Too heavy in my book, but we will see.
Supposedly there is a 20% fuel saving over the ULS. Hard To believe, but I really don't have any personal knowledge.
Too heavy in my book, but we will see.
Supposedly there is a 20% fuel saving over the ULS. Hard To believe, but I really don't have any personal knowledge.
I find the 20% number very difficult to believe. It takes X amount of fuel to achieve X amount of hp. If the hp is the same, that says that these carburetors are EXTREMELY inefficient. While I believe that this carb set-up is somewhat inefficient, I can't believe it is that bad.
Just my $.02.
I know I will come under fire for this but........Not to excited about the E part of EFI considering some of the E glitches I had to overcome. The Bings have been around awhile. Carbs seem to fail gradually while E's seem to turn off.
Jersey
rv6ejguy said:Remember there is no provision for leaning the Bing carbs manually so they are a compromise.
There is a kit available to lean the mixture of the Rotax carburetors.
One pilot showed me his installation in the Europa with a 912.
More info: HACman
I think the word supposedly is a correct word to use at this point. There is not enough real world experience to yet validate the new fuel economy claims. I don't doubt that it is better than the carbed engine, but I am not yet convinced it is 20% better.
Case in point...
If you fly an RV-12 with the carbed engine, at max continuous cruise power, you will not get the fuel economy that was typically published 6 years ago when Van's first started playing with the 912 in the yellow prototype.
Sure, you can match the claimed numbers, but at a reduced cruise speed.
So, is the 20% fuel flow claim, a reduction from what we know a carbed engine burns at max. cruise power, or a 20% reduction on what it was always claimed to burn?
I guess what I’m saying is that from a marketing standpoint they can say there is a 20% decrease in fuel burn. The reality is that leaning the mixture 20% from best power F/A is an 8% reduction in HP. So if you had a 180 HP engine running 16 GPH then leaned the mixture 20% leaner (12.8 GPH) the engine would make 166 HP. Likewise just reducing the throttle to 166 HP keeping the same F/A the engine would use 14.7 GPH. That’s a 13% reduction in fuel flow. So the real difference is only a 7% gain in fuel economy by leaning the mixture. The problem here is that you can’t run the engine at 7% lean let alone 20% lean at the manifold pressure to make full power. Aircraft engines have been running LOP for a long time. Big radials ran like this all the time in the 40’s and 50’s to extend their cruise performance. So this is no big revelation.
We have 2035 FM units in the field. 90% of these are in aircraft installations and have overhauled over probably twice that many Bendix fuel injection systems in our 29-year existence. I would guess there are over 1.5 million flight hours on the FM systems. We have accumulated thousands of hours of dyno and test stand time running on various engines from 2-stroke, rotary and 4-stroke, turbo, supercharged, Nitrous, alcohol, 80 HP to 2500 HP engines. It’s amazing how similar all this stuff acts. Physics is always present. And this holds true even for the Rotax. As Ross stated in his observations with the addition of his EFI on the Rotax 912 (5-8% gain in HP and 5-10% reduction in fuel burn for the same power) was pretty much the same change that we saw with our mechanical system (8-13% gain in HP and 4-6%r reduction in fuel burn) on the Rotax 912.
So again, there’s no free lunch. What kind of value do you get for your dollar?
Don
I guess what I?m saying is that from a marketing standpoint they can say there is a 20% decrease in fuel burn. The reality is that leaning the mixture 20% from best power F/A is an 8% reduction in HP. So if you had a 180 HP engine running 16 GPH then leaned the mixture 20% leaner (12.8 GPH) the engine would make 166 HP. Likewise just reducing the throttle to 166 HP keeping the same F/A the engine would use 14.7 GPH. That?s a 13% reduction in fuel flow. So the real difference is only a 7% gain in fuel economy by leaning the mixture. The problem here is that you can?t run the engine at 7% lean let alone 20% lean at the manifold pressure to make full power. Aircraft engines have been running LOP for a long time. Big radials ran like this all the time in the 40?s and 50?s to extend their cruise performance. So this is no big revelation.
We have 2035 FM units in the field. 90% of these are in aircraft installations and have overhauled over probably twice that many Bendix fuel injection systems in our 29-year existence. I would guess there are over 1.5 million flight hours on the FM systems. We have accumulated thousands of hours of dyno and test stand time running on various engines from 2-stroke, rotary and 4-stroke, turbo, supercharged, Nitrous, alcohol, 80 HP to 2500 HP engines. It?s amazing how similar all this stuff acts. Physics is always present. And this holds true even for the Rotax. As Ross stated in his observations with the addition of his EFI on the Rotax 912 (5-8% gain in HP and 5-10% reduction in fuel burn for the same power) was pretty much the same change that we saw with our mechanical system (8-13% gain in HP and 4-6%r reduction in fuel burn) on the Rotax 912.
So again, there?s no free lunch. What kind of value do you get for your dollar?
Don
Let's also remember Rotax is controlling ignition and can run the spark timing right up to just short of detonation for maximum cylinder pressure at all times.
No they can't. Their system has provision for knock sensors, but they are not installed. Without that they are risking detonation unless they use fixed, overly conservative fuel and timing curves. If they try to really retard or advance the timing for a specific engine in a particular regime, they will end up blowing up a lot of engines that are running under different conditions.
I saw an interview with a Rotax engineer a while back that said the "phase II" EFI engine will include knock sensors and dynamic timing.
so when time comes and they stop making the 912 ULS then Vans engineers will sit down and make it happen.
I'm sure you're right, Jetguy. Does sound nice, but I suspect N737G will be stuck with her dual carbs forever....
What I'm waiting for is this stuff:
http://www.youtube.com/watch?v=Bch5B23_pu0
Bob Bogash
N737G
Never be an "early adopter".
Bob Bogash
N737G
... says the man who jumped on Skyview V10 as soon as it became available!