Siezed low-time neglected turbocharger

[Gordon]

AeroVee Turo Fiasco...........?

I hear your comments Robbie and wonder about some of these new (?) builders speculating all sorts of "fixes" to bring back this "dead horse" for extinction (my opinion). The idea of water cooling the turbo or having a separate oil system is definitely going down the "experimental road" a lot farther than I would care to go. There are way too many failure points that they will be creating.

I guess these folks have never flew or hostile country or large bodies of water like I have and likely you have as well. Reliability is PARAMONT.....! Extracting more than 80 hp from a VW is risky and fool hardy at best.

I admire their courage............! (?)

Gordon........Onex....Hummel 2400

[NWade]

1. Is there any downside to having a completely separate oil system for just the turbo with a second oil cooler?

In addition to the weight and complexity comments by others, I want to add something you may not be thinking about: Heat Capacity. A small volume of oil on its own circuit is going to be able to absorb less heat than a large volume of oil, and a shorter oil circuit is going to circulate the same oil back through the "hot section" more often. So unless you add a large oil cooler and/or a large oil sump on your separate turbo oil system, it will likely cool the turbo less-effectively than the current system.

From what we know (and I say this as a builder who's studied the Turbo a lot but only run my own unit on the ground so far), the Turbo cools just fine in the air. Its the on-ground/post-shutdown heat-soak that's the problem. So you're adding weight, complexity, and failure modes to all aspects of the system in order to fix an issue that only crops up a small amount of the time. Furthermore, the oil system of the turbo is primarily there for lubrication, not heat-rejection. Oil only flows through a very small area of the turbo and only in a limited quantity.

The water-cooling passages, however, are larger and designed for cooling. A small separate water cooling system with an electric pump would be roughly the same weight and complexity as a separate oil system, and likely do a better job at actually reducing the oil coking problem.

Finally, to return to thinking about failure modes: we know that a running Turbo seems to continue running just fine without water; therefore a failure of a separate water-cooling circuit would be far less catastrophic than the failure of an oil circuit.

Extracting more than 80 hp from a VW is risky and fool hardy at best.

Gordon - While I agree with you that the Turbo has been a "problem child" and was not ready for prime-time when it was released, its important not to let hyperbole take over. VWs have successfully run over 80hp in many arenas, and I'm not aware of exhaust valves being a major/common failure point on the Turbos. If folks have borescope images showing green exhaust valves on their Aerovees (along with evidence that they were not running excessive CHTs and a lean mixture), I'd love to see it. But we haven't seen that chatter on the Forums here. The Turbo issues have revolved around the oil coking far more than anything else.

Take care,

--Noel

[Gordon]

Sonex Needs More Power.......???

Dale........you have it EXACTLY right. If you think you must have more than 80 hp (and I agree more is better in that regard)...then skip right on past the VW engine and just put in a bigger engine. If you want that kind of cruise speed the 100 hp Turbo Aerovee gives you then install a 120 Jabiru or 130 hp (UL power) engine and cruise along throttled back, asking it to give you that "100 hp cruise" speed. The engine will be MUCH happier and it will be a much safer flight for all concerned (you may be taking you wife or kid along). So don't risk their lives just because you are trying to prove a point that it IS possible to get that elusive 100 hp from the VW.

Gordon......Onex....Hummel 2400

[NWade]

Seems to me that the weight and complexity arguments are moot and that this project is heading in the wrong direction. Doesn't it make more sense to start from the beginning and just install a larger HP, air-cooled, direct drive engine and be done with it? Of course I like the Corvair conversion but Jabiru is still making 120 HP engines, & UL Power is available as well as others.

Dale -

Its true that the Aerovee Turbo has crept towards the Corvair in terms of weight, and the factory has changed their stance on some of these engines. However, the Aerovee and the Turbo still appeal over the alternatives in the following ways:

1. Cost: The Rotax, Jabiru, and UL Power engines are all 2 - 3 times the cost of a Turbo. The Corvair is the only other engine in its cost bracket.
2. Weight: The Turbo is still under 200 lbs, whereas Corvairs are ~225lbs. The Rotax and Jabiru beat both by a handy margin; but then it goes back to the "cost" line.
3. Zero-time parts: Corvairs are all "salvage" engines, right? A lot of folks (myself included) are uncomfortable with the idea of an engine block that's got no history and has been sitting out in the elements for an unknown length of time. You can inspect it in-detail and clean it up, but you can never know what it went through before you found it.

In the end, as with all Experimental projects, it depends on your wallet size and what your priorities are: If you want maximum simplicity and care less about weight, then the Corvair is a bright star. If you need 100% new parts, then the Turbo has the potential to be the best bang-for-your-buck. If you want maximum support and a well-understood FWF system, then the Rotax is the clear winner. And on, and on... If there was only one "right" choice for every circumstance, we'd all be doing it! :-D

--Noel
P.S. The frustrated cynic in me is compelled to point out that I've got experience with zero-time parts that are still wrong or have failed. :-P

[n307tw]

Thanks for the constructive feedback. I think keeping the oil system stock and adding a separate cooling fluid on a timer circuit is the best bet so we will see what the factory comes up with or if I beat them to it, I’ll come up with something. Experimental Aviation has experimental at its core so there is definitely an element of testing yet to be done. To think the Aerovee Turbo is a dead horse is comical, there are plenty Turbo and naturally aspirated Aerovee engines still flying and if I had the extra 10 grand to throw away for an extra 20 more horsepower then yeah I’d probably install a Jabiru but for now it’s more cost effective to go the Aerovee route. Unless I win lotto - then I’ll be going the SubSonex route :-D

[MichaelFarley56]

I think you hit the nail right on the head Tim. For many builders, a primary reason the Sonex was chosen is the performance per dollar. When I built mine, you could finish a Sonex with an AeroVee and have it in the air for $30,000-35,000 total. Sure, to many the AeroVee is a fun kit to assemble and having the knowledge of how to build the engine and maintain it is welcome for a lot of builders. Plus the cost of replacement parts, especially as compared to certified airplane engines, is amazing! My father overhauled his 200 hp IO-360 Lycoming for around $35,000 which is a lot more than my total Waiex!
When the turbo came out, the promise of 100 hp for only a few thousand dollars more was music to my ears. We all know now that the kit may have been a little rushed to be offered for sale, but I do hope the factory is able to figure things out and make a reliable engine option. As far as I know, you can’t find any other 100 hp engine option for only $11,000 except if you build up your own Corvair like what Dale has suggested. And Dale knows much better than I do, but I’m pretty sure the Corvair is gaining a lot of interest in the Sonex community!
If I had the means to afford an extra $10,000 back then I would have installed a Jabiru 3300 as well. That still may happen someday, but for now, I’m happy to fly behind my AeroVee!

[Brett]

Switched to a fully synthetic oil.

3rd flight so far.

[rizzz]

If you’re going to go to a water cooling system on a VW engine to cool the turbo, you might as well go all out and do this as well:


(this was a Great Plains experiment, liquid cooled heads)

But seriously, I agree with Dale here 100%.
At what point do you stop adding weight and complexity and just start looking at different engine options?

[Rynoth]

Just briefly chiming back in here as the original poster of this thread. The key word in the title of the thread is “NEGLECTED”. 4 things I'll point out that I stated at the beginning:

#1: My issue occurred after the engine sat unused for a prolonged period of time.
#2. My siezed turbo issue was easily detectable on the ground via a normal engine run-up.
#3: The engine still produced darned-near full "naturally aspirated" power despite the turbo not turning.
#4: The fix for my particular issue took 1 tool and about 10 minutes to perform.

The service bulletins on the turbo took me a couple hours to perform and are all aimed at addressing the post-shutdown heat-soak issue, along with the practice of a cool-down period after hard engine running (which should be a best-practice in any turbo and/or gas turbine engine, automotive or otherwise.) To me this is all reasonable. I have no plans to install additional turbo cooling at this time, but will stay tuned to this forum and Aeroconversions for more guidance.

Basically, I'd like to opt out of being a card-carrying member of any "Turbo Fiasco Club" for the time being, and fully intend to ride behind my Aerovee Turbo for my first flight (Coming Soon!)

[Brett]

I'll make this my last post then.

Just a note as per your first post, when the turbo is seized on take off you CAN still climb with the cruise prop. Climbs at about 180-200 fpm at 27" map, as stupidly I have done it.