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CAT probe on Ellison TBI

wjnmd

Well Known Member
I’m in the process of installing a Dynon SkyView SE into my biplane with a Lycoming 0-360. It has an Ellison TBI. The Dynon EMS came with a carburetor air temperature probe but I can’t seem to find where it goes. It appears that it might require drilling and tapping a hole on the side of the TBI intake. I’m reluctant to do that but the Ellison is supposedly prone to icing. I might be better off just using carb heat routinely although I have never used it since moving to Florida.
 
As I understand it, the Ellison has no venturi so there is little or no temperature drop in the inlet, so by nature it is unlikely to have "carb ice".
 
From Ellison

Quoting the Ellison manual: “Contrary to common belief, the Ellison TBI can accumulate ice. For these reasons, all TBI installations must include an induction heating system capable of providing an inlet air temperature rise of 90 degrees F.”
I’ve lived without a carburetor air temp probe for years so I’m sure I can live without it going forward but since I have it, I’d thought I’d see if I could install it
 
Ellison carb heat

My -4 has good carb heat, per the manual. I too have the Dynon CAT, but didn’t install it. For what you want to know, it may be easier to just drill a hole in the TB to FAB baseplate rather than drill in the TB. I may do this at next condition inspection for the heck of it. Remember, if you think you’re suffering from carb ice with an Ellison, carb heat along with a cycle of the throttle will dislodge as the variable Venturi slide wipes the spray bar. This may risk the slide seal though. I count say I’ve ever knowingly had a case of ice, but I check the RPM drop and run up,and part of pre landing sequence.
 
I would advise against drilling into the Ellison TBI. Those things are as rare as hens teeth anymore and getting them serviced is nearly impossible and you have no idea what introducing a probe (obstruction) into the airstream is going to do.

Yes, there is that *disclaimer in the Ellison literature and yes I'm sure they can ice up under very specific conditions but the Ellison is known for _not_ icing up like a typical carburetor will. I put 500 hrs on my Ellison equipped RV-3 over 7 years and although I did apply carb heat as a precautionary measure at times, I never experienced icing. Even induction icing which is different.

Having said all that, I think carb icing and/or induction icing is a very real thing and much more common that people realize and causes many more accidents than we realize as well. It's like being shot with an "ice bullet". I'm also not sure there is a good and wide spread understanding of icing out there in the pilot world. There is lots of good literature though.

I don't understand the "never used it since moving to florida" comment. Isn't Florida a high humidity state? I don't live there and have only visited once but it seems to me florida would very often have temp/humidity conditions that would be conducive to icing.

I have a NOS Ellison 4-5 that I'll be installing on my Acroduster next year and will be providing carb heat as suggested in the manual but no probe.
 
may I ask why they have become so rare?

anything wrong with them? I need to figure out how to get my own checked out...or replace it altogether.
 
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