Cessna 150 Rotax Conversion

You missed the point. The poster I responded to was claiming efficiency based on horsepower per displacement. HP per displacement is irrelevant unless you’re racing in a class limited by displacement. I stated earlier that I have no doubt that the rotax clearly excels in HP/weight and fuel efficiency. In an aircraft, however, reliability trumps everything. When there is enough data to prove the toy engine to be more reliable you will be able to win me over. When you come up with that conclusive data, let me know.
 
So what is the love/hate relationship with the Rotax engines here sorry I don't follow this much... But, if you could give a 150 some more ponies other that a O-320.... why not?
 
Call me biased but I think the Rotax 914 is an amazing engine. 115hp and I have a real 4 seater at high DA. Uses no oil and you only have to burp the inline if you check the oil and the level is low.
I have had to do this once in 9months and 75h ownership.

I think the major issue with putting them into a C152 is the airframe weight but obviously they have thought about this. I think overhaul cost is probably similar to a ‘traditional’ engine.
 
Ventucky Red said:
So what is the love/hate relationship with the Rotax engines here
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The only thing I can think of is people who have only recently heard of Rotax, or think they only make 2-stroke engines, or are unaware that the 912 series has been in production and has seen continual improvements and upgrades since 1984 -- 35 years ago. Some of them may also be shocked to learn that women can now vote, and Dewey actually lost the election.
 
Ventucky Red said:
So what is the love/hate relationship with the Rotax engines here sorry I don't follow this much... But, if you could give a 150 some more ponies other that a O-320.... why not?
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I used to own a stock 150 with the 100hp Continental. It could barely get out of its own way. Two male adults and you were overgross with full fuel--not even close. Hot days were sporty close to max gross. I don't know the price of the rotax stc but I bet its way more than an overhaul of the Continental O-200 or even a factory new O-200. So the rotax doesn't get you any more hp but it is newer technology and with a variable pitch prop, more efficient.

I've got a lot of time towing gliders with a 180hp (O-360) Cessna Aerobat. It's a rocket ship compared to a stock 150. I always thought a O-320/150hp Cessna 150 would make a sweet ride in a personal 150 if it had a higher max gross. I don't see the benefits out weighing the cost of converting a continental to a rotax installation for no net gain in hp.
 
Witmo said:
I don't see the benefits out weighing the cost of converting a continental to a rotax installation for no net gain in hp.
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The only real sweet spot I could see there is refurbing old 150s with run-out or damaged engines (dirt cheap to buy) for use as trainers. Yeah, the engine swap is definitely going to cost you, but the fuel and maintenance savings could pay off well over a 2K hour TBO... if you run mogas. Just the gas will save you several bucks per hour -- figure even if your consumption is the same, you're paying a buck or two less for it. Plus, if you're not burning leaded gas you have 3 liters of oil every 100 hours -- and none in between, including MX downtime for more frequent oil changes. It could add up.

Or maybe there's an untapped market in Europe that we're not seeing.
 
DaleB said:
Dewey actually lost the election.
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Since when.
Deweytruman12.jpg
 
MBDiagMan said:
reliability
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I cannot find the link now, but another rotax thread that I had started someone posted reliability numbers published from the genuine source, it was either something government based or from aopa.. it showed that rotax, Lycoming, Continental were all basically equal in reliability. That's pretty incredible given that the rotax are often placed in experimental aircraft and may face more abuse than what a typical continental in a bonanza does.. it also showed near parity between continental and Lycoming which dispelled some of the myths I've heard of continentals being poor power plants compared to Lycoming


I'm not saying that rotax is the ultimate end-all-be-all, but what I am saying is that it's nice to see a manufacturer pushing out modern power plants instead of the same sand and diecast power plants for the last 80 years
 
Capt. Geoffrey Thorpe said:
I suspect that it's mostly weight and not running pig rich and ****ing fuel out the tailpipe like so many like to do with the automobile / sewing machine derived engines.

25% seems optimistic to me.
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Wouldn't the higher engine RPM also help squeeze more HP from the displacement, and then less displacement is less fuel? Those are high revving engines geared down to the prop.
 
MBDiagMan said:
Even if it did, in aviation, I am not willing to trade reliability for efficiency. Not while MY family is flying in it.
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Producing trustworthy data on aviation engine reliability is black art at best. But what data I've been able to find seems to suggest the Rotax 912/914 series are for practicable purposes about as reliable as anything Lycoming or Conti ever made. Whether that data is valid or not is debatable of course.

But one thing that isn't debatable is that a pilot who chooses to fly a piston single engine aircraft while looking down his nose at another brand of piston engine used in single engine aircraft while talking about the 'safety of my family' brings up mental images of that guy rearranging the deck chairs of the Titanic. :rolleyes:
 
Witmo said:
I used to own a stock 150 with the 100hp Continental. It could barely get out of its own way. Two male adults and you were overgross with full fuel--not even close. Hot days were sporty close to max gross. I don't know the price of the rotax stc but I bet its way more than an overhaul of the Continental O-200 or even a factory new O-200. So the rotax doesn't get you any more hp but it is newer technology and with a variable pitch prop, more efficient.

I've got a lot of time towing gliders with a 180hp (O-360) Cessna Aerobat. It's a rocket ship compared to a stock 150. I always thought a O-320/150hp Cessna 150 would make a sweet ride in a personal 150 if it had a higher max gross. I don't see the benefits out weighing the cost of converting a continental to a rotax installation for no net gain in hp.
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That Aerobat was a hoot to fly.
I have my doubts about the cost effectiveness of the STC, but my experience with the Rotax powered birds down there in Boerne was all positive.
 
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Todd82 said:
Wouldn't the higher engine RPM also help squeeze more HP from the displacement, and then less displacement is less fuel? Those are high revving engines geared down to the prop.
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More power from the displacement, but that does not lead to less fuel consumption. Each cylinder displaces less per stroke, but you have more strokes per minute - power comes from the fuel, to reduce fuel consumption you have to make the use of your fuel more efficient.

To reduce fuel consumption you need to change one of the following:
Reduce unburned fuel - not running rich
Reduce heat loss to the cylinders - this is where the big cylinders with a smaller surface to volume ratio have an advantage.
Reduce heat loss out the exhaust - higher expansion (compression) ratio, optimizing spark timing for the operating conditions, etc.
Reduce pumping losses - running at a higher manifold pressure, reducing losses through intake / exhaust.
Reduce mechanical friction.
A lot of other things done in the auto world (shutting off at traffic lights, hybrid, etc.) don't really work for aircraft that tend to run at constant power output.
 
I wonder when you factor in the cost of maintaining the wobbly prop if this aircraft has lower running costs than the o200 powered variant.

If you fit a wobbly prop on a rotax then there is no space for a vacuum pump. Hence the Venturi. I think they should drop this and fit a G5.
 
Capt. Geoffrey Thorpe said:
More power from the displacement, but that does not lead to less fuel consumption. Each cylinder displaces less per stroke, but you have more strokes per minute - power comes from the fuel, to reduce fuel consumption you have to make the use of your fuel more efficient.

To reduce fuel consumption you need to change one of the following:
Reduce unburned fuel - not running rich
Reduce heat loss to the cylinders - this is where the big cylinders with a smaller surface to volume ratio have an advantage.
Reduce heat loss out the exhaust - higher expansion (compression) ratio, optimizing spark timing for the operating conditions, etc.
Reduce pumping losses - running at a higher manifold pressure, reducing losses through intake / exhaust.
Reduce mechanical friction.
A lot of other things done in the auto world (shutting off at traffic lights, hybrid, etc.) don't really work for aircraft that tend to run at constant power output.
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Forgot to look further outside:
Lower propeller RPM can be more efficient along with variable pitch prop.
Cooling drag - this can be pretty significant - not directly related to the engine, but if you are coming up with an STC, taking the time to improve under cowl air flow is a win-win.
 
Witmo said:
I've got a lot of time towing gliders with a 180hp (O-360) Cessna Aerobat. It's a rocket ship compared to a stock 150. I always thought a O-320/150hp Cessna 150 would make a sweet ride in a personal 150 if it had a higher max gross.
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I have flown a 150/150... basically a 172 and I get that.... fun little scooter to fly... have even heard some urban legends of the 172 wing being fitted to them... what I don't get is why folks around don't like the ROTAX engines. From what I understand the are pretty bullet proof at least in the marine, snowmobile, and ATV applications... is that not the case with aviation?
 
DaleB said:
The only thing I can think of is people who have only recently heard of Rotax, or think they only make 2-stroke engines, or are unaware that the 912 series has been in production and has seen continual improvements and upgrades since 1984 -- 35 years ago. Some of them may also be shocked to learn that women can now vote, and Dewey actually lost the election.
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\

And the Doobie Brothers broke up....:D
 
Hi everyone.
One important fact that is not being mentioned, and I do agree that the Rotax has it's uses, is overheating. I've flown Rotax with the latest and greatest packages but if you have a long taxi with the wind behind you in temps in the 80F or above you may as well be prepared to stay on the ground for a while. Everyone , Evektor, Czech, Flight Design.... will overheat on you. You can stay on the ground and watch the rest take off, unless you are willing to take a chance and take off in an unsafe condition.
Until they can fix that problem that plant is not a good choice in an acft, in my opinion.
 
bluesideup said:
Hi everyone.
One important fact that is not being mentioned, and I do agree that the Rotax has it's uses, is overheating. I've flown Rotax with the latest and greatest packages but if you have a long taxi with the wind behind you in temps in the 80F or above you may as well be prepared to stay on the ground for a while. Everyone , Evektor, Czech, Flight Design.... will overheat on you. You can stay on the ground and watch the rest take off, unless you are willing to take a chance and take off in an unsafe condition.
Until they can fix that problem that plant is not a good choice in an acft, in my opinion.
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Surprised to hear that. Mine has never, ever, overheated. Not even close.
 
Capt. Geoffrey Thorpe said:
Surprised to hear that. Mine has never, ever, overheated. Not even close.
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Nor has mine. The Rotax in my CTLSi runs hotter than the Rotax in my AeroTrek, but that's due to the cowling design - not the engine. The difference is that the AeroTrek has an oil cooler door that's adjustable from the cockpit.
 
bluesideup said:
Hi everyone.
One important fact that is not being mentioned, and I do agree that the Rotax has it's uses, is overheating. I've flown Rotax with the latest and greatest packages but if you have a long taxi with the wind behind you in temps in the 80F or above you may as well be prepared to stay on the ground for a while. Everyone , Evektor, Czech, Flight Design.... will overheat on you. You can stay on the ground and watch the rest take off, unless you are willing to take a chance and take off in an unsafe condition.
Until they can fix that problem that plant is not a good choice in an acft, in my opinion.
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The Apollo Fox I was flying down at 5C1 had that problem initially, too, but it was more a problem with the cooling design than the engine. The designers were in cooler temperatures and didn’t set the plane up for Texas heat, but after we got permission to move the oil cooler the plane was fine. I think it’s a design issue, not the engine’s fault.
 
Hi.

Capt. Geoffrey Thorpe said:
Surprised to hear that. Mine has never, ever, overheated. Not even close.
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I am not sure where you are flying, or what, but there was more than one time that I had to abort the takeoff due to hi temps even in acft with the Sport package, it's a fact.
Just recently, in a 27C day, 600 Ft MSL, and about 3000 Ft taxi do the a very quick run up and waited about 30 sec for an acft on final, estimated total time ~4 minutes, and we did not wait for the temps to get to 122 before we started taxiing, and we had to abort, shut down and wait and taxi back, and this was in Sport package with larger radiator....
If you can manage to take off, before it overheats, it will fly and stay within the safe limits, but in the newer models with computer controlled, where the errors get logged and get all these safety alerts, you will be violating factory recommendations and void the warranty, and maybe worse, end up with a blown engine.
I have yet to see one Rotax that does not do that.
On the other hand the C162, O200, I do not recall having to ever abort a take off due to overheat.
 
I had a car like that in college. It cooled down when I drove it faster. I assume a rotax plane is similar? Maybe higher idle RPM = lower oil temp?

If only they could find a way to put a giant radiator fan on the nose of the thing. :D
 
schmookeeg said:
I had a car like that in college. It cooled down when I drove it faster. I assume a rotax plane is similar? Maybe higher idle RPM = lower oil temp?

If only they could find a way to put a giant radiator fan on the nose of the thing. :D
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Reminds me of air cooled VWs higher rpm kept engine cooler, low rpm or lugging on hills caused them to run hot
 
OK, the overheating caught my attention because I'm saving up to buy an LSA. A bunch of Googlin seems to indicate that it depends on the mounting. Some manufacturers rarely have the problem, others have it commonly.

(That's judging from type forum posts on the Web.)

The type of coolant makes a big difference as well, but I couldn't find a consensus. But the most common fixes either involved more venting or changing coolant.

Hmmm.
 
Stephen Poole said:
OK, the overheating caught my attention because I'm saving up to buy an LSA. A bunch of Googlin seems to indicate that it depends on the mounting. Some manufacturers rarely have the problem, others have it commonly.

(That's judging from type forum posts on the Web.)

The type of coolant makes a big difference as well, but I couldn't find a consensus. But the most common fixes either involved more venting or changing coolant.

Hmmm.
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If you think about it a lot of that has to do with where a bunch of those planes are being manufactured. A designer near the Alps just doesn’t have the mindset that a Texas company might have with regards to cooling. The problem isn’t the engine.
 
RyanShort1 said:
If you think about it a lot of that has to do with where a bunch of those planes are being manufactured. A designer near the Alps just doesn’t have the mindset that a Texas company might have with regards to cooling. The problem isn’t the engine.
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Yes, the engine itself is fine.

And as far as overheating goes, I've seen plenty of posts, here and elsewhere, about Lycomings and Continentals doing the same thing in some aircraft. It all boils down to ensuring that the cooling air makes it in.
 
Hi everyone.
I am not sure why some people think the engine is Not the problem?
If you have 5 / all manufactures of LSA that are having issues the engine Is the problem. Ca it be made to work? Maybe, but if you pay $200K for an acft you should get something where you can fly it, not sit on the ground and watch 50 years old acft do touch and gos, departing...

Stephen Poole said:
The type of coolant makes a big difference as well, but I couldn't find a consensus. But the most common fixes either involved more venting or changing coolant.
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I can confirm that the type of coolant makes No difference, and "more venting" you cannot do much about in an SLSA you can try to play with it in an EAB... and I have read some reports where some say that they made them work in some ELSA, but that is not the point.

If the engine overheats the Engine Is the problem, the fact that someone else may be responsible for it does not change that fact that the engine is what is causing the problem.
Maybe if you are AlaskAustria and you fly in the 70F and below you are OK, but then you should have the limitations placed on it.
 
bluesideup said:
Hi everyone.
I am not sure why some people think the engine is Not the problem?
If you have 5 / all manufactures of LSA that are having issues the engine Is the problem. Ca it be made to work? Maybe, but if you pay $200K for an acft you should get something where you can fly it, not sit on the ground and watch 50 years old acft do touch and gos, departing...


I can confirm that the type of coolant makes No difference, and "more venting" you cannot do much about in an SLSA you can try to play with it in an EAB... and I have read some reports where some say that they made them work in some ELSA, but that is not the point.

If the engine overheats the Engine Is the problem, the fact that someone else may be responsible for it does not change that fact that the engine is what is causing the problem.
Maybe if you are AlaskAustria and you fly in the 70F and below you are OK, but then you should have the limitations placed on it.
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It’s not the engines fault unless every install overheats. Chevy put millions of 327s in lots of different cars with no heating problems, but ask anyone with one in a corvette if they have had overheat problems. Cooling design issue not engine. There are a lot of Rotax installs that work great, there are some that have really bad cooling designs.
 
Never had or heard of anyone else having overheating issues with the Rotax 912 in the Tecnam Eaglet (P92) when I instructed in them. This includes a busy summer of touch and go practice with near 100° surface temps.
 
bluesideup said:
Hi.


That is one case in one plane. I've flown in many SLSAs, you can add the Remos to the bunch, and they all have overheating problem.
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Not all. You may have flown quite a few but I doubt you've flown all of them. Have you flown the RV12? There are lots of them in service and vansairforce.net is a very active forum of owners and builders. A search there of overheating reveals that almost none of them have had over heating issues. For the few that did, Vans redesigned the exhaust system to move the muffler and the problem seems to have disappeared.

Its not an engine problem, its an airframe problem, its both. Use that engine in an airframe with a poorly designed cooling system and cooling can be a problem. Design the cooling system right and there is no issue. Or use a different engine which won't have the same cooling requirements but will likely also be heavier and eat into an already limited useful load. No such thing as a free lunch.
 
bluesideup said:
That is one case in one plane. I've flown in many SLSAs, you can add the Remos to the bunch, and they all have overheating problem.
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There you go. It's not a Rotax problem, it's an SLSA problem.
SLSAs have the problem, EABs don't.
 
bluesideup said:
Hi everyone.
One important fact that is not being mentioned, and I do agree that the Rotax has it's uses, is overheating. I've flown Rotax with the latest and greatest packages but if you have a long taxi with the wind behind you in temps in the 80F or above you may as well be prepared to stay on the ground for a while. Everyone , Evektor, Czech, Flight Design.... will overheat on you. You can stay on the ground and watch the rest take off, unless you are willing to take a chance and take off in an unsafe condition.
Until they can fix that problem that plant is not a good choice in an acft, in my opinion.
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I’ve got to disagree here. I’ve flown the CT, Remos, Sky Arrow, RV-12 and the Sling. Never had an issue. Flew the first two in Florida and experienced 90+ degrees with long warmups and didn’t have overheating issues. NOW say that about my Tiger (Heat issues) and I’d agree with you 100%.
 
We fly an RV-12 with the original design muffler (a little too close to the radiator) and we never — not once — have had it overheat. There are a couple other on the field, I know for certain one hasn’t had any issues and I haven’t heard anything from the other group. I flew 7 Young Eagles yesterday, with temps for the last few on the 90s. It gets plenty hot here in summer. Overheating problems are not the fault of the engine... it’s either design or implementation, like kinked hoses or a radiator poorly placed or partly blocked.

Not to state the obvious, but any engine can overheat when it’s not properly cooled.
 
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