Aeromomentum AM20T 260HP

[robcaldwell]

Today I spoke with Mark Kettering of AeroMomentum aircraft engines http://aeromomentum.com/index.html. Beginning in 2019, they will be offering a completely new 260HP engine for less than $20,000. The AM20T is 4 cylinder liquid cooled, fuel injected, turbo-charged with tune exhaust, ECU (no mixture control), prop gear reduction, and can burn mogas. AeroMomentum has been building engines for more than a decade. Mark Kettering is an engineer x2 and is extremely knowledgable. Intriguing is all I can say...

[Isilverone]

Don’t you dare!!! Lol. They are intriguing but 5,800RPM to get the 260 makes me sick to my stomach. I think auto engines are a slippery slope. Most (not all) of the people that do it, wish they hadn’t. It will severely devalue the aircraft ,, IMHO

[Peter Girard]

his type of engine offers some benefit, but the big problem is that the gearbox that does not have reliable ca would take a guarantee of 1000 hours. you will lose your $$$$ and your time

[robcaldwell]

Oh, I'm not. Just wish we could get better affordability from L and C.

[whee]

Kinda interesting. But since it doesn't have a constant speed prop option I think it is a dud. But I'd be pretty happy to install a LS series GM V8 on my BH if a properly engineered, prop governor equipped, reasonably priced PSRU was available. But that will likely never happen so I'm stuck with a Lyconasaurus.

[robcaldwell]

One of these? http://www.aerotechllc.net/ls3-aircraft-engine.html .

[zkelley2]

You could probably always install one of the electric MT's.

[cgalutera1]

Even without the constant speed prop option, it still a viable option. The fuel consumption and engine overhaul alone in time outweighs the Lycoming engine. So I don't understand why it is a "dud" without the constant speed prop option.

[Archer39J]

Even without the constant speed prop option, it still a viable option. The fuel consumption and engine overhaul alone in time outweighs the Lycoming engine. So I don't understand why it is a "dud" without the constant speed prop option.

I mean, build the airplane that's right for you, but to quote alaskabearhawk a fixed pitch would be like being stuck in 2nd gear forever. Plus we can have CG issues with 360s, lopping another 60-ish pounds off that makes this even less attractive.

[schu]

Ah yes, the old car engine discussion.

There are a couple of significant issues with the auto conversion. But the biggest is the PSRU. When shopping for a PSRU be sure to ask the vendor which prop and engine combination they have done torsional vibration testing on. If they don't have specific test results for the specific engine and prop you want to run, then you are now fully in the realm of experimental engines that may suddenly come apart if you happen to operate in a harmonic of its resonance frequency.

Don't let anyone tell you that it doesn't vibrate, the engine vibrates. The crank speeds up and slows down even if slightly while each piston is doing its work. If you have a gearbox between that engine and the tuning fork, I mean prop, then knowing where it resonates is absolutely critical, unless of course you are super lucky.

Other factors are the weight of the engine, cooling system, and psru, are rarely lighter than the lycoming, unless you are taking a little engine and spinning it to high heaven, which might not be the end of the world if it has a short stroke, but not if it's running on the verge of detonation.

Consider this: A 2.0L engine running 10.5:1 compression WITH a turbo is a TON of cylinder pressure, and it's almost certainly going to need a pretty smart ECU to know when to back off the boost or timing to not destroy itself. That ECU comes in the car, but I wouldn't run it in an airplane because it probably has various limb mode type protections you don't want. Of course you can run an SDS aftermarket EFI unit on it, which is great, dumb EFI on an airplane is desirable, but not on an engine that is on the edge like this one.

Bottom line: Anyone claiming 1800TBO on a 2.0L turbo engine producing 260HP at 5500rpm needs to back that up with some serious data before I'd write a check, and even then you have the prop, psru, ecu, and fuel pumps to deal with. All said and ton, as long as you actually fly it, the lycombing is VERY reliable, and really not any more expensive by the time you consider the time, effort, and cost involved.

[Battson]

They are intriguing but 5,800RPM to get the 260 makes me sick to my stomach.

Plus the turbo issue. Bringing the turbo and doing lots of STOL are incompatible in my view, that thing will pop in no time.

Turbos are great for cruising at 15,000ft with bottled Oxygen, and climbing out of hot & high situations. Definitely have a valuable place in aviation, but it depends how you want to use your Bearhawk.

[svyolo]

Inline 4's are probably the worst choice for a conversion. They all have 2 bad harmonics that a prop and gearbox wouldn't appreciate.
A long time ago I liked the idea of auto conversions, but less expensive experimental versions of Lycomings made me give that idea up.

There are still a few conversions I like. I like the Corsair and VW, and maybe someday the LS1 will get there as well. I also have a lot of experience with Subarus, but they are a bit heavy for the power they put out reliably. The EG33 in particular is a really smooth motor, but is probably at least 100 lbs heavier installed than the O-540 sitting in my shop.

I think there are multiple reasons why almost all current aircraft engines are either flat or round. Nowadays, mostly flat.

[cgalutera1]

IMHO:

There are no differences between car engines and Lycoming, and Continental. The rod, crankshaft clearances are all the same. They all fall within 0.001-0.003 mils. Regardless whether it is an inline or horizontal opposed, it is very important for the engine to be dynamically balance. During the building process, the crankshaft, rods, pistons, flywheel are all balanced static at first and dynamically last. Some blueprinted engine(s) go as far as balancing the pulleys. Basically, anything rotating are balanced within less than 5 gms. It would be nice if the prop+spinner can be balanced with the crankshaft, rods, pistons, flywheel at the same time. Only then, one will have a smooth running engine. Balancing the prop separately doesn't really do it because it will always be out of phase once bolted to the flywheel.

Some will say the Lycomings are spinning 3000 rpm while car engines are at 6500 rpm. If the engine is built with a roller or a full counterweight crankshaft, it doesn't matter whether it runs 2500 rpm full power or 6500 rpm at full power. The limiting factor will be on the cams. Put a different cam then. I am ignoring in this conversation about oil galleys and oil pump volume. Both of these can be done also. Those Lycomings will not last past 3000 rpm because those jugs are too big. The case will split in half regardless whether it is shuffled pin or not. One can put bigger jugs in a car engine as long as there exist enough wall thickness.

If these are all possible, then why are Lycomings and Continentals are soooooo expensive as compared to car engines? The answer is liabilities. Manufacturers have to cover their ass*s. The FAA and all other regulations must also get their hands dipped in the bucket full of cash. Take a look at an old Cessna 172 and a new 172. Ignoring the electronics and nice seats, the design is pretty much the same yet the price is about $500,000 plus. OK, one will argue about the electronics. Do you really think those electronics really should be that much? As an engineer, I once designed a touchscreen for Garmin gps. It's very surprising to know that the components in a standard $80-$100 car gps are all pretty much the same as the garmin avionics. All of the validation testings are all the same regardless whether air or land. Garmin is not making a killing on these prices. They also have to pay all these regulators.

My only concern in a car motor in an airplane is when it comes to cooling failure. What if the head gasket fails and coolant starts leaking. In less than 5 mins, the car engine will stop. An air-cooled engine will not. Surely compression loss will occur but the motor will still work long enough to land.

[yateselden]

You guys are kinda making me feel like an outcast! The Mazda Rotary makes a better aircraft power plant than a car engine. Problem now is Tracy Crook/ Rotary Solutions has seemingly disappeared/desolved. No one has picked up where he left off.

[JimParker256]

I think all the comments here relate to piston engines. The Mazda Rotary is more related to the turbines when it comes to smoothness. And maybe fuel efficiency - LOL.

[yateselden]

Im just seeing your post Jim. That's funny, not entirely true but funny non the less! 😆

[Bcone1381]

There is a difference between auto and aircraft engines.

I believe imbalanced engine parts are not the cause of vibration/harmonic issues, rather the individual cylinders power pulses applying a strong force to the crank at regular intervals and frequency we can't hear or feel.

If price is the issue, give Bob Barrows a call about a Lycoming. I believe he can build an engine for less than the price of an AM20T.

If experimentation is the desire, I heartily send encouragement your way. I hope you succeed!! For experimentation is what makes this hobby so exciting. Keep us updated.

[svyolo]

Concur about calling Bob. Worked for me as well.

I still like seeing people experiment. Especially when it is me.

[schu]

IMHO:

There are no differences between car engines and Lycoming, and Continental. The rod, crankshaft clearances are all the same. They all fall within 0.001-0.003 mils. Regardless whether it is an inline or horizontal opposed, it is very important for the engine to be dynamically balance. During the building process, the crankshaft, rods, pistons, flywheel are all balanced static at first and dynamically last. Some blueprinted engine(s) go as far as balancing the pulleys. Basically, anything rotating are balanced within less than 5 gms. It would be nice if the prop+spinner can be balanced with the crankshaft, rods, pistons, flywheel at the same time. Only then, one will have a smooth running engine. Balancing the prop separately doesn't really do it because it will always be out of phase once bolted to the flywheel.

There are a huge amount of differences between car engines and airplane engines:

Fix timing mags vs electric ignition
mechanical injection or carbs vs fuel injection
Very long stroke high torque vs short stroke high rpm
air cooled vs liquid cooled
Boxer/inline 6 vs inline 4 or v8 (not many auto options in the 260hp range that use 6 cyls)
2 spark plugs vs 1 spark plug
Needs no PSRU, huge crank bearing vs needs PSRU, needs crank bearing
Usually doesn't need return to tank fuel vs usually needs return to tank fuel
Torsional vibration testing done for certified props vs little torsional vibration testing done because it works against a huge dampener (the weight of the rotating running gear/tires/vehicle)
Can run on gravity fed fuel or mechanical pumps vs needs redundant high pressure pumps

Some will say the Lycomings are spinning 3000 rpm while car engines are at 6500 rpm. If the engine is built with a roller or a full counterweight crankshaft, it doesn't matter whether it runs 2500 rpm full power or 6500 rpm at full power. The limiting factor will be on the cams. Put a different cam then. I am ignoring in this conversation about oil galleys and oil pump volume. Both of these can be done also. Those Lycomings will not last past 3000 rpm because those jugs are too big. The case will split in half regardless whether it is shuffled pin or not. One can put bigger jugs in a car engine as long as there exist enough wall thickness.

Lycomings are specifically designed to not go past 2700 rpm because that is as fast as you can reasonably spin a prop, and a direct drive engine is WAY less complex to deal with from a weight and vibration perspective.

Also, piston speed is a factor. If you compare a lycoming 540 to the subaru EG33 you notice the piston speed of the lycoming at 2700rpm is 48.75 feet per sec and the subaru at 5400rpm is 77.03. That's quite a lot faster for the subaru. Not that I would care, a subaru at 5400 doesn't both me, it's the PSRU that scares me.

If these are all possible, then why are Lycomings and Continentals are soooooo expensive as compared to car engines? The answer is liabilities. Manufacturers have to cover their ass*s. The FAA and all other regulations must also get their hands dipped in the bucket full of cash. Take a look at an old Cessna 172 and a new 172. Ignoring the electronics and nice seats, the design is pretty much the same yet the price is about $500,000 plus. OK, one will argue about the electronics. Do you really think those electronics really should be that much? As an engineer, I once designed a touchscreen for Garmin gps. It's very surprising to know that the components in a standard $80-$100 car gps are all pretty much the same as the garmin avionics. All of the validation testings are all the same regardless whether air or land. Garmin is not making a killing on these prices. They also have to pay all these regulators.

There are a lot of reasons. Some parts are x-rayed, there is a lot more documentation in regards to lots or batches, which means if you a have a part let go and it causes a crash, and the FAA sees a second or third one, they can issue an AD on that part, and in theory limit it to only the affected batch.

Liability is there too, the precision carb guy that was up a last summer said that they are in the middle of 10 lawsuits at any given time. If the engine sputters over an airport and you freak out and stall the airplane and spin into the ground, it's absolutely the fault of the carb... right?

My only concern in a car motor in an airplane is when it comes to cooling failure. What if the head gasket fails and coolant starts leaking. In less than 5 mins, the car engine will stop. An air-cooled engine will not. Surely compression loss will occur but the motor will still work long enough to land.

Here are my concerns with a car motor in an airplane:

PSRU harmonics
Prop limitations/issues
Prop governor issues
Electric fuel pumps at high pressure
More complex fuel system which might require single fuel tank ports
ECU failure
Alternator failure with poor battery life
Engine mount or isolator failure because vibration profile is unknown
CG issues as all up weight is hard to know ahead of time
Availability of parts should the PSRU vendor go out of business
Extensive amount of time needed to build custom engine mount, cooling system, fuel system, etc.
Possible issues with lining up the prop with the thrust line while still making the cowl fit.

Now, all of that said, I'm also quite well aware of the advantages:

Preheat is trivial with a freeze plug heater
Hot restarts aren't a thing anymore
Real heat in the cockpit with little chance of getting gassed
Much lower cost to rebuild engine
Potential for much higher HP with turbos and such
No more mixture or carb heat depending on setup
Smoother due to high frequency and smaller pulses

Anyway, unless you want to dive into serious engineering and be a test pilot, or you are doing something that's been done before a LOT (corvair, VW), I'd say stick with a lycosaur. They work pretty well.

schu

[PFalkner]

I think the reliability of the auto engine has come along way. I have multiple chevy trucks with 250,000 miles and only thing ever done is oil changes. Here is another option http://www.autopsrus.com/bearhawk

[yateselden]

I think the advantages and disadvantages are somewhat equal for both auto and aircraft engines. Aircraft engines lagging because of all the red tape the manufacturer has to deal with. Running drag racing engines for years, if you balance all components, use high end parts, time ignition and fuel for each cylinder with a good ecu, an auto engine can live at moderate RPM for a long time. My race motor is a SBC 427 @ 8200 making 820hp built in 2007 was reringed and bearing twice but had little wear. I just think the technology of auto engines are far beyond aircraft engines. They're just not certified and that's what keeps these aircraft engine companies alive. But not just anyone can deal with some of the complications of Installing an auto conversion.

[cgalutera1]

I agree with you. But one thing to avoid when using automotive engines is to avoid putting any axial load on the crankshaft. The bearings weren't made to take it. Installing a PSRU eliminates that. The unit bolts on to the block thus eliminating axial loading.