Rotec Throttle Body Injector

There is a picture of the Rotec TBI being tested on William Wynne's website with some useful comments about setup. They tested the TBI-3 model. As of July 2011, the price of their TBI is close to $1,000, so it is currently no cheaper than the Ellison.

Much of the following information comes from Rotec and has not been independently tested. They have several models:

• Rotec TBI-40-S: Standard Spigot style mount to suit Jabiru, Rotec and Rotax
• Rotec TBI-40-3: Aviation flange #3 i.e. smaller aircraft engines like 0-235
• Rotec TBI-40-4: Larger aircraft engine 0-320 etc
• Rotec TBI-48-4/5: For large engines 0360 and above

Fuel pressure and delivery are controlled via the Rotec "on demand" fuel pressure regulator which is connected to the inlet side of the throttle body and supplies the precise amount of fuel to the injector bar. This system is claimed to be self regulating and not affected by the fluctuation of fuel levels or pressures.

Rotec claims that atomization of the fuel is ultra fine that should give greater performance and economy. They claim that regular carburetors do not atomize the fuel nearly as fine or as well. Ultra fine atomization leads to the reduction of mixture temperature and as a result should burn better.

The TBI-40's absence of any butterflies in the air stream results in a reduction in the total wetted area and drag, giving more throat area for the same size bore.

An advantage of the slide throttle control is that unlike the butterfly valve, the fuel mixture is not deflected into the side walls of the inlet track where the mixture tends to accumulate and lose the benefit of fuel atomizing, The Rotec TBI-40 does not deflect the mixture into the side wall and so the mixture remains freely and completely atomized.

The Rotec TBI-40 can run a wide range of fuel pressure from 0.5 to 6.0 psi including gravity fed mode too. The TBI-40 is not attitude sensitive as it has no float chamber, so it is able to run upside down.

Starting the engine from cold requires depressing the diaphragm over-ride button on the Rotec fuel supply regulator, giving the engine a squirt of fuel while cranking. Typical primer nozzles can also be utilized if the airframe has existing primer systems.

Idle speed is set via typical throttle aperture stop and bypass mixture screw which sets the idle fuel mixture. The slide throttle and mixture levers are controlled via typical Bowden push pull cables. The air cleaner side of the TBI-40 is of the standard aviation four bolt flange, designed to fit the standard range of aviation air intake ducting.

CarburetorHeat is a mandatory requirement.

The Rotec TBI-40 is suitable for all of their Rotec radial engines and will attach to the typical Bing rubber coupling. This coupling makes the TBI-40 ideal for retrofitting many other engines. On request Rotec can supply a variety of custom engine couplings to suit any Experimental engine including Lycoming and Continental engines.

List serve comments:

• More expensive than the Aerocarb, but doesn't leak fuel when the engine is shut off and there is no messing with needles.
• It looks very similar to an EllisonTBI and the price does too. Although others disagreed, saying that it more closely resembled a Posa with an external regulator using a similar principal as early Propane carbs that goes back to the Tillotson H series carb and early Walbro regulator carbs for inspiration.
• MarkLangford said that if it was like his Ellison, fooling around with the mixture is something you would have to do every time the throttle setting changes appreciably.
• ScottDawson said he had been told by one TBI user that: It was difficult to set up and he had all sorts of troubles sorting out the glitches but has it running well now and he's happy with it. It has a very fine filter before the regulator to prevent the regulator from getting stuck, but the filter causes blockages. Another individual has one on his Subaru aero conversion. He said he likes it now he has it running properly. The problem with his was that he had the regulator mounted slightly higher than the TBI and the slighest bit of fuel pressure would cause a syphon effect and the fuel would just run through it in to his airbox. He has remounted the regulator to just below the TBI and he said its good now. His parting words were that people who fit them need to be patient and learn about them to get the right setup.

External link:

Rotec TBI site

Related Terms

FuelPressureRegulator , FuelPump