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

Jim in NC said:
Yep, you get the prize for the reduced hp at auto cruise correct. There is a big difference between maximum RPM with a partialy open throttle, and a wide open throttle at maximum RPM's.

Problem is, that has little to do with why auto engines are not widely used, or considered unsuitable by many people.

As Ron Want-a-jaw said, <g> few internal parts, or parts of the basic auto engine are causing failures in airplanes. It is all the stuff that has to be added, such as home-baked ignitions, electrical systems, fuel supply/inductions, cooling systems, and redrives, which of course can cause the crank or bearings to fail if not correctly implimented. It also would be interesting to see what the reliability factor was for the auto engines once they got sorted out, past say 200 hours. Ron, you want to get on that new study, right away, please? <g>

I'll bet that they are more reliable than certified engines, after that. Most never get that far, because most do not build on the experiences of others, and the owners get tired of fixing instead of flying, or scare themselves.

Take for example, a very popular V-6 engine in homebuilts, the Chevy 4.3 L, or you could as easily say the Ford V-6. (3.8L, I think)

That same engine is taken from the casting line, machined, has stock auto cranks and pistons, valves and all the rest put into it, and sold to a company such as Merc-Cruiser as a boat engine. Different cooling pumps, ignitions and inductions are normally used, to do away with the computer, among other things. Still, it is the same basic package that starts its life as a so called "industrial engine" in a power boat.

If a boat engine has the right prop on it, it will be at wide open throttle, and at near redline, or at least at the maximum torque to RPM value. These engines DO spend their life at these very high HP levels, and will happily do so for hundreds if not thousands of hours. I don't know of a single airplane engine that is run as hard as 90% of these boat engines, and if it is one of my boat engines, darn right, I expect it to run at 100% of its rated HP, for an hour or more at a time, and still expect it to start reliably, and run, for many years to come. Would I run an airplane engine that hard? Not quite, but would not hesitate to ask full power for takeoffs, or very near to it. I would throttle down to 75% of the maximum HP while in cruise, but mainly for noise reduction, and fuel consumption; not for fear of blowing up. I have proven to myself that the engine is good for very extended runs at 100% power, but on the other hand, there is no sense pushing luck! ;-)

If a boat engine has the right prop on it, it will be at wide open throttle, and at near redline, or at least at the maximum torque to RPM point.

Can you do this to every auto engine out there? No. VW beetle, for one. Many of the inline 4's might have some problems. But, if it is based on one of the popular GM or Ford V-8's, (as are the GM and Ford V-6's) then you have nothing to fear from the basic engine, itself.

You had better do your homework when it comes to all of the other stuff that makes engines run, though. It's those items that pose the "gotcha."

Why did Orenda not make it? Too large a goal, I think. 600 HP out of a V-8 puts it up there near racing engine outputs. Racing engines do not live hundreds or thousands of hours. Also, the other missconception is that Orenda was a stock GM engine. It was not. It was based on one, but was its own casting, and had some other modifications done to it. Still, some people were very happy with them. It is a lot of tradition to buck, to be put on one company, to get everyone to accept an auto style engine as being equal to the accepted old style piston airplane engine.

So, is an auto engine going to come along to be the next accepted airplane engine? No, not any time soon. Is it possible to fly behind an auto engine safely? It is possible, but you have to make up your mind; are you going to tinker, engineer, study other's attempts, or you going to put something in that everyone accepts, and fly it?

Your choice. Be prepared to do your homework, and break some new ground.

Jim in NC
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A few things here I'd like to address:

Few internal parts failures, no, not true for either of those engines. Cranks fail and rods fail on a completely frequent basis, if these engines are run 75%+ power, they make 400-700 hrs typically, and there are may ancillary parts that fail as well, and these parts are NOT weight optimized, they have plenty of spare meat to them and weigh in like it, and since they have a higher BSFC, there is greater drag required for the radiators to handle the higher waste heat, and more fuel translated to waste heat rather than thrust. Neither of those engines is a good design for an aircraft engine regardless if people are using them. Remember, 80% of everybody is stupid. If I wanted an automotive V-6, I would use the old 60* Ford 2800 from the old Capris or old 60*2800 Chevys from the old little Blazers (it's the one with the mount bosses for longitudinal mounting). Both of these engines can be made strong enough on a reasonable budget to put out a solid full time 260 with a 32 TO/power.
You can increase the power to weight ratio of similar power ConLycosauruses for performance applications, but you won't see the efficiency, and you'll be in it for the same money if you want it to be reliable. The good thing is that it's very cheap and easy to throw in a new set of bearings to prevent failure (less than $120 with gaskets and oil) and re ringing and honing is a simple matter. As long as you don't hurt the expensive parts like the Aluminum block and Heads, the billet crank and titanium rods, get multiple overhauls out of the pistons, keep the same valve train.... you can overhaul several times for $1200 or so. However, you have to build a good re drive gear unit, and that takes some design and fabrication. I can build it from raw metal and off the shelf gears and bearings, but it's very time consuming and won't be cheap, but mine will last, I'd probably use a 2 speed Lenco transmission stage gear set for T/O-Low altitude operation and and shift for high altitude and cruise ops. It'll cost a bit more than building a 1 speed reduction and a bit more hassle, but it'll be worth it. I haven't seen any experimental re-drives that I'd want to use myself.

I have big bock Chevy (Orenda base) racing engines out there in offshore racing boats that put out 1200hp+ and last several seasons, over 1200hrs and going strong. It just depends on how you build them, and you're looking at $35,000+ in parts, machine work and labor and you have to know how to design the bottom end parts and work the heads. The Orenda's real problem is poor marketing but it does better on fuel than the turboprops it competes with but not what a diesel could get. I'd like to get one of the V-12 Audi TDIs to work with, it's perfect and needs no major redrive. Will be cheap in no possible consideration of the term. I'd look at over $100,000 for each producing thrust on an airplane, but it will produce a lot of thrust. I could probably replace a lot of ag plane turbines if I got it certified.

Bottom line, you can run an automotive gasoline engine in an aircraft, but to do it properly you will have to spend as much or more as on an aircraft engine and give up some BSFC. Need to go diesel.

Also "Redline" is arbitrary to the cam, compression and fuel delivery system, and "High Horsepowers" is really relative again to the above. I don't consider "high horsepower at less than 2 hp per Cubic Inch.
 
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Although the initial cost may be there to put an Auto engine in an airplane, as Henning mentioned you get your money back year after year.

Who runs their engines at rated HP all the time anyway? In the Bellanca cruising through 5000 I am already loosing MP by the time I am at 9000 I'm down to 50% or so. I cruise just a little higher RPM than I do in a car on the freeway.

For the smaller engines the GEO runs down the freeway going 70 at the same RPM it would run in cruise on the plane. These little GEO engines are making very nice plane engines in the HP to HP range. Using a planetary re drive from a Ford you have very little problems.


By the way the new Corvette is at 635 hp I wonder how fast my Bellanca would go with that hung on the front.:smilewinkgrin:
Dan
 
stingray said:
Although the initial cost may be there to put an Auto engine in an airplane, as Henning mentioned you get your money back year after year.

The folks I know who have gone this route have saved huge bucks on fuel. Because they are always redesigning/reengineering/rebuilding their powertrain and rarely fly.

Who runs their engines at rated HP all the time anyway? In the Bellanca cruising through 5000 I am already loosing MP by the time I am at 9000 I'm down to 50% or so. I cruise just a little higher RPM than I do in a car on the freeway.

At 9,000', you are probably down to 70% or thereabouts. Most cars on the freeway are producing <30% power.

For the smaller engines the GEO runs down the freeway going 70 at the same RPM it would run in cruise on the plane. RPM Yes. Manifold pressure and HP, No. These little GEO engines are making very nice plane engines in the HP to HP range. Using a planetary re drive from a Ford you have very little problems.

The end-all, be-all question auto conversion skeptics (like me) usually revert to is "Find me a dozen of (insert auto conversion brand here) with a thousand hours. Compare the service history to a Lycoming or Continental."

You won't find an auto conversion where there are a dozen examples with a thousand hours. One day there may be, and we'll get a reasonable comparison. Until then, you can't make a meaningful comparision.




By the way the new Corvette is at 635 hp I wonder how fast my Bellanca would go with that hung on the front.:smilewinkgrin:
Dan
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I think your Bellanca would go very fast on 635 hp. You'd probably get to the departure end of the runway faster than ever. The problem is that it wouldn't go fast for long and might not make it back to the approach end. ;-)
 
kyleb said:
I think your Bellanca would go very fast on 635 hp. You'd probably get to the departure end of the runway faster than ever. The problem is that it wouldn't go fast for long and might not make it back to the approach end. ;-)
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More horsepower doesn't translate into a lot more speed. Drag increases by the square of the increase in speed, so theoretically to go twice as fast you need four times the horsepower. The heavier engine will add to drag, so it'll take more than 4XHP to do the job.

The higher power shows up in takeoff and climb. The initial acceleration is much better and the climb angle and rate improve. You can see the inverse just be reducing your RPM (fixed-pitch) by about 50 on takeoff, and see what happens. Big difference.

Dan
 
Dan I thought it was the Square Cube rule... 2 times the speed results in 4 times the drag needing 8 time the HP.
 
vontresc said:
Dan I thought it was the Square Cube rule... 2 times the speed results in 4 times the drag needing 8 time the HP.
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Four times the drag needs four times the thrust to overcome it. Since thrust and HP are roughly related in a linear fashion, four times the HP is needed. A typical lightplane engine/prop combination will produce around three pounds of static thrust per HP.

Now, if that higher HP is coming from an engine that turns its prop faster, more of that HP is lost to drag in that faster-moving propeller and the squared-drag thing goes out the window. That's why the best thrust-to-HP ratios come in geared engines that run larger props at lower RPM. The most extreme example is the helicopter's huge slow-turning rotor, where 150 hp will generate 1200 lb of thrust, maybe more. In the airplane that 150 hp won't deliver more than 500 lb from the prop.

Dan
 
Dan Thomas said:
Four times the drag needs four times the thrust to overcome it. Since thrust and HP are roughly related in a linear fashion, four times the HP is needed. A typical lightplane engine/prop combination will produce around three pounds of static thrust per HP.

Now, if that higher HP is coming from an engine that turns its prop faster, more of that HP is lost to drag in that faster-moving propeller and the squared-drag thing goes out the window. That's why the best thrust-to-HP ratios come in geared engines that run larger props at lower RPM. The most extreme example is the helicopter's huge slow-turning rotor, where 150 hp will generate 1200 lb of thrust, maybe more. In the airplane that 150 hp won't deliver more than 500 lb from the prop.

Dan
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Actually the HP required is approximately equal to the cube of the airspeed increase. That's because power equals thrust times velocity and as you stated thrust and drag increase approximately as the square of the velocity.

drag@v2 / drag@v1 = (v2/v1)^2
thrust@v2 / thrust@v1 = (v2/v1)^2
HP@v2 / HP@v1 = thrust@v1/thrust@v2 * v2/v1 = (v2/v1)^3

This is ignoring things like compressibility, Reynolds numbers, and transonic flow so it only works over a relatively narrow range of speeds.
 
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Dan Thomas said:
More horsepower doesn't translate into a lot more speed. Drag increases by the square of the increase in speed, so theoretically to go twice as fast you need four times the horsepower. The heavier engine will add to drag, so it'll take more than 4XHP to do the job.

The higher power shows up in takeoff and climb. The initial acceleration is much better and the climb angle and rate improve. You can see the inverse just be reducing your RPM (fixed-pitch) by about 50 on takeoff, and see what happens. Big difference.

Dan
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There's this thing called a tongue in cheek post....
 
All I know is the FAA stats on accidents is very sobering. If I remember right (that's tough this late) auto conversions in experimental aircraft account for 33% of the accident cause - versis - 12% in experimental aircraft having "traditional" aircraft engines. It was staggering to me anyway.

I'll stick to Lyclones in my RV's thank you very much.
 
lancefisher said:
Actually the HP required is approximately equal to the cube of the airspeed increase. That's because power equals thrust times velocity and as you stated thrust and drag increase approximately as the square of the velocity.

drag@v2 / drag@v1 = (v2/v1)^2
thrust@v2 / thrust@v1 = (v2/v1)^2
HP@v2 / HP@v1 = thrust@v1/thrust@v2 * v2/v1 = (v2/v1)^3

This is ignoring things like compressibility, Reynolds numbers, and transonic flow so it only works over a relatively narrow range of speeds.
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Doesn't agree with what I was taught, but I never had formal physics training either. I'll go with what you say and apologize to those I disagreed with.
At any rate, it sure takes a pile more power to go faster, huh?

Dan
 
Dan Thomas said:
Doesn't agree with what I was taught, but I never had formal physics training either. I'll go with what you say and apologize to those I disagreed with.
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I suspect that you were taught (correctly) that drag and the required opposing thrust increases as the square of the airspeed but forgot (or were never told about) the relationship between thrust, speed, and power.

At any rate, it sure takes a pile more power to go faster, huh?
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That's always a safe bet.
 
Dan Thomas said:
More horsepower doesn't translate into a lot more speed. Drag increases by the square of the increase in speed, so theoretically to go twice as fast you need four times the horsepower. The heavier engine will add to drag, so it'll take more than 4XHP to do the job.

The higher power shows up in takeoff and climb. The initial acceleration is much better and the climb angle and rate improve. You can see the inverse just be reducing your RPM (fixed-pitch) by about 50 on takeoff, and see what happens. Big difference.

Dan
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That all depends on where you fly. If your 260 hp engine is only getting you 120 hp at altitude 635hp would give you a lot more speed. It may not give you much more at sea level but who flies at sea level. This also has a lot to do with how fast the plane was designed to fly.

Dan
 
Henning said:
As for hot starts, I never have a problem hot starting engines. Just understand what is going on and purge the injector lines with fresh fuel before you crank and all is well.
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Ed Guthrie instructed Brent and I on how to hot start the IO-360 in the Mooney, and it works like a charm every time. Simple, even.
 
Henning said:
There is the counterpoint though, and that is for the same money as it would take to get it to compete with the 310hp 550, I can make it have 450-600hp. I tried working with the FAA to let me hang a V-8 Chevy on my Ag Cat, but they wouldn't go for it unless I bought an Orenda.
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Why replace a P&W R-985? One of the best and most reliable engines ever produced.
 
Rotor&Wing said:
Why replace a P&W R-985? One of the best and most reliable engines ever produced.
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The 985 most definitely is and I wouldn't replace one. However I had a 1340, and it isn't. I was also trying to up my horsepower into the 900hp- 1200hp range to up my capacity to 600 gallons so I could cover a pivot in one load. I can build a a BB Chevy to put out 1200hp a lot more efficiently and reliably than an 1820 or the PZL version thereof. They would have let me mount it and go experimental for certification trials, but I wouldn't have been able to work the plane in that time.
 
N801BH said:
I fly one several times a week in my experimental. Making one work is ALOT of work but I enjoy being on the cutting edge of progress and it is very satisfying to me to see it all pan out, Thats why we call them "Experimental"....

Get an adult beverage, relax and watch these videos.


http://video.google.com/videoplay?docid=-7272451917550730841&hl=en

http://www.youtube.com/watch?v=AOF6eT6FRmY

:D





Ben.
www.haaspowerair.com
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Thanks, that first one is very informative on a number of parts he's using.

The 7 & 801s are great airframes, especially when they have the thrust available from engines like the Ford/Windsor.
 
Dave Krall CFII said:
Thanks, that first one is very informative on a number of parts he's using.

The 7 & 801s are great airframes, especially when they have the thrust available from engines like the Ford/Windsor.
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You are most welcome. The second video is my first attempt at filming anything and my neighbor who ran the camera had no experience either. The main gist of it was for the audio,, if you are a true motor head the small block V-8 roaring down the runway is music,,, at least to me. :smilewinkgrin:

Merry Christmas guys...
 
N801BH said:
You are most welcome. The second video is my first attempt at filming anything and my neighbor who ran the camera had no experience either. The main gist of it was for the audio,, if you are a true motor head the small block V-8 roaring down the runway is music,,, at least to me. :smilewinkgrin:

Merry Christmas guys...
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Oh yeah, YOUR plane (note to self: pay more attention to N#s!).

Great rig you have there, I almost went for the 801 myself and may still build one in the future if the wings can be folded which I don't think would be too hard. I ended up with the STOL Highlander on tundra wheel amphibs which is a little less work but not as big either. Stop in if your up north in Seattle.

You've got plenty of power, so I guess you don't feel the desire for a blower with heavy loads at high DA?
 
Dave Krall CFII said:
Oh yeah, YOUR plane (note to self: pay more attention to N#s!).

Great rig you have there, I almost went for the 801 myself and may still build one in the future if the wings can be folded which I don't think would be too hard. I ended up with the STOL Highlander on tundra wheel amphibs which is a little less work but not as big either. Stop in if your up north in Seattle.

You've got plenty of power, so I guess you don't feel the desire for a blower with heavy loads at high DA?
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Any more power and I would have to notify the NTSB of a future plane crash about to happen.. :yikes:
 
SkyHog said:
<snip>
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.

<snip>.
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The numbers don't support this and the issue isn't (entirely) RPM it is horse power. My little model airplane engines easily turn 20,000 RPMs but only produce a fraction of a horsepower.

My spreadsheet left over from my aircraft design days say a 172 requires about 112 HP (75% power) to achieve 120 MPH. It only requires requires 27.4 HP (18% power) to do 75 mph. It probably requires some more since my spread sheet doesn't factor in induced drag very well, but it would be a pretty accurate number for a car with the same wetted area of a C-172. Most cars I would guess have less wetted area than C-172 and thus use even less horse power at 75mph.

Brian
CFIIG/ASEL
 
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