2 engine Jabiru

[Bruce Tuncks]

Gosh, 40 L/hr  is what a Lancair 360 does for 190 knots. I guess the retracts help with the Lancair but the Lycoming is a lot bigger engine than the Rotax.

 

 

[Thruster88]

Gosh, 40 L/hr  is what a Lancair 360 does for 190 knots. I guess the retracts help with the Lancair but the Lycoming is a lot bigger engine than the Rotax.

 

Downunder and Bruce, The 40L/hr for the lycoming 0-360 would be cruise power

 

I liked the 915.....until I saw the fuel consumption figures.

 

In a nutshell...something like a 50% gain in power for a 100% gain in fuel usage....

 

Reports of 40lph flat out....and 30 something in cruise.

 

I don't consider 40 lph for 140hp too flattering...

 

It baffles me how such a high tech engine can have such poor fuel consumption compared to the non-boosted 912is...

 

 

 

Gosh, 40 L/hr  is what a Lancair 360 does for 190 knots. I guess the retracts help with the Lancair but the Lycoming is a lot bigger engine than the Rotax.

 

The 40 L/hr for the lycoming I0-360 would be a cruise power setting so 75% of 200hp = 150hp, the Rotax 915 produces 141hp at full throttle so 40L/hr is not unreasonable. All engines have similar brake specific fuel consumption. If an engine is not using much fuel it's not producing much power.

 

Google "brake specific fuel consumption" there is a nice list.?  

 

The 160 hp lycoming 0-320 in my musketeer uses about 33L/ph at 75% and only goes 100 knots the same engine in a RV6 will also use 33L/hr but go much faster 150? The engine burns the fuel not the airframe. 

 

 

[facthunter]

It might turn out to be an expensive dud especially here in relation to Europe where there's more access to servicing. It's a highly complex engine. Being able to maintain power with height increase might be a plus for some operations, because you are only getting about 75% power available above say 6,ooo feet on most other engines.. That height is enough for most ops here. Europe (again ) might have a use for higher alts in some regions as does the US if you operate near the Rockies.   We should be able to produce engines cheaper than the 915 .Nev

 

 

[Thruster88]

Speed quoted  at 150 kts would then be 10 kts into red zone if no airframe changes,that's all i was thinking.

 

150 kts  TAS would be 129 indicated at 9500, VNE 140 indicated. 

 

 

[Jaba-who]

Too much jumping from indicated  to TAS here. Even in same sentence comparing indicated speeds of one engine  to TAS speeds of the other. 

 

 Ball park figures when you compare  the same category of speed ( TAS or Indicated) is actually so close that it would be pointless spending so much more money for the 915 to achieve very little. 

 

 

 

 

[KRviator]

I liked the 915.....until I saw the fuel consumption figures.

 

In a nutshell...something like a 50% gain in power for a 100% gain in fuel usage....

 

Reports of 40lph flat out....and 30 something in cruise.

 

I don't consider 40 lph for 140hp too flattering...

 

It baffles me how such a high tech engine can have such poor fuel consumption compared to the non-boosted 912is...

 

Rotax has published their owners manual that contains the fuel flow tables. All 2,480 lines of it. After much crunching of data in Excel, it would appear that the sea-level 100% fuel flow is a staggering 56.27 LPH. I don't think my OX-340 (165HP, FP) gets that on takeoff, even though the fuel flow meter squawks on the Dynon...

 

 

[Thruster88]

Rotax has published their owners manual that contains the fuel flow tables. All 2,480 lines of it. After much crunching of data in Excel, it would appear that the sea-level 100% fuel flow is a staggering 56.27 LPH. I don't think my OX-340 (165HP, FP) gets that on takeoff, even though the fuel flow meter squawks on the Dynon...

 

Many successfull aircraft engines run very rich mixtures at take off power to protect the engine. I am sure at cruise  power the brake specific fuel consumption is similar to other successfull aircraft engines.

 

Your lycoming clone ox-340 at 165hp is doing it easy and would not require the very rich mixture at take off power..

 

 

[facthunter]

 That's true as it gives more power due more mass airflow and also cools the charge with the evaporation of more fuel, same but not as good as if you had water methanol.  Nev

 

 

[Bruce Tuncks]

Is it true that airliners inject water at take-off power for cooling? If so, why don't smaller planes use this too?

 

Even if you didn't inject it into the engine, a small amount into the cooling air would be very effective I reckon.

 

 

[facthunter]

 The RR Dart is the only one that I had anything to do with  in the F 27 but the FW 190 had it and it's a fairly easy and safe method of increasing power for situations like taking off.. If you had no water meth left in the Fokker you had a much reduced TOW .It's a significant "kick in". You know when it happens. The engine (S) have torquemeters. to measure POWER (with rpm as well) Nev

 

 

[turboplanner]

Is it true that airliners inject water at take-off power for cooling? If so, why don't smaller planes use this too?

 

Even if you didn't inject it into the engine, a small amount into the cooling air would be very effective I reckon.

 

Cost, complication and the nuisance of filling up the water bottle, when you can achieve the same result by using the fuel to do it.

 

 

[facthunter]

If you do that with some jets and turboprop engines you will overtemp the  turbine wheels.. The methanol has a good cooling effect but does combust. The water is a controlled % and adds mass to the equation.

 

       You operate a jet to two limits (actually 3.) Revs N1 which you check before putting fuel in), EPR (pressure ratio) and TIT or TGT (TEMPS) which is only different in where it's measured EPR is POWER but so is fuel flow for a quick reference/check Your temps are limit figures and you would only be above them in an emergency. Do not continue operate above so you reduce the throttle to keep that engine in the right range this usually means the engine has lost some efficiency and you are NOT getting the rated thrust. Jets are really quite easy to operate . Far easier than BIG radials and about 20 times less likely to fail. (at least).  Nev

 

 

[Old Koreelah]

Later models of Mitsubishi's Zero used Water Methanol injection to boost power. During the war the Japanese never had high-octane fuel, but produced lots of alcohol fuels.

 

Electric power is now getting so close to viable, perhaps the IC engine won't be developed much further.

 

 

[facthunter]

IC engines are pretty grim even though they have character if they are reciprocating, All of them are likely to fling bits at you, catch on fire or melt.  The novelty of them doing that wears off pretty fast.  Nev

 

 

[Old Koreelah]

Agreed, Nev. When we all have quiet, efficient, reliable electric aeroplanes, cars and bikes there will be great nostalgia for the by-products of ICEs- particularly the sound. 

 

Ducatis with Conti pipes and big round aero engines will have starring roles at future vintage rallies- if they haven't been entirely banned.

 

 

[facthunter]

We will find some alternative fuel to run them on, OK. Nev

 

 

[Old Koreelah]

Electric cars are so quiet there are moves to mandate a noise generator to improve safety near pedestrian zones.

 

I bet artificially-produced rumbling FordV-8 sounds become popular.

 

 

[facthunter]

There should be plenty of sound systems out of crashed VN Commodores that could do the job.  Nev

 

 

[Thruster88]

Attended the Jabiru seminar at airventure today which covered the gen 4 engine (i was impressed) and the twin development. A new steel engine mount saves weight and eliminates the unwanted aerodynamic pitch down of the old canard mount. The engines will be even closer together, from 2metres down to 1.5. The engine is being repackaged to fit in a lower drag nacelle. Drag was mentioned a few times  and that due to the high drag of the current model it is slower with 160hp than the single with 120hp. Single engine performance was not mentioned but hopefully they can reduce drag enough to get some. They are hoping for a TAS of 130kts.