Turbocharged engine options for a 2 seater - what would you consider?

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dwalker

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I am late to the party, and while I like the Subaru engine, I like the turbo rotary better.
Personally I used to hate turbocharging because way back when most of the work I did was with Porsche, and the tuning bits were terrible and we would literally get a car running quite well, making good power and staying cool and really performing well. Then.. something would change, the weather, the fuel, whatever and next thing you know melted piston. I had a bucket full of 911 pistons with melted tops. As the engine management has improved along with various refinements in the actual engine building, I became a boost addict. Something I very quickly learned is there is a fair amount of mythology coupled with a lot of misunderstanding when it comes to dealing with turbo engines in any application, be it auto, marine, or aviation.
I am sorely tempted to build a turbo VW motor for my Dragonfly and, at least for now, ignore the Corvair I had intended to use.
I have a turbo 13B for my Long-EZ, whether it goes in the one I am building or I choose to take the easy way out and buy a much further along abandoned project/formerly flying airframe and put the 13B flight engine into it.
I have an 0-235 for my Vari-EZ that, assuming the Wing Attach Points pass inspection, I will rebuild with EFI, DIS/Coil Near Plug, and potentially a turbo.
I likely just muddied the waters more, but bottom line is turbos are cool.
 

cluttonfred

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What about just ordering a 100 hp Aerovee Turbo off the shelf? It’s a simple system with a fixed waste gate but, according to the manufacturer, at altitude a Sonex with that engine outperforms a Sonex with a 6-cylinder 120 hp Jabiru 3300.

 

Vigilant1

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I'm wondering how they cool these engines at this hp level and high altitude? Pretty challenging at SL, more so above 12,000 feet in the mountains with much lower mass flow available.
That's true. And, in the case of air-cooled engines, the lower ambient air temps at altitude don't come close to making up for the reduced air density. The impact of reduced air temps at altitude are more significant in the case of liquid cooled engines.
 

dwalker

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That's true. And, in the case of air-cooled engines, the lower ambient air temps at altitude don't come close to making up for the reduced air density. The impact of reduced air temps at altitude are more significant in the case of liquid cooled engines.

Well we have to remember that when we say "air cooled" we actually really mean "oil cooled" in most cases. Without knowing much about the Aerovee turbo i can only speak to my strategy for a turbo VW.
First thing is to use the "right" head casting. In my case I am looking at the Brazil or Asian "041" clone castings which allow for a very balanced airflow through the fins while maintaining enough surface area to get the job done.
Next is the use of coatings on the cylinder head itself. Specifically a thermal barrier ceramic coating on the combustion chamber, valve faces, and exhaust port. The goal here is to reduce heat transfer from the combustion chamber into the head casting.
The valves are kind of a tough piece. On the one hand using a sodium filled valve makes a lot of sense, on the other hand they can suffer from failure- specifically the head of the valve popping off, so beryllium copper seats with titanium valves make the most sense, albeit on the pricey side. Fortunately Del West makes a suitable stem length and head diameter in common use. A simple stainless valve will likely be just fine with its face TBC coated though, and an easy place to start.
The pistons will be coated with a thermal barrier coating on the top, a dry film lubricant or "anti scuff" and oil retaining coating on the skirts, and an oil dispersant -sometimes called an oil-shed- coating on the underside of the piston. Here the goal is to keep the heat out of the piston and prevent hot spots with the TBC, reduce friction and some heat with the DFL skirt coating, and maximize heat transfer from the piston to the oil with the oil shed coating.
Next up is to drill the case for piston squirters. these will provide a constant spray of oil to the underside of the piston top to help cool them.
A standard type3 oil cooler along with an external oil cooler is a no brainer.
Other measures, such as water or meth injection, etc. are not out of the realm of reality. Assuming the need for meaningful boost only at full throttle instances- take-off, short duration climb, etc. the use of a Water/Air Injection system could really help to reduce cht and limit the potential for damage.
 

dwalker

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I am still trying to get my head around the notion that a turbo'd VW would be a good fit for a Wittman W8 operating at a 9000ft DA, which is what the OP is trying to power...

Because he lead with this-

The big points I would like to consider are:

Under 220lbs installed
Minimum 90hp @ 9000ft DA
Ability to run on pump gas I can buy anywhere (including E10)
Forced induction for consistent takeoff performance
Installed price of under $20K

Which leads my thinking in the direction of either a turbo VW or standard or Turbo Corvair. Obviously the weight will be tight, but not really by much.
 

Marc Bourget

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I spent many an hour, over the course of 15 years of bi-weekly Saturday afternoons talking all things aviation with John Thorp. He was an engine specialist as well as a designer. His position with Lockheed before WW2, was the Liaison to all the engine manufacturers. In the 70's he was a consulting engineer with Rajay Turbochargers. Interesting aspect with cooling turbocharged engines is what it would do to mixture distribution and resultant cooling loads. If, say a Mooney, typically ran Cyl #4 hottest, they'd find with a turbo, that Cyl #1 ran hottest under boost.

These were serious studies. Rajay had an environmental chamber that could vary altitude, temperature, etc. (remember, the cooling ability for "air" drops with altitude).

Well, back to the point I was going to raise. Some T-18 builders were wanting to Turbo a 0-360. I could understand that after departing Rock Springs [to OSH] on a hot day. 18JT at gross felt like a C-172.

But the request frustrated John, who was of the opinion that adding a turbo required increasing wing aspect ratio (to optimize the potential of the turbo) but that would, in domino fashion, cause redesign of the whole aircraft.

Be careful what you wish for. You might achieve a benefit in a small part of the performance window and suffer throughout the rest.

I'll ignore the gain in bragging a turbo'd backfire #3 engine will bring to the builder.

FWIW

mjb
 

challenger_II

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Because he lead with this-



Which leads my thinking in the direction of either a turbo VW or standard or Turbo Corvair. Obviously the weight will be tight, but not really by much.

D, you are overlooking matching the engine to the airframe. While the VW is a viable engine (after all, I do fly behind one), I do not see any VWs powering aircraft the size of the W-8.
 

dwalker

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D, you are overlooking matching the engine to the airframe. While the VW is a viable engine (after all, I do fly behind one), I do not see any VWs powering aircraft the size of the W-8.

I had not looked, but it looks like a Tailwind needs about 80-85hp, which is doable with a VW, and certainly with a turbo vw giving 100hp at takeoff. I know Bill Clapp but a Corvair 110hp motor in one, but I'm not sure how it flies.
 

Vigilant1

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There are W8s flying with C75s and C85s. But because of the big prop they'll turn, those engines will give better takeoff and climb performance than we can expect from any hopped-up VW turning a prop at 3400 HP.
At cruise speed, the performance could be close to the same.
Maybe somebody can make a reliable aero 100HP VW Type 1. It will take more than exotic cooling approaches, oil squirters, high volume oil pumps, coatings, and exotic valves. The magnesium case should also be swapped for an aluminum one if there's to be hope for the bearing saddles to survive the pounding long term, so be sure to include weight for that.

Maybe this is a quest, like building a 100mph grocery cart. Put a suspension on it, 60 HP engine, roll cage, slicks. Is it really a grocery cart anymore? If we want to go 100 MPH, is a grocery cart the best starting point?
 
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dwalker

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There are W8s flying with C75s and C85s. But because of the big prop they'll turn, those engines will give better takeoff and climb performance than we can expect from any hopped-up VW turning a prop at 3400 HP.
At cruise speed, the performance could be close to the same.
Maybe somebody can make a reliable aero 100HP VW Type 1. It will take more than exotic cooling approaches, oil squirters, high volume oil pumps, coatings, and exotic valves. The magnesium case should also be swapped for an aluminum one if there's to be hope for the bearing saddles to survive the pounding long term, so be sure to include weight for that. Maybe this is a quest, like building a 100mph grocery cart. Put a suspension on it, 60 HP, roll cage, slicks. Is it really a grocery cart anymore?
I never planned to use anything but the aluminum "Super Case" myself, so we agree there. In fat the lure of the VW is the fact that every part would be brand spanky new.
Aerovee already does make a reliable 100hp VW engine, it is even turbocharged. I am not sure it uses any of the things I would do "if" I build a VW flight engine for my Dragonfly, but it is for sure still a VW. I like your shopping cart analogy, except all the parts start out as plain ole VW bits, just refined a bit in the interest of making life easier.

Regardless, the question was asked and I gave an answer to that question, for all I know the OP is building a BD4 or a Bearhawk and just used the Whitman as an example.
 

Vigilant1

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Aerovee already does make a reliable 100hp VW engine, it is even turbocharged.
They do sell a kit for a turbocharged VW based engine. I think you'll find a lot of disagreement about whether it is reliable. I know two people who had good, reliable Aerovee engines, installed the turbo kit, and threw in the towel after months of trouble.
I'm sure somebody has had better luck.
 
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dwalker

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They do sell a kit for a turbocharged VW based engine. I think you'll find a lot of disagreement about whether it is reliable. I know two people who had good, reliable Aerovee engines, installed the turbo kit, and threw in the towel after months of trouble.
I'm sure somebody has had better luck.

I have not looked in a while but my understanding is they only offered the turbocharged engine complete currently, not as an add on kit. I could be wrong about that as I am not really thier customer.
ETA- I have a strong dislike of anything carbureted to begin with, but an even stronger dislike of anything boosted with a carburetor. which is why I lost interest. Initially the price was quite appealing, but.. no carbs man..
 

Vigilant1

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I have not looked in a while but my understanding is they only offered the turbocharged engine complete currently, not as an add on kit. I could be wrong about that as I am not really thier customer.

Thanks. Just to clarify for others:
1) According to their website, customers who have an Aerovee can buy the turbo kit. New customers can buy the engine and turbo kit together.
2) Sonex (Aeroconversions) doesn't sell complete engines, they only sell kits.
 

TFF

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A VW is too small for a Tailwind. Bill Clapp’s Corvair flew, but he didn’t develop it; it could have done a little better. The plane needs a bigger prop and the horsepower, not just the horsepower.
 

dwalker

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I'm wondering how the actual Aerovee turbo cools at 12,000 feet producing 100hp. My guess is it doesn't...

It's the wrong engine to use for high altitude in a turbocharged format IMO.

I tried to find where I read it but for some reason I remember reading it limited boost to make 100hp to 1minute or so of boost for takeoff etc and the rest of the time it was basically turbo-normalized. Now that I look for it I cannot find where I read it so I could be mis-remembering.
 
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