scoutdsa wrote:
So I am at this exact spot. I am building a Zenith Cruzer and was pretty solid on the UL Power 350i until I ran across the issue with the pistons. The Rotax 912iS was also my second choice, but I am struggling with understanding what the loss of 18 hp will do to the performance. Would you share your final decision and any issues you have run into. Appreciate it.
I haven't finished my decision yet but I'm pretty sure I'll go with either a Rotax 912iS or 915iS if I buy a Bristell, or Jabiru 3300 if I buy the American made Lightning LS-1. This is what I have found out in my research of a bunch of different aviation engines. I am not an expert in aircraft engines but this is what I have concluded. It isn't exhaustive and I've left a lot out of considerations like price, size, and weight but I hope it will help someone or spark discussion or additions. Also I couldn't find any detailed information on Lycoming IO-233-LSA only a bunch of broken links.
Rotax 912iS Sport
URL:
https://www.flyrotax.com/produkte/detai ... ort-2.html
Stats: 100hp @ 5800rpm, 1352cc, 10.8:1 CR, 4 cyl, liquid cooled, geared transmission, dry sump, fuel injected, normally aspirated
This is my favorite because they are liquid cooled which means they run at lower temperatures. This has an important effect because it decreases expansion of metals which lets them use much tighter clearances. And because of the reduction drive it lets the engine run at the optimal rpm for the best power curve and I believe Rotax has very well perfected the gearbox's reliability. I like the fuel injected models the best (912iS Sport and 915iS) for the efficiency as well as redundancy (fuel injectors, critical sensors, electric pumps, ECU, generators, and of course ignition systems aka ignition modules, and spark plugs). Component lifetime is increased because the fuel injectors and ignition systems are alternated on every cycle so only one plug+injector fires at a time instead of both together. They also have a very wide support network and iRMT classes let you learn how to do most maintenance yourself. Best of all they are really really light engines and have the best power to weight ratio of them all.
It has a few downsides though like the increased complexity of the gearbox, dry sump, and liquid cooling. Also it doesn't like to run 100LL without extra maintenance. And some of the redundancy is not perfect for example the fuel injected models have the dual generators (or dual magnetos and single generator) are housed in the same stator and are only electrically isolated, not physically isolated. I also don't like the carbureted versions because of the need to sync carbs and if they're going to go the way of more complex designs, why not go all the way and make it fuel injected? Also I've heard that the 914UL turbo has its own set of problems that are not present in the 915iS turbo.
Edge Performance EP912STi
URL:
https://www.edgeperformance.no/
Stats: Up to 177hp @ 5800rpm, 1621cc, 11:1 CR, 4 cyl, liquid cooled, geared transmission, dry sump, fuel injected, turbo-normalized
It is an aftermarket mod for Rotax 912ULS which improves horsepower with a performance camshaft, more displacement, and a fuel injection system. The boost in horsepower is huge at almost 177 (instead of 100) although the max continuous power is only 135. But for a similar price I could just get Rotax 915iS which has the same max continuous horsepower even if the WOT power is only 141. And the 915iS has a lot more redundancy for the same price. The EP912STi has almost no redundancy. But I do trust its designer to know what he is doing so I do not think it is a bad aftermarket mod at all. For me the tradeoff for getting the EP instead of the 915iS is that I lose a lot of redundancy as well as factory support but I gain more horsepower at WOT and a much lower weight (about the same weight as the 912ULS or even a little less). It is great if your mission is extreme maximum power for STOL or if you want an adequately high max continuous power of 135hp and don't care about redundancy, but you don't want the extra weight of the Rotax 915iS.
MW Fly B25G-R-155-B
URL:
http://www.mwfly.it/engine%20feature%20 ... %202.0.pdf
Stats: 155hp @ 4700rpm, 2549cc, 10.5:1 CR, 4 cyl, liquid cooled, geared transmission, semi-dry sump, fuel injected, normally aspirated
This is a fuel injected Italian engine and it's a little obscure but it has a similar paradigm to Rotax because it opts for liquid cooling and an optional gearbox to reduce weight and improve efficiency at the expense of being more complex. Early MW engines had really bad problems with the gearbox failing and even improvements didn't help a lot but I heard that lately they are using a much better gearbox. I think their gearbox uses a separate oil system from the main oil system for the gearbox so that it can use 100LL without clogging the gears over time. The MW engines pride themselves on using a lot of redundancy and safety features like using gears to reduce the speed of the camshaft chains (there are two) to give them a longer life but to be honest I don't trust them as much as I trust Rotax for reliability especially because they are less well known and tested and because of having dual chain driven camshafts.
ULPower 350iS
URL:
https://ulpower.com/en/engines/ul350/ul350is#1-specs
Stats: 130hp @ 3300rpm, 3503cc, 8.7:1 CR, 6 cyl, air cooled, direct drive, wet sump, fuel injected, normally aspirated
They are direct drive fuel injected engines that look great on paper but according to myulpower.com they have a whole lot of problems like piston slap, low quality third party automotive pistons, rich running, and a small oil tank that leads to overheating. They also use solid lifters which not everyone likes. The person who created Edge Performance used to work for ULPower but left because of these issues, I think. I would not recommend this engine for anyone based on all the things I have read.
Jabiru 3300
URL:
https://jabiru.net.au/wp-content/upload ... ressed.pdf
Stats: 120hp @ 3300rpm, 3300cc, 8:1 CR, 6 cyl, air cooled, direct drive, wet sump, carbureted, normally aspirated
They aren't fuel injected but they are simple (eg it uses a real rotating distributor instead of a wasted spark ignition system) which makes maintenance easier. The old engines had severe reliability problems with thru-bolt fractures which would destroy the engine and gave them a bad reputation. Gen 4 Jab engines are supposed to have fixed this totally. Other than being less efficient (carbureted) and a bit heavier they look really nice. But the only problem I saw which is a little worrying but is total hearsay is someone on a forum supposedly knows of some problems with the gen 4 pistons or cylinders or something but which he can't talk about. I don't know if it's crappy tolerances or something more sinister.
Continental O-200D
URL:
http://www.continental.aero/engines/200.aspx
Stats: 100hp @ 2750rpm, 3292cc, 8.5:1 CR, 4 cyl, air cooled, direct drive, wet sump, carbureted, normally aspirated
I didn't look into them very much at all because I don't like using 100LL and because they are quite heavy for such low horsepower. I've heard stories about them producing less hp in the real world than they are rated for and that their quality control is not the best (that last statement comes from an anonymous person's blog comment claiming to know this from speaking with one of their engineers so take with a big grain of salt). I would never go with O-200D in a modern plane that deserves a modern engine.
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