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Dillpickle

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Piny Woods, Tx
Sorry Tom, but in fact there are now very few direct drive options left anymore. Those that exist are very expensive and only produced a few hundred per year....The high volume auto engine conversions like Viking, have a reduction gearbox.
Your argument handily ignores the two highest production auto conversions ever, the VW and the Corvair. I'd hardly call Viking "high volume." The VW alone probably outnumbers every other auto conversion combined, and I'd gamble that more people are/have built more Corvairs than Hondas. You can buy off the shelf every single part to build a half or whole VW., and the few builders out there building them professionally are swamped. Google experts said you can't put a VW on a low and slow airplane. "No torque!" "Too heavy!" Good thing Leonard Mulholland and Morrey Hummel didn't have Google to stop them. They produced a couple of the most popular LEGAL ultralights being homebuilt today. They also spawned an industry that keeps a few engine builders busy full time, and some parts suppliers hopping as well. Huh. Also the cheapest option out there, which is why they remain popular.
 

KeithO

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Jackson, MI
Dill, when last did you try to find an affordable Corvair core ? There are not many around, the people who have them are asking a lot of money for them and there are people who were flying corvairs that broke crankshafts twice, destroying the entire investment. The great plains flywheel drive engine package is running about $5000 without the carb and a bunch of other parts. The 150hp R18 Honda engine can be had all day long with less than 20k miles for $1000 and if one takes the most expensive gearbox out there, the Skytrax 3 gear set that is $3400, so engine and gearbox together for less than $5k. I didnt have to pay any money to tear it down, clean everything up and then pay some shop to rework the block, cylinders, crank, connecting rods etc.

I agree that historically many of those types of engines were built but it was because people didnt have better options. Going forward it does not mean that trend is going to continue.
 

KeithO

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Maybe if the Subaru had been a reliable engine........ (I do own a 2009 Forester, BTW...) Anytime an engine is not reliable, there is a strong demand for used engines and the price is proportionally high. Add to that the fact the Subaru is the lowest volume Japanese OEM in the US and it doesnt help either. Now Honda on the other hand sells a great many Civics and HR-Vs and the R18 engine was probably used in more than just those cars, but the junkyards can barely give away those engines.
 

Dillpickle

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Piny Woods, Tx
Dill, when last did you try to find an affordable Corvair core ? There are not many around, the people who have them are asking a lot of money for them and there are people who were flying corvairs that broke crankshafts twice, destroying the entire investment. The great plains flywheel drive engine package is running about $5000 without the carb and a bunch of other parts. The 150hp R18 Honda engine can be had all day long with less than 20k miles for $1000 and if one takes the most expensive gearbox out there, the Skytrax 3 gear set that is $3400, so engine and gearbox together for less than $5k. I didnt have to pay any money to tear it down, clean everything up and then pay some shop to rework the block, cylinders, crank, connecting rods etc.

I agree that historically many of those types of engines were built but it was because people didnt have better options. Going forward it does not mean that trend is going to continue.
Found three corvair blocks on my street....only a few million made. Gotta wonder why people aren't flocking to that five thousand dollar, 150 hp engine though. Probably because it doesn't exist yet. How many flight hours are on yours? CAM was converting Hondas for airplanes what, 25 years ago? I've heard the same arguments back then, and for Mazda, Subaru, and the like. The simple truth is, PSRU's and car engines aren't new. The Maximizer was designed in the sixties.

I'm not poking fun at you. I'm seriously asking. Every single water cooled car conversions I've seen have ended up costing as much as certified used/rebuilt, and don't have any where NEAR the safety record. Wasn't much wrong with the Corvair in Pietenpols, but when they started putting them in highly maneuverable aircraft, the cranks failed. Quite a few vw cranks failed too. But the volume of sales were there, enough so that the problems were identified and corrected.. thousands of fleet hours, if you will.. But a good number of PSRU converted auto engines have also failed, and over the decades, belts, rubber donuts, gears, cases...the failures are many!
And a psru designed for one type motor may fail abysmally with another. There are several threads documenting those failures in this forum. Glib statements like "less than $5000" set my teeth on edge, because in the decades I've been building and flying, there aren't ANY manufacturers delivering on that kind of promise. There aren't any groups of people going "hey look, this worked (or didn't work in the case of the broken corvair cranks)
It's not for lack of trying. And the low hp Geo conversions actually did well on psru's. But not at a power, price and weight where a 2 stroke Rotax couldn't kick its ass.

Build yours. Test it. Fly it. Document it. And see why no one else is claiming to be able to do it at that price point.
 

challenger_II

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Jul 15, 2009
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Fisher County, Tx. USA
100% spot-on.

Found three corvair blocks on my street....only a few million made. Gotta wonder why people aren't flocking to that five thousand dollar, 150 hp engine though. Probably because it doesn't exist yet. How many flight hours are on yours? CAM was converting Hondas for airplanes what, 25 years ago? I've heard the same arguments back then, and for Mazda, Subaru, and the like. The simple truth is, PSRU's and car engines aren't new. The Maximizer was designed in the sixties.

I'm not poking fun at you. I'm seriously asking. Every single water cooled car conversions I've seen have ended up costing as much as certified used/rebuilt, and don't have any where NEAR the safety record. Wasn't much wrong with the Corvair in Pietenpols, but when they started putting them in highly maneuverable aircraft, the cranks failed. Quite a few vw cranks failed too. But the volume of sales were there, enough so that the problems were identified and corrected.. thousands of fleet hours, if you will.. But a good number of PSRU converted auto engines have also failed, and over the decades, belts, rubber donuts, gears, cases...the failures are many!
And a psru designed for one type motor may fail abysmally with another. There are several threads documenting those failures in this forum. Glib statements like "less than $5000" set my teeth on edge, because in the decades I've been building and flying, there aren't ANY manufacturers delivering on that kind of promise. There aren't any groups of people going "hey look, this worked (or didn't work in the case of the broken corvair cranks)
It's not for lack of trying. And the low hp Geo conversions actually did well on psru's. But not at a power, price and weight where a 2 stroke Rotax couldn't kick its ass.

Build yours. Test it. Fly it. Document it. And see why no one else is claiming to be able to do it at that price point.
 
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pilot103

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May 13, 2003
Messages
124
Yes and no on the Corvair numbers. Yes they made a little over 1.8 million but of those less than 600 thousand were the ones used for conversions. and the newest of those is over 50 years old.
 

Hawk81A

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Sep 3, 2021
Messages
271
Maybe if the Subaru had been a reliable engine...... Add to that the fact the Subaru is the lowest volume Japanese OEM in the US ...the junkyards can barely give away those engines.
Subaru's aren't reliable????? Lowest volume????? I've had 7 Subarus. Currently have 5 NONE are under 100K miles, and 2 are over 200K miles. Yes, there were SOME head gasket issues, but there are special head gaskets available that eliminate that possibility. as far as "low volume" Other than the one I may be driving, I can't hardy go anywhere without seeing multiple Subarus. Often, I'm at a light and the car in front of me or behind me (or BOTH) is a Subaru.
On the Corvairs: Only 1964 and up were the 164 CID engine, which I would consider the only real option for aircraft conversion. (I've owned close to 25 Corvairs in my time)
"Junkyards" rarely give away ANYTHING. Even the "U-pull" yards the price of a complete engine is now above 300.00 - and that should be considered a rebuildable core. JDM (Japanese Domestic Market) used engines from Japan (low mileage due to taxes and emissions requirements - and sold by several US vendors) are usually around 1,000.00.

There are many options. Each has their own complications and benefits. It doesn't have to be a NASA type conversion. I recall a guy at Sun N Fun who designed and built his own plane. it was called "Little Red". A fabric covered wood high wing. He had a junkyard (older) Honda Civic engine and it was mated to a belt redrive removed from a two stroke UL engine. Just that simple. Dennis
 

KeithO

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Nov 29, 2009
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729
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Jackson, MI
The snippets below are from a 2021 write up in kitplanes magazine.
The cheapest Corvair option is already $9500+ and it has a distributor and carb.

The Honda or Mitsubishi options are coil on plug, EFI and in some cases variable valve timing.
In my mind the primary barrier is not having off the shelf adapter plates to mount the gearboxes to the engines and the flex plate / coupling to transfer power from the engine into the gearbox. And finally the lack of availability of 3 gear gearboxes to put the prop flange in the right position needed on the cowling.
At least for now, Skytrax is the only supplier to have all their gearboxes be 3 gear sets. But for now dedicated to the Yamaha engines only. Aeromomentum have a 3 gear set for the 3 cylinder engine, except that they are not in production yet after being announced more than 5 years ago. Right now, demand for the AM 13 and 15 is such that they may never get to the smallest engine configuration. I believe that on the larger AM engines customer demand is driving development of a 3 gear set gearbox. If that comes through then we will be all set for gearboxes for the higher HP options. Just missing at the bottom end. The Rotax E box has all the usual problems, a long axial length and also a 2 gear set which provides inadequate cowling clearance for an easy vertical engine install.

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Dana

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Every single water cooled car conversions I've seen have ended up costing as much as certified used/rebuilt...
And there's the problem. We say, "car engines are made by the millions, so they're a lot cheaper than a Lycoming that's made by the thousands." Economy of scale, right? So far so good. Then we take that cheap car engine and slap on a redrive made in the hundreds if not tens... with the economy of scale the redrive maker doesn't have, you end up with a powerplant approaching Lycoming cost, without the decades of experience Lycoming has.
 

PMD

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Apr 11, 2015
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Martensville SK
And there's the problem. We say, "car engines are made by the millions, so they're a lot cheaper than a Lycoming that's made by the thousands." Economy of scale, right? So far so good. Then we take that cheap car engine and slap on a redrive made in the hundreds if not tens... with the economy of scale the redrive maker doesn't have, you end up with a powerplant approaching Lycoming cost, without the decades of experience Lycoming has.
As I have said before: the same thing applies to certified auto conversion engines. The modifications, redrive, special bits and pieces end up costing Lyc and MORE bux and due to the short product life cycle leaves the aviation market with an orphan in the future that can not tap the cheap auto aftermarket for low buck fixes.

IMHO there is no doubt that the future of genav lies in gear reduced, higher revving engines to get best prop efficiency, but so far, NOBODY has found the magic formula to do that at high enough power density and low enough weight, never mind reasonable cost. That applies to E/AB and certified engines. For now Lycosaurus roams the earth supreme.
 

KeithO

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All trash. As a certified powerplant in the power range discussed in this thread Rotax reins supreme. And all of their solutions employ reduction drives. Without meaningful competition, they can charge for these engines whatever they like. The only outlier is Jabiru, who more or less came from no-where. Reason for their existence was basically geographic isolation and rip off import agents for all of the imported engines that more or less resulted in the local prices being double what it was in the US or worse. When the Jabiru engines first appeared on the market they were more modestly priced compared to where they are now. As their market penetration grew, so did the prices. They are no longer inexpensive engines. $15k for 80hp ? I think the Jabiru cost structure is to charge 75% of what Rotax wants for the same power. In the meantime, Rotax is getting close to being on par with the pricing structure of Continental and Lycoming in $/hp.

Those who are making reduction drives are selling at $2400 to $3400 per drive, that covers Rotax E box for $2400 to Skytrax with their cnc from billet 3 gear reduction drives for the Yamaha engines at $3400. The "cost" of the drives is less, if one was an OEM engine builder and was going to integrate them into an engine package in volume. So the cost of the reduction drive is not driving system cost. If one is going the recycle engine route as per Viking, then the engines themselves will range from $600-2000 at most. $2000 being for the turbocharged 4 cylinder engines in the 200hp range. There have not been reliability issues with any of the mentioned reduction drives so far. Viking had an aluminum flywheel/flexplate fail on a couple of occasions so they switched to a CrMo flywheel.

Aeromomentum is taking on the job differently with all the engines starting as piles of new parts and being assembled from scratch. In some cases the parts are modified by CNC porting with hand finishing to improve the flow properties of the new cylinder heads that they buy. Their turbo motor is converted from direct injection to port injection, thus they have to plug the ports for the GDI injectors and add fuel rails that did not exist for the original engine together with new intake manifolds. So Aeromomentum has a pretty big labor charge that goes along with building one of their engines that is simply not the case for Viking at all. Not to mention all of the parts inventory that they have to hold for all of the engine variations. For people who absolutely want to have, and are willing to pay for a zero time engine, assembled by someone in the US, then Aeromomentum is the way to go. They also dyno test every engine before it ships. One just has to remember, these engines are not really close to a factory engine anymore. In some respects like component balance etc, they may in fact be superior. But there have been some problems with some of the custom parts like the new fuel rails cracking, the fuel line connections to the rail being held on with a worm drive clamp instead of something better and other detail issues which they are totally capable of correcting and hopefully will.

But there is a cost. The AM15T is now close to $17k (1.5L turbo 160hp). The "upright" regular AM15 engine is $12k for 117hp
The small 3 cylinder AM-10, which is supposed to be the Rotax replacement, has languished now for many years. In the meantime, Viking has been selling/delivering/installing the 3 cylinder Mitsubishi based engine with 90hp, 159lb and $10k even price tag. Compared to a Corvair, Jabiru 2200 and of course the 912 this is a pretty good deal. Remember those competitors have carbs and magneto's. Its competitive on power, weight and price. Until someone starts selling a 3 gear reduction drive comparable to the one made by Viking, it is going to stay a dream for the DIYers. One could build it with the Rotax E box right now but that being just a 2 gear reduction drive one would have issues with the position of the prop flange relative to the cowling. Aeromomentum has a 3 gear gearbox for their AM-10 engine but development of that entire package has just been too low a priority since customers want engines at the upper end of the power spectrum, or at least those are the more vocal customers SO FAR (in times past one had the HKS option, the 912 and of course 586 and 503 2 stroke options, but many of those are no longer available anymore). So for once Jan has seen the opportunity, developed a solution and has been aggressively marketing it, including installs of the engine at customer sites to get more examples flying. In the meantime, Jans competitors - do nothing.

Picture of the AM-10 reduction drive that so far is not available due to perceived low demand from the market.
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Yellowhammer

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Born In Alabama, reside: Louisiana (unfortunately)
I always change oil and check the adjustment of the valve lash at 25 hrs and record the measuments I found to catch any problem. Just about an extra 10 minutes while doing the oil change.
I have somewhere about a million miles driving behind a VW type 1 engine. Oil change and valve lash check at each 3K miles and new plugs and point and condenser at 10K miles. On a 1600cc engine the mileage reduces from 32 mpg to 28 mpg between 10K and 12 k miles.
My job required a lot of driving and for many years drove a VW 1000 to 1200 miles a week . Bought a new 1969 VW Bug and put 78K on it in 18 months. Yes, I got paid mileage, and paid more than it was costing me.


That is a lot of driving Pops.
 

KeithO

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Nov 29, 2009
Messages
729
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Jackson, MI
Must have had quite a few close calls in that much driving... I commuted weekly from SE Michigan to Dayton for 4 years and I saw a lot of things go down on I75 over that period. That was not even 100k miles...
 

Geraldc

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Nov 12, 2011
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843
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nz
I am building a Gazaile 2. The redrive parts are available from the designer.
I am almost at the price of a new Rotax but I have a free plane thrown in.
 

KeithO

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Jackson, MI
See the latest 3 gear gearbox from Aeromomentum on their 2.0T engine which is 200hp. This gearbox puts the prop flange at the right position for the cowling with the engine in the vertical orientation.
 

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