Backcountry Pilot

[Zzz]

Compiling some thoughts from the other thread about the Viking/Honda 110hp auto conversion...

Getting philosophical about purpose built auto vs purpose built aircraft engines, one has to ask what the real objective is. Taking money out of the equation, I think the appeal of most auto conversions is the pursuit of better technology-- EFI, electronic ignition, tighter ring gap and more consistent compressions that are enjoyed by the more even and effective liquid cooling. Technology for the sake of technology isn't inherently better though.

If the pursuit is simplicity and consistent optimization, then true FADEC and the automation of combustion optimization are a huge improvement over the current state of the purpose-built aircraft engine. But really, which is the simpler system? A mechanical carburetor with a few moving parts and a manual mixture control, relying on the pilot's own judgment and interpretation of realtime data from his engine monitor(or the old lean-until-roughness-then-enrichen-a-little trick) --or-- a computerized combustion monitoring system that can make changes at a high frequency interval, always giving you optimum power or efficiency, or both?

It seems that the reliability of the old Conti and Lyc boxers stems mostly from mechanical simplicity, looser tolerances, lots of oil, and a maintenance mentality (conservative) that keeps a keen eye on known trouble areas. We've been using these same engines in one form or another for 70 years, and they are proven. I sometimes sense though that some of the resistance to adopting newer engine technologies is not solely the classic "FAA certifications requirements stifling development," but rather our own sense of conservative tradition, enjoying the easily understandable and comprehendible classic opposed, air-cooled, carbureted, magneto-ignition'd, direct-drive engine.

Electronic ignition provides always perfect timing, and dynamic retard/advance throughout the RPM range. Ignition curves can be remapped depending on the application. Perhaps there is an optimum for swinging a prop at constant RPM, verses the short bursts of power needed in an automotive application? Of course, modern automotive electronic ignitions make you totally dependent on the battery/alternator for ignition. A conventional magneto ignition engine will continue running without input current.

I saw a video on Youtube once of these guys trying to destroy a Toyota R22 4-cylinder engine by draining all the oil and pinning the throttle. It took something like 15 minutes for it to even begin seizing. Yet the story of the oil starved Continental/Lyc always has complete lock-up only a few minutes after loss of oil pressure. What's the disparity there? How can one engine be so resilient and another so delicate? I admit to knowing little about lubrication system design.

Weight, shape, volume, mounting options...many variables. What are the benefits of opposed vs inline cylinder arrangement for a 4-cylinder engine? Seems more obvious for 6 and 8 cylinder engines, but same principle I guess.

Fantasy engines aside (we have threads for vaporware diesels), where would you start if you wanted to aviation-harden a proven engine core but retain the things about modern small bore car engines that eclipse the reliability of the most common aviation classic engines?

[EZFlap offline]

The latest version of the LS-1 Corvette V-8 engine is a good candidate. At anything around the stock 400HP they appear to be "bullet proof". There are definitely a few things to do in order to make the engine control computer and systems correct for an airplane. But the basic engine is very solid, puts out good power to weight, and gets very good fuel economy for the power. One or two people are making gearboxes for it. There were one or two Republic Seabees that were modified with this engine, with very good results.

One of these engines rated at the full 400 HP for a 5 minute takeoff, then de-rated down to 250-300 HP continuous, might be a winner. This opinion is based on common knowledge and the opinions of people who know more about engines than I. Another possibility is direct drive to a large propeller, which will de-rate it by itself, but the engine has tremendous torque. Reportedly this can make a 250+HP direct drive engine with very low wear and very high reliability.

Ben Haas has actual hands-on experience that very few have. So his experiences with the V-8 are very valuable, more so than any of us who do not have the hands-on experience on this engine.

[shorton offline]

From my research I am given to understand that one of the biggest problems with any sort of auto engine conversion is the size of the main bearings, not only are they NOT made for end loading but they are tiny compared to aircraft engines. The mains on a Lyc and the massiveness of the crank are not to handle the power of the engine pulse but to handle the gyroscopic forces of the prop disc.

You can take a gear box that will handle a 1000 hp and utterly destroy it when you put a prop on it. The prop disc really wants to stay in the same attitude all the time and when you force it to change that attitude by pitching up or kicking the tail out it will impart tremendous forces to the crankshaft and main bearings.

How ever, (there's always a However) I have an airboat with a 350 chev engine and a direct drive prop that I turn right under 3000 rpm and I force the prop disc to change it's alignment and attitude VIOLENTLY and CONSTANTLY and so far have not had it fly apart on me. This engine has nothing for thrust bearings except the little side plates on three of the mains, so there ya go.

As to control systems, while the newer electronic marvels are vastly better and more dependable I can take a rubber band, a hair pin and some spray paint and make the damn thing run but when your CPU is dead it's just dead.

I did see a couple of bushmaster or bushwhacker planes that were using the Ford v6 SHO engine, about 235 shaft hp, fuel injection, alum block and heads. Smooth as silk with lots of power, don't know how they worked out tho.

[dirtstrip offline]

Compiling some thoughts from the other thread about the Viking/Honda 110hp auto conversion...
Of course, modern automotive electronic ignitions make you totally dependent on the battery/alternator for ignition. A conventional magneto ignition engine will continue running without input current.

The logical thing then would be to keep one magneto as backup for the primary electronic ignition. A second battery for backup then would still be used for powering the electric fuel pump for the fuel injection. With an automotive engine as a platform of course this casting does not exist for the magneto drive. Which in my opinion the perfect aircraft engine platform begins with a conventionally configured aircraft engine designed from start for aircraft use.

I saw a video on Youtube once of these guys trying to destroy a Toyota R22 4-cylinder engine by draining all the oil and pinning the throttle. It took something like 15 minutes for it to even begin seizing. Yet the story of the oil starved Continental/Lyc always has complete lock-up only a few minutes after loss of oil pressure. What's the disparity there? How can one engine be so resilient and another so delicate? I admit to knowing little about lubrication system design.

This has to do with oil providing not just the lubrication but also a large portion of the cooling for the traditional aircraft engine. Ultimately the oil is air cooled also, but in losing its oil the liquid cooled engines will still have its fluids to provide cooling to the cylinder heads delaying piston expansion seizure against the cylinder walls and valve train failure. I am not sure if any aircooled engines have ceramic nicasil jugs to better withstand heat but I don't know why they cannot. It would also require something besides aluminum for the heads to take that heat, again ceramic coated or build a much better oil cooling system. Once the cooling is addressed then the tolerances of the engine can come down. As it is these air cooled aluminum engines need room to expand. The critical halfway point on aluminum is that 400 degree mark where aluminum softens to about half its strength.

Weight, shape, volume, mounting options...many variables. What are the benefits of opposed vs inline cylinder arrangement for a 4-cylinder engine? Seems more obvious for 6 and 8 cylinder engines, but same principle I guess.

The benefit of opposed engine design lies in the raising of the crankshaft high in the cowling while maintaining a low profile for visibility over it. Also this provides the greatest height for prop clearance. This is why you see direct drive aircraft V block engines such as the Deltahawk being inverted. Of course reduction drives can restore the height of the propeller in the cowling but the reduction drives add an additional failure rate and their performance history over the years in homebuilt engines has not been great. The direct drive engine will continue to have that advantage. I believe in keeping it simple.

Fantasy engines aside (we have threads for vaporware diesels), where would you start if you wanted to aviation-harden a proven engine core but retain the things about modern small bore car engines that eclipse the reliability of the most common aviation classic engines?

Theoretically, there is nothing that can't be fixed with any of these problems as long as it is someone else's checkbook. In my opinion the best bullet proof engine will be purpose designed for aircraft and be as simple as possible.

[TonyG offline]

Zane,

Figured I'd post into this thread as opposed to keeping the old one going. The auto parts that have failed on the RV-4 (or that we've replaced as we went along) were mid-to-low range "generic" aftermarket parts. An oil cooler, relays, a handful of lesser things. There was something else major (like the oil cooler) that we caught prior to failure, but I'm damned if I can remember what it was. I'd have to check the logs. Maybe the boost pump. (this was 10 years ago -- after the first year or two of owning it, we'd gotten most of the weak parts replaced.)

And, to be fair, we've also had to replace the engine-driven pump and a few aviation sourced parts.

These old aircraft engines are inefficient throwbacks compared to what you can do now, but they're pretty reliable. You can run them 1500-2000 hours at rated power. My subjective thinking goes along with EZ-flap's derating idea. As an example: my daily commuter is a Yamaha YZF-1000R. Great bike, 1000cc engine that makes 145 hp. I've got 60k miles on it, so maybe 1000 or 1500 hours. (And a lot of folks would say that's a lot of miles) So far, so good, but I'm at what, 15-20% power on average? I don't know how well the engine would hold up at 75-85% power, day in, day out. (If I ran anywhere near that, I'd be a hole in a guardrail somewhere.) The engine may do fine, may have trouble after a few hundred hours. I don't know enough about that industry to know if they factor in the typical duty cycle into the design. You could ask the race guys how many hours they get, but that's not really a fair comparison. (58Skylane would know)

Ben Haas has done it with a V-8 though (he's who I meant in the prior post.) Be good to know how he operates and what his experience has been.

As with everyone, my opinions are tainted by what I think I know -- reality be damned. My take on a perfect engine would be motorcycle-like: short stroke, high revving (put those two together and the piston speeds stay low), with geared reduction. Water cooled, so you'd never have to worry about shock cooling. Just so long as it kept running. Whatever you decided for an experimental -- here's an idea for hardening it: Plan on building 2 (or more) engines. Build the first, and run it, under load (on a dyno or other means), for a bunch of hours. Fix what breaks when you build the second one. Probably won't address the thrust load (or gyro loads if it'll be an acro machine), but it'd give you more confidence.

--Tony

[Jaerl offline]

If your running a gearbox, the thrust bearings or lack of thrust bearings wouldn't be a factor because the gear box would take the force from the propeller. If you figure just about any auto engine will go 200K these days. At 30 MPH Average that is 6,666 hours. At 50 MPH it is 4,000 hrs.

I paid pretty good attention to the SeaBee conversions and the one site that sold conversions made a good point. You can buy a Corvette engine for around $8,000. When it has 2,000 hrs you pull it and sell it on ebay. Then just go and buy another new one. Considering a Franklin engine is around 20K+ to rebuild it makes a lot of sense. Plus you have a plane that will out perform a stock one by a long ways.

Metals and manufacturing has come a long way in regards to auto engines. I'd feel comfortable behind one.

[EZFlap offline]

My friend Klaus Savier (mfg. of the LSE electronic ignitions that have won him many of the CAFE races in the world's fastest Vari-Eze)said it best... in the last 50 or 60 years, the average car has double the horsepower, and double the gas mileage, from about the same displacement. That's freakin' HUGE.

The basic design of rods, pistons, heads and crankshafts has not changed. The two big things that have changed are the computerized ignition control modules, and the fuel delivery (injection) system.

Unfortunately these changes did not happen in airplane engines, for what seemed like perfectly valid reasons (certification costs and risk reduction mentality).

Having a magneto that makes its own electric current is great. Of course a battery or computer black box can fail. Also there are moving parts and failure points in a magneto that can take a sh*t. So you have a newfangled electronic system on the lower mags (can blast through oily plugs better than the mags) and have the old-school magneto on the upper plugs for backup You'll get 80-90 percent of the benefits of the E system but you still have that magneto backup.

Fuel injection systems are not highly prone to failure. So you don't have a stroke and quit the program, you just have one or even two backup fuel pumps to make absolutely sure you have fuel delivery.

And you test this stuff extensively on an airplane lie Ben Haas' 801, which can land safely in a short area in case you do find a failure-prone component or whatever.

[175 magnum offline]

In 2003 we completed our scratch built bearhawk. We chose to use a 4.6litre Landrover motor, build our own redrive and use a composit prop. We picked up a junk yard motor with 2500miles and left it stock except for the headers. We installed dual SDS ecu's and designed for 4800rpm on take off(max power) and 3200 cruise(max torgue) The firewall forward package was within 5lbs of an o-540 and identical cg's. The plane will run with any 540 and burns the same fuel as the 540 at any given speed. But has the ability to slow down to to 100mph @ 2800 rpm and burn 5gph and have all the egt's stay even and oil temps good. Big air cooled motors do not like this set up. The only change we made was the addition of an adjustable cowl flap. We wanted to climb all day at full throttle and 65mph @ 100*f and not overheat. The cowl flaps allowed this and still got good speed when in cruise. We burn 87 or 92 car gas or 100ll, but car gas most of the time. That 100LL is the mechanics best friend as it ruins more motors that you shake a stick at. The plane now has 1000hrs and the motor is just like new. It gets an oil change once a year(uses 1ltre) and we look at the plugs an check the compression and they are excellent.
Recomendations:
-use factory rated horsepower and rpms and don't get caught in the hopped up engine deal
- use 3 cubic inches of radiator for each horsepower
- wherever posible just buy a factory crate engine or low milage one from the auto wreckers, there are so many available these days that are very light and inexpensive.
- plan on spending an extra 2to 3 years on you project for the firewall forward portion and do not think you are going to save piles of money- you aint.

[Mongo offline]

My airplane has the P.O.S. Bendix Dual mag which they have stopped supporting (thanks a lot way to stand by your product), so I plan at my next annual if I cannot find a shop to service my mag I will be switching to a dual light speed ignition system.
I must say in my short flying career (250 hours)I have had 3 mag issues and I have never had an electronic ignition of any sort fail on a car, motorcycle or race car. On the race car every time one runs like crap the first thing we do is change the ECU, and that never fixes it, it is always a mechanical failure of some sorts. That being said we do run redundant sensors and occasionally the ECU will switch to the backup due to a sensor failure, but it keeps on going.
In racing the electronics always get blamed for an engine failure by the manufacture do to public relations,for example we fell out of a 12 hour race once because of an "electrical issue" (Porsche)the alternator had been ripped off the side of the engine when the connection rod came out the side of the block......

[bumper offline]

My airplane has the P.O.S. Bendix Dual mag which they have stopped supporting (thanks a lot way to stand by your product), so I plan at my next annual if I cannot find a shop to service my mag I will be switching to a dual light speed ignition system.

My 87 Mooney 201 came with the "POS" Bendix D-3000 dual magneto. Can't imagine why or how it ever go certified. Left me stranded and/or limping home a couple of times. When it came time for overhaul I just bit the bullet and bought a brand new individual mag engine. Pricey, but I did a quick price check on my butt and figured I was worth it.

If still stuck with the dual mag, you might check with Sacramento Sky Ranch for parts/service. http://www.sacskyranch.com/bendix.htm

[TomD offline]

Back to the approved engines.

I just saw on AOPA that the 230hp Diesel SMA 305 has received European approval and FAA is supposed to come shortly.

http://www.smaengines.com/?lang=en

An issue is it evidently weighs 70lbs more than comparable Cont or Lyc 230-235hp engines. On the plus side it will run Jet-A or biodiesel

TD

[EZFlap offline]

if I cannot find a shop to service my mag I will be switching to a dual light speed ignition system.

I believe you will have a very good experience with LSE. Although I cannot in any way speak for Klaus, I suspect that if you will go to Santa Paula, CA airport with the intent to seriously consider his system, you might get a ride in his Vari-Eze so you can see and feel it for yourself.

I actually squeezed my fat ass into the back of that airplane many years ago, and Klaus took me on one of his test flights while developing the unit. The capabilities of his electronic unit are amazing. You can remove the engine starter and substitute your index finger, it starts that easy. He is getting 230 miles an hour high cruise speed (not flat out either) on an O-200 engine. Then he pulls it back and goes into his "hyper lean" cruise mode and can economy cruise at something like 180 or 200 MPH at 3.5 gallons an hour. A lot of that speed and efficiency is in the airframe of course, but the engine economy and performance is truly awesome.

Not having anything to do with his ignition system, but my life has been trusted to flying behind Klaus' products a few times and they never let me down.

[Savannah-Tom offline]

Back to the approved engines.

I just saw on AOPA that the 230hp Diesel SMA 305 has received European approval and FAA is supposed to come shortly.

TD

Here's a 500 hp diesel for you guys with big planes:

http://www.dieselair.com/2010/11/introd ... -aero.html

tom