Harley-Davidson Twin Cam Fuel Injection Overview

Harley's use of fuel injection has changed the game. It is far more tuneable than the carburetted models, but requires a substantial investment in equipment and continuous education, in order to correctly tune with any performance upgrades. Here at Powerglides, we have made this investment, and as such can offer true "one stop, turn key packages" for any of our Twin Cam performance upgrades.

As the UK's leading Harley-Davidson fuel injection tuning specialist, we now only use the excellent Direct Link Flash Tuner for remapping the ECMs, and have a continuous development program for new performance upgrades, as well as staying up to date with all of the Harley-Davidson ECM and software changes. We don't just sell parts, we install, and tune, with them. Below is a potted history of the many engine, and engine management changes Harley-Davidson have made since the Twin Cam was introduced.

1999 When Harley-Davidson introduced the Twin Cam 88 for the 1999 model year, only the FL range was offered with Fuel Injection. This inherited the Magneti Marelli system from some of the Evolution models, but with a different software level in the ECM. The MM system uses a dual 38mm throat, one piece throttle body, with individual manifold runners. The whole system is somewhat limited in airflow, and parts are becoming more expensive and harder to get. Having said that, it does support the more moderate performance builds.

This MM system was not very well understood at the time, and although it uses rather outdated alpha-n technology, and requires some mechanical adjustments, our Direct Link Flash Tuning system can deal with it. In fact, Direct Link is now the only tuner on the market that allows us to build engine specific maps on the dyno, and reflash the ECM. 2001 The Softail range had the new Delphi speed/density system as an option, which was a major step forward, especially for us tuners, as it gives far more control over fuel delivery and ignition timing than the best carburetors or conventional ignition systems can.

These 44mm single bore throttle bodies have a seperate manifold, and use 4.3g/s injectors. The bolt pattern on the face of the throttle body, where the air cleaner backplate attaches, is the same as the CV carb.

2002 The FLs switched over to the far superior Delphi system and use the same throttle body and injectors as the Softails.

2003 All of the Twin Cams now have the INA roller bearing bearing instead of the superior Timken bearings on the sprocket shaft of the crank.

2004 The Dyna models gained the Delphi fuel injection, using the same thottle body and injectors as the Softails and FLs.

2006 This was a major change, as the Delphi system was upgraded further, and carburetors were dropped completely. The throttle bodies became one piece with a 46mm bore, and the injectors were now 3.89g/s. Early 2006 (55 plate) used injectors with an 8* spray pattern which can cause issues at low speed, so part way through the model year H-D switched to 25* injectors, which are still currently used on the cable driven bikes. Many of the early 06 models had the injectors upgraded as a matter of course, but this needs to be checked prior to tuning.

The Dyna models used a closed loop system and have 18mm oxygen sensors in the header pipes. All models also received the new style cylinder heads with better ports, and the intake flanges became symetrical. The Dynas also have the 6 speed gearbox, different primary drive, and new style camshafts, support plate, chains and tensioners, and higher volume oil pump.

2007 All standard Harley-Davidson Twin Cams are now 96" with a 6 speed box, new primary drives, and the new upgraded camshaft drive arrangement. The CVO models introduced the 110" engine, which have different cylinder heads and automatic compression releases actuated by the ECM.

All models retained the same 46mm throttle body, and run closed loop with the 18mm O2 sensors.

2008 The FL models now use a 50mm Drive By Wire throttle body, and the 2001-2005 4.3g/s injectors. The front head is machined to take the repositioned top stabiliser mount.

2010 The FL models have a different software level and heated 12mm O2 sensors.

2011 The FL models now have the 103" engine and the same ACRs in the heads as the CVOs, and another software level in the ECM.

The Softails use a CANbus communication system and have a different ECM, but still use the 18mm O2 sensors.

2012 The Dynas now use the CANbus communication, and both these, and the Softails, use 12mm heated O2 sensors, and a new software level. Some models are now 103.

2014 The FL models are substantially changed, and are the result of Harley-Davidson's Project Rushmore. The Twin Cooled Ultras have water cooled heads and higher compression, as well new camshafts and air cleaner also used with the air cooled Strret Glides and Road Kings. These use Bosch ECMs and have new software, and a CANbus communication system, as well as Drive By Wire.

All models are now 103, (although the Streetbob is available as a 96).

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