General FAQ

 

How does it work? Is it like other slide type carburetors?

The Rotec TBI Fuel System is not a carburettor, but instead a mechanical fuel injection system. It self meters fuel supply using a cleverly calibrated negative pressure fuel regulator. This in effect dynamically compensates for any variations in power requirement by the engine or fuel pressure from the fuel supply. Other slide type carburettors do not do this.

 

Applications (Motorcycle, Car or Boat Engines)?

The Rotec TBI Fuel System is currently in use on a number of motorcycles engines. There is no reason why it cannot be used on a car or boat engine. The TBI will be an upgrade to most engines using a carburetor. For engines running EFI systems, the Rotec TBI Fuel System will not interact with any electronics and is therefore an entirely independent fuel system (i.e. no injectors, injector fuel rail, mass airflow meter, throttle butterfly/throttle position sensor). Note: Rotec Aerosport has specialised in recreational aircraft installations. We cannot offer significant installation advice in regards to non-aviation engines.

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Aerobatic 

The Rotec TBI Fuel System can be mounted to an engine at any attitude and at any angle. It can even be mounted upside down, making it the perfect aerobatic fuel system. The system has no float, so it can fly at any attitude too.

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Permance - Power Increase

Comparative data for all engines is currently unavailable. Although as an example, when testing our Rotec Radials, replacing the Bing Carburettor with a Rotec TBI Fuel System results in a 150 RPM increase at WOT. Any increases in power are a result of a more efficient fuel burn. Performance changes vary depending on the engine and fuel system being replaced. Performance figures submitted by users can be found on the projects page. If you have performance figures to submit, contact our technical team.

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Fuel Consumption

Changing over to the Rotec TBI Fuel System can expect varying reductions in fuel consumption. Any reduction in fuel consumption is a result of the spray bar offering superior fuel atomization, resulting in a more efficient fuel burn. Adding to the general increase in efficiency, you’re able to lean the mixture at cruise power settings. As an example, our Rotec Radials see a 15 – 20 % reduction in fuel consumption when leaned at cruise power settings. Fuel consumption can be monitored using the Rotec Fuel Flow Meter. Fuel consumption changes vary depending on the engine and fuel system being replaced. Performance figures submitted by users can be found on the projects page. If you have performance figures to submit, contact our technical team.

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Fuel - Rotec Fuel Flow Meter

The Rotec Fuel Flow Meter provides a wide range of information useful including; range, reserve flying time and fuel consumption. Calculated each second, this allows you to easily trim your mixture settings, optimising fuel consumption of the Rotec TBI Fuel System. It can be used with both small (40 hp) and large (250+ hp) engines, as the fuel flow gauge (see Figure 1) has a minimum detection rate of 1.5 L/h (0.4 gal/h). Install the fuel flow sensor (see Figure 2) on the pressure side of the fuel pump, before any regulator. In the unlikely event of the fuel flow sensor seizing, fuel flow will be unaffected. Hence, there is not added risk adding the system to your installation, only the certainty of how much time you can spend in the sky. The TBI system has meter fuel delivery and is very accurate, however, it does not automatically adjust the mixture with a change in atmospheric condition.  These mixture changes must be done manually by the pilot.Documents: Rotec Fuel Flow Meter Manual – Installations and setup instructions. Rotec Fuel Flow Meter Calibration – Fine tune calibration.

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Jabiru Engines 

Upgrading your Jabiru engine with the Rotec TBI Fuel System can increase fuel system performance, and as a result increase power output. Installation Examples: Close up of an induction flange on a Jabiru 2200. Close up of an induction flange on a Jabiru 2200. As limited room is available on some aircraft, a snake pipe for induction can be used. As limited room is available on some aircraft, a snake pipe for induction can be used. Figure 1: Regulator mounted using bent aluminum pipe between fittings. Figure 1: Regulator mounted using bent aluminum pipe between fittings. A Jabiru 3300 with an engine mount extension. A Jabiru 3300 with an engine mount extension. A Sonex using an airbox for induction, as limited space is available. A Sonex using an airbox for induction, as limited space is available. A Jabiru 3300 with enough room from the fire wall for top mount induction. A Jabiru 3300 with enough room from the fire wall for top mount induction. We have had no reports in differences between horizontal and vertical orientation of the TBI on the Jabiru Although you can experiment with orientations for better cylinder fuel distribution. Standard Jabiru Bing 94 induction examples can be found here. Why stop upgrading there? Fly without a CHT worry in the world. Rotec Liquid Cooled Heads will give you peace of mind with a cooler, more reliable engine. The simple ‘bolt on’ Electronic Ignition Upgrade will allow you to start first time every time, even on a near flat battery. Adding the Alternator Upgrade Kit will mean you’ll never need worry about your charging system again.

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Rotax Engines

The Rotec TBI Fuel System is flexible in providing choice on how to convert engines, depending on the skills and materials available. There is no difference in power depending on the conversion option chosen (single or dual TBI), as the Rotax is not under-carbed. Single TBI Approach We recommend Rotax owners simplify their engine by replacing the dual standard Bing carburettors with a single Rotec TBI Fuel System. This simplifies the installation, no longer requiring dual; fuel lines, throttle controls, chokes, air filters, cables and hoses needed to accommodate dual carburettors. All that is required is a bridge manifold to converge both intakes. Steve Schultz’s of Ion Aircraft adapted a TBI-40-3. More details on the bridge manifold used as well as testimony can be found here. OLYMPUS DIGITAL CAMERA Ion Aviation TBI-40-3 with manifold Ion Aviation TBI-40-3 with manifold Rolf Summerhayes fabricated a manifold for his Rotax 912UL to accept a single TBI-40-S. Rolf Summerhayes,Rotax 912, TBI-40-S Manifold 2 Rolf Summerhayes,Rotax 912, TBI-40-S Manifold 1 Rolf Summerhayes,Rotax 912, TBI-40-S Manifold 3 Note: We do not have premade manifolds available. Any fabrication shop can fabricate an induction system if provided with a dimensioned drawing. We have some fabrication ability and can quote on submitted engineering drawings, although it is usually easier and cheaper to have custom induction systems made locally. Dual TBI Approach Alternatively the dual Bing carburettors on the Rotax can be replaced with dual TBI-34-S‘s. Some opt for this solution as minimal induction system piping is required. Fabio from Italy claims they worked very well at all attitudes. See comments on inverted aircraft testing below. Fausto Italy TBI Fausto Italy TBI Fausto Italy TBI From: Fausto Tongiorgi Sent: Wednesday, 2 February 2011 12:01 AM To: sales@rotecaerosport.com Subject: Inverted flight with TBI Hello Paul, I have installed a my own kit for inverted flight on COMET with Rotax 912S. I am using two Rotec TBI-34-S in place of the dual Bings. The performance is a big improvement. The engine you can see the running tests in some photos. The engine is running perfectly up side down!!! The engine does not know whether you are up or down!! Best Regards, Fausto Rotax 2-strokes Rotax 2-strokes also easily accept dual TBI’s as seen on this converted powered paraglider. This particular engine has used dual TBI-34-R‘s. Rotax 503 dual TBI-34-R with filter. Rotax 503 dual TBI-34-R with filter. Rotax 503 dual TBI-34-R without filter. Rotax 503 dual TBI-34-R without filter. Turbocharged Rotax Engines The Rotax 914 uses a turbocharger in push (blow) through configuration. This means the turbocharger is feeding the carburettors pressurized air box. This configuration does not work with the TBI, as the spray bar requires a negative pressure in order to draw fuel from it. To have the TBI work, you must modify the induction system to have the turbocharger in pull (suck) through configuration. Put simply, this requires the Bings be replaced with induction piping and then mounting the TBI before the turbocharger. 

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