Finicky Plane Engines.....Why not a proven Auto?

[sheldon957]

I state right off the bat that I know almost nothing about the conversion procedures that would have to take place, but most approved engines are finicky at best. Ever try Hot starts with Conti & Lyc? Weight would be one consideration, but VW, corvair & Porsche are all finicky too.

I know for the majority you would have to have liquid cooling, but say a smooth running Lexus V8 that never breaks down, and can go forever it seems. I don't know if the computer can calibrate appropriately for higher altitudes?

I have seen where they used a corvette engine in a copy of a P51.

How hard, & why not in an experimental?

 

[tonycondon]

often, auto engines have proven to be finicky plane engines. i have no experience flying behind an engine that wasnt designed for an airplane. ive heard good and bad.

 

[kevin47881]

One reason may be that aircraft engines run close to 100% at all times versus an auto engine which much runs less than 50% almost all the time. I haven't seen auto engine life span if operated as an aircraft engine but it MAY be a reason. Just thinking out loud here.

 

[tonycondon]

kevin, i think thats a big part of it, plus the RPMs where cars get the most power are way too high for props to turn, so then you have to deal with gearing to get the prop RPMs down to reasonable values. its just easier to have an engine that was actually designed for the operation it is being used for.

 

[SCCutler]

Ha!

Toyota wishes they built an engine as stout and reliable as a Continental or Lycoming.

Fact is, car engines (like, for example, a Lexus V8, or even better, a Cadillac Northstar V8 or a Corvette engine) are really great stuff, run reliably for 100,000 and more, but they spend nearly that entire time at something on the order of 15% of their rated power output. Given the duty cycle that the typical aircraft engine endures, most car engines would not last 200 hours.

Add to all of that, the importance of reliability of systems (eg, no modern car engine can run without a functioning electrical system, while aircraft have redundant magnetos which care not one whit whether there are any electrons in the electrical system at all), and the serviceability, and you quickly come to understand why there are no Big Surprises in aircraft power.

 

[Capt. Geoffrey Thorpe]

I state right off the bat that I know almost nothing about the conversion procedures that would have to take place, but most approved engines are finicky at best. Ever try Hot starts with Conti & Lyc? Weight would be one consideration, but VW, corvair & Porsche are all finicky too.

That's a function of the air fuel metering system, not the engine design. Mechanical injection systems leave a lot to be desired when it comes to hot / cold starts.

I know for the majority you would have to have liquid cooling, but say a smooth running Lexus V8 that never breaks down, and can go forever it seems. I don't know if the computer can calibrate appropriately for higher altitudes?

Liquid cooling has it's advantages and disadvantages.

A Lexus V8 isn't likely to keep running any longer than a Lycoming Flat 6 - likely less since it isn't designed to run at the same loads.

I have seen where they used a corvette engine in a copy of a P51.
How hard, & why not in an experimental?

Lots of auto engines have been converted into lots of different aircraft over the years. From Ford model T engines in Pietenpol's, VW's in lots of things. Aluminum Buick blocks have been popular. I assume your "corvette engine" is a small block Chevy...

Results are mixed and tend to have reliability problems.

 

[stagecoachco]

Here is a web sight where you can buy a Subaru conversion.

http://www.eggenfellneraircraft.com/Introductionl.htm

 

[Dan Thomas]

Here's a site for the engine conversion enthusiast. Do a search or see the Firewall Forward forum:
http://www.homebuiltairplanes.com/forums/

As others have already stated, aircraft engines work at very high power levels for long periods. Many auto conversions have failed due to those loads, and the limited cooling capacity of the engine's jackets mean that some just won't make it. The VW's heads have insufficient finning to dump the excess heat when at high power and the valves burn out after just a few hours. Speed reductions are absolutely necessary to get the max performance out of the heavier auto engine, and anything other than planetary gearing imposes radial loads on the crankshaft that have to be dealt with somehow. A direct-drive conversion not only results in a poor power-to-weight ratio, but can result in crankshaft failure since that shaft was never designed to deal with the gyroscopic and thrust loads imposed on it by the propeller. Some guys have used extension shafts and heavy bearings to take those loads, but the extension shaft then gives resonance and fatigue problems.

I installed a Subaru 2.2 130-hp in a Glastar, along with an RAF redrive. There were numerous issues to deal with, and cooling had to be well thought out. The engine redlined at 5600 and had to cruise at around 4700 RPM just to get anything near a halfway respectable cruise speed. At that RPM the tiny valves (four per cylinder) burned easily if it was leaned at all and the fuel consumption was a bit ugly. The noise was awesome. The airplane was designed for a 125-hp Lyc, and with that engine it would cruise at about 130 mph at 2500 rpm, redlining at 2700. With the Subaru it would only cruise at about 110 mph at 4700 rpm. Running the Subaru as close to redline as we could with a Lyc would destroy it rather quickly; the piston speeds are high and the excess heat becomes too much. Just a casual comparison between the exhaust valve from a Lycoming and that from the Subaru is enlightening. Huge difference. The valve from the Soob looks like something from a lawnmower; its stem is about 1/4" in diameter and the head is quite thin. The Lyc has 7/16" stem, sodium-filled for heat transfer, and the head is at least four times as thick as the Soob's.

I make my living as an aircraft mechanic. Lycomings are stout and will last almost forever if they're properly cared for and operated. The O-320, for instance, is certified to produce maximum continuous power output for its entire 2000-hour life, and some fleet operators such as pipeline patrollers can often get 3500 hours out of it without any hiccups. There are absolutely NO auto engines that would ever do that.

Most aircraft engine problems arise from things like magnetos (so there's two of them, and they need opening up and checking at least every 500 hours), corrosion from inactivity or very short flights (cars suffer that, too), gunked-up fuel systems and the like (more inactivity) and rotting hoses (age). None of this is unusual for any machine that's neglected.

Dan

 

[Dave Krall CFII]

I state right off the bat that I know almost nothing about the conversion procedures that would have to take place, but most approved engines are finicky at best. Ever try Hot starts with Conti & Lyc? Weight would be one consideration, but VW, corvair & Porsche are all finicky too.

I know for the majority you would have to have liquid cooling, but say a smooth running Lexus V8 that never breaks down, and can go forever it seems. I don't know if the computer can calibrate appropriately for higher altitudes?

I have seen where they used a corvette engine in a copy of a P51.

How hard, & why not in an experimental?

Some car engines run at well over 4000 rpm for non stop freeway commuting for years with no problems and are therefore suitable for aircraft. The slanted inline 4 provides great engine cooling while the lateral space created by the slanting also provides a much cooler place for a turbo charger, since the ram air from the cowl nose blows unobstructed right through there.

On my application I went to a remote cooling bank (under cockpit floor, outside) for space limitations under the cowl, as well as for CG reasons due to max weight FWF because of high HP for the airframe. One positive side effect that system has shown is massive cooling of not only engine water but engine oil, and turboed intercooler air as well, due to circuits of thin wall stainless steel and/or milspec plumbing that provide as much cooling capcity as the actual cooling radiator elements themselves.

It runs very cool at sustained full power static runups on hot days. It should be even cooler when flying.

Checkout:

http://www.raven-rotor.com/

 

[SkyHog]

The only 2 engine conversions I'd ever fly behind (at the moment, shy of researching some other options) happen to be engines that fill me with more faith than our trusted Lycoming and Continental engines.

First, Eggenfellner bases their engine on the Subaru 2.5L engines, and have a better safety record than Lycoming (this is disputed by some because they are looking for one specific statistic, which doesn't exist...easy to deny a claim by asking for an unattainable statistic). They use less fuel than Brand C or Brand L, and they are usually faster in the same planes.

Second is the Aerovee conversion, with is a Volkswagen engine converted for use in smaller planes. The only real comparison to these is the Rotax engines, and the price alone makes Aerovee worth looking at. They provide very similar performance and very similar fuel burns, but cost about 1/5th the price of the Rotax engine. Parts are cheaper for replacement, and there are enough flying to know they are reliable. Unfortunately, I have no safety statistics on the engines because I never bothered to look.

There are definitely options besides Lycoming and Continental and Rotax, but you have to remember, half of the people that bash auto engines are bashing them because they have a vested interest in an aircraft engine (they either own an airplane that uses a Brand L/C/R engine and don't want to see them obsoleted, or they work for a company that produces them, or they have stock in said company), or they are repeating facts that they've heard from others without research (like slipping with flaps in a Cessna).

FWIW - the 75%/25% argument is usually invalid, since if you compare RPMs to RPMs, the engine is working just as hard on the road as in the air, sometimes less: 4500RPM in the air is a lot less than 6000RPM, sustained, on the highway.

And I'm done. Don't be a sheep, do your own research, and make your decision. Stay objective, and you'll find that they may be a viable option for you, or, if you want to spend a lot more money for the same or less product, you may find an aircraft engine that fits the bill.

 

[timwinters]

FWIW - the 75%/25% argument is usually invalid, since if you compare RPMs to RPMs, the engine is working just as hard on the road as in the air, sometimes less: 4500RPM in the air is a lot less than 6000RPM, sustained, on the highway.

Agreed, also if you look at it in terms of HP per CI you'll see that the engine going down the highway is working just as hard or harder. Our aircraft engines are significantly derated because of the low RPM limitations. Run an engine at 2400 RPM and it will last forever. Look what happened to the reliablility of the venerable O-300 when they geared it up in the skylarks.

If a car mfgr designed an engine with 470 CI that only produced 230 HP they'd be laughed out of the industry.

 

[Trapper John]

Ha!

Toyota wishes they built an engine as stout and reliable as a Continental or Lycoming.

Fact is, car engines (like, for example, a Lexus V8, or even better, a Cadillac Northstar V8 or a Corvette engine) are really great stuff, run reliably for 100,000 and more, but they spend nearly that entire time at something on the order of 15% of their rated power output. Given the duty cycle that the typical aircraft engine endures, most car engines would not last 200 hours.

Add to all of that, the importance of reliability of systems (eg, no modern car engine can run without a functioning electrical system, while aircraft have redundant magnetos which care not one whit whether there are any electrons in the electrical system at all), and the serviceability, and you quickly come to understand why there are no Big Surprises in aircraft power.

Remember the Orenda V-8? They spent a boatload of money (something like $100 million) trying to get 600 HP from a Chevy engine before they gave up.


Trapper John

 

[jmaynard]

FWIW - the 75%/25% argument is usually invalid, since if you compare RPMs to RPMs, the engine is working just as hard on the road as in the air, sometimes less: 4500RPM in the air is a lot less than 6000RPM, sustained, on the highway.

The 3.5L V6 in my Lexus RX350 runs between 1800 and 2200 RPM at highway cruise (depending on speed). Yes, it's a 270-HP engine, but it rarely puts out that much power in actual driving: that horsepower rating is at 6200 RPM, and max torque is at 4700. The same goes for the other Lexuses, and every other automobile engine out there. Drivers don't want an automobile engine to put out 75% power for extended periods of time, because they're noisy and inefficient there. They want to have lots of power available to get on the freeway and pass that slow semi on the 2-lane road.

Aircraft are designed differently for different missions. So are engines. The aircraft mission is fundamentally different from the automobile mission.

There are lots of things that can be done differently in an aircraft engine from what's been done in the past. One look at the Lycoming TEO-540 will show you that the aircraft engine manufacturers aren't ignoring the desire for modernization. Even so, it's still quite different from the engine in a Lexus.

 

[jmaynard]

Look what happened to the reliablility of the venerable O-300 when they geared it up in the skylarks.

The GO-300 is quite reliable when it's operated according to the book. It got its terrible reputation because the tach shows engine RPM, and pilots just couldn't wrap their heads around running at 3200 RPM for long periods.

 

[ScottM]

First, Eggenfellner bases their engine on the Subaru 2.5L engines, and have a better safety record than Lycoming (this is disputed by some because they are looking for one specific statistic, which doesn't exist

If that statistic that it has a better safety record does not exist then how can you make a such a claim?

Seems to me that making a claim such as that without the ability to point to some stat or study makes it real easy to dispute that it is an actual fact.

 

[Skip Miller]

One reason may be that aircraft engines run close to 100% at all times versus an auto engine which much runs less than 50% almost all the time. I haven't seen auto engine life span if operated as an aircraft engine but it MAY be a reason. Just thinking out loud here.

It is a lot of the reason. The problem is getting rid of the excess heat at high power loadings. As has been pointed out elsewhere, the typical auto engine is loafing along at highway speeds, whereas the GA engine is 65% - 75% power at cruise.

This doesn't mean that auto engines cannot be designed to do this. International Harvester, a truck/industrial equipment manufacturer, used to (don't know if they still do) test 100% of their engines for 200 hours at full rated power, then pull them apart for signs of burnt valves, etc. Of course these truck engines were significantly larger and heavier per hp to handle the loads and heat. And they developed the high power at high rpms. In aviation uses, that would require gearing to slow the prop, or much shorter multiblade props.

All in all, a purpose-built engine like the Lyconentals is an excellent compromise, better than anyone has been able to certify from an auto conversion. Don't let this stop you, though. Grab an auto engine, modify it as required, and get it certified!

-Skip

 

[wanttaja]

If that statistic that it has a better safety record does not exist then how can you make a such a claim?

Seems to me that making a claim such as that without the ability to point to some stat or study makes it real easy to dispute that it is an actual fact.

I took a look at the relative safety records for auto engines vs. certified engines in my study of homebuilt accident reports from the 1998-2006 period. There are no reliable statistics on how many of each type of engine is installed in homebuilts, so it's impossible to arrive directly at a failure rate for each type of engine.

However, most NTSB accident reports list the type of engine. It's easy to determine how often a loss of power was the cause of the accident, and compare the rates for traditionally-powered aircraft with those mounting auto-engine conversions. Obviously, a higher percentage means a higher relative number of engine failures.

My study showed that about 12.2% of accidents that occured to aircraft with traditional engines (Lycomings, Continentals, Franklins, etc.) were attributed to problems with the engines or with the engines' related systems.

For auto-engine conversions, the rate was 30.5%. If only fixed-wing aircraft are considered, the difference is even more striking: The traditional-engine rate was about the same, but the auto conversion rate jumped to about 37.5%.

In other words, if a fixed-wing homebuilt has an accident, the probability is three times higher that the engine was the cause of the accident if an auto-engine conversion was installed!

The classic anti-auto-engine argument is that the engines themselves are not up to the strain imposed by aviation use. This doesn't seem to be the case; auto engines seem to suffer from internal problems at a lower rate than traditional aircraft powerplants.

Auto engines are worse in three major areas: Ignition systems, cooling systems, and reduction drives.

The need for a reduction drive on most auto engine conversions provides a failure source that the traditional engines don’t generally face. Neither do traditional engines have external cooling systems—though some of those Internal Failures may well be due to poorly-baffled engines. The water pumps, belts, hoses, and radiators on many auto conversions provide another failure source the traditional certified engines avoid.

​

The biggest difference is in ignition system failures: Auto engines suffer them four times as often as conventional aircraft. Sure, aircraft magnetos are primitive, and individually are probably less reliable than a modern electronic ignition. But the vast majority of homebuilts with Lycomings and Continentals carry two magnetos that are completely independent of any other aircraft system.

​

Several of the ignition failures in auto conversions were due to electrical power problems with electronic ignitions. Electrical systems do fail, so a completely independent backup power source is vital.

This data was based on homebuilt aircraft accident reports in the 1998-2006 time period, about 1900 total reports. A summary was published in the October 2008 issue of KITPLANES magazine.

Ron Wanttaja

​

 

[timwinters]

As has been pointed out elsewhere, the typical auto engine is loafing along at highway speeds, whereas the GA engine is 65% - 75% power at cruise.

But, I think the point that's trying to be made by some here, Skip, is that the aviation engine is also "loafing along" at 70% power just as the auto engine is "loafing along" at highway speeds. This because the aviation engines are so significantly "derated" in HP per CI terms.

The auto engine at highway speeds is turning the same RPM and cranking out as much (or more) HP per CI than the airplane engine is at cruise and 70% its "rated" HP.

 

[SkyHog]

If that statistic that it has a better safety record does not exist then how can you make a such a claim?

Seems to me that making a claim such as that without the ability to point to some stat or study makes it real easy to dispute that it is an actual fact.

The statistic exists (I'll search for the one I've used before), but its not accepted because it doesn't include certain, unnecessary information that can't be obtained.

Something like "Well, how many total aircraft flying the engine have had non-consequential engine issues?" I don't remember the argument, but I'll find the stat for ya.

Edit: Looks like Ron Wattaja did a lot of the work himself on this. One thing I'd like to see is the rate of incident between RVs with auto conversions and RVs with Lycoming engines. I suspect the statistics will follow every other suit here, and show that Eggenfellner conversions are still more reliable.

 

[SkyHog]

International Harvester, a truck/industrial equipment manufacturer, used to (don't know if they still do) test 100% of their engines for 200 hours at full rated power, then pull them apart for signs of burnt valves, etc.

All auto engine manufacturers do the same, test at 100% power for more than 200 hours (some up to 1200 hours) and check for defect. Find a Lycoming design that was factory tested for anywhere near that at 100% power.

 

[Capt. Geoffrey Thorpe]

But, I think the point that's trying to be made by some here, Skip, is that the aviation engine is also "loafing along" at 70% power just as the auto engine is "loafing along" at highway speeds. This because the aviation engines are so significantly "derated" in HP per CI terms.

The auto engine at highway speeds is turning the same RPM and cranking out as much (or more) HP per CI than the airplane engine is at cruise and 70% its "rated" HP.

Not even close. I just walked downstairs and asked for the dyno setting at 50 mph - 17.5 hp for a F150 diesel (this is at the rear wheels) - figure less than 20 hp at teh crank which is about .07 hp/in cubed. For an O-360 (at the same hp/ cu in), this would be a grand total of 24 hp - I think you typical O-360 will put out more than 24/0.7 = 32 max horsepower.

 

[Dan Thomas]

But, I think the point that's trying to be made by some here, Skip, is that the aviation engine is also "loafing along" at 70% power just as the auto engine is "loafing along" at highway speeds. This because the aviation engines are so significantly "derated" in HP per CI terms.

The auto engine at highway speeds is turning the same RPM and cranking out as much (or more) HP per CI than the airplane engine is at cruise and 70% its "rated" HP.

Don't make the mistake of equating RPM with horsepower. There's another factor involved called Torque. One HP is equal to 33,000 foot-pounds per minute, and we arrive at an engine's HP by multiplying its RPM times 6.28 times the torque it is producing, divided by the 33,000. An auto engine running at 70% of its redline RPM is not producing 70% power by any means, and not only because the throttle isn't wide open at that RPM; power output is not linear with RPM either.

I can run my auto engine up to its redline RPM of 5700 when it's sitting in the driveway in neutral, but it's only producing about maybe 5% power doing that. On the highway the throttle is open maybe a third of the way. Power output wouldn't be any more than 25 or 30% at the most.

Dan

 

[Skip Miller]

All auto engine manufacturers do the same, test at 100% power for more than 200 hours (some up to 1200 hours) and check for defect.

For 100% of the engines?

-Skip

 

[Dan Thomas]

All auto engine manufacturers do the same, test at 100% power for more than 200 hours (some up to 1200 hours) and check for defect. Find a Lycoming design that was factory tested for anywhere near that at 100% power.

All Lycomings, to get certified, must be run at rated RPM and torque output for their entire life. If it has a 2000 hour TBO, then that's as long as it runs at full power. The larger engines might have a 5-minute limit at full rated power, so they'll cycle in and out of that.

Dan

 

[Skip Miller]

But, I think the point that's trying to be made by some here, Skip, is that the aviation engine is also "loafing along" at 70% power just as the auto engine is "loafing along" at highway speeds. This because the aviation engines are so significantly "derated" in HP per CI terms.

Let's start thinking in terms of heat produced. How many gallons of fuel per hour does your auto engine consume at cruise? Say 60 mph and 30 mpg. One hour equals 2 gallons. How many for the av-engine? 6-8 per hour for a small one, 10-12 per hour for a big'un. Yes, some of the heat is converted to energy sent to the prop or drive shaft, but since the engines have about the same BSFC, the av-engine is producing three to six times as much heat because it is consuming lots more gasoline per unit time, in cruise flight, than does the auto engine. And heat is the enemy of all engines.

-Skip

 

[wanttaja]

Edit: Looks like Ron Wattaja did a lot of the work himself on this. One thing I'd like to see is the rate of incident between RVs with auto conversions and RVs with Lycoming engines. I suspect the statistics will follow every other suit here, and show that Eggenfellner conversions are still more reliable.

There is a lot of difficulty in producing what I call a "fleet rate" (number of annual accidents for planes of a given type or engine/Total number registered), basically due to the need to merge databases produced by differrent organizations.

Let me use NSI engines as an example. How many NSI engines are installed in the homebuilt fleet? It's easy to search the FAA database to come up with a number. But thousands of homebuilts are listed as having only "EXP/AMAT" engines...and thousands MORE don't list an engine type at all. How many of those are NSI engines?

Note how this hurts the apparent safety record of NSI engines...the value is the denominator of the "fleet rate" statistic. I'll run some numbers when I get home tonight, but obviously if there are only 100 aircraft with NSI engines listed in the FAA registry but there are really 200 aircraft out there, that will really skew the results in a negative way.

So let's take a look at the numerator of the Fleet Rate statistic, the number of accidents that involve NSI engines. The NTSB is pretty good about listing the engine type in accident reports. But what does it mean when the report says "Subaru"? Does that mean it WASN'T an NSI powerplant? Not necessarily.

And if it DOES say NSI, does that mean that the powerplant was purchased as a complete package? Or was it just the reduction drive? Or did the builder just pick up an NSI sticker at a fly-in and slap it on the mount?

Finally, we get to the raw numbers involved. IIRC, my nine-year database contained about 300 accidents involving auto-engined aircraft. These include Fords, Chevys, Mazdas, VWs, Subarus, Hondas, GEOs, etc. etc. By the time you get to a particular model of engine, there aren't all that many examples. By the time you get to a particular model of engine mounted on a particular AIRCRAFT model, you have fewer still.

One has to be very careful with the conclusions drawn based on limited data.... 300 accidents are a pretty good sample, but 3 are not.

Ron Wanttaja

 

[Dan Thomas]

Let's start thinking in terms of heat produced. How many gallons of fuel per hour does your auto engine consume at cruise? Say 60 mph and 30 mpg. One hour equals 2 gallons. How many for the av-engine? 6-8 per hour for a small one, 10-12 per hour for a big'un. Yes, some of the heat is converted to energy sent to the prop or drive shaft, but since the engines have about the same BSFC, the av-engine is producing three to six times as much heat because it is consuming lots more gasoline per unit time, in cruise flight, than does the auto engine. And heat is the enemy of all engines.

-Skip

And BSFC is a good way to determine hp being produced, too. Assuming that the aircraft engine is properly leaned and the car's computers are doing the same for it, we get some accurate numbers. if they're both running at around .45 BSFC, the 180-hp IO-360 in our new 172S, at about 6500' and 2500 RPM, is burning at least 8.3 GPH. That's 49.8 pph (pounds per hour), divided by .45 to give us 110.67 hp, or 61.5% power. (This conforms with the POH figures, too.) My little Chevy Cavalier gets 35 miles per US gallon on the highway with its "115 hp" engine at 60 mph, or 1.71 gph, 10.29 pph. Divided by .45 we get 22.9 hp. A long ways from 115 hp, right? That's 20% power. The engine is loafing big time compared to the Lycoming. And the car is heavier than the airplane yet has a smaller engine; airplanes, like planing boats, need a lot of power to overcome massive drag.

Now, those figures are a litle suspect because the car will get a bit better than .45 BSFC, but not likely below .4. It's a liquid-cooled engine and can run a bit leaner than the airplane's engine, especially at those low power levels. If it was to run at 70% in an airplane we couldn't get .4 BSFC without burning something up. And that's exactly what I found with the Subaru in the Glastar.

Dan

 

[steingar]

Car engines are enormously advanced, but are built for a fairly specific purpose. Because a lot of them get built, they have the whole economy of scale thing going for them. Cheaper and better is very attractive, and lots of home builders have gone that way to try and take advantage. However, car engines are specialized to power cars. To get them to power airplanes additional systems (cooling, gear reduction, etc...) are needed. Since not many people do this (few fly airplanes, fewer build, and even fewer try and engineer things like this) each installation is an experimental "one-off" where many of the components must be fabricated. You therefore substitute the money you would spend on an aircraft engine with lots of work making the auto engine do something it was not designed to do. Finish off with the fact that your powerplant is now heavier (water is heavy) and has extra systems that can break. Plenty of people have crossed all these hurtles successfully, and there are aircraft flying with car engines. But I'll bet that they went through a lot of work and teething pains before they got there.

 

[timwinters]

Not even close. I just walked downstairs and asked for the dyno setting at 50 mph - 17.5 hp for a F150 diesel (this is at the rear wheels) - figure less than 20 hp at teh crank which is about .07 hp/in cubed. For an O-360 (at the same hp/ cu in), this would be a grand total of 24 hp - I think you typical O-360 will put out more than 24/0.7 = 32 max horsepower.

You drive 50 mph on the highway? So, you were one of those people in my way when I was heading back to Oshkosh yesterday!

My assumptions may be off a bit but give me the numbers at 80...not 50!

I run down the highway at 80 all day long in my 4runner (for almost 200000 miles now). That's at least 2,500 hours at 2200RPM (IIRC), just under 5 GPH and it's still going strong.

 

[SkyHog]

You drive 50 mph on the highway? So, you were one of those people in my way when I was heading back to Oshkosh yesterday!

My assumptions may be off a bit but give me the numbers at 80...not 50!

I run down the highway at 80 all day long in my 4runner (for almost 200000 miles now). That's at least 2,500 hours at 2200RPM (IIRC), just under 5 GPH and it's still going strong.

My Dodge Dakota, running a 2.5L drives about 90MPH on the highway at abour 3600-4000RPM steady for hours on end too.

 

[Dan Thomas]

I run down the highway at 80 all day long in my 4runner (for almost 200000 miles now). That's at least 2,500 hours at 2200RPM (IIRC), just under 5 GPH and it's still going strong.

It should still be running strong after 2500 hours. It's only producing 72 HP, assuming 4.8 GPH and .4 BSFC. Is that a 3.4L rated at 183 HP? If so, you're operating it at 39% power. Most of that's fighting drag at 80 mph.

Dan

 

[timwinters]

And BSFC is a good way to determine hp being produced, too. Assuming that the aircraft engine is properly leaned and the car's computers are doing the same for it, we get some accurate numbers. if they're both running at around .45 BSFC, the 180-hp IO-360 in our new 172S, at about 6500' and 2500 RPM, is burning at least 8.3 GPH. That's 49.8 pph (pounds per hour), divided by .45 to give us 110.67 hp, or 61.5% power. (This conforms with the POH figures, too.) My little Chevy Cavalier gets 35 miles per US gallon on the highway with its "115 hp" engine at 60 mph, or 1.71 gph, 10.29 pph. Divided by .45 we get 22.9 hp. A long ways from 115 hp, right? That's 20% power.

The IO-360 is producing 0.3074 HP/CI.

Your Cavalier is a 2.2 liter engine which converts to 134 CI. So, it's producing .17 HP/CI. Crank it up to 80 MPH (assuming your mileage drops to 30 at that speed) and you'll be producing about .265 HP/CI.

So, we're talking roughly the same output per CI.

My base argument is that you can't talk "percent HP" because the airplane engines don't make much HP at 100% considering their huge displacement. At 100% they're already only making 50%...so to speak.

 

[timwinters]

It should still be running strong after 2500 hours. It's only producing 72 HP, assuming 4.8 GPH and .4 BSFC. Is that a 3.4L rated at 183 HP? If so, you're operating it at 39% power. Most of that's fighting drag at 80 mph.

Dan

207 CI or .35 HP/CI...more than the IO-360!!

Edit: By the way, I'm in no way trying to make a case for putting automobile engines in airplanes. I'm simply making the case that automotive engines are far superior in HP output, efficiency and durability than aircraft engines.

 

[Hiperbiper]

207 CI or .35 HP/CI...more than the IO-360!!

Edit: By the way, I'm in no way trying to make a case for putting automobile engines in airplanes. I'm simply making the case that automotive engines are far superior in HP output, efficiency and durability than aircraft engines.

As long as they're hooked to a multi-speed redrive system (transmission).

V-type and inline water cooled engines have powered aircraft before without any reduction drives. Hispano-Suiza Mercedes and the Liberty engines of WWI come to mind. Properly cammed, carbed and combusted an engine CAN be made to run efficently with it's HP and Torque curves at a low RPM.
It can be done but there's not much market for it...

Making a car engine do something for which it wasn't designed to do serves only to prove that given enough money and time you can make said engine almost as good as a 1940's tech Lycosauras. Not better, just different.
Tucker did just the reverse on the Tucker automobile; he used old flat, aircooled helicopter engines for his car. They were cheap and more reliable than the car motors of the day. He got laughed at too... .

Chris

 

[steingar]

No argument there. More produced, more research, no regulations from Uncle Sam saying what you can and cannot do. Auto engines are lots better. At powering cages. No so good for airplanes, which is why there aren't so many out there. Also, the most successful auto engines used for aircraft are normally air cooled.

 

[Anthony]

We are often asked about using non-aircraft engine conversions. We’d like to pass along a quote from a colleague in the homebuilt airplane business:
"the best conversion I know is to take $8000 and convert it into a good used Lycoming." This may sound a bit narrow-minded, but it reflects the basic truth: no non-aircraft engine has yet proven to be as reliable, available, and inexpensive (everything considered) as a traditional aircraft engine.

It seems that magazines are always printing stories about automobile engines bought for junkyard prices, mated to inexpensive reduction drives and flown off into the sunset. It simply doesn’t work like that in the real world. The reliability we have come to expect from aircraft engines is the result of years of development and refinement of engines designed specifically for the task. Automobile engines function well in their intended application: delivering low cruising power in vehicles with well designed transmissions and power trains. Using them successfully in an airplane requires continuous high power outputs and reduction systems coupled to the propeller. This is completely foreign to their design intent. (You can imagine the car engine designer banging his head slowly against his desk..."no, no, no. If I’d known you wanted to do that with it, I would have designed something different....)

That's from Van's website and I think it accurately sums up what others have said.

http://www.vansaircraft.com/public/powerpla.htm

 

[DGlaeser]

I have an Eggenfeller Subaru H6 in my RV-7A. It's been flying since March 29th - almost 90 hours to date. There are a couple of hundred Egg Subies out there - quite a few 4 cyl and now some of us with 6 cyl.

I've also been involved in the auto industry working as a contractor (EDS) for about 15 years. I spent a couple of years doing a project for GM Powertrain Dyno Labs. I can tell you that the torture they put engines through is way beyond anything the FAA puts aircraft engines through. If you do a search on the Vans AirForce forums, it's all been hashed out there. The mechanicals of an auto engine are not an issue. They can (and do in the dyno) put out 100% power as long as you want to run them.

There is a lot of engineering involved in putting any engine in an airplane (my degree is Aerospace Engineering). The Lycoming solution is well defined and straight forward. Liquid cooled engines that require speed reduction units are not new to aircraft, but they are not the norm for light aircraft. That is what Experimental aircraft are all about - doing something that is not the norm (like building it yourself)! If you don't go with the 'standard' engine solution, there is more time and effort, and trial and error involved. Lots of folks have done it. Most don't want the hassle and just go with the Lycoming. We have the freedom to choose!

 

[Dan Thomas]

The IO-360 is producing 0.3074 HP/CI.

Yeah, at 6500 feet AGL and 2500 RPM and 61% power. At sea level it would produce a lot more at 2500 RPM. At full rated power it's .5 hp per cubic inch, which is one reason it lasts as long as it does. Auto engines can produce a lot more per CI but they often suffer the effects of it, as many converters have found out. The 100-hp Continental O-200 can be forced to produce 200 HP too, at 4000 RPM with a tiny toothpick prop in the Formula Vee racers, but it sure doesn't last its 1800 hours anymore. They run a chunk of stout cable around the engine and anchor that to the firewall in case the engine throws a rod or otherwise seizes and tears itself off the mounts. That can be bad for the CG.

If it was so easy we'd have many flying examples of some particular engine, which we don't. The VW is likely the most common but if they're really examined you find that burned valves and broken crankshafts are distressingly common. Many of the "factory" VW conversions use forged cranks, stronger rods, aftermarket heads with more fins, bigger oil pumps, and so forth. The result is an engine that's as heavy and almost as expensive as an aircraft engine. If you Google images of, say, Continental A-65 or C-85 cylinder/head combos and compare them with the VW cylinder and head, you'll see a big difference in cooling capacity.

Other engines that I can recall having been tried in the years I have been in homebuilding (since 1972) include the Ford Model A, Corvairs, various Chev small-blocks from the 283 to the 350, Buick aluminum V-8 (263 CI?), British Rover V-8 (Buick knock-off), Ford 351, various Ford and Chev V-6's, Corvette LS1, Honda Civic, Subaru, Mazda rotaries, Suzuki three- and four-bangers, and likely many more I don't know about. Not one of them has been successful and cheap enough to have been widely accepted, and many homebuilders have become so fed up with the endless tinkering involved in making them run right that they pull them off and install an aircraft engine instead. The most successful conversion I can think of was the Geschwender Ford 351 conversion that saw extensive service in "Experimental" Pawnee crop sprayers. Even the old wizard Steve Wittman, I'm told, pulled the Buick V-8 off his last Tailwind after he had too much trouble with it.

If I had the time I'd love to do another conversion, but I'm aware of the huge amount of time it can take and the expense that can be completely unrecoverable. The Glastar that got the Soob ended up selling for at least $75K less than it would have been worth with the Lyc; similar Lyc-powered examples were selling for that much more at the time. And the entire installation ended up costing as much or more than the Lyc, after all the dorking around.

I'd like to see a Jaguar V-12 in a small P-51 replica. It should at least sound decent. Failing that, an old Navion converted to a taildragger and having a 350 with a redrive on its nose should get the blood going about as well.

Dan

 

[jmaynard]

Not one of them has been successful and cheap enough to have been widely accepted

The Corvair, derated to 100 HP, seems to be gaining popularity in the Zenith homebuilt community. There are more than a few 601s flying with them. Even so, there are many fewer of those than there are Rotax or Jabiru or O-200s.

 

[Hiperbiper]

Truth be told, the 1930's technology-based flat-4 configuration aero engines are damn near perfect for what they do. With the minimum number of parts and simplicity of design they have been doing Yeoman service for 70-80 YEARS! That ain't too shabby!

There have been advances in materials and manufacturing techniques, new tech applied like Mechanicial FI and roller base lifters, different cam profiles and anti-corrosion coatings...

On the Homebuilt front you have even more stuff spawned; injection type (pressure) carbs for inverted flight, more efficent exhaust systems including "Tuned-Pipe" systems, and a bunch of ignition systems that actually allow variable ignition timing...and the list goes on.

IMPO; the Lycoming flats are the most bullet-proof motor on the planet next to the VW 30-40HP engines of yesteryear!
Much has been done to maximize the ignition systems in the last dacade or so, my current fave is the P-Mag self powered mag with variable timing curves.
Now all we need is an direct port fuel injection system that mimics EXACTLY what the pilot does with the BRK (big red knob), adjust mixture based on EGT/CHT information only. No other info required. 1/10 second updates to the controller. Control servo inline with the manual mixture knob to give the pilot a manual override. Like an autopilot for the mixture..

A simple, reliable engine with a good power to weight ratio with state-of-the-art controlling. WOW! What a concept!

Hey! I can dream can't I?

Chris

BTW; (and lest you think it's impossible)
In 1939 the BMW 801 series radial was put into a German Fighter called the Focke-Wulf 190A6. It featured a control on the left wall of the cockpit that pilots were awed and distrustful of 'till they got used to it...
It was a single-lever control for the engine RPM, mixture and prop pitch. It worked well enough to last till the Kurt Tank tried to replace the FW190 with the TA152 in 1944. FADAC without the "electronics" part.
Think of a 1939 Cirrus...
Burt Rutan said it best: "Sometimes Engineers seem to complicate things just so they have problems to solve..."