08. The wideband sensors were installed into each pipe.
A butterfly is still present to control airflow into the intake, and through 2007 was controlled by throttle cables. For 2008, H-D eliminated throttle cables and introduced electronic throttle control (throttle-by-wire; fly-by-wire). Sensors inside the right grip communicate throttle position to the ECM, and based on the map, RPM, and engine load the proper amount of fuel and air are delivered to the throttle body. A motor opens and closes the butterfly to control airflow. The ECM is simultaneously controlling ignition timing as well.
Although we won’t delve into every aspect of how the ECM gathers and uses information, there have been two general ways EFI does its job, and Harley has used both methods. Through 2001, the Magneti-Marelli (MM) produced EFI is what’s called an Alpha-N based EFI. Throttle position and RPM determined the amount of fuel to deliver. Harley also added an intake air temperature (IAT) sensor within the throttle body to make adjustments to the fuel mixture. A problem with the sensor in the MM system was that the measured air temperature was not an accurate reading of what the intake temp really was. Relying on temperature close to a hot motor was not the best way to determine intake air temp. When the air enters the venturi of the throttle body, it speeds up, thereby changing its temperature. In addition, the throttle body sits right above the hot motor, compounding the problem of accurate air temperature measurement. Some of the problems reported with the MM EFI were hard starting, erratic idle, and difficulty in tuning. For performance motors, the dual-plenum throttle body, with independent runners feeding each cylinder, was too small to pass the required air into the engine. An advantage of throttle-based control is that there’s no dependence on intake-manifold pressure, which benefits motors with radical cams.
09. The front sensor wires were routed across the brace in front of the engine and along
The next generation Delphi manufactured EFI uses a speed-density method to calculate how much fuel the motor needs. Speed-density systems use RPM and manifold pressure (via a MAP sensor in the intake manifold/throttle body) to determine the load on the motor and report back to the ECM for fuel changes. Again, H-D incorporated intake temperature but accuracy was improved by moving the sensor into the throttle body.
In summary and very generally, from ’95-01 H-D EFI used a throttle-position based system and from ’02 to now a manifold-pressure based EFI.
There are two other important EFI operating methods: an “open loop” and “closed loop.” In open loop (’95-06) the ECM uses preprogrammed maps to control EFI. Sensor data is “read” by the ECM and then matched to a map/table/database; the maps have instructions for the amount of time an injector is on as well as ignition timing. Since the maps are fixed (read only in computer terms) even small changes to airflow (pipes, airbox) require reprogramming the map and often requiring expensive dyno tuning.
10. The rear lead was routed between the transmission top cover and the starter then bene
11. The factory O2 sensor to ECM connectors were capped off and not used.
12. Next, the factory ECM was removed by spreading the plastic latches on either side of
A closed loop system has preprogrammed maps but can be modified (read/write). Oxygen (O2) sensors located in the exhaust pipes continuously monitor the spent gas to determine and maintain the proper air:fuel ratio and ignition timing on the fly in real time. For ’07-09 the O2 sensors were located close to the cylinder head; the sensors needed the heat to operate correctly. For ’10 smaller, heated O2 sensors were used and located before the catalytic converter, under the transmission area. The heated sensors control emissions better when the engine is cold. Small changes in airflow or even poor gasoline quality can be overcome by the ECM but due largely to environmental concerns, air:fuel ratios are varied within a small range due to the stock narrow band O2 sensors. What narrow really means is the measurement range is small and the sensors don’t work well with performance modifications. For government compliance the air:fuel ratios fall more on the lean side. Leaner mixtures (larger A:F) get better fuel economy, have more complete combustion (clean burning) for better emissions and fuel economy, but generate excess heat. Richer mixtures have the opposite characteristics while delivering maximum power.