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912is performance?


markmn

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After talking to a few pilots and reading all the reviews I am starting to think the injected engine may have less performance than the carberated engines.

I have not personally flown the CTLSi yest but the Tecnam seemed a bit down on power. We did not have the same props so were not able to get an exact comparison. Rotax shows the injected engine to have a lower torque rating and thats just how it felt to me. It may have just been the prop though. Wondering what you CT guys are finding?

 

Obviously it will have the fuel efficiency and no carb balancing advantage.

 

Mark

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My Demo airplane is a 2012 CTLS with the Sensenich prop. I just delivered a CTLSI with the Neuform propeller. I have flown in it 8 hours including a 6 hour cross country flight, and found it to have noticeably more performance. I would estimate it's 5 knots faster and a gallon an hour less fuel burn. It certainly climbs faster too. It starts better and is quieter, though it sounds 'beefier'. Two seperate fuel tanks means you don't have to worry about fuel bunching up in one tank while doing pattern work. The CFI who owns the LS and I took both planes up together and confirmed the SI is faster.

Ron

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Im glad to hear that Ron. We did not have like props on the different aircraft so that is likely the issue.

Rotax shows the carberated engine has a higher torque rating than the injected and I was hopful this would no translate

into a lower performance engine.

No doubt all the other benefits of the injected engine make it nicer.

 

Mark

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Fuel injection ensures the optimal mix is give to EACH cylinder in realtime, and adjusts and varys that in realtime as the flight proceeds...Fuel injection DYNAMICALLY does the same thing only on a cylinder by cylinder basis all the time.

 

Well, I think that there may in fact be fuel injection systems that operate like that, but the majority of systems in use in aviation don't - fuel is still pressure fed to a "rail" or equivalent and dumbly goes to individual cylinders via fixed ports. You can see that when leaning when one cylinder invariably peaks first, and it's why effort is made to "balance" injector nozzles.

 

Again, I don't doubt that some modern automotive systems may meter fuel as you describe, I just don't want people to get the impression that that's how it always works.

 

Does anyone have a description/diagram of the new ROTAX system? That would settle whether each cylinder is metered individually or not.

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The problem with comparing is all things are not equal. I would bet my 2006 SW and Ed's SW are faster than the CTLSi right off the container and I have been around all these and would be willing to put money on the line.

The reason things are not equal, but could be changed to make a difference; prop rpm at WOT (HUGE difference in performance), weight ( a150 lb. pilot verses two people (400 lbs) or full fuel (214 lbs) verses only 10 gal (63 lbs) total). Weight is a HUGE factor for the LSA (CT) top speeds and climb. The CTLSi probably weighs more than 60-80 lbs more out of the box than our planes. Could or should the CTLSi be faster, yes it could be once things were made equal, but not out of the right out of the container. FD doesn't set it up or fine tune it like we do. The CTLSi also needs to run at higher rpms than the 912ULS (that's published too).

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Hold those Ha's there is a ton more to come.

 

I've already talked to Rotax about the specs and operating parameters. Interpretation and translation isn't what it should be. Public classes on the new engine will start in approximately June as soon as they get a Heavy Maint. Manual published. The distributor class was just held this last week in the Bahamas. It is a completely different engine and different requirements. Not any A&P will be able to work on them much farther than oil and plug changes without a donegal which is going to cost a pretty penny with 2-3 different levels, not to mention people will absolutely need a Rotax class on this engine.

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Probably a dumb question, but when I was studying for the written exam the way to lower engine temperatures in the air cooled engines was to run rich. I'm assuming that the Si is running leaner than the ULS to get the better fuel economy, could this lead to higher engine temperatures? I know the heads are liquid cooled but still might go up?

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Dan,

 

Yes, excess fuel cools the engine, hence sufficiently ROP keeps thing cool.

 

But "lack of fuel" (LOP operations) can keep thing cool as well.

 

Remember 75° ROP is exactly the same temp as 75° LOP (EGT). You can find many pilots and mechanics who somehow think LOP is inherently "hotter" than ROP, which is logically and practically untrue.

 

The danger can come from leaning back from ROP, but not leaning "enough". That can lead to high CHT's and combustion chamber pressures which can lead to a preignition/detonation event. I can come up with a link to some good "Pelican's Perch" articles on the topic if you would like.

 

Modern fuel injected engines are designed to run LOP when able - that's where the efficiency gains come from.

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Are you joking? Fuel injection is not just more fuel effiicient. Computerized balancing of fuel and air also increases overall horsepower and torque. Carbs are archaic. Do you still see carbs on ANY race car? Laughing. The CTLSi will be at least 20% faster than the older 912 carbed little brother. Sonoma Flight center is getting the correct data.

 

I have a friend with a drag car that does nine second quarter mile passes, in a 3800lb car with carburetors, just like every other car in his class. Fuel injection does NOT mean more power. It usually means easier tuning and better efficiency across the entire RPM range. It does not necessarily imply greater peak horsepower.

 

20% faster, really? A regular CT will do 120 knots, so you are saying a CTLSi will do (1.2 * 120) = 144 knots straight and level? Are you smoking crack? How do you suppose this 144 knot wonder is able to be certified as an SLSA?

 

You constantly come in here and just launch these torpedoes of BS that are verifiably false, in spite oe people constantly showing you exactly how and why they are wrong. I don't understand your mindset, frankly. I'd think you'd get tired of being made a fool of.

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Andy,

 

bigs claims at least 20% faster lets see it takes 8 times as much power to double your speed...

 

Not to take away from your general point, but I thought it was 4 times the power to double speed (22).

 

I remember the power required increases as the square of the increase in velocity.

 

Right?

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We have already determined that I am now too old to do math :(

 

 

So going more from pure gut feeling I bet it would take 180hp lyc IO360 or more to get in the 150kt ballpark.

 

I also believe you could get close to those speeds above FL140 with a 914.

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We have already determined that I am now too old to do math :(

 

Not to worry.

 

My mom always said she should write a book called "Esta Benson On Everything But Math".

 

She never did, so the title is still available. With the obvious name change, of course!

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Kinetic energy is the energy of motion. The formula for Kinetic energy is 1/2 M x V squared. That is one half of the mass of an object times the square of the velocity.

 

Think about it. If you are going 10kts then that is a factor of 100 x 1/2 of the mass. That is how much energy of motion you must create. If you are going 12kts then that is a factor of 144 x 1/2 the mass. In this case, based on a constant mass, for a 20 percent increase in speed (2kts) it will require a factor of an additional 44 multiple of energy.

 

Basically, a lot more energy required for a little more speed.

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