One of those 6 cylinder ULPower engines at 180 hp would look sweet under the hood of my 170 I think. That said a light weight Rotax at 140 hp might work just as well with it’s lower weight.

I seem to recall that when Rotax whiz Lonnie Smith managed to stuff a 915 into the narrow confines of a S7-S's cowl, and then flew it to Alaska from Mississippi he averaged 6 GPH, when all was said and done.

While I usually callout others, at much lower elevations then mine, who think they NEED (HAVE to have.... pilots that live at sea level or nearly so) a turbo install I have to admit it sounds like a good match for your wants and needs, go for it!

OK , Someone check my math , but it looks to me that Rotax list the 915is fuel burn at .46 to .51 LB/BHP/HR
and that,s with in a 2 or 3 % points of what Lycoming list the 0320-B
??

Probably right Brown Bear, as efficiency fuel to brake horsepower wise really hasn’t changed since WWII. Fuel injection gives a small gain, and direct injection another small gain as you move towards diesels which take the crown for efficiency in terms of fuel relative to output.

The issue with those numbers is they’re from 100% rated power, and ignore engine weight. Now have a look at the 915 vs 320 in hp/lb. I think you’ll also find the 915 does better in cruise at altitude, a factor not considered in WOT HP relative to fuel flow. In other words that measurement paints only part of the picture. Basically they could make a 454 look good compared to an ecoboost.

But... it would be good only accurate at takeoff and initial climb, which is the minority of the flight. Weight, and altitude would be ignored as well, leaving a lot out of the discussion.

Ardent,
Maybe watch the EAA webinar the Randy (RANS Aircraft) had a few weeks ago. In the webinar there is discussion about his trials and tribulations with the 915. I think it is a great designed engine but think there are a few bugs that need to be tended to before it will be the engine it was truly designed to be. RANS no longer sells a FWF kit for the engine from what I understand. My jist from the presentation was, the Titan 340 was less of an issue to stay within engine parameters and is now the recommend power plant.

PS, I'm a Murphy Rebel fan also.

Appreciate that lead, I’ll look it up and would be helpful

WWhunter wrote:Ardent,
Maybe watch the EAA webinar the Randy (RANS Aircraft) had a few weeks ago. In the webinar there is discussion about his trials and tribulations with the 915. I think it is a great designed engine but think there are a few bugs that need to be tended to before it will be the engine it was truly designed to be. RANS no longer sells a FWF kit for the engine from what I understand. My jist from the presentation was, the Titan 340 was less of an issue to stay within engine parameters and is now the recommend power plant.

PS, I'm a Murphy Rebel fan also.

On the other hand, I've heard from several folks that Mark Pringle at Rocky Mountain Kitplanes in Utah (a long-time RANS dealer) has developed a 915iS package installed in a handful of S-20 and S-21 kitplanes built as EABs. Somehow, they've managed to get an intercooler that works to fit inside a cowl that may or may not part of the "factory" firewall-forward kit...

The challenge Randy Schlitter (RANS) was basically one thing: He was having trouble meeting Rotax's very low engine inlet temp limits (<= 50ºC) while still fitting the intercooler inside the cowling. And since RANS is building and selling factory-build S-LSAs, the ASTM standards say they MUST adhere to any limitations that Rotax publishes. With something like 95% of their orders specifying the O-340 engine option (MUCH less expensive than the Rotax 915iS), and given the fact that RANS has more than a 12-month kit backlog, it just got to the point that it wasn't worth spending any more time developing that package.

Zzz wrote:Rotax parts are not cheap.

Yep, but that's true of Lycoming, Continental, and everything Raytheon (Cessna / Beech) as well... We're starting to see some aftermarket parts become available that are lower cost. Cranks, rods, and pistons/rings are available from a few different sources. Several of them offer power increases as well, all for less cost than the Rotax factory parts. But most of these are for experimental aircraft only at this point. One example is the notorious carburetor floats Rotax supplies for the Bing carbs... There are now much better replacement floats available from Marvel-Schebler that cost about the same, but should not suffer the same "loss of flotation" the standard Rotax-supplied floats routinely suffer...

Zzz wrote:And I think they [Rotax] have some mandatory service items at TBO that are pretty costly.

Those "mandatory" service items, and even TBO itself, apply only to "certified" Rotax engines installed in "certified" (both Standard and S-LSA) aircraft. If you're flying an experimental (including E-LSA) compliance is optional, though recommended. Inspecting and cleaning the PRSU is one example of something where a little money invested on a regular basis can prevent a major expense over the longer run.

Most of the Rotax "mandatory" items are basically common sense items. The "big" one is replacing of all the rubber hoses on the engine every 5 years, to the tune of around $3K each time. But now even Rotax has (grudgingly) begun to acknowledge that the newer "permanent" teflon-type hoses need only be replaced "on condition"... Those of us in the "experimental" world have been migrating to those for a while now.

The fleet hours on Rotax engines is rising astronomically, because they are used to power several military and commercial drone aircraft. Some of the higher-performance options developed based on the needs of that marketplace. Their deeper pockets pay for the R&D that you and I benefit from... Finally, our tax dollars at work doing something favorable for aviation!

Excellent responses JP256. I had read that Mark Pringle was taklling the issue, but had nothing concrete to add.

The new Edge Performance 300 HP Yamaha Apex motor specs are VERY seductive and have demonstrated excellent performance. That said, Steve Henry trailers his aircraft everywhere; so that begs the question; is it really suited to be in a daily driver/cross country aircraft? Time will tell, but I am watching...

On the Rotax front, you can burn Mogas and it uses automotive spark plugs which adds a considerable cost savings component to the overall operational costs.

DeltaHawk is actively offering their Jet A/Diesel 2 stroke 4 cylinder plant with an installation caveat to the experimental market. I believe the current offering is 180 HP w/ turbo and supercharger. Pretty heavy though, I think in the 380lb range; but they have scrubbed those specs from their website.

https://deltahawk.com

I tend to be a 'match it to the mission' guy first and foremost, so If I have to fly like a nervous nellie, because I'm afraid my 70 cubic inch motor that's sweating it's nuts off to do what a 520 cubic inch motor does without without even warming up... well that kinda kills the fun. For me, that's a deal breaker.

Last year I was on may northern pilgrimage with a grower friend of mine. He's a fairly accurate example of today's corn fed big boy American, and as such traveled the whole way up in shorts and a tee shirt, flip flops to boot. I think it was somewhere over Icy Bay that he looked at me, white as sheet... I said hey man, you good? and he replied, I just realized that if everything went to hell in a hand basket right now, you could probably land us ever so gingerly on that liquid ice and I probably still wouldn't make it... 'not 5 minutes' I said finishing off his thought.... (probably worth noting here and now, that he is a techno junkie AND motor head) and at that moment I think he would have had his happy ass out of the plane hugging that antiquated tractor motor if he could have...

High strung motors don't sound high strung because it's cool.... they sound high strung because they are. Ever watch an R-985 split a jug? it belches, farts, and then drives you on home. a stuck valve at 37,570 rpm? I don't even want to know what that sounds like, but if it sounds anything close to what a turbine sounds like when it's eating things... I know I don't want to go there...

Cubes is cubes. If a techno wonder mini mite is whooping an oldie five times it's size, it's because you are not comparing apples to apples. 175 is spot on. You CAN have an O-320 that zips... and you can have an O-320 that does it normalized. What you CAN'T have, is an O-320 that does all that at TSIO-70? (work with me here) weights, because you have to account for the weight of those extra cubes somewhere.

Were it me, if I was building a Valdez, OshKosh, 'Texas, we want stol too', rig, well hell yeah and yee hah too, I'd want a NO2 drinking slingshot that turned from zero to 30,000 rpm right now as well.

Since my fun buggies have been known to carry me over terrain that will NOT give you a second chance without one hell of a fight, I don't want the one that looks good on paper, I want the one that has been good for .... going on a century. Nope, it ain't the lightest. It don't turn the fastest, doesn't make the last tenth of an MPG, but it starts (almost) every time I hit the key, and if it don't, it does when I swing the prop.... that, is my jam.


Your mission may vary.....


Take care, Rob

Good to hear from you Rob.

I’m with Rob on this one. There is no substitute for cubic inches!

UpNorth

I’ve got about 70 hours behind a rotax, both 912is and 914. Besides sounding like a sewing machine I really love it.

The only issue I see is the FAA. Getting these things approved for any legacy aircraft is a nightmare unlikely to happen anytime soon.

JP256 wrote:

WWhunter wrote:Ardent,
Maybe watch the EAA webinar the Randy (RANS Aircraft) had a few weeks ago. In the webinar there is discussion about his trials and tribulations with the 915. I think it is a great designed engine but think there are a few bugs that need to be tended to before it will be the engine it was truly designed to be. RANS no longer sells a FWF kit for the engine from what I understand. My jist from the presentation was, the Titan 340 was less of an issue to stay within engine parameters and is now the recommend power plant.

PS, I'm a Murphy Rebel fan also.

On the other hand, I've heard from several folks that Mark Pringle at Rocky Mountain Kitplanes in Utah (a long-time RANS dealer) has developed a 915iS package installed in a handful of S-20 and S-21 kitplanes built as EABs. Somehow, they've managed to get an intercooler that works to fit inside a cowl that may or may not part of the "factory" firewall-forward kit...

The challenge Randy Schlitter (RANS) was basically one thing: He was having trouble meeting Rotax's very low engine inlet temp limits (<= 50ºC) while still fitting the intercooler inside the cowling. And since RANS is building and selling factory-build S-LSAs, the ASTM standards say they MUST adhere to any limitations that Rotax publishes. With something like 95% of their orders specifying the O-340 engine option (MUCH less expensive than the Rotax 915iS), and given the fact that RANS has more than a 12-month kit backlog, it just got to the point that it wasn't worth spending any more time developing that package.

Makes a lot of sense and very informative posts. The Rebel has an extremely broad firewall, could fit a small radial, so the packaging issue won’t be a problem there. Makes a lot more sense and explains the small package plane (S7 etc) issue, as I was scratching my head at that.

DeltaRomeo wrote:The new Edge Performance 300 HP Yamaha Apex motor specs are VERY seductive and have demonstrated excellent performance. That said, Steve Henry trailers his aircraft everywhere; so that begs the question; is it really suited to be in a daily driver/cross country aircraft? Time will tell, but I am watching...

On the Rotax front, you can burn Mogas and it uses automotive spark plugs which adds a considerable cost savings component to the overall operational costs.

DeltaHawk is actively offering their Jet A/Diesel 2 stroke 4 cylinder plant with an installation caveat to the experimental market. I believe the current offering is 180 HP w/ turbo and supercharger. Pretty heavy though, I think in the 380lb range; but they have scrubbed those specs from their website.

https://deltahawk.com

Yeah, but Steve is running his set up not only for the 300+ HP (pretty well maxed out for gasoline), but also using Nitrous Oxide to boost it above that. It's a "competition only" setup, I think.

I believe that the Yamaha Apex engine itself should be pretty reliable making 150 HP. Going above that starts to move you down somewhat on the reliability curve, but probably not very steeply until you get above 200 HP or so...

The question in my mind – as it always is with an engine that turns faster than the prop – is how reliable is the PRSU at that HP rating? It is notoriously difficult to engineer PRSUs that don't develop some sort of harmonic vibration mode when swinging a propeller at "some" combination of prop/engine/gearbox RPM. (Remember the Subaru and Chevy V-6 conversions that were all the rage for a while? Then the PRSUs started failing right and left, and most of them went back to Lycomings...)

So I'll be sitting on the sidelines a bit, and flying my Rotax for a while longer. Once there's some history with the PRSU they're using, I'd be a lot more interested.

Just wondering how these new Rotax/UL motors like 100LL? In 2003 we finished our Bearhawk with the Landrover v8 and it did not like 100LL for many reasons so taking fuel along on a cross country flight was a pain in the butt and I suspect the same will be true for the Rotax/UL type motors. Premium unleaded gas is readily available in Europe but not so much in the Great Bear Rainforest country. I have found that there is a fair amount of 100LL and regular grade auto fuel around that neck of the woods as long as you can use it in your motor. When you go above 200hp the selection of PSRU's is very limited. We designed and built our own belt drive system and it has worked trouble free for over 2000hrs.My current project is an experimental(amateur built) c175 with the LS3 motor and I am using a redrive from the airboat industry, well proven and reasonably priced

I’ve flown the Rotax 912 on avgas a good deal, in a Rans S6 a long time ago before anyone put anything but Avgas in planes here. It worked just fine, and the engine is certified on 100LL, as is the 915.

This said, the owners of the plane changed oil at short intervals as lead sludge accumulates in the 912 oil when running Avgas, which will be the same for the 915. This is openly discussed by Rotax in their engine manual and I believe they have a maintenance schedule available for running straight Avgas. The engine will happily TBO on Avgas you’ll just be changing more oil and filters.

This said, on the coast on floats we just run marine premium off the boat dock in engines that don’t require 100LL. It’s ethanol free here and really good fuel.

I haven't got any experience of the 915 but I have plenty of experience of the 912.

I'm also not sure comparing the O-320 (160hp in most versions) to the 915 at 140 is really fair.

I've put over 5200 hours on my 912. Its never had a sticking valve, a cylinder off in fact the engine itself has never had any work done to it whatsoever. I know people go on about the high part prices well frankly it doesn't matter as none of the high priced parts have ever failed.

What I have had to replace is consumables and I would include carb rubbers in that. I’ve also had sinking floats , the last time being about 200 hours ago so I got both carbs overhauled and that still worked out cheaper than what previously paid for an overhauled carb for an O-200.

Oil is cheap, spark plugs are cheap and the 600 hour gearbox overhaul is also cheap also. Although I’ve been told my gearbox wont overhaul again. So at 5600 hours I’m simply going to pull the engine and replace it with a second hand engine with about 1000 hours on it.

AVGAS isn’t a major problem you just have to change the oil every 50 hours and the spark plugs every 200 hours. The oil is dirt cheap semi-synthetic and the plugs are only a few dollars each so I just replace them. And as already mentioned when run on AVGAS the sump needs all the lead cleaning out. In fact my airframe and engine is cleared for 10% ethanol which certainly makes things easier.

My experience with conti and lycoming is not very good. In fact my last 6 engines have failed to make TBO. Two of them were factory rebuilds as well. I think they are just junk

In the 915 the fuel consumption is bound to be less than an O320 and I know people keep going on about specific fuel consumption being the same. But in practice its not going to be the Rotax with all its sensors is adjusting the mixture far more accurately than any pilot can with a mixture lever.

The Rotax 915 might have some teething problems but once they get sorted out it will corner the market just like the 912 has for LSA. Anyone for a O-200D? No thanks

You are making time in grade, which is what it will take to make the engine acceptable in the insurance and old codger world.