Air filters

by Phill Hooker in General Tech Discussion 8 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.

Page 1 of 2

Start
Prev
1
2
Next
End

Re: Air filters

by Roger Lee » 8 years ago

Roger Lee

125 5.12k 4.52k

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 MARK JACKSON » 8 years ago

MARK JACKSON

12 332 11

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 James Ott » 8 years ago

James Ott

22 322 358

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 Roger Lee » 8 years ago

Roger Lee

125 5.12k 4.52k

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 James Ott » 8 years ago

James Ott

22 322 358

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

Page 1 of 2

Start
Prev
1
2
Next
End

You do not have permissions to reply to this topic.

Title	Category	Replies
Washed airplane, now have a generator issue	General Tech Discussion	8
Air Filter Sizing	912 / 914 Technical Questions	4
914 Oil Seepage From Airbox Intake Tube	912 / 914 Technical Questions	8
914 Turbo Induction/Air Intake Hose	912 / 914 Technical Questions	1
Air- (Windmill-) Starts with "Soft Start"	912 / 914 Technical Questions	1

Air filters

Recent Videos

Safety First!

ROTALK News

Prize Giveaway!

Log In/Out

Login