fbpx
Login

 

Jump to Forum..

Air filters

in General Tech Discussion 9 years ago
hi all, just wondering on your thoughts about placements of the air filter. I notice some aircraft have the filter clamped directly and gets its air(hot) from under the cowl in the engine bay. Others have it next to an air intake on the side of the cowl(cold air) Going back to my basic ppl theory (last century) the cooler the air the better the performance of the engine. Why do some manufacturers ignore very basic facts and install it under the cowl to breath very hot air?? defies logic.

  • Re: Air filters

    by » 9 years ago

    Hi Phill,

    You are right. Colder air is better than hot under the cowl air. Some MFG's just don't have room under their cowls to use an airbox that is open to the outside air. Maybe some just want to save time and money? When they run air filters directly on the carb under the cowl it is like running with carb heat on all the time. That also makes the carbs run rich and hot air isn't as good for combustion.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Air filters

    by » 9 years ago

    Hi Phil

    Like Roger says, drawing in hot air is like running with carb heat on all the time, which is why a lot of manufacturers do this, to prevent carb icing.

    If you are drawing cold air from the outside, it would be a VERY good idea to have some form of carb heat. Carb icing is real.

    Cheers Mark
      
    Report

  • Re: Air filters

    by » 9 years ago

    Providing you have properly sized inlet ram air openings and more importantly outlet openings, the outside air flow thru the cowl area is such that I doubt that there is a huge difference in outside air and under cowl air temperature during normal cruise and takeoff. During low speeds and rpms as during landing this difference is greater, but of course that is what you want to prevent carb ice.
      
    Report

  • Re: Air filters

    by » 9 years ago

    Hi James,

    If that were true then there wouldn't be as big a need for oil coolers and coolant radiators and probably not as big a temp spread. An open air engine would be the closest thing (like on some pushers) and even they have coolers.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: anthony foran
      
    Report

  • Re: Air filters

    by » 9 years ago

    With an approx 100 mph (assuming no baffles) wind blowing thru the cowl area how much time does that air have to heat up inside the cowl? I am betting not much more than a 20F rise. Would be interesting to see some actual test figures on this. If it really is only 20F, that calculates (see page 5-7 in the Rotax 912 Operator's Manual) to be a little less than a 4% reduction of engine power. That is measurable but maybe not worth adding a lot of outside air ductwork, airbox, and carb heat controls. Just thinking out loud on an interesting subject.
      
    Report
You do not have permissions to reply to this topic.
Related Topics
Title Category Replies
Air Ingress at Oil Change 912 / 914 Technical Questions 1
912 air filters replacement 912 / 914 Technical Questions 1
Service Instruction: Installation of a propeller by usage of round-neck nut set for ROTAX® 912, 914, and 912 i (Series) Aircraft Engines General Tech Discussion 9
PSA: South Mississippi Light Aircraft Refused Refund Rotax-Owner Community 9
Anyone who can repair/re-weld 912 exhaust system? General Tech Discussion 5
Follow Us

Recent Videos

Safety First!

 

To receive critical-to-safety information on your ROTAX Engine, please subscribe to
ROTAX-OWNER.COM

Prize Giveaway!


SUBSCRIBE NOW
to automatically enter this years draw!

Login