What engine would YOU build

Discussion in 'General Auto Conversion Discussion' started by Winginitt, May 15, 2019.

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  1. May 15, 2019 #1

    Winginitt

    Winginitt

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    This thread is for everyone else but me to describe what conversion engine they would build if they had a clean slate and a reasonable amount of money to build it. The rule here is that you can only select one power adder to build it. That means you must limit your engine to using either a supercharger, a turbo charger, or a reduction drive of your choice, or nothing at all but the engine. It's your choice. Hypothetically we can shoot for 200 HP or thereabouts as I feel that most builders would be happy if they had a 200 HP certified engine fall from the sky and land under their Christmas
    Tree. Maybe that wasn't the best choice of words for an aviation site, but you get the idea. The rules are loosely applied except for using only one power adder. You can build more or less HP if it suits you .
    The idea here is what do you think is the best way to economically build a conversion engine. Would a turbo engine be a better choice than just a reduction drive and WHY? Does a supercharger work better than the other options, or suit a specific need or situation for you...and WHY? What do you think you could build it for$? Are smaller engines at higher power levels the way to go....and how best to get there. What do YOU think is the best setup?

    After this initial post, I promise that I personally will not participate in the thread and offer any second guessing. I just want to see if everyone agrees or why they see a different method as the best way to go
    When comparing the different ways to attain the power they desire.
     
  2. May 15, 2019 #2

    pfarber

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    The current (2019) crop of auto engines is about as good as it is ever going to get. All aluminum, computer controlled, high reliability.

    That said, what I would spend my money on would be modifying a block and head that reduced weight. Current engines are still sand cast and that limits the wall thickness and requires cores. Also heads are not optimized for weight. Taking an AL head and carving off un-needed wight would lower the install weight even more. I know you can get v8 blocks CNCd from billet http://www.cnblocks.com/index.html 30% stonger, lighter, but no v6 options.

    I don't mind PSRUs as they are reliable if maintained.
     
  3. May 15, 2019 #3

    Dana

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    A reduction drive doesn't add power, it just lets the power be delivered at a more reasonable rpm.
     
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  4. May 15, 2019 #4

    TFF

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    Simple explanation is a normal airplane engine that is direct drive to the prop is designed to operate at the prop’s required RPM. Using an auto engine where the power output is not matched to the prop design requires a gearbox to match the two. Automatically you have an extra component that has weight and complexity that the other does not. The real question is can the airplane you want able to absorb extra weight ok or can you keep a small high rev engine alive. Matching to the airplane is the hard part.
     
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  5. May 15, 2019 #5

    Hot Wings

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    Unfortunately the engine design is also coupled to the intended air-frame. For example, I personally would only consider a water-cooled engine if the engine were designed in isolation from the rest of the project. If I were doing this as a for profit aircraft engine project I would most likely choose air-cooled. This is because to for water cooling to be a clear advantage in the market place the air-frame needs to be designed with this in mind. Since most aircraft have been designed around air-cooled your potential market is already defined.

    This logic applies to the choice of PSRU, or not, as well. If prop diameter is limited then direct drive is probably the path to follow. Adding in the potential for serial or parallel hybrid drive may tip the scales to a smaller high RPM ICE with reduction.

    But to more specifically answer your question:
    I'm interested in the low Hp range of engines. At the moment that means conversion of the larger industrial engines is my focus.
    A significant percentage of the air-frames where these might be used impose limits on prop diameter. That tends to favor direct drive.
    Direct drive gets it's power from displacement or forced induction. If you need more than about a half a hp per cubic inch that points to forced induction.
    Supercharging is fine for ground bound vehicles or racing aircraft. IMHO it's a waste of time and energy for GA aircraft when turbocharging is so well understood.

    The only problem for me is that the small turbos for 1L engines are VERY inefficient compared to larger turbos. Electric boost for climb phase may be an option?

    If I were doing a clean sheet design which I have dabbled with. I would, and did, go down the same path that the O-100 did. Use as much off the shelf hardware as you can to keep costs down. There wasn't a single aircraft engine part specified except off the shelf dynofocal rubbers.... and standard prop bolt patterns.
     
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  6. May 15, 2019 #6

    Pops

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    Low rpm, high torque at prop rpm's,direct drive. That means large cubic inches not your typical high rpm, low torque auto engine of today.

    Why do you think is the reason for the low TBO's for the aircraft geared engines.

    When I first built the SSSC I was using a 1200cc , 40 HP VW engine. ROC of about 550-600 fpm at redline rpm of 3600. Cruised at 3200 rpm at 65 mph. Not a good match for the airplane. Went to the 1835cc, 60 hp, VW engine that had a 1200+ ROC at 3200 rpm and cruised at 2650-2700 rpm at 80 mph. Using about 32 hp at cruise. A far better match for the airframe and engine life will be far longer.

    Did you every drive an old Packard, Husdson, Buick, etc straight 8 engine with the standard transmission? Rarely had to down shift for high gear on steep hills. Now the low torque auto engines down shift at any slight grade. Reason the transmissions wear out far before the engines.

    If its not there, it can't break. If I can make simple meet the mission, I'll take simple over complex every time.
     
  7. May 15, 2019 #7

    BJC

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    Yes. My wife allowed me to drive her’s on occasion. Wish that we had kept it and fully restored it. That straight 8 is way too massive to consider for a flying machine.


    BJC
     
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  8. May 15, 2019 #8

    TFF

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    I got one running for a a friend. Pretty intake manifold. He had lots of Hudsons. I ended up with a short nose for a while.
     
  9. May 15, 2019 #9

    Vigilant1

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    If I had a pile of "extra" money (ha!) and needed a hobby business, I'd design and sell a modular, opposed-cyl, liquid cooled engine. The basic building block would be a block (crankcase and cylinders) with opposed approx 400cc cylinders, all the water passages are already in there. Stack together as many as you need (2-12 cylinders), it has two "end" pieces, with the front one having a built-in PSRU and prop bearing. Sell the needed crank and camshafts for every version. Turn it at about 5500 RPM (2500 prop RPM), expect about 70 HP per 2-cylinder "block.
    Even if using OTS pistons, valves, springs, seats, etc this would be a pricey thing to get set up--it would never make money. I figure the small industrial engines and VW already have the small air-cooled market covered well.

    If I had a smaller pile of "extra" money, I'd throw in with a bunch of much smarter folks here and build a generic external bearing and prop hub for 20-40 HP direct drive industrial engines. Then, maybe work on lightening things for these engines and developing aviation-focused induction, exhaust, ignition, electrical, engine mounts, and other associated bits to smooth the road for folks wanting to use these industrial engines in airplanes.

    And I'd need another pile of money to hire lawyers to insulate my family from any liability for the above projects. I don't have much, but there's always someone looking to make a play for whatever can be gotten.
     
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  10. May 15, 2019 #10

    blane.c

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    I like the D motor. I wish they made something like it in USA.
     
  11. May 15, 2019 #11

    poormansairforce

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    Just an Ohioan
    How?
     
  12. May 15, 2019 #12

    blane.c

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  13. May 15, 2019 #13

    BJC

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    If I had money to burn, I would try to find Henry Bouley’s design data, and put his six cylinder aircraft engine into production and also complete the development of the four cylinder.


    BJC
     
  14. May 15, 2019 #14

    blane.c

    blane.c

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    Any pictures of Henry Bouley's engine?
     
  15. May 15, 2019 #15

    BJC

    BJC

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    Saw some years ago, but can’t find any today.

    Was hoping that someone here would have some info on them to share.


    BJC
     
  16. May 15, 2019 #16

    Vigilant1

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    That's about the HP/displacement expected for modern water-cooled engines at 5500-6000 RPM. About 12-13cc/HP. Maybe if we just have a simple 2 valve cylinder it might be less.
     
  17. May 15, 2019 #17

    pictsidhe

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    Money no object? Sleeve valved turbo-compund 2 stroke.

    Back to reality, my 103 is quite likely going to have a briggs small block vanguard driving a huge prop via an impedance matcher (redrive).
    For extra power. Tuned intake and exhaust, probably some port massaging. CV carbs as they have inherent crude altitude compensation. Higher CR and water injection for the top 1/4 of power. Since it will be limited to around 16hp at cruise for legal reasons, the water injection won't be used very much and will help with climb power. I would also like to lose the fan and use an exhaust ejector pump to move the cooling air. Despite what people think, hanging cylinders out in the breeze is not loss free. It's the reason for the NACA cowl on just about every radial aircraft since NACA invented it...
    Yes, more than one power adder. But hey, it's my engine!
    160psi BMEP isn't an unreasonable goal, 41ft-lb. I'm thinking around 5000 max rpm, so nudging 40hp.
    I am expecting far more difficulty keeping it cool and reliable than getting the power. If I can weld up the heads to run oil through current air passages, that would be a huge help, piston squirters too. Water injection will also help. It'll need stronger rods. Custom steel rods can be had for a reasonable sum, failing that, billet aluminium rods.
    I also have an idea for a 'novel supercharger', but that's unlikely on my current project.
     
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  18. May 15, 2019 #18

    Pops

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    Yes, way to heavy, but the young ones today don't know what a low rpm, high torque auto engine can be like at low speeds, in high gear on hills.
     
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  19. May 15, 2019 #19

    Vigilant1

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    What is this "gear" thing? They wouldn't appreciate the big engine because they've only driven 25 speed electronic controlled automatic transmissions and cars with tons of soundproofing and vibration damping/isolation. They just step on the pedal and it goes, like an electric golf cart.
     
  20. May 15, 2019 #20

    rv6ejguy

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    The old straight eights might be remembered fondly but they are inferior in almost every way to comparably sized modern engines. A 6L L96 puts out 340 lb./ft. at 2000 rpm, Packard 6L 330 at 2200. The L84 puts out 140 more hp on the top end and an LS3 (6.2L) puts out more than double the hp of the Packard (can do twice the amount of work per unit time and probably 3 times with proper gearing). The LS engines weigh about half of what these old straight 8s weigh. Fuel economy, longevity, emissions are all vastly superior. This is why the LS engines are looked at for aircraft. A 5L Ford Coyote puts out 400 lb./ft. at 3850 rpm. Dodge and Toyota 5.4L V 8s exceed 330 lb./ft at 2000 rpm as well.

    The modern V6 turbo engines like the Ecoboost have staggering torque at low rpm- over 400 lb./ft. from 2000 rpm all the way to 4500 rpm- from only 3.5L and run on 87 octane. Rather impressive.
     
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