... I guess we'll see how the fleet ages and if engine departure ever actually does occur. I would think having a dangling engine there (possibly still running) would be worse than just losing the whole thing, but then of course your weight and balance is severely upset so lesser of two evils I suppose


Thanks, between those two options number 2 does sound worse, but I'll have to do some more research about why you couldn't (or wouldn't want to) have say 1,4,2,3 order so I can better understand. I remember reading a while ago that firing order was also the reason that 6 cylinder engines were more "smooth" than 8 cylinder engines, despite there being less cylinders

The tethers on the Diamond Diesel are at each of the four engine mounting points, across the rubber isolation blocks. In the picture below you will see they are quite short tethers. There is little chance of all four mounts failing at the same time, so there would not appear much chance of a "dangling" engine. Presumably good pre-flights and routine maintenance inspections will catch a problem. The tethers would seem to be an additional precaution, but are imo indicative of one the differences to be considered between Diesel cycle and Otto cycle aircraft engine installations. Bottom line, the problems can all be engineered out, but a recip Diesel replacement for conventional aircraft engines is not as "perfect", simple or as straight forward as some people might imagine.


What I believe you are referring to in the 6-cyl vs 8-cyl comment is automotive engines? Your observation is applicable to in-line 6-cyl engines only. The common 60 degree and 90 degree included angle V-6-cyl engines are notorious for vibration and manufacturers have applied all manner of dynamic aids, including balance shafts, to make them acceptably smooth

An in-line 6-cyl engine is the only configuration where the second order (and fourth order) inertial forces sum to zero. This "magic" of physics, no secondary harmonic, is part of what gave rise to the enduring reputation for legendary smoothness in the Jaguar and BMW in-line 6-cylinder engines (among others). Personally I wouldn't own a BMW automobile with anything other than an in-line 6. When I lived in the Middle East I owned a Toyota Land Cruiser with a 4.5 litre in-line 6 and that thing was as smooth as a turbine.

 

[Ted]

That is somewhat disconcerting... I guess we'll see how the fleet ages and if engine departure ever actually does occur. I would think having a dangling engine there (possibly still running) would be worse than just losing the whole thing, but then of course your weight and balance is severely upset so lesser of two evils I suppose

I'm not worried about a diesel falling off the airplane. It hasn't happened yet, the mounts all seem designed fine, plus the straps.

You really don't want an engine falling off an airplane. Even in a twin it doesn't usually work well, but is usually still (poorly) flyable. In a single the CG shift will probably send the plane into an unrecoverable nose up followed by a stall/spin.

Thanks, between those two options number 2 does sound worse, but I'll have to do some more research about why you couldn't (or wouldn't want to) have say 1,4,2,3 order so I can better understand. I remember reading a while ago that firing order was also the reason that 6 cylinder engines were more "smooth" than 8 cylinder engines, despite there being less cylinders

1-4-2-3 still has both cylinders on the same side at once. 2 and 4 are on the same side. To get it going on opposite banks would be 1-2-3-4.

Like I said, it takes a while of looking at the different possible combinations to see why the 1-3-2-4 layout is a good compromise.

 

[asicer]

1) Have two cylinders on one side fire followed by two cylinders on the other side
2) Have all pistons move in the same direction at the same time

I'm a little confused. Which one of these fits this animation?

 

[GRG55]

I'm a little confused. Which one of these fits this animation?

Your 4-cyl animation fits Ted's #1 in your post.
You will see the two cylinders on one side fire and then the two on the other bank follow. E.g. 1-3-2-4

 

[wanttaja]

The question is not how many built using a car engine but how many are flying regulary with one. Likely none to few.

If that were the case, we wouldn't see many auto-engined accidents in the NTSB accident database. But about 14% of the homebuilts listed have auto engines. A number of them had over 1,000 hours at the time of the accident.

While auto-engined homebuilts have a higher percentage of engine-caused accidents, plain 'ol pilot error still predominates. Again, this indicates the planes are flying.

You have to remember that "auto engine" is a rather broad definition. VWs have a long tradition of use, and derivatives such as the Aerovee are still being produced. A lot of gyros (as well as fixed-wing homebuilts) use Subarus. It's not all shade-tree mechanics and a V-8 pulled from Grandma's Buick.

Ron Wanttaja

 

[asicer]

Your 4-cyl animation fits Ted's #1 in your post.
You will see the two cylinders on one side fire and then the two on the other bank follow. E.g. 1-3-2-4

OK, I get it now. 1-3-4-2 firing order applies whether it is front-pair-upstroke/rear-pair-downstroke or it is one-diagonal-pair-upstroke/opposite-diagonal-pair-downstroke.

Thinking more about it, @Ted DuPuis 's #2 (all 4 cylinders on the upstroke at the same time) would result in half as many firing pulses per turn, right?

Also, it's theoretically possible to have the right pair on the upstroke when the left pair is on the downstroke which would result in a 1-2-3-4 or 1-4-3-2 firing order, no? I'd hate to have to balance such an engine, though.

 

[Ted]

OK, I get it now. 1-3-4-2 firing order applies whether it is front-pair-upstroke/rear-pair-downstroke or it is one-diagonal-pair-upstroke/opposite-diagonal-pair-downstroke.

Thinking more about it, @Ted DuPuis 's #2 (all 4 cylinders on the upstroke at the same time) would result in half as many firing pulses per turn, right?

Also, it's theoretically possible to have the right pair on the upstroke when the left pair is on the downstroke which would result in a 1-2-3-4 or 1-4-3-2 firing order, no? I'd hate to have to balance such an engine, though.

My #2 was right pair on upstroke with left pair on the downstroke. I was not talking about all 4 cylinders on the upstroke at the same time. Doing that would result in having two cylinders fire at once (they could theoretically be on opposite banks) and that would be really shaky. Or you could work it as a 2-stroke... even worse.

 

[barneymac2]

Converting airplane engines for automobile use is far cooler, man.

Volkswagen corvair

 

[Spring Ford]

Converting airplane engines for automobile use is far cooler, man.

Does it count if you only use two of the cylinders?

 

[flightdelayed]

Posting this to help someone who may be inexperienced with engines; is wide-eyed about the information on their website; is not deterred by the owner's sketchy past; is on the fence; is looking for an opinion from someone experienced with conversions and modern fuel injected engines; and who desires an objective analysis using readily available evidence. In this endeavor, I apologize for the length of this post. The main and perhaps only advantage I see is that if someone is dead set on this conversion, all the hard work has been done. Most of the conversion parts such as fuel systems/ tuning, engine mount, and gear box, etc are already fabricated and tested. This is huge and I have to give a lot of recognition for the amount of work and testing and attention to detail that went into this conversion. This is no small feat and is nothing short of an impressive demonstration by dedicated craftsmen. Much of the experimenting appears to have been performed by customers willing to participate in experimental aviation for the joy of it, and joining these ranks must irrevocably be considered as a part of the decision-making process. The 130 hp engine you receive for $14k will be complete, ready to run, and has the advertised power. Unfortunately, this is where any advantages seem to end. This is impressive for that price until you delve a bit deeper. In order to create a marketable and profitable product, price, power, and weight parameters must be optimized. While the weight is unimpressive and can be considered a disadvantage, the inherent marine-service design plus custom engine tuning make this aircraft conversion appear worthy. Without the tuning, power to weight crosses the red line, as the power provided for the engine weight is not acceptable. This is where things get a bit sketchy. The engine provided is a used automotive salvage engine factory-rated at about 95 hp. Even the most powerful marine version of this engine is rated at 100 hp. As mentioned, tuning is utilized to squeeze the extra juice to make power to weight more palatable. While the 30%-plus tuned power gain over the factory rating seems impressive, it is also concerning as there is no testing or evidence outside of customer experimentation demonstrating these engines can be reliably run with this much power. Certainly, Honda engineers did not design this engine to make this much power and are not crawling over themselves to claim it can safely do so. Therefore, the margin for risk of mechanical failure is thinner and the customer must be comfortable within the realm of experimentation. This power/displacement information is available from Honda Motors and Honda Marine. This begs the question of sound investment via reconciliation of: 1) reliability from a used auto engine, 2) the price paid for it, and 3) the warranty provided. Reliability is self-evident, as most auto junkyards give at most 30 days. Even though this is experimental aviation, the gorilla in the room is a highly-tuned junkyard auto engine enduring power demands well beyond its engineered design capability. In addition, it behooves one-self to consider that many would not feel comfortable driving in their car through the bad part of town with such a used engine. From what I can gather there is effectively no warranty unless the owner of the company will freely admit fault, and I can find no evidence of that any more than I can find high-hour examples of their engines. What I have found without difficulty are examples of aircraft on their second or third engine. Clearly, it would not be outside of normal expectation to see the actual cost of the engine easily become the cost of two or three engines, etc to meet the nominal expected TBO of an actual aviation engine. Considering this, certainly any minute price advantage vaporizes. Beyond having no concrete price savings, if one is stubborn enough to require further demonstration of reliability differences then look no further than the "48 state challenge", which is nothing more than about 100 hours of tachometer time in a matter of about 10 days. This is normal-duty for a flight-school Cessna, which may see 100-hour inspections 2-3 times per month. Imagine how ridiculous it would appear if any other aircraft engine company used this challenge to demonstrate reliability, which should in competitive terms be in the thousands of hours of tachometer time for this investment, not in the tens or even hundreds of hours. So, is there anything here left to salvage? No pun intended. Well, that brings us full circle, back to the Honda Marine virtues of the engine. Along with the conversion parts being sold, a new marine engine may be worth consideration, especially with the price of an entire brand-new Honda BF100 outboard hovering around $10k. Not many would argue that a brand-new marine engine actually marketed for continuous high-output duty is not better than an automotive salvage engine. I dont know if anyone has done this, if its worth doing, if it will be more reliable, or if it will even work, but is there anything here left to salvage besides experimentation? Conclusively, experimentation must be the goal of the endeavor itself, as better options certainly exist. However, that is exactly where we started.