VW conversion economics

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Pops

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We have some really good books and even DVDs on aero VW engines, but discussions like this indicate we still don't have everything tied up in a bundle anyplace. The Hoover mods, tricks to get the pushrod tubes to seal, inspection and maintenance ("how much should my crankshaft move when I pull on the prop hub?), etc.
Crankshaft end play is .003" to .006". I have always set my at .006" and check by hand before hand starting.
 

Pops

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When I was selling used VW's I bough some that had about 1/8" end play and the rear main seal would be dripping oil. Knew the engine was very wore out. At the time I could take the engine out and do a complete overhaul in 8 hour of work. Had a separate shop just for the engine rebuilding. When I shut it down, I had enough parts to build about 25 engines. 3 pickup truck loads of engine parts.
Had to either quit my day job or quit my 4-6 hr a day evening job. Kept my day job.
The reason I still have a few engine parts.
 

ToddK

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Personally, I think there is a lot of mythology around the VW. Some of it is based on pretty old info, hearsay, an actual bad experience, and a lot is Bovine Scatology. I look around and see people (especially in Europe) flying airplanes (well) with Limbach's and Sauers that many of the home building commentariat would scoff at and say it would never work.

It also does not help that there is a guru with a blog who's opinions are often are taken as gospel, and are often misunderstood.

A good rule of thumb in 2022 is that a VW in one configuration or another can be a good fit for a fairly clean airplane with a gross of 1200 lbs or less.

It all comes down to priorities. A man wanting *sufficient* performance, on an fairly light weight engine he can build, maintain, and own for a modest price will be content with an appropriately sized and configured VW.

If you want back in your seat STOL performance in a high wing at gross, you better make sure its a very light airplane, or check out Rotax and be ready to pay for it.
 

dwalker

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Way back when I was a young fellow I built several Formula Vee racing engines. The challenge of getting hp out of an engine legally was massive, and the fellows that had been running Vee since it originated with the Formcar could tell almost immediately when you were cheating, and how you were cheating, and if they could prove you were cheating or it was a good "work around". It taught me a lot about how critical everything is even in the simplest of engines.
 

challenger_II

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Personally, I think there is a lot of mythology around the VW. Some of it is based on pretty old info, hearsay, an actual bad experience, and a lot is Bovine Scatology. I look around and see people (especially in Europe) flying airplanes (well) with Limbach's and Sauers that many of the home building commentariat would scoff at and say it would never work.

It also does not help that there is a guru with a blog who's opinions are often are taken as gospel, and are often misunderstood.

A good rule of thumb in 2022 is that a VW in one configuration or another can be a good fit for a fairly clean airplane with a gross of 1200 lbs or less.

It all comes down to priorities. A man wanting *sufficient* performance, on an fairly light weight engine he can build, maintain, and own for a modest price will be content with an appropriately sized and configured VW.

If you want back in your seat STOL performance in a high wing at gross, you better make sure its a very light airplane, or check out Rotax and be ready to pay for it.

Please define "fairly clean"...

Longster 2.jpeg
 

Vigilant1

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Yes, the VW can do fine on a "dirty" airplane. It won't turn a prop that as is as long as an A-65 might, so it won't turn HP into thrust as effectively at 50 MPH. But, if efficiency were the name of the game, the plane wouldn't have all those wires in the breeze to begin with. :)

The problem, IMO, comes when somebody wants to fly around at 50 MPH using 80HP from a 2180cc VW. PSRU or not, that's not going to work.
 
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dwalker

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The problem, IMO, comes when somebody wants to fly around at 50 MPH using 80HP from a 210cc VW. PSRU or not, that's not going to work.

I'm sure it's something that's never occurred to me, and I'm sure you meant 2100cc and not 210, but what application would need 80hp to go 50mph? The 80hp Sonerai has no issue going far faster.
 

Vigilant1

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I'm sure it's something that's never occurred to me, and I'm sure you meant 2100cc and not 210, but what application would need 80hp to go 50mph? The 80hp Sonerai has no issue going far faster.
Yeah, I meant "2180cc" (I fixed it).
The planes with good baffling and higher speeds don't typically have a problem with 75-80 hp. But, if the same planes climb out steep enough (e.g. so they are at 65 kts, but still asking for 80 HP) there's generally going to be a CHT problem.
Similarly Wayne Clagg made a good go at using a VW Type 1 to power his Zenith 701. He fitted it with a PSRU and was able to turn a big prop with that engine, he probably made 100 HP at the RPMs/fuel flow he was seeing. But, it ultimately didn't work out due to heat. At the speeds that engine could pull a 701 (even a light one), the available air and especially air pressure couldn't be made to cool the engine sufficiently. Too draggy.
 
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TFF

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For the non engine people, understanding that 65 hp comes in different forms. They don’t get that in pure form an A-65, 65 hp VW, and a 65 hp Harley engine do not make 65 hp with the same power curves. They don’t understand how that and propellors mesh. The dream from the 70s was putting a 65 hp VW on a Piper Cub, hence the 80 hp and 50 mph comment. Too much airplane for the the biggest VW without a gearbox and it’s still screaming it’s little heart out. Even a Corvair which is closer to apples to apples still has to swing a smaller prop to make horsepower. That relationship is not understood.

Flying a Limbach use to be required in Europe. The rules were too hard for home grown engines. Somewhere with the microlight rules, it became easier. While the Limbach is VW based, it’s still a certified engine. It’s not just an engine an average guy digging a core out of a rusty shell in a field engine, like most people seem to dream of as VW.
 

ToddK

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8
Personally, I think there is a lot of mythology around the VW. Some of it is based on pretty old info, hearsay, an actual bad experience, and a lot is Bovine Scatology. I look around and see people (especially in Europe) flying airplanes (well) with Limbach's and Sauers that many of the home building commentariat would scoff at and say it would never work.

It also does not help that there is a guru with a blog who's opinions are often are taken as gospel, and are often misunderstood.

A good rule of thumb in 2022 is that a VW in one configuration or another can be a good fit for a fairly clean airplane with a gross of 1200 lbs or less.

It all comes down to priorities. A man wanting *sufficient* performance, on an fairly light weight engine he can build, maintain, and own for a modest price will be content with an appropriately sized and configured VW.

If you want back in your seat STOL performance in a high wing at gross, you better make sure its a very light airplane, or check out Rotax and be ready to pay for it.
My infrence was in relation to weight. VWs work fine Dirty and Light. Dirty and heavy don't tend to work very well.

Rex T. experimented with a VW on a Cub. Supposedly it performed about like the a65.

A custom head would be great.
 

dwalker

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For the non engine people, understanding that 65 hp comes in different forms. They don’t get that in pure form an A-65, 65 hp VW, and a 65 hp Harley engine do not make 65 hp with the same power curves. They don’t understand how that and propellors mesh. The dream from the 70s was putting a 65 hp VW on a Piper Cub, hence the 80 hp and 50 mph comment. Too much airplane for the the biggest VW without a gearbox and it’s still screaming it’s little heart out. Even a Corvair which is closer to apples to apples still has to swing a smaller prop to make horsepower. That relationship is not understood.

Flying a Limbach use to be required in Europe. The rules were too hard for home grown engines. Somewhere with the microlight rules, it became easier. While the Limbach is VW based, it’s still a certified engine. It’s not just an engine an average guy digging a core out of a rusty shell in a field engine, like most people seem to dream of as VW.

I'm with you on most of this. But the Limbach heads I've seen- granted only a couple of sets and not recently- have had the same issues as many other VW engines with regard to cylinder heads and valve issues.

I like and understand what Sonex has done with the turbo Aerovee engine, using short duration boost to get off the ground and climb so as to avoid the use of a psru.

I guess the biggest thing is find interesting is how literally hundreds of VW powered aircraft- KRs, Sonerais, midget mustangs, Dragonflys,, etc. have flown successfully for so long and now, when we have arguably the best engineering available ever, no one seems to even try to make it work.
 

dwalker

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Rather than edit, let me add that when I consider the VW for the Dragonfly my thought process is simple-
New everything.
Latest gen case machined and reinforced as per Hoover HFX, with the addition of piston squirters for increased cooling
Very specific coatings for pistons, valves and combustion chambers to control heat and friction
New heads, the 041 or similar heads with the best airflow I can find
top mount oil cooler and external oil cooler
Deihl top mount starter/alternator case
lawn tractor alternator
321 turbo manifold
inconel heat shields
turbocharger
intercooler
fabricated aluminum intake to central throttle body over the engine
EFI


My expectation would be that every 500 hours the heads would need to be rebuilt or thrown away and replaced, Given the current cost of about $300 a side plus coatings etc. not terrible and at 1500 hours I would pull the engine off, sell or gift it to a buggy guy, and install the new engine I would have had the foresight to build while flying. At that point I am still money ahead vs a certified engine.
I feel like part of the "issue" with VW engines is this seemingly recent idea that they should be a set and forget thing. I could be wrong about.
 

Vigilant1

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I feel like part of the "issue" with VW engines is this seemingly recent idea that they should be a set and forget thing. I could be wrong about.
I think you are correct. They require care. The idea of manually checking/adjusting the valve lash every 25 hours sounds like something from the stone age to folks who grew up driving Hondas and Toyotas that required little more than oil changes for a LONG time.
In addition, the VW engine isn't like a liquid cooled automobile engine. Heck, tighten up stuff on one side and things get out of whack on the other. There are lots of little tricks, some are really important.
 
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Pops

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A Fournier RF-4 powered sailplane flew across the Atlantic ocean powered with a 39 Hp, 1200 cc, VW engine. Cruising at 3200 rpm.
Good story.

 
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