I understand why icing occurs in carburetors and I have personally endured a carb icing incident in a tripacer aircraft (huge pucker factor in a single engine aircraft ("quick full carb heat on!"). What I don't understand is why icing doesn't seem to occur with the throttlebody of a EFI intake. It has the same air dynamics. I have never had any icing issues with my EFI KTM. Although there isn't the pilot and main jets to affect, the icing could certainly affect airflow and AFR potentially leading to flooding or insufficient air within the EFI intake. Any wisdom out there?
Why no icing in EFI throttle body intake?
- Thread starter whistlerhawk
- Start date
I have had the same carb icing problem on my first solo cross country.
It is the effect of the vaporization of the fuel that sort of super cools the air in the venturi. Also throttlebodies dont have the same venturi effect.
Review 2-19 in your Jeppsen Private Pilot book for more info.
It is the effect of the vaporization of the fuel that sort of super cools the air in the venturi. Also throttlebodies dont have the same venturi effect.
Review 2-19 in your Jeppsen Private Pilot book for more info.
I think also a carb is made of cold metal eft system is probably plastic so the ice dosnt stick to anything?
the throttle bodies can get ice in them as well, thing is, the throttle body doesnt have the tiny air bleed ports to maintain proper AFR. so a tiny bit of ice plugging those holes doesnt really affect airflow, it just botches the carbs ability to regulate fuel flow. hence the vehicle running poorly, throw a little ice on the sides a throttle body and maybe you lost 1% airflow, not a big deal, but when suddenly your carb is seeing super messed up signals, no good!
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mtn-doo
Well-known member
The EFI bodies are Aluminum, not plastic. Same as the Carburetors. The throttle bodies on an EFI system are straight bore. Same size front, rear, and center, like a pipe. Volume and velocity are consistent front, rear and center. A carburetor has a Large inlet, "bell shaped opening" from the air box, small necked down center, then a slightly larger exit into the engine. The reason for this is to create a "vacuum" which a carb needs to draw fuel from the float bowl through the jets. "Suction" from the venturi effect of the design. Otherwise known as a "mode of flow valve". The EFI system does not rely on air acceleration or suction to draw fuel from a reservoir. It is electronically "sprayed" from the injector. Therefore, no venturi needed for vacuum or suction.
Ice is formed when air density and temperature are reduced by a pressure and consequently a temperature drop, and when air/moisture is near saturation. A venturi reduces that pressure and drops temps to cause the moisture to form and "stick" to what ever it can. The straight bore of an EFI system does not accelerate nor drop pressure from the air entering because of it's straight bore. Air is not accelerated, not the extreme vaccuum and pressure drop, ice doesn't have the physical principals to accumulate.
Ice is formed when air density and temperature are reduced by a pressure and consequently a temperature drop, and when air/moisture is near saturation. A venturi reduces that pressure and drops temps to cause the moisture to form and "stick" to what ever it can. The straight bore of an EFI system does not accelerate nor drop pressure from the air entering because of it's straight bore. Air is not accelerated, not the extreme vaccuum and pressure drop, ice doesn't have the physical principals to accumulate.
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portgrinder
Well-known member
The main reason is there are no small fuel/air inlets on a TB so the ice does not change the fuel delivery. You could coat a TB in 1/8in of ice and it wouldn't change much, where's a carb one small piece of ice in the right spot (like an air screw opening) changes the fuel delivery greatly.
Fuel injectors don't wildly change their open time due to a small restriction in flow. If it's a higher end efi system with a MAP sensor not just TPS, it would actually compensate a bit.
There is still a large pressure change through a throttlebody. Thats how MAP sensors on an efi system work. The bell or straight overall shape would have little effect vs the actual slide or butterfly valve, as that is what meters the air and causes the pressure drop.
Fuel injectors don't wildly change their open time due to a small restriction in flow. If it's a higher end efi system with a MAP sensor not just TPS, it would actually compensate a bit.
There is still a large pressure change through a throttlebody. Thats how MAP sensors on an efi system work. The bell or straight overall shape would have little effect vs the actual slide or butterfly valve, as that is what meters the air and causes the pressure drop.