There is a reason that there is not hydraulic lifters as explained in there literature. The adjustments are easy to do at annual time and electric constant speed props are available. The engines have been in production well over 20 years and very popular in Europe and the rest of the world. Runs on a avgas or Mogas, even with 15% ethanol
Can you tell us what problems you have had and when?
It was very difficult to find negative criticism on the forums.
I'm not being tribal about it - I have no loyalty to either brand. Just some personal experience. A few things I'd say, from my experience and otherwise just my personal opinions...
Firstly, ULP engines are not popular in Europe (where I am). They are still an unusual choice here. Rotax and Lyc dominate by far, and Rotax has totally cleaned up the UL market here which is full of 600kg mtow factory built aircraft. That category does not exist in the US.
Things I liked on ULP:
- The parts were pretty cheap, and almost all automotive so they were even cheaper when you sourced them from automotive suppliers
- Started right up every time, regardless of whether it was hot or cold
- Looks nice (for whatever that's worth)
- No worries about vapour lock
- Overall simple design, no gearbox which was a bonus compared to the Rotax
Things I disliked:
- Real world power output is WAY lower than expected. This is because the power is quoted at 3300rpm which you will never use. I had the UL260i which is rated at 97hp, yet the aircraft underperformed quite badly when compared to the same type with an 80hp Rotax 912UL. A local guy has converted a Sling 2 to operate on a UL350 in place of the usual 100hp Rotax, and it's an absolute slug. Not what you'd expect for a supposedly 30hp increase?
- It was far louder than the Rotax
- Electric CS props are very slow to actuate and no good for aerobatics or formation
- The ECU isn't exactly bullet proof. Yes I know you can make a reliable dual electrical system, but it's a lot of extra work. Look what happened to the beautiful RV7 PH-MNX. Loss of power to the ECU, sure that could be just down to the builder making a mistake, but if I had a total electrical failure in my RV... the engine would just keep on running.
Personally an electrically dependent engine is a step too far
for me in my homemade plane. Others will have different opinions which are all valid.
- The ECU, not a fadec (still has manual throttle control) is open loop and doesn't actually give very good fuel consumption. It's no better on fuel than a leaned Lycoming, and my 260 was considerably more thirsty than a carb Rotax.
- Lots of issues reported over the years, see this website for example
http://www.myulpower.com/
- Quite a few issues with pistons, they've used a number of different designs over the years. In the last couple months a UK ULPower owner had a piston crack in half. This might be resolved now with latest design revisions but I didn't want to be a beta tester.
Finally, my last straw with UL Power is their attitude towards problems or complaints. They are totally dismissive of any problems. For example, there's been problems with leaking seals such as on the pushrod shrouds and crank position sensors. Once they finally acknowledged this, they said it was a "small number" of engines (basically every single one in reality). Their solution in the SB was to just add some silicone RTV to the O ring seals.
Another example, I tried to speak to them at Aero Friedrichshafen about which propeller type they recommended. The guy was immediately defensive and said "we are not a propeller manufacturer"... Sure, but you make aircraft engines, which only work with propellers, so can't you offer any advice? Nope.
Yea, I know Lycoming are similar when it comes to problems with their engines. But as they are the industry standard product there is oodles of support and experience, with virtually zero unknowns.
Hopefully that explains why
I do not want to own another ULP engine. I wish you the best of luck with yours but it's not a suitable replacement for a Lyc IMO.