Siezed low-time neglected turbocharger

[daleandee]

[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.

--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

I can't speak to other engines but I have owned and flown a NA VW conversion and a 3.0 Corvair on these air frames. I'd like to address answers to the comments above as directed at the Corvair engines.

1) Cost - Currently the Turbovee is 11,000.00 dollars for 100 HP. The 100 HP Corvair will be substantially less if assembled by the builder (both engines are builder assembled). Even if buying the complete "engine in a box" kit the price is near the same for the same HP.

2) Weight - If the Turbovee with all it's additional parts (additional oil pump, lines, pipe wrap, turbo heat shield & cover, etc) is still under 200 lbs ... it ain't by much and the proposed cooling system that adds complexity will also add weight that will certainly violate the 200 lbs FWF rule. As to the Corvair; my 3.0 is 218 lbs and the 3.0 & 3.3 with the newer billet cranks are even lighter as the billet crankshaft is less weight. Add to that the 20-25 more HP from these engines.

3) Zero Time Parts - True the Corvair reuses the case halves, head cores, and oil cover plate from the rear. But consider that every moving part is replaced with high quality, time tested, new parts. One can reuse the factory crank but new cranks are available, stainless steel valves, guides, rocker arms, purpose designed "dual fuel" forged pistons, forged connecting rods, new cam and gear, high volume oil pump, 5th bearing for prop loads, etc.

To your point about new parts being substandard ... there have been many horror stories on this list about builders receiving parts that had to be returned. The factory has used several suppliers of kit parts and there appears to be no symmetry or even a method to the madness. I'm not against a VW conversion on an airplane and even a lightly built, polished tail dragger that will fly lightweight people in the cooler parts of the earth. This is a great approach for the budget builder.

I stated before; "TANNTAAFL" and that is still true. Can a turbo be made to work on a VW and make enough power to fly this airplane in a manner that gives safety & reliability? I think the jury is still out on that question ...

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
168.7 hours / Status - Flying
Member # 109 - Florida Sonex Association
https://www.youtube.com/watch?v=1VP7UYEqQ-g

[peter anson]

I have a dumb question from a non-turbo flyer. I recall that when turbos first started appearing on cars they sometimes had an arrangement where after you turned off the engine, it continued to idle for a few minutes while the turbo cooled down and then shut off automatically. Would it be possible to solve the turbo oil coking problem simply by running the engine at low idle for a while before shutting down? I know it's not as convenient when whizzing propellers are involved, but I often sit in the aircraft for a few minutes after I shut down while I fill out my log book so having the engine idling wouldn't be too inconvenient.

Peter

[Rynoth]

Would it be possible to solve the turbo oil coking problem simply by running the engine at low idle for a while before shutting down? I know it's not as convenient when whizzing propellers are involved, but I often sit in the aircraft for a few minutes after I shut down while I fill out my log book so having the engine idling wouldn't be too inconvenient.

Peter

This is a procedure that the SB for the Aerovee Turbo calls far, a 2-minute idle cooldown before shutdown. This procedure is also standard in turbine powered aircraft, and is a good practice in any turbocharged engine, automotive or otherwise.

[Rynoth]

"lots of engine comparisons"

Dale, I’m just quoting you since you're the most recent post, but as the OP of this thread I'd like to steer this conversation away from engine comparisons and back onto Aerovee Turbo, specifically the Turbo SB and coking issues/solutions/experiences. These types of threads have been very useful to me in the past when I encounter an issue while looking for other similar builder experiences along the same lines. I hope this thread can be one of those.

It's also in the Aerovee forum.

[Rynoth]

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.

Brett, thank you for posting this data, to me it is very valuable and is consistent with the readings I had when my turbo was seized (again through my own negligence.) I would bargain that an Aerovee Turbo with a siezed turbo is producing very similar power to a normally aspirated Aerovee, and that the performance difference is actually due to the prop pitch being too aggressive when this happens. Put an 80HP prop on a Turbo Aerovee with a siezed turbo and you might get the same 80Hp performance?

I might additionally bargain that the air filter itself obstructs more airflow through the engine than a turbocharger that isn't turning.

[MichaelFarley56]

I have a dumb question from a non-turbo flyer. I recall that when turbos first started appearing on cars they sometimes had an arrangement where after you turned off the engine, it continued to idle for a few minutes while the turbo cooled down and then shut off automatically. Would it be possible to solve the turbo oil coking problem simply by running the engine at low idle for a while before shutting down? I know it's not as convenient when whizzing propellers are involved, but I often sit in the aircraft for a few minutes after I shut down while I fill out my log book so having the engine idling wouldn't be too inconvenient.

Peter

That’s been tried many times and measured by the factory, along with at least one turbo operator. According to everyone’s data, you can sit and idle for 5 seconds or 5 minutes; it won’t matter. As long as the engine is running and there’s oil pressure, the turbo doesn’t get that hot. The oil itself absorbs that heat and returns it to the engine. The problem is after engine shut down (regardless of how long it idles before shut down). After shut down, the turbo casing gets really hot for a certain length of time (15-30 minutes), thus causing the coking issue. I’ve talked to the factory about idle cool down times and those I’ve talked to all agree...an idle of a few minutes is a good thing in principle but the turbo will still heat up after shut down.

And just to offer the information out to everyone...I always idled my engine for 3-4 minutes before shut down and had the coking issues while other operators shut theirs down immediately and have generally had better luck. Take that for what it’s worth!

[kevinh]

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!)

Best wishes on your flight! I'm about six months behind you (also with a turbo aerovee).

Kevin

[Bryan Cotton]

I've said it before that I would not be an early turbo adopter, and I wanted my kids to learn to fly with minimum power. But, I hope the turbo issues are worked out. I'd like to convert I get the kids through college. I've had one flight in a Sonex - Josh's turbo trigear. It was awesome.

[daleandee]

"lots of engine comparisons"

Dale, I’m just quoting you since you're the most recent post, but as the OP of this thread I'd like to steer this conversation away from engine comparisons and back onto Aerovee Turbo, specifically the Turbo SB and coking issues/solutions/experiences.

Hi Ryan,

Perhaps you can point me to the quote above? I couldn't remember it and can't find it now ...

I do understand your desire to keep the thread pointed at the initial subject but the reason for the problem and the reasoning behind a solution (if there is one) that includes the complications of adding complexity and weight along with the other options available for those that desire them should be part of any discussion. In my last post I was simply responding to some information that needed to be corrected. If you want to focus extensively on the actual opening subject you might have a bit of difficulty finding very many turbo users that had a seizure before their first flight.

But at your request ... I'm out!

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
168.7 hours / Status - Flying
Member # 109 - Florida Sonex Association
https://www.youtube.com/watch?v=1VP7UYEqQ-g

[Rynoth]

If you want to focus extensively on the actual opening subject you might have a bit of difficulty finding very many turbo users that had a seizure before their first flight.

Au contraire, it was after discovering that my turbocharger had siezed and having reviewed the full service bulletin, it was made quite clear that my issue was a KNOWN issue. This was, in fact, the POINT of my creating this thread.... that I encountered an issue that was DIRECTLY addressed by the turbo SB before I even saw the issue.

Reference this link contained in the SB: http://www.taturbo.com/TAT%20SI15-02%20 ... turbos.pdf

Partial quote:

“This condition occurs when the turbocharger is new or newly overhauled and heat and normal operation have not yet formed a protective layer on the internal parts that protects them against oxidation.
During periods of prolonged inactivity (typically several days to weeks, and more frequently in humid weather) these deposits from oxidation may cause a restriction so that on initial engine start up, the turbocharger does not spin up.
This condition will normally be detected by the pilot during initial engine full power application on the runway. "

I am the living embodiment of this known service issue, I'm not alone, the guidance in the SB was spot-on, and that's why I made this post, in the Aerovee section of this very informative and very helpful website... to raise awareness of this potential issue. This is why Im trying to cut through the noise in this thread.