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CTLSi or CTLS


NC Bill

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I hear you.  A big bore kit might be worth doing on a high time but well running engine, or if you can afford to just throw away an engine that grenades.  Personally, I'd be too chicken to do this until TBO is passed or at least close.  I'd love to see some performance numbers for a 115hp big bore on an E-LSA CT.  You'd probably have to coarsen the prop and add a prop pitch limitation to the POH to keep it LSA speed legal.  I bet the climb would be "startling".     :)

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I watched a 185 with 1 onboard use up about 7-800ft of runway today taking off, and shortly there after a Helio with 260hp and 2 onboard use about 1000+ ft .... elevation is brutal. About an hour after they took off, I used about 180ft. Different airplanes are different of course, but that Helio for example has really good short field performance at sea level.

 

I don't know what the life expectancy will be with my big bore setup, and obviously guys like Roger have a more accurate opinion of what to expect... but considering I probably still don't make stock ULS sea level power up here, I'm hopeful it will/should live a long life if properly used and maintained (and maybe that doesn't mean the same lifespan as a stock one), there is always a trade off.. considering a lot of stock 912's reach well, well over TBO, I think it's feasible to assume a big bore can get some good time on it.

 

For those flying at low elevations, I can see where someone would say it's not really needed, and that makes perfect sense... up here, it's wonderful to have the extra power.

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I don't know what the life expectancy will be with my big bore setup

 

I think there's a fair amount of evidence that the big bore kits may actually extend engine life.  

 

The 1484 cc 114hp version is a bolt on kit - nothing but new pistons and barrels, which means you make no permanent modifications to your engine and can reinstate it to its original spec. in a few hours. (I'm not referring to the 1600cc version which requires machining the engine case and is prohibitively expensive.)

 

The pistons and barrels used are stock items manufactured for Porsche racing engines and the quality is far better than the Rotax pistons and barrels, which are cast rather than machined. 

 

Not only do you have better quality parts ,but the pistons, although larger, are substantially lighter.   A significant reduction in piston weight makes a very large difference in the forces exerted on the con rods and crank at 5500rpm.  

 

And despite the greater displacement, the compression ratios are the same (or substantially less on the 104hp version) so the stresses in the compression stroke remain about the same.  

 

The barrels are also machined and have the same nicoseal finish as Rotax; they also have far better cooling than the Rotax barrels.

 

When you take these four factors together - better quality parts, less mass being thrown around, better cooling and no increase in compression stresses - I find it hard to see how this kit could be troublesome.  

 

As far as I can tell, the 80hp, 100hp and 115hp Rotax engines use the same engine core, so even upgrading an 80hp to the 114hp big bore kit will not exert any more forces on it than the stock turbo motor does.

 

I cannot see any reason why they aren't a substantial improvement to the existing engine.   ???

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Stuck in Podunk, KY, with a plane that won't start, the carbs would be far easier to tinker with.

 

 

 

Or, stuck in Podunk, Alaska. Somewhere on this forum is the adventure of a trip to AK where the CTLSi had to be left behind for a few months in Nome or Unalakleet. There are worse places in AK to be stuck but I would take Podunk, KY over any of them. At least you can drive out of Podunk, KY. :)

 

Perhaps what happened to that CTLSi was a rarity and not likely to happen very often. Can't remember and too lazy to look it up.

 

Personally, I would rather have the injected engine except for the weight which is really critical in light sport. One thing I really like about the installation, at least in the CTLSi, is the header tank with it's own low fuel warning. In my CTSW I get a little edgy if my fuel gets down to 10 gallons. I don't think I would have that concern in the LSi.

 

Maybe it's time I thought about dropping a few pounds. Ice cream every night is not as easy to deal with as it was a few years ago. :giggle-3307:

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Or, stuck in Podunk, Alaska. Somewhere on this forum is the adventure of a trip to AK where the CTLSi had to be left behind for a few months in Nome or Unalakleet. There are worse places in AK to be stuck but I would take Podunk, KY over any of them. At least you can drive out of Podunk, KY. :)

 

Perhaps what happened to that CTLSi was a rarity and not likely to happen very often. Can't remember and too lazy to look it up.

 

Personally, I would rather have the injected engine except for the weight which is really critical in light sport. One thing I really like about the installation, at least in the CTLSi, is the header tank with it's own low fuel warning. In my CTSW I get a little edgy if my fuel gets down to 10 gallons. I don't think I would have that concern in the LSi.

 

Maybe it's time I thought about dropping a few pounds. Ice cream every night is not as easy to deal with as it was a few years ago. :giggle-3307:

Maybe it's apples-to-oranges, or Rotax specific, but I flew Cirrus's since 2001 with fuel injected engines.  Never did I have a mechanic in Podunk complain about it's being fuel injected.  Not exactly cutting-edge technology, even for airplanes.  Am I missing something?

 

Andy

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Andy,

 

The fuel injection in the Cirrus is pretty much "legacy", such that any Podunk mechanic will be familiar with it.

 

A 912is requiring a certain "dongle" and/or ROTAX-specific training to troubleshoot, not so much.

 

Hopefully, that will change over time, but it's a stark reality in the here and now.

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By the way, I do feel that the electronic ignition, also part if the 912iS, is pretty cutting-edge.  Maybe that's the "Podunk" issue.

 

Andy

 

Does the 912iS ignition actually vary the timing based on RPM, Load or both? I can't remember.. that would be a nice feature. Fixed timing works well enough in an airplane, but your giving up some efficiency somewhere....

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