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  #1  
Old 04-14-2006, 10:57 AM
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Default Unneeded rebuild comparison

Every once in a while i see someone wondering if an auto conversion will make it to 2,000 hours before rebuild.

MMMMM - first of all, most lycomings are RATED at 2,000 hours and most continentals are rated at 1400 hours. I personally know of a commercial operator that, because of operating history, was able to increase his TBO to 2900 hours on his continentals.

Don't have the stats, but it is common knowledge that many airplane engines do not make it to TBO, many needing a top end.

On the automotive conversion side, a BIG reason that most want to go conversion is rebuild cost - a mere pittance compared to rebuildin a certificated engine.

So in my book, ifin the auto conversion engines are makin it 1,000 hours - good to go
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Old 04-14-2006, 11:23 AM
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David Staten David Staten is offline
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Default Unneeded rebuttal

Quote:
Originally Posted by Dust
On the automotive conversion side, a BIG reason that most want to go conversion is rebuild cost - a mere pittance compared to rebuildin a certificated engine.
Front end costs are also pertinent.
NEW rotary woulda been $5k. PLan on 180 hp, Mistral says 190 hp on normally aspirated. (they also sell 30k complete package, and are pursuing certification)

controller/monitor: $2k
PSRU: $2.8k
Incidentals such as radiators and other things air cooled engines need: Less than $1k.

Prop, alternator, oil coolers and other things that both air cooled and water cooled engines need are not included in that figure.

Thats a NEW package buy in of approx $10-11k US Dollars. New MISTRAL with PSRU is $30K USD

So.. whats the cost of a NEW lycosaurus? in the 180 hp range? the 200 hp range?

If You go mistral, its near break even til the first rebuild.
If you roll your own, you are in the game for 30-50% of the ante. I could rebuild the engine every 150 hours and still cost the same as a NEW lycosaurus that makes it to TBO. And if I do it right, I wont be rebuilding ANYTHING anytime soon.

I can assure you, it wasnt JUST cheap rebuilds that motivated us.

Dave
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Old 04-14-2006, 11:34 AM
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Quote:
Originally Posted by David Staten
I can assure you, it wasnt JUST cheap rebuilds that motivated us.

Dave
Dave - I'm on your side on this one - just sayin - why look at 2000 hour TBO when, if they work, 1,000 hours should be good to go!
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Old 04-14-2006, 12:10 PM
Nathan Gifford Nathan Gifford is offline
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Both of you make very valid observations. One of the questions I would have about certified engines is how do they make a recommended TBO? Is this based on soley on empirical data?

Conversions installations, with very few exceptions (Eggenfellers, for example), are unique that follow some general guidelines generated by a combination of theorical or empirical data. This makes, in my opinion, TBO speculative. That said a SWAG TBO is probably good enough since the rebuild costs are so low. Heck you could put together a complete engine core ready to go for a pittance of the cost of a certified engine's TBO.

For non-certs the major drawback has been reliability. It would be hard to believe that Mazda or Subaru is going to loose much sleep over an experimental aircraft crash involving one of its engines, but I will bet Lycoming or Continental will.
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Old 04-14-2006, 12:24 PM
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Stupid sube question - RV6guy - you gonna replace pistons and such when you rebuild or just replace as needed?

what do you figure a 4 and 6 cylendar rebuild will cost?
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  #6  
Old 04-14-2006, 02:32 PM
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Quote:
Originally Posted by Nathan Gifford
Both of you make very valid observations. One of the questions I would have about certified engines is how do they make a recommended TBO? Is this based on soley on empirical data?
Its all data based. An initial (typically low) TBO is set based on wear data attained during certification tests... from there an engines TBO can go up or down depending on how it performs in actual service.
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Old 04-14-2006, 05:46 PM
Glos Glos is offline
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What about when you get to TBO. This is another important consideration. Check out what these people have to say. (URL is Below) I just had my engine done by them.

I got new cylinders, pistons, rings, bearings, intake and exhaust valves,seals, all the AD's, New slick mags, new wires, rebuilt carb and rebuilt starter with their respetive AD's and pick up and delivery.

It is not to "within" limits but to new limits. I have a O-235-L2C and the price was $11,700

Even if you get to TBO, the rebuild can be anything within limits, not always new limits.

If you shop you can get a certified engine O-320 or O-360 from 10K to 13K with 1000 hours on it. If you fly 100 hours per year you get 10 years out of
it if was in decent shape in the first place. The O 360 rebuild at PGA was about 13K.

That means you would have to put $108/month away for the impending cost of the rebuild.

http://www.poplargroveairmotive.com/Overhaul/facts.html

http://www.poplargroveairmotive.com/...aoverhaul.html

If my memory serves correctly either way the TBO is now in the experimental catagory and can be whatever makes you feel safe. I could be mistaken on the last point but that is another discussion.

Another thing. My engine was out of a storm damaged 1978 Cessna 152. 27 years later I could still get parts for it.
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Old 04-14-2006, 06:28 PM
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Quote:
Originally Posted by Glos
If my memory serves correctly either way the TBO is now in the experimental catagory and can be whatever makes you feel safe. I could be mistaken on the last point but that is another discussion.
For part 91 piston operations TBO is a suggestion. The feds could care less if you have your o-320 with 4500 hours and a 10 year since overhaul constant speed prop on your plane... as long as you are part 91.

Turbines, Part 121, 135, etc have different requirements that have to be met.
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Old 04-15-2006, 02:51 PM
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Quote:
Originally Posted by Dust
Stupid sube question - RV6guy - you gonna replace pistons and such when you rebuild or just replace as needed?

what do you figure a 4 and 6 cylendar rebuild will cost?
On race engines, we are more concerned about high tension loading causing cracks in the ferrous parts like rods, cranks and main caps. We do magnaflux testing on these parts at every rebuild. The pistons/ bearings often last many rebuilds but the time between rebuilds was usually less than 40 hours in the case of road racing engines. I see different parts wearing in an aircraft application which is 4000-6000 rpm rather than 7500-8500 rpm on a race engine. The lower revs in aircraft put the stresses far below the critical limits of these components which is why they should last much longer.

I think rings and cylinders will take more of a beating due to the long term, high continuous gas loads driving an aircraft along at high power settings.

My Subaru EJ22T had 26,000 miles on it when I got it. Everything was mint inside. No detectable wear on anything. I reused the bearings in their original locations. I installed new forged JE pistons built to my specs and rebored the cylinders for the correct clearance. Ring end gaps were carefully set to my specs. Reground the valve faces and seats. Exhaust seats on turbo engines, I make wider than stock for higher heat transfer rates. Other than that, all stock.

All engines have some weak link in racing. Once this is known and either checked frequently or fixed with a design or part change, reliability can be expected within a given lifespan. There really is no excuse for failures if this is so in a race engine. I told a couple of customers when they'd have to do teardowns and checks on certain components. Both ignored my advice and both eventually suffered catastrophic failures at 1.5 to 2.5 times the projected lifespan. No surprise there. It's not if, it's when.

On any rebuild, all parts have to be measured. If they are close to being out of spec, they should be replaced. Typically on turbocharged engines, the top piston ring lands take a beating from the high temps and gas loading. A good piston and ring choice can mitigate this as does Mobil 1 oil. I've gone up to 6 rebuilds on the same pistons and bearings on one very high output engine before the block was beyond specs. The trick is, that all these parts are pennies compared to cert engine parts so the rebuilds are usually less than $2000 even with new pistons if you DIY.

The EJ Subes seem to easily go 1000-1200 hours between overhauls. Some of the Egg units are over 1500 now with zero oil consumption and good compression. It would seem than many of these will easily exceed 2000 hours and judging by wear trends may even exceed 3000 hours. Only time will tell.
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