Honda Fuel Injection System

8/12/2019 Honda Fuel Injection System

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Development of the ECU-integrated throttl e body module

To allow for application to a small motorcycle, the FI system had t

and down-sized considerably from the conventional one. The deve

packed various functions into the compact yet simple system that

installed in the place of a conventional carburetor by modularizing

body, various sensors, and the engine contro l unit (ECU) into an i

Aims of integrat ing and modularizing the throt tle body and ECU

In conventional motorcycle FI systems, the ECU is mounted to th

Also, various sensors for detection of the control information are

various places in the engine or vehicle body as an independent c

Because of that, many wire harnesses are required to connect va

to the ECU. Consequently, the conventional system is complex, a

apply to a small motorcycle having a 50cc-125cc single cylinder e

attempt to practically apply a compact PGM-FI in place of a carbu

throttle body, which controls the intake air volume, and the ECU

controls engine operating conditions, have been integrated into othe wire harnesses eliminated, the size of the module has been r

same size as a carburetor.

Example of

conventional FI system

for motorcycles

Cut model of FI for

small motorcycles

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Outlines of system

The newly developed compact PGM-FI system has a two-split con

consisting of the throttle body and the ECU module. This configur

for replacement of a throttle body having a bore size suitable for

engine displacement, thus realizing a FI system applicable to vari

with a high level of application freedom. The throttle body and E

incorporating various sensors are connected with 4 bolts. The idl

grooved on the mating surface, and by sealing with an O-ring, th

passage is formed, thus contributing to the integration and down

ECU module unit consists of the plastic box (device body), ECU b

cover. Various sensors are housed in the device body, and the Econnected directly to the input and output terminals of the senso

the cover from above, the inside is packed with potting resin to s

internal parts and to prevent water entry.

Layout of sensors

The throttle body module has 3 sensors in the device body.

1. Intake air temperature (Ta) sensor: To allow

measurement of intake air temperature, the sensing

tip of the sensor is exposed in the intake air passage

before the throttle valve. For down-sizing, the sensor

terminals are directly mounted on the ECU board.

2.Throttle position sensor (TPS): Located on the end of




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ECU board

The ECU board used in the PGM-FI system for small motorcycles i

designed for single cylinder engines. The size is reduced by provi

injector driver circuit and an ignition circuit for one cylinder, allo

on the side of the throttle body. The CPU used for the controller i

The large parts such as the power supply condenser are located i

between various sensors in the device body, contributing to redu

width to the same level as a conventional carburetor. The ECU bo

layer structure to reduce the surface area for various circuits. In

harness connector, which takes a large amount of space in a conhas been down-sized to approximately 1/2 from the conventional

a terminal-to-terminal pitch of 2.6mm32 pin design. The reducti

to-terminal pitch becomes possible by using an adhesive gel shee

connector from water. To allow application of additional function

immobilizer, the number of pins is set at 32.

Idle air control device

the throttle shaft, directly detects the throttle

opening. The throttle shaft and the sensor rotor are

connected via a spring to eliminate a hysteresis in

the operation. The TPS is directly fit into the device

body and sealed from outside by potting.

ECU

3.Manifold vacuum (Pb) sensor: The sensor terminals

are directly mounted on the ECU board, and

connected to the connecting passage provided afterthe throttle valve in the throttle body.

Compared to a large motorcycle, less volume of intake air

has to be controlled for a small displacement motorcycle

engine. To cope with the stringent exhaust emission

regulations, delicate control capabilities are also required.

At the same time, to make an FI system applicable to smallmotorcycles, down-sizing is the key. To satisfy these

demands, the slide-valve-type air control valve (SACV)

driven by a stepping motor is applied to the PGM-FI system

for small motorcycles. In conventional direct drive type, a

stepping motor of 20mm was required to maintain the

operating torque to overcome the intake vacuum. In this

system, the size of the stepping motor has been reduced to

14mm by using the slide valve design.

Co

FI system cont rol

The PGM-FI system for small motorcycles controls the fuel injecti




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injection timing and the ignition timing based on signals from the

position sensor (TPS) in the ECU module, the manifold vacuum (

the crank position sensor that detects the rotation angle. The fuel

volume, the injection timing and the ignition timing are further c

the engine temperature, intake air temperature and the atmosph

to ensure optimum controls under various environmental conditio

Fuel in jection control

Ignition timing control

For ignition timing, the map control determined by the throttle op

engine revolutions is executed to control the ignition timing at th

timing.

O2feedback control

To efficiently use the 3-way catalyst in the exhaust muffler, the f

For the control of fuel injection volume, two kinds of maps are st

ECU and an appropriate map is selected and used depending on

opening and the engine revolutions.

1.When the loads are low, the delicate changes in throttle openi

detected by the manifold vacuum, and the manifold vacuum mby the manifold vacuum and the engine revolutions is used.

2.When the loads are high, the throttle map determined by the t

opening and the engine revolutions is used.




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system using an O2sensor is app ie to contro t e mixture near

stoichiometric ratio.

Control of idle air control device

The idle air control valve regulates the intake air volume dependi

operating conditions such as the starting, warming up and idling.

starting, the intake air is supplemented by opening the idle air co

depending on the engine temperature for easy starting. The opencontrol valve is regulated depending on the increase of the engin

to control the intake air volume at the optimum level. After the e

the prescribed temperature, the intake air volume is controlled to

idling at a constant speed by the revolution-feedback control. Thi

control eliminates the conventionally required idle speed adjustm

eliminating the need of maintenance to compensate for the secul

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Honda Fuel Injection System

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