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RIVERFOX
08-05-2010, 07:39 PM
I have a 1991 IV-1050 with the carb heat system containing one large K+N filter located just behind the gearbox. Two long scat tubes going to the carbs. It's really restrictive and I want to go to two individual K+N filters directly on the carbs but I have almost no room behind the carbs. Has anyone got any info or correct filter # ?

HighWing
08-06-2010, 06:39 AM
My first kit - 1993 - came with the offset flat filter. I have seen guys with the tapered filters as well. My new project has even less room so I opted for the tapered angled filters. My guess is that what ever fits will work fine.

Lowell

miclar1
08-06-2010, 06:55 AM
Mine is a 1993 IV-1050, flying since Feb 97, with the same carb heat installation. I have not yet found adequate filters that would fit, with clearance, between the firewall and the carbs.

You're right, the present installation is restrictive, but I'm not sure I would modify it if I found the proper filters. In 500+ flt hours I've experienced carb ice at least twice and was glad to have carb heat.

HighWing
08-06-2010, 12:12 PM
The only time I have ever heard of carb ice or it's possibility without the carb heat box was reports during an ealry flight to Alaska by several - maybe eight - Kitfoxes in the late 90s. The report mentioned burps in the engine as if the carbs had ingested ice . Beyond that nothing. I flew for nine years without the carb heat system - many of those along side others without carb heat as well. I still have the parts on a shelf. The only instances of actual carb ice I have ever heard of was from pilots flying with the carb heat box. I know this might sound crazy and a bit disingenuous as carb heat capability gives a real feeling of security having the set-up, especially with real icing a few times. But there are hundreds of thousands of hours in Kitfoxes without the carb heat boxes with nothing to report. And as I understand it, with the exception of Kitfoxes in Europe where it is manditory, very few have it installed. I've been to lots of factory fly-ins over the years and don't recall ever seeing one.

The theory is that the intake air at the back of the engine compartment is just warm enough to prevent icing whereas the intake air at the front is ripe for icing. The other issue I hear has to do with the friction in the carb heat system and the additional power from having the engine breathe more air.

If there are other instances of suspected icing without the heat box, I am all ears. My new project will simply have filters at the backs of the carbs.

Lowell

desertfox1
08-06-2010, 01:12 PM
I have over 1900 hours in Kitfox's fitted with filters, no carb heat.
Alaska, Canada, no indication of icing. At Oshkosh this year I
was inspecting the engine install on the newest Tecnam from
Italy. No plenum or carb heat, just filters on the Bings. I agree
with you Lowell, hot air at back of cowl seems to obviate the
need for carb heat.

Phil

DesertFox4
08-06-2010, 01:19 PM
About the same number of hours for me too and no icing problems with just filters on the carbs. I flew in very high humidity this week and never any suggestion of icing. The Rotax ran beautifully and never once missed a beat.