Considering the Rotax 915

[NoWingsAttached]

FYI: https://www.flyrotax.com/produkte/detail/rotax-915-is-isc.html

Rotax builds great engines, no argument there. I always wanted one, but could never come to grips with the cost. The latest and greatest is the 915. It puts out 140HP up to 15,000 ft. by finally getting on board with what I have been complaining about all these years: Why go to all the trouble, expense and added weight to build a turbo charged aircraft engine (914) with no intercooler? Without one it's a flying grenade, useful only to normalize for altitude or very short bursts of limited power. Boring. Expensive. Heavy.

The new 915 weighs 185 lbs...plus oil cooler, radiator, plumbing, so more like ~195 lbs.

The advertised price is $35,000.00, plus radiator, oil cooler, plumbing and sales tax. Total: $38,200.00.

TBO is 2000 hrs, thus $18.00/hr depreciation rate. If you sell the engine after 200 hrs it will be worth estimated $32,400.00 on the open market, a loss of $5760 out-of-pocket, or $28.80/hr.

Now we are ready to compare apples to apples: Rotax's best against Mohawk Aero's best, 915 turbo vs YG4 EXUP. You can have one, slightly used, Rotax 915 for $32,400.00, or you can have 3 similarly slightly used Yamaha YG4's for $27,000.00.

	Rotax 915	MAC YG4
Cost	$ 38,200.00	$ 9,000.00
HP	140	165
Weight	195	165
HP/ Lb.	0.72	1.00
TBO	2000	1500

The latest MAC YG4 comes with titanium EXUP valved exhaust system, which increases midrange power as well as top end.

At 5000' MSL the YG4 matches the 915 at 140 HP, while still besting Rotax's claims, quoted from the above Rotax link: "Based on the proven concept of the Rotax 912 / 914 engine series, the Rotax 915 iS engine offers more power, the best power-to-weight ratio in its class, full take-off power up to 15,000 feet (4,570 m) and a service ceiling of 23,000 feet (7,010 m)."

For another $4000 you can double up on the YG4 head gasket, slap a turbo kit on it and reliably produce 200HP up to 15,000' with only 20 lbs added weight. You can have two turbo YG4's for the price of one 915, and fly with about 50% more power at a bit lighter weight.

Edge Performance showcased a 300 HP YG4 at Oshkosh this year in Steve Henry's latest Highlander STOL build. (This is the same type aircraft Steve built with the MAC YG4 conversion adapter kit on it which won Grand Champion at Oshkosh last year.)

This newest arrival to the scene is a completely rebuilt Apex engine with every imaginable thing done to it to make it far better than new. Although it is capable of 500+ HP as-built, it is not being sold as such and they are claiming just 300 HP as limited by the redrive capabilities.

These folks acquired 5 brand new Yamaha Apex engines directly from Yamaha, to be sold as turbo charged monster-killer motors for aircraft. I already know there isn't a single person reading this who is interested in buying one, but if you want more info on Yamaha conversion engines - including the Edge Performance edition - please feel free to contact me at any time at [email protected]. I just bought my third YG2 80HP, and should have it ready to go for a gyro very soon. The Quicksilver float plane you should by now be familiar with is tearin up the Bayou, & lovin' every minute.

That's all I wanted to say about that.

 

[XXavier]

If the Yamaha conversions are cheaper, better, lighter, and more powerful than a Rotax 914, I wonder why the Rotax is the de facto standard for all factory-made gyros...

 

[Abid]

I appreciate alternatives to aircraft engines. There is a place for them for certain people but trying to compare these alternatives to a proven design made for aircraft from a company that does not use components from crashed sleds is a bit of a stretch comparison and being called apples to apples. If Yamaha was itself providing this engine as an aircraft engine, that would be more apples to apples.

BTW, some of your facts are wrong on the 915 such as price and TBO. Those are worse. TBO 1200 to start, but that's besides the point.

 

[loftus]

I don't think there is any question about the overall superiority of the Yamaha engines particularly when comparing power to weight ; I often wonder why Yamaha does not actually commit to developing a dedicated aircraft motor with proper support etc, even if they just go after the non-certified market at first. I know it's probably a liability thing, but it would seem it's a large enough company to do it. Probably then prices would go up to more closely match Rotax though.

 

[WaspAir]

Here are some critical parts of the business model for a very big successful company:

Yamaha pianos are not dangerous. Nobody sues.
Yamaha guitars are not dangerous. Nobody sues.
Yamaha electronic sound system components are not dangerous. Nobody sues.
Yamaha motorcycles are dangerous, but not from engine failures, and the engine manufacturer is rarely sued over crashes (typically, a car driver or a reckless operator is found to be at fault).

Predictable profit margins for those businesses are all a result of those conditions.

Compare:

Aircraft are dangerous, engine failures cause crashes, and aircraft engine builders get sued all the time.

If you were on the Yamaha Board of Directors, would you vote to offer aircraft engines, and if you did, how would you price them? (By the way, for the curious, the old Yamaha conglomerate is still the biggest shareholder in the motor company, even though they are technically described as a spin-off; check the trademark logo and you will still see three crossed tuning forks.)

Honda has recently gone into the high end of aviation, the biz jet, using completely independent technology from their road engines, not leveraging their other expertise. They don't offer aircraft piston engines based upon their power sport designs insofar as I am aware.

 

[Abid]

Rotax sells sum total of 3750 aircraft engines a year. Its peanuts for numbers. Rotax stays in aircraft engine business because their board of directors has a couple of people who are aircraft enthusiasts and the price they set is the price where the small volume, liability etc. are justified. Aircraft are expensive because the numbers are peanuts. There is no volume. There is no robot in any aircraft factory. This answers the annoying ridiculous question of why small aircraft are more expensive than a SUV. SUVs are made by the million. No one sues a SUV manufacturer if there is an accident generally. They sue the insurance company of the driver

 

[ultracruiser41]

Well....in my opinion....lots of engines run....it’s how they’re attached to the propeller that makes a difference! I’ve ordered a gyro with a Yamaha on it and will prove to myself if it’s better than all the Rotax’s I’ve had.

Rotax is still an aircraft engine....Yamaha is a sled engine.... high cost of Rotax is directly a result of aircraft use...liability...etc. Right now.....my money’s on Rotax but only hours flown will determine if the Yamaha is better.

 

[PW_Plack]

If that's an "apples to apples" comparison, one is rotten - the completely made-up TBO number for the Yamaha. That number needs to be disinfected, given where you pulled it from.

I didn't see an apple called "warranty" on that list, either, let alone one for "factory support."

Rotax can deliver enough brand-new engines, with warranty and a support network, to match an OEM's production needs, given enough advance notice on the order. You cannot deliver even one.

The Yamahas are great engines, and can work very well in experimental aircraft. That's likely the extent of their potential without factory support.

 

[NoWingsAttached]

Hi
Without a turbocharger @ what rpm do you get your 165 hp out of your yg4, and @ what sort of rpm do you get your cruise say 80 hp please ?

165HP comes on with maximum cam timing on this version of the Genesis 4-stroke around 10,500 ERPM. That sounds like a lot, but let's put that in its proper perspective. The engine is the tried and true Yamaha R1 1000cc motorcycle engine that has been run on street and track for two decades with a redline at 15,000 ERPM, and often gets raced much higher.

So at about 2/3 of the red line rev limits of the engine it produces 165HP.

Let me add the following narrative to put Rotax in perspective. It used to be you only really had two choices: Rotax, or a very heavy, somewhat unreliable automotive conversion. Then we were presented with Yamaha Genesis power plants in 2007. Nothing has been the same since in the EAB world.

Rotax built their first 4-cycle 912 series motor in 1989. Yamaha was already building 4-strokes 15 years earlier in 1979.

Rotax sold 50,000 4-strokes from 1989 to 2014, $1 billion in sales.

Yamaha did $1.5 TRILLION in sales in 2014 alone. Dividing by $14,000 average per unit (this is a very high, very conservative number) sold we get 100 MILLION engines for motorcycles, boats, snowmobiles and ATVs. Granted that includes both 2- and 4-stroke engines, but there are no figures that are available that break it down and they sell more 4-strokes than 2. Let's call it 50,000,000 4-strokes sold in 2014.

That means that during 2014 Yamaha sold 50,000 4-stroke engines in about 9 hours.

Nine hours.

In the motorcycle racing world there has been no doubt about Yamaha's dominance since the late 1960's, but the Formula 1 auto racing venue is the coup de gras for any engine manufacturer's R&D, the undisputed pinnacle of piston motor engineering. Yamaha participated in F1 1990-1997, with 16 points finishes placing as high as 2nd.

I haven't heard of a single forced landing by any of the 150 Yamaha conversions built and flying in the last 12 years.

A guy flying to the STOL competition at Oshkosh this year broke his 912 series motor en route.

 

[NoWingsAttached]

I don't think there is any question about the overall superiority of the Yamaha engines particularly when comparing power to weight ; I often wonder why Yamaha does not actually commit to developing a dedicated aircraft motor with proper support etc, even if they just go after the non-certified market at first. I know it's probably a liability thing, but it would seem it's a large enough company to do it. Probably then prices would go up to more closely match Rotax though.

Jim, I have to wonder the same thing. Yamaha makes and sells UAV helos in Japan using 2-stroke engines for crop dusting. http://barnardmicrosystems.com/UAV/uav_list/yamaha_rmax.html


They have more money than god to spend on legal and R&D, if they ever decide to get into the same aero market niche occupied by Rotax it would spell disaster for the comparatively tiny Bavarian engine builder.

 

[NoWingsAttached]

If that's an "apples to apples" comparison, one is rotten - the completely made-up TBO number for the Yamaha. That number needs to be disinfected, given where you pulled it from.

I didn't see an apple called "warranty" on that list, either, let alone one for "factory support."

Rotax can deliver enough brand-new engines, with warranty and a support network, to match an OEM's production needs, given enough advance notice on the order. You cannot deliver even one.

The Yamahas are great engines, and can work very well in experimental aircraft. That's likely the extent of their potential without factory support.

The only CERTIFIED Rotax are the 100HP 912-S and 80HP 912-F, & -A.

I am glad that this has developed into a healthy conversation including many respected gentlemen in the community. I did try to clarify the standards for used Rotax engines to be compared to used Yamaha engines at the start.

 

[NoWingsAttached]

Well....in my opinion....lots of engines run....it’s how they’re attached to the propeller that makes a difference! I’ve ordered a gyro with a Yamaha on it and will prove to myself if it’s better than all the Rotax’s I’ve had.

Rotax is still an aircraft engine....Yamaha is a sled engine.... high cost of Rotax is directly a result of aircraft use...liability...etc. Right now.....my money’s on Rotax but only hours flown will determine if the Yamaha is better.

Sounds like you are getting yourself a Tango to add to your stable, congrats - I hope it makes you

 

[NoWingsAttached]

I appreciate alternatives to aircraft engines. There is a place for them for certain people but trying to compare these alternatives to a proven design made for aircraft from a company that does not use components from crashed sleds is a bit of a stretch comparison and being called apples to apples. If Yamaha was itself providing this engine as an aircraft engine, that would be more apples to apples.

BTW, some of your facts are wrong on the 915 such as price and TBO. Those are worse. TBO 1200 to start, but that's besides the point.

I have never installed nor re-sold a motor from a wrecked sled, let's be perfectly clear on that. I used to buy the sleds, run them myself, then pull the motors. Later, as business picked up, I had to farm this work out. All of the engines I resell are from sleds from reputable shops that are 100% intact, and which are test run prior to stripping for parts sales by businessmen who specialize in this.

 

[Steve_UK]

"...........................for the comparatively tiny Bavarian engine builder"


They are based in Austria not Germany.


The 9,000,000th Rotax engine was delivered in 2018


more here

BRP-Rotax - We get your heart beating

We develop and manufacture high-tech premium engines for motorised recreational products.

www.rotax.com

 

[Vance]

I haven't heard of a single forced landing by any of the 150 Yamaha conversions built and flying in the last 12 years.

I know several people who have had inflight problems with their Yamaha engine aero conversions.

I don’t know anyone who has had a trouble free Yamaha Aero engine conversion experience.

Writing in most general terms it is usually the installation that fails.

Propeller speed reduction unit, electrical system, fuel system, exhaust system, engine mount system are the ones I am familiar with.

Please understand I am not suggesting a Rotax four stroke engine is trouble free.

I am only suggesting based on my observations that Yamaha aero engine conversions are not as trouble free as Greg writes.

 

[WaspAir]

Sorry folks, but having spent about 20 years teaching math, I can't let this go with out some corrections.
First, a little one:

Rotax built their first 4-cycle 912 series motor in 1989. Yamaha was already building 4-strokes 15 years earlier in 1979.

That's only ten years earlier, not fifteen, but it probably doesn't make much difference to the point being argued.
But now, the big one:

Yamaha did $1.5 TRILLION in sales in 2014 alone. Dividing by $14,000 average per unit (this is a very high, very conservative number) sold we get 100 MILLION engines for motorcycles, boats, snowmobiles and ATVs. Granted that includes both 2- and 4-stroke engines, but there are no figures that are available that break it down and they sell more 4-strokes than 2. Let's call it 50,000,000 4-strokes sold in 2014.

That means that during 2014 Yamaha sold 50,000 4-stroke engines in about 9 hours.

Nine hours.

No, no, no, no, no.
That's 1.5 Trillion JAPANESE YEN, NOT U.S. DOLLARS.
Check the chart on page 16 of the YMC annual report for 2014 here, and you'll see it's in Yen:

https://global.yamaha-motor.com/ir/annual/annual2014/pdf/2014annual_all_E.pdf

(The world's biggest company, measured in revenue, is Walmart, with sales only reaching about $500 billion, or 1/3 of the 1.5 trillion mark. Yamaha is not three times the size of Walmart.)

A yen is worth just under a penny ($0.0094 as of this morning). That means you need to divide all the numbers by 100. The dramatic number at the end should be 500 4-strokes in 9 hours, not 50,000.

Granted, it's still about one a minute, which is impressive, but NOT 100 per minute, as the original statement suggests.

I hope people are happy with Rotax, Yahama, Lycoming, or whatever they fly, and I won't be arguing for or against Yamaha here, but I have a bit of an obsession with handling large numbers carefully.

As former Senator Everett Dirksen used to say, "a billion here, a billion there, pretty soon you're talking real money."

 

[C. Beaty]

Back in the good old days when Rotax was a small, struggling, hole in the wall Austrian engine builder, I purchased my first Rotax engine, a 2-stroke with propeller redrive for ~$500.

Then, along comes Canadian mega conglomerate Bombardier, purchasing Rotax lock, stock and barrel and the rest is history.

 

[NoWingsAttached]

2014 Yamaha Motor Co. Sales Yen $1,521,000,000,000​ USD $14,349,056,603.77​ Units Sold, @ $14k ea 1,024,933​ Daily Production 2,808​ hourly prod 117​ per min 2​

Gerg dropped a decimal, and pulled Bavaria out of his butt. Thanks for keeping me honest, politely. Another correction: https://global.yamaha-motor.com/about/history/timeline/ First Yamaha motorcycle mounted 4-stroke was 1970, 19 years before Rotax's first 4-stroke. I seem to have juxtaposed diesel introduction in 1976, and then typo'd 9 for 6 while using the math for '76. Keeping in mind that list price on a 2019 4-stroke Yamaha Zuma is only $3000, and I was using the price based on a top-of the line R1 or sled, it would be fair to say the average price is more like $8000 per unit. Units Sold, @ $8k ea ave. 1,793,632​ Daily Production 4,914​ hourly prod 205​ per min 3​ Someone posted that Rotax sold 9,000,000 engines as of 2018. The company was founded in 1920, so it took 98 years to accomplish this. Yamaha does it about every 4.5 yrs. Speaking again to reliability of Yamaha conversions, an in-flight problem is not the same as a forced landing. The challenges for putting power to the prop as addressed by Ernie, first, to me, and others, have been minor and ALL failures in gearboxes have been limited 100% to Rotax equipment failures - bearings going bad. So far as we can tell these failures were likely due to contamination or assembly/installation error. Using the Russian gearboxes which do not require pulling the cases apart just to install them, we know of zero problems of any sort. MAC and Tango Gyro sell variants of the PSRU distributed by Air Trikes as the SPG4. Tango's PSRU is listed as SPG, MAC's is AK7. I have built, flown and sold dozens of YG4 aircraft conversions, using Rotax C, Arrow, Airgear, and even my own prototype silent chain PSRU. Not a single in-flight issue has been experienced by myself, nor reported to me by anyone. As for clutches, we used to think that a clutch was necessary to start all Yamaha Genesis engines. This is not true. The engine needs to be in good tune condition, and if hard starting is experienced we have found that adjusting the valves is all that is required for excellent cold starting characteristics with a direct-coupled (no clutch) rubber flex shaft coupling. One vendor tried using the Rotax C type rubber donuts and these failed almost immediately. MAC uses heavier-duty BMW style flex shaft couplings, and there have been no signs of wear of failure. RK400 clutches and other centrifugal clutches are popular for smooth starting. These all have their own set of issues and maintenance requirements. I decided to get around centrifugal clutches with one-way roller ramp clutches. The first design was faulty and allowed the clutch's hub to shift in relation to the outer race, resulting in overrunning failure when shutting down the engine. After a redesign in 2017, the clutches have not shown any indications of failure. I did have an electrical short to ground in 2013 after my first 20 hours. It was connection that had broken on the bench prior to installation when the motor tipped over during work, and my repair job failed. The regulator fried, and the engine ran off the battery until the display went dead. After that I continued on to fly back to base w/o any loss of engine power, a distance of about 7 miles. This is about as honest and straight forward as I can be. I am very proud and quite pleased to announce that I successfully built and sold the first reproducible, commercially available, Yamaha Phazer 80 HP, 4-stroke, 130# engine conversion kit this year. Put side-by-side in comparison as an alternative (about same price) replacement for the popular Rotax 582, 2-stroke, 65 hp, ~123 lbs 12 years of Yamaha gyroplane (oh, yeah, and FW came later, too) history proves this is the engine for the future.

​

 

[Abid]

..

I haven't heard of a single forced landing by any of the 150 Yamaha conversions built and flying in the last 12 years.

A guy flying to the STOL competition at Oshkosh this year broke his 912 series motor en route.

Hey that is not true. I know of at least 2 Yamaha conversion engine outs in trikes alone. I think they were 130 HP (claimed but never materialized).

The STOL guy who broke his 914 enroute and documented it on youtube, had a bastard 914 on his plane. It was his 914 assembled from used parts from parts from various sources and aftermarket parts. Devil is in the details. Its not that 91x series never have engine outs. Its that people in conversion market make claims that are not verifiable or complete fabrications and the fleet size is low.
Can I ask what is the fleet size of your Yamaha based conversions right now and how many hours have the top 5 conversions flown? 100, 200, 500 etc.?

I absolutely hate the fact that some of the Yamaha conversions require a clutch because they shake the hell out of themselves with load at idle.

 

[Abid]

Using the Russian gearboxes which do not require pulling the cases apart just to install them, we know of zero problems of any sort. MAC and Tango Gyro sell variants of the PSRU distributed by Air Trikes as the SPG4. Tango's PSRU is listed as SPG, MAC's is AK7. I have built, flown and sold dozens of YG4 aircraft conversions, using Rotax C, Arrow, Airgear, and even my own prototype silent chain PSRU. Not a single in-flight issue has been experienced by myself, nor reported to me by anyone. As for clutches, we used to think that a clutch was necessary to start all Yamaha Genesis engines. This is not true. The engine needs to be in good tune condition, and if hard starting is experienced we have found that adjusting the valves is all that is required for excellent cold starting characteristics with a direct-coupled (no clutch) rubber flex shaft coupling. One vendor tried using the Rotax C type rubber donuts and these failed almost immediately. MAC uses heavier-duty BMW style flex shaft couplings, and there have been no signs of wear of failure. RK400 clutches and other centrifugal clutches are popular for smooth starting. These all have their own set of issues and maintenance requirements. I decided to get around centrifugal clutches with one-way roller ramp clutches. The first design was faulty and allowed the clutch's hub to shift in relation to the outer race, resulting in overrunning failure when shutting down the engine. After a redesign in 2017, the clutches have not shown any indications of failure. I did have an electrical short to ground in 2013 after my first 20 hours. It was connection that had broken on the bench prior to installation when the motor tipped over during work, and my repair job failed. The regulator fried, and the engine ran off the battery until the display went dead. After that I continued on to fly back to base w/o any loss of engine power, a distance of about 7 miles. This is about as honest and straight forward as I can be. I am very proud and quite pleased to announce that I successfully built and sold the first reproducible, commercially available, Yamaha Phazer 80 HP, 4-stroke, 130# engine conversion kit this year. Put side-by-side in comparison as an alternative (about same price) replacement for the popular Rotax 582, 2-stroke, 65 hp, ~123 lbs 12 years of Yamaha gyroplane (oh, yeah, and FW came later, too) history proves this is the engine for the future.

​

Ok so if you are buying SPG-2 or SPG-3 from Vassili Tarakanov in Canada, you should know you are paying more than double. These are built in Bella Roos and originally cost like $500 or less. I would not buy anything from Vassili or have a business relationship with him. I dealt with him for over 4 years. That was more than enough for a lifetime. There is German company manufacturing an improved version of these gearboxes for Chinese military drones in China also.

What is the longest a single Yamaha conversion for aircraft of yours (current configuration with gearbox) has gone in terms of number of hours without any major change/maintenance. Years do not mean anything in this ... hours do.

BMW coupler is a bit stronger but it should also be changed every 500 hours on SPG gearboxes.