tuned airbox and exhaust for 912

[markmn]

Roger,

I was reading on the rotax site about the tuned airbox and stainless steel tuned exaust. Said they are required to attain the full 100hp.

 

I dont believe I have ever seen these installed on a light sport. then again Im not sure I was really looking for them either.

 

Can you enlighten us?

 

Mark

[Roger Lee]

Hi Mark,

 

The airbox are on the CTLS aircraft. They can not be retro fitted to an SW. We all have the exhaust..

[markmn]

Roger,

 

Do most LSAs have the tuned airbox and exhaust?

Which ones do or dont?

Does it really make a performance difference or not?

 

Mark

[Roger Lee]

Hi Mark,

 

Some LSA and some Experimental's have the standard Rotax airbox, but just as many don't. Many people just have a K&N filter on their Rotax. Does it really help, some, but not enugh that an individual could tell without being setup on a dyno. Do I think it is a better setup than just a K&N filter? Yes

It isn't a big enough difference to sell your plane and get one with it. For many years Rotax didn't have the airbox and many people just used regular air filters just like they do today and every thing worked and works today just fine.

I always tell people don't get hung up or frustrated about the little stuff. Just go out and have fun flying and you'll never know the difference and it will go to TBO just like all the others.

[Angelitomon]

Hi Roger : I have a 08 ctls and dont have a tuned exhaust. What do you guys mean by the tuned exhaust.right now im looking for two tuned exhaust here in europe. One both from french companys. One is the one that does the tuned exhaust for dynaero , and teh other is one that was in air venture two years a go , scaitech.com.

Please give a look at them and tell me what you think.

Im probably going to fly yo annecy ( close to geneva) to have the ones that make the dynaero one make me a 3D scan of my installation to build an spacific one for my engine.

Its supose to give me an incease of 7% in power , 14% in fuel reduction and a 20% in noise reduction.

Thank yiu

Angel

[Roger Lee]

Hi Angel,

 

The tuned exhaust is the stock stainless steel exhaust that comes from Rotax. It is on our planes. The air box is the aluminum tube airbox up on top of the engine to the rear. I don not mean the air filter. The SW's didn't have it and at some point and I don't know where the cut off was the LS does have the Rotax airbox. Many Mfg's that make exhaust systems make some pretty lofty claims, but usually don't deliver and the owner couldn't tell the difference anyway. It would take a dyno set up to really see the difference one way or the other. Some exhaust systems actually make performance worse. Everyone needs to remember that when you talk about or read about things people do to the Rotax, that Rotax is sold world wide and many people don't use the stock tuned exhaust or the Rotax airbox and use things they themselves make up or some after market set up with big claims. People think they are saving a lot of money and or getting better performance, but most of that is wishful thinking. You might even get something a little better, but at a cost of a few thousand dollars for 1-2 mph. It isn't cost effective and you don't always know what it will do to the engine in the long run..

[Angelitomon]

Thank you agian Roger.i have in my aircraft the stain exhaust,but i dont think that this one is tuned at all. Im talking about the doble flow exhausts with same distance on all tubes . Do this one snot work ar all? What a disapoint.

Thanks for the advise.

[Roger Lee]

Hi Angel,

 

They do make after market exhaust for the 912ULS and those guys make all kinds of claims. Personally I would save my money. Trying to eek out 1-2 mph for the cost involved isn't worth it for our type of flying. I have seen the double seperate type exhaust. They do sound different. Rotax warns against it is not being better. Like I said no one would know with out putting each on a dyno and comparing.

[207WF]

I think you should get it and report back to the rest of us how things changed, so we can find out on your nickel! Don't forget the LOA. WF

[Jeremy MacGregor]

Only about 10% of the slsa mfgs use the tuned aurbox and even fewer of the experimentals even mention it in there construction Manuel. The idea is to stablize the airflow between booth carbs by first running all intake air into a single filter and then ensuring that both carbs are having identical airpressure entering the venturi. This set up translates to a smoother running engine and thus in turn increases power very slightly. The other added advantage is the ports for the floatbowl vent lines. This ensures even pressure on the fuel in the bowls and allows for more even EGTs. These are two features that FD attempted to copy on the early SWs and there system works well enough.

 

Exhaust however is more critical. The power an engine can produce is heavily dependant on the amonut of back pressure the exhaust imposes on the cylinder. Too much pressure and the engine will choke down and lose power. Not enough pressure (which is the case in most twin exh. Setups) and you risk burning exh valves becuase the fuel is still burning as it leave the combustion chamber rather than burning completely inside.

 

The same principle with smooth running applies to the intake are along with the exhaust air exiting. (equal pressures= smoother operation and less oposition the engine had to throttle response.)