912is performance?

[FlyingMonkey]

If the injected engine were the same weight as the S/ULS models, the choice would be pretty easy. But the significant weight penalty of the new engine makes the benefit much murkier. Power is the same or close enough to not matter much, and the fuel efficiency argument is counterbalanced by increased weight and cost. The few thousand dollar difference in cost will buy a lot of mogas, after all.

[Jim]

If the injected engine were the same weight as the S/ULS models, the choice would be pretty easy. But the significant weight penalty of the new engine makes the benefit much murkier. Power is the same or close enough to not matter much, and the fuel efficiency argument is counterbalanced by increased weight and cost. The few thousand dollar difference in cost will buy a lot of mogas, after all.

 

You nailed it. The injected engine is nice, but for those of us that have to earn our aviation dollars day-to-day, I don't think it's worth it.

[Jim]

13lbs for the better engine? I find it weird people get hyped over these small weight differences when the pilot and passenger dwarf all such comparisons. FD designs the CT to fly with an 80hp Rotax which more than meet the minimum flight power needed to fly the plane. The CT climbs at over 1000fpm, the 912i even faster. What more do you need?Aside from the ECU and obvious sophistication of the entire layout of the 912i. Here are some basics from BRP/Rotax.Fuel consumption savings 21 % at 5.000 rpm at 5.000 ft compared to Rotax 912ULS and CO2 emissions up to 70 % lower. The argument over whether the 912i produces more power or torque than the older 912ULS at the same horsepower rating is an infinite loop.Those who have flown the CTLSi know the plane is more responsive, climbs faster, and starts fare more easily than the older planes.

"CO2 emissions up to 70 % lower" Really? Got a cite? Got a link?

[Ed Cesnalis]

13lbs for the better engine? I find it weird people get hyped over these small weight differences when the pilot and passenger dwarf all such comparisons. FD designs the CT to fly with an 80hp Rotax which more than meet the minimum flight power needed to fly the plane. The CT climbs at over 1000fpm, the 912i even faster. What more do you need?

 

Aside from the ECU and obvious sophistication of the entire layout of the 912i. Here are some basics from BRP/Rotax.

 

Fuel consumption savings 21 % at 5.000 rpm at 5.000 ft compared to Rotax 912ULS and CO2 emissions up to 70 % lower. The argument over whether the 912i produces more power or torque than the older 912ULS at the same horsepower rating is an infinite loop.

 

Those who have flown the CTLSi know the plane is more responsive, climbs faster, and starts fare more easily than the older planes.

 

There is no infinite loop, you cannot manufacture additional horse power or speed in your imagination and claim it as fact.

• The 912iS does not have more power - there is no mod to produce more power.
  
• The CTLS is less responsive - due to longer moment arms.
  
• The CTLSi does not climb faster - that requires less weight but its heavier, or more power but it has no additional power, or less drag but it has the CTLS air-frame.
  
• The CTLSi does not f[l]are more easily - that would be the CTSW with the shorter moment arm.
  

[Tom Baker]

gbigs, most CT's here in the states are 100hp, and not 80hp. The CTLSi, CTLS and CTSW's all have 100hp. The injected engine has less torque that than the Bing equiped engines per Rotax. How you think that it can climb faster with the same HP and less torque is beyond me. You are correct that the fuel injection system is more sophisticated with reduced fuel consumption, but that alone doesn't justify the extra cost. Flight Design says it cost $12,800 and is just under 22 pounds extra in the CTLS. A 20% reduction in fuel would amount to 2000 gallons over 2000 hours at $4 a gallon that is $8000 spread out over TBO. The CTLS and the CTLSi are the same airplane except for the engine, with the CTLSi being over 20 pounds heavier at any given time I don't see how it could be more responsive. I will agree that the new injected engine should start easier.

[Ian]

Far be it for me to confuse the discussion with facts but Rotax themselves don't seem to claim any increase in HP for the injected version - not sure where the weight increases being quoted come from but as far as I can see the "basic" increase in weight is 15.7 lbs

 

ULS i data here: http://www.flyrotax.com/enginesImpressum/product-rangeImpressum/InjectedImpressum/912-iS-100hpImpressum/ENGINE-DATA-PERFORMANCE.aspx

 

ULS data here: http://www.flyrotax.com/enginesImpressum/product-rangeImpressum/carburetedImpressum/912-100hpImpressum/engine-data-performance.aspx

 

gbigs says 13 lbs, Tom Baker says "over 20 lbs"

 

All I can add is I'm very, very happy with my non-injected CTLS and there is no way I would justify trading it in just for the supposed benefits of fuel injection!

[Tom Baker]

My figure of under 22 pounds came from the original Flight Design press release. This is for the system installed in a CTLSi including airframe changes for the installation.

[FastEddieB]

Isn't a more robust (and heavier) electrical system required?

 

Legitimate question, since I don't know but kinda remember hearing that.

 

It could account for the difference between the increased engine weight and the larger overall increase.

[Ed Cesnalis]

Rotax has not published anything specific to torque or HP in regard to the different engines.

 

HP is not determined by debate. You do not debate you simply repeat statements.

 

Rotax has published torque and HP curves that's how we know the the 912iS has less torque and matching HP.

[sandpiper]

I just looked at the FD website. It states the CTLSi has a weight increase over the CTLS of "less than 22 lb".

 

In the spec chart it shows the empty weight of the CTLS as 790# and the CTLSi as 810.

 

So, until FD changes this I would say the weight penalty is between 20 and 22#.

 

6kg, last I checked, is about 13.2# which falls short of FD's stated 20-22#.

 

They show max speed for both planes to be the same but they do show the CTLSi as having one more gallon of fuel (due to the header tank) and noticeable increased range due to more efficient use of fuel.

[Jim]

Ask your wife if carrying 22 pounds less baggage is "insignificant"

[Doug G.]

I believe the extra weight comes from the fuel system - header tank & fuel valve + the extra tubing it takes. (I also seem to remember the auxilary alternator was necessary to run the injection pump - although I am not certain of this.) This would mean there would be more weight in the CTLSi than would be indicated by the increase in the engine itself.

[FastEddieB]

Ask your wife if carrying 22 pounds less baggage is "insignificant"

 

That's hilarious.

 

I just posted to the Sport Pilot Talk website how Karen and I had to pack for our Page trip:

 

http://sportpilottalk.com/viewtopic.php?f=3&t=2727&p=22500#p22500

[Sonoma Flight Center]

Ask someone who works for Rotax about the 912IS engine. It's a huge improvement over the carb engine, day and night. Fly a CTLSI and you will be impressed, the difference is very noticeable. When you prime the oil system, the SI engine takes a lot more are strength to turn the prop, probably due to more compression. Start one on a cold day, big diff. My demo CTLS has a larger diameter Sensinich propeller than the CTLSI with the Neuform propeller. Sometmes the engine will get hot on warm days with a performace climb. When I picked up the brand new CTLSI in North Las Vegas, it was a 90 degree day, full fuel and over gross, climb out was smooth and engine was cool. I was flying at 8500 feet 4.1 GPH true airspeed was 127 knots. The CT is a way better match with the injected engine, power trim and two fuel tanks. Thats why all the last 25 FD CT orders are fuel injected. Nobody is ordering the carb engine. Fly one when you get a chance, it's a quantum leap no bull. If you can afford one great. If not the CTLS or the CTSW is still heads and shoulders above everthing else. Quit all the crap. In high school it was "run what you brung", same goes now. There are to many wonderful things to chime in about. We are very lucky to do what we do. Get there how ever you get there, don't forget the journey is what's important. Ron

 

[Roger Lee]

"If you can afford one great. If not the CTLS or the CTSW is still heads and shoulders above everything else. Quit all the crap. In high school it was "run what you brung", same goes now. There are to many wonderful things to chime in about. We are very lucky to do what we do. Get there how ever you get there, don't forget the journey is what's important. Ron"

 

 

Hear Hear

[Dan Kent]

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.

 

Been away from the forum for a few days.

 

Eddie,

I think what your telling me is that my carburator 912 is probably running rich of peak, and the injected version is probably running lean of peak, so their temperatures are probably about equivalent. Make's sense.

[Ed Cesnalis]

Eddie and Dan,

 

You guys are focused on detail when there is a far larger issue here.

 

First a disclaimer, there are some here who maintain that the bing carb's main fuel circuit does not gain control of the mixture at high altitude and that the needle circuit still comes into play and does some leaning. For the sake of simplicity I'll address the bing's limited leaning as designed.

 

At my normal cruise, 10,000' my throttle is wide open and my main circuit controls the mixture and the main circuit is a rich / fixed setting. There is no leaning to a temp ROP or LOP instead the carb is supplying more fuel in the mixture than can be used, by a meaningful amount.

 

In my WOT condition a lot of fuel is wasted or 'used for cooling' this doesn't mean that the mixture is going to effect oil temps or CHT, it will of course effect EGT.

 

To allow your bing to lean as designed you have to retard the throttle so that the needle circuit controls the mixture. The adjustment is accomplished by pressure changes and to think it can target a specific temperature so many degrees ROP doesn't make sense to me. Nothing reads my EGT gauge to adjust to a ROP or LOP temp, its merely a crude adjustment.

 

My guess is the 912iS is efficient because it can lean to targeted EGTs regardless of throttle setting where the carbs can only lean, by design in a given throttle setting range. This range that is capable of leaning cannot be used above 7,500'DA if you want to access 75% or if 75% isn't available all available power.

[Ed Cesnalis]

...the SI engine takes a lot more are strength to turn the prop, probably due to more compression. ...

 

Ron,

 

Countless wild claims have already been made about 912iS performance, I can understand your excitment but it is best to limit claims to reality. Look at the charts from the Opperators Manuals below and you can see the compression is lower not higher.

 

http://flyrotax.com/...okus/d05183.pdf

 

 

http://www.flyrotax....okus/d05487.pdf

 

[chanik]

And really the ratios are identical. Same stroke, bore and volume which defines the CR. They just rounded in one chart and not the other. There is no magic with injection, it just manages to lean much better than the carbs which Rotax biases to be exceptionally ROP so they have lots of margin for bad fuel and poor cooling using the quite wasteful practice of evaporating fuel for extra cooling. All IC engines basically follow this chart in fig 2 http://www.diversiorum.org/sape/pilotage/Engines/index.html The only difference is the liquid cooled heads suppress the CHT from these values given for an air cooled Lycoming.

peak EGT is roughly ideal stoichiometry or 14.7:1 air/fuel ratio by mass. Maximum power and Cylinder heating is 50deg ROP, about 12.6 AF ratio and best economy is 50 LOP with ~15.5 AF ratio.

Even on #1 needle position I figure I'm still ROP by about 70 Deg and that's on Mogas. 100LL would be even richer. I do have about 15% less fuel burn then what I recorded on #3 needles though so I already reap most of the benefit that the injected system would provide and I'm much better off when climbing over the Sierras which I do frequently.

[Sonoma Flight Center]

 

 

Ron,

 

Countless wild claims have already been made about 912iS performance, I can understand your excitment but it is best to limit claims to reality. Look at the charts from the Opperators Manuals below and you can see the compression is lower not higher.

 

http://flyrotax.com/...okus/d05183.pdf

 

 

http://www.flyrotax....okus/d05487.pdf

 

Eddie, Have you flown a Fuel Injected CT yet? The truth is in the flight not spec's.

 

 

[Ian]

Eddie, Have you flown a Fuel Injected CT yet? The truth is in the flight not spec's.

 

Completely agree - it would be most instructive for someone to do an accurate set of test flights and publish the results - so far the reporting on the CTLSi is largely heresay - what's needed is for an impartial tester to do a controlled set of tests - in the UK each year for the revalidation of the EASA Permit to Fly a CAA accredited test pilot does such a set of tests - so before long there should be some real data available.

[Ed Cesnalis]

Kurt,

 

A rounding error, makes sense I didn't think there was a compression ratio change.

 

I think the gross ROP bias is because the leaning method is not precise and Peak temps need to be avoided so a gross amount of margin is needed.

 

Ron,

 

Flying is believing on some issues but not things like hp, torque, compression, extra speed and climb without additional hp, ...etc.

 

As Kurt pointed out the engines have the same bore, stroke and volume, therefore the same compression ratio, its just not subject to a test flight.

 

You point at new sales as proof of your point, but if your sales pitch over sells the FI then you could be the reason for all FI motors on your new sales.

 

There really isn't a big need to sell me or anyone on the benefits of FI these benefits are already well accepted. It crosses the line when the benefits are enhanced with things like power, speed and climb differences that aren't there and when the benefits are sold as having no downside.

[sandpiper]

A lot of the discussion isn't about the merits of the new engine, it's about the attitude of a certain poster and that his facts are mostly wrong.

 

If I was buying a new light sport, it would be the CTLSi. Why? Because I like having the latest technology and I like the new fuel system with tank selection and the header tank. I am sure I would also be able to tell the difference at the controls. The difference in weight between the LS and LSi could easily be made up by reducing fuel on board to equal the range of the LS. I seldom carry more than 25g anyway.

 

But, I have a perfectly good plane. If I used a plane as part of my business like several of our posters do, then I would probably have an LSi on order.

[S3flyer]

Ron, given you're a dealer and should have access to both a CTLS and CTLSi, you're in a perfect position to provide a comparison. The test would be simple. Fill both aircraft with full fuel, remove all cargo to set a base weight then go out for a simple 1 hr test flight with each plane:

 

* Record conditions (temperature, winds, runway, Take-off weight including pilot, etc)

* Time and/or measure take-off roll

* Once out of the pattern at 1000' AGL, time a climb to 6000' AGL using best climb

* Do simple speed tests at 6000, 5000, 4000, 3000, 2000, 1000 AGL at 5000 to WOT in 100rpm increments

* Dump the Dynon EMS data for both flights

 

Post the results.

[Ed Cesnalis]

Ron, given you're a dealer and should have access to both a CTLS and CTLSi, you're in a perfect position to provide a comparison. The test would be simple. Fill both aircraft with full fuel, remove all cargo to set a base weight then go out for a simple 1 hr test flight with each plane:

 

* Record conditions (temperature, winds, runway, Take-off weight including pilot, etc)

* Time and/or measure take-off roll

* Once out of the pattern at 1000' AGL, time a climb to 6000' AGL using best climb

* Do simple speed tests at 6000, 5000, 4000, 3000, 2000, 1000 AGL at 5000 to WOT in 100rpm increments

* Dump the Dynon EMS data for both flights

 

Post the results.

 

Which ever aircraft has the flatter pitched prop will win all categories here. If you introduce enough variables and resulting error you can end up proving the dynamometer wrong. That won't buy you anything but support for wild claims.