Auto engines for homebuilt aircraft

[DavidHarsay]

Originally Posted by seattle smitty

What I MEANT, and expressed without the necessary disclaimers and caveats...

I figured as much, just having some fun with you since whenever I even think of making any statements stereotyping, someone jumps right in to straighten me out.... and I usually deserve it.

For aero-engines, we really need to start at the aircraft level... weight and CG, packaging, complexity (acceccories, fixed pitch or variable pitch or constant speed, pressurized cabin...), design intentions for use (cruise, aerobatics, exhibition, economy) , propeller limitations, cost considerations... and also certification requirements. Is this a P51 replica, Sopwith Camel replica, small economical composite aircraft, ultralight, sophisticated high altitude time machine... etc.

The engines may be direct drive (prop attached to the end of the crank with the possible addition of an extension) or reduction drive (belt system, planetary gearbox, adapted marine or aircraft specific)... autogas, avgas, jet-fuel powered diesel... may be normally aspirated or turbocharged... flat 4 or 6 boxer type engines, carb or mechanical or electronic fuel injection (altitude and safety concerns are big here) air cooled or liquid cooled (as a side note, I heard about the Porsche Mooney engine project that liquid cooled engines on an aircraft make about as much sense as air cooled engines on a submarine... just a joke, nobody get bent out of shape now).

Reliability and redundant systems are a consideration... and generally performance is focused on a few points... max takeoff power is primary, max continuous power (climb), and cruise power (efficiency) are also important... but all this depends on the application.

A Model T Ford engine found in some aircraft is on one end of he spectrum. I was considering building an e-racer at one point, aluminum block V8 power with a boat reduction drive unit... settled with a Long EZ with Mazda Rotary power and Ross Reduction drive unit. Many examples of both flying out there currently.

Subaru-VW-Rotax engines are popular as they are easily adapted to horizontally opposed aircraft engine designs.

DV's example of the 300 degree cam is typical of the stock engine designs which have been frozen in time... the theory was that the design is for performance at one specific RPM level, (2600-2800 typically) and then the rest is whatever it ends up. There were some specialty shops which improved on the standard aircraft design, but they are generally very expensive projects due to certification and liability considerations. Most auto power is in the experimental category.

It is important to get aircraft industry knowledge in any auto power design, it gets pretty easy to kill people with what works well on the ground, and not so well in the aircraft (turbulence effects, carb ice, electrical connections, cooling, exhaust cracking, mixture control, vibration) and we can't just pull over.

Light weight, packaging, and reliable design and systems are primary considerations in my opinion. How fast you can turn the prop before the tips get supersonic is another factor.

Just rambling... what sort of an aircraft are you thinking about?

[mlilja]

Funny your mention about the cams, David. I worked a lot on an engine, Lycoming TIO-541 (6 cylinder with turbocharger) which had all sorts of cam and lifter problems. Turns out the lifters were made of an inferior metal or processing of the metal. Anyway, I saw many cams rejected for no perceivable reason. Turns out when they were measured, they were out of spec. Funny, but most of us working on those engines suspected they were bad from the factory.

As it happens, the cam is made by a well known cam manufacturer, which I don't remember at this point, to Lycoming specification, but apparently not a very good standard. You can get the specs from Lycoming, but not the cam manufacturer. Aircraft engine cams have a really poor profile, but Superior Aircraft Engines developed and has FAA approval of a replacement cam that is much better designed. They advertise it as making for a smoother running engine, but I believe it also creates a little more power and gives you a better fuel burn. The other thing they claim is that it puts less stress on your valve train.

Mike

[LJW]

Have any of you flow bench gurus tested a Lycoming 360 head?

[seattle smitty]

Mr. non-offended A&P Garage-Sweeper Harsay . . . glad you have a sense of humor!! I take your point about the inadvisability of some of us ambitious amateurs flying over innocent neighborhoods with engines built to satisfy Detroit bean-counters. As crude as the approved engines are, at least they are relatively SIMPLE, and they are not fastened with Chinese bolts and studs, and they were designed specifically for aircraft use, and they get looked at by professionals like you on a regular basis. And I strongly concur that car guys shouldn't imagine that they are going to show the airplane guys the error of their ways, end of story.

However, I'm not sold on the idea that air-cooled engines are always the best answer for aircraft, and evidently Lyc and Continental don't think so either, since they draft new designs for liquid-cooled engines from time to time (which are dropped when THEIR bean-counters run the numbers).

My opinion is that there is a big enough knowledge base among auto engine builders and racers to identify likely candidates (NOT Ford V-6's) for aero conversion, and enough good parts (ARP fasteners, Carillo rods, etc.) to build acceptably reliable machinery. Real airplane engines cost far too much for recreational flying, as do brand new factory airplanes. Homebuilding takes flying back to the fun aspect of its early, experimental years, but with all the modern technical advantages, and it makes hobby-flying cheap enough that you can justify the expense, if you cross your fingers behind your back . . . .

Besides, all those flat-fours SOUND so danged ugly and monotonous!!

I was looking into buying the middle of a Bakeng Deuce project, but don't know if it will pan out. Bushplanes have always been a favorite, and if I don't do the Deuce, a Christavia Mk4 with a stroker Rover looks good. I'm watching the aero-diesel thread, but suspect that initial purchase price would overwhelm any later savings in fuel costs.

[mlilja]

I do not have any first hand data, but my grapevine information says the angle valve version is actually not too bad. The knock-offs, Superior and ECI, have better flows than the Lycoming original.

[crazyman]

For you home brewer's knowledge base, geo metros and geo trackers are suzuki and have all aluminum construction. The three cylinder makes 55hp stock, the 1.3 8 valve is like 70ish hp. If you're lucky, you'll find the swift gti motor, also a 1.3, but with forged internals, two cams, and 100hp. I can't comment on the hp of the 1.6 liter out of the tracker though. The gti head does in fact bolt on to a 1.6 liter block though.

[briankk]

There's a niche magazine devoted to auto engines in aircraft, called Contact!.

Contact! Magazine Website

Gotta have mag for those who actually plan to use auto engines in their planes.

I'm working on a Stol King to be powered by a Corvair engine, which I came to after a lot of research of diesels and Subaru engines of various kinds...

[comp]

Originally Posted by briankk

There's a niche magazine devoted to auto engines in aircraft, called Contact!.

Contact! Magazine Website

Gotta have mag for those who actually plan to use auto engines in their planes.

I'm working on a Stol King to be powered by a Corvair engine, which I came to after a lot of research of diesels and Subaru engines of various kinds...

go any updates on yours for us ???

[seattle smitty]

DV, I tried Google-ing Magnum Engines, Ontario, CA without a hit. Got any more info?

[nomad]

I'm not an airplane driver but, as I only live 10 miles from Sun'n'Fun I visit every year. This year next to the Lincoln Welding tent there was an outfit that had an LS1 powr module for an RV-10. It had a three blade prop on it and made lots of noise and wind.