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					Design of an Electronic Fuel Injection Controller for the 2003 FLHT

                   Harley-Davidson Motorcycle

              Avishesh Dhakal, Brian Patterson, Jonathan Stoker

                                Contact Info:



Executive Summary

       We are designing a fuel injection system that allows access to timing parameters in

order to control the fuel injection and ignition for performance enhancement of Harley

Davidson motorcycles. Due to the increasing trend in customizing motorcycles with aftermarket

add-ons, an increase in the demand of motorcycle tuning has occurred. With the addition of

add-ons, performance of motorcycles will decrease. This is most evident in the fuel injection

and ignition of motorcycles. By having the ability to tune the parameters of the fuel injection

and ignition, performance drops from add-ons can be compensated. In order to have the ability

to tune fuel injection and ignition, current manufacture-built electronic fuel injection systems

need to be replaced by systems that allow access to the timing parameters. This report outlines

the design of such a fuel injection system that allows access to timing parameters for a 2003

FLHT Harley-Davidson motorcycle. This report discusses the assessment and circuitry choices

made to allow minimum power consumption while maintaining a small overall board size. By

choosing low power and small components for the design, achieving a controller that will

operate on a 12 volt battery and can be easily concealed on a motorcycle can be achieved

relativity inexpensively.


       Many Harley Davidson buyers have the urge to modify their new motorcycles to meet

their expectations. Though this does produce great results in the areas of cosmetics and power,

it can also have an undesired effect of decreasing fuel efficiency, engine life, and environmental

issues. This is mainly from the fact that the Harley’s factory engine control unit (ECU) is a black

box that doesn’t allow user to manipulate the variables of the electronic fuel injectors (EFI).

Because of this, there is a need to bypass the main engine control unit with an easily

configurable interface for the EFI control. Changing the fuel maps or the spark timing offers an

effective solution to this problem which could be done by a custom built engine control unit.

The ECU monitors and controls the parameters such as engine temperature and revolutions per

minute through the fuel maps and provides feedback through the fuel injectors thus making

them open for the calculated duration.

Problem Definition

       The goal of this project is to design an engine control unit for use on a motorcycle that

could enable the end-user to fine-tune the parameters to govern the functioning of engine. The

ability to change the fuel maps of an EFI is required in order to maintain performance and

environmental protocol if the user has made modifications to their motorcycle. Because of this,

the whole controller needs, low power consumption, ability to run off of a 12 volt battery,

ability to interpret/convert input signals for the controlling algorithms in the microcontroller,

ability to interpret/convert output control signals to the injectors/ignition coils, and the least

amount of circuitry required reducing the size of final board. Cost is another big factor that has

to be considered while designing the EFI. It draws constrain in assembling the components

within a low budget so that it can be made available in the market at an affordable cost to the


       This project focuses on the design of the supporting circuitry of the EFI controller, not

the derivation of the controlling algorithms. This controller will use a derivation of the

MicroSquirt’s algorithms to control the actual circuitry when implemented in the lab. The

supporting circuitry will contain circuitry to interpret/convert input and output signals allowing

the microcontroller to use that information.

Due to the unique nature of this project, we are focused in designing the hardware to meet our

requirement rather than spending time in looking for possible alternatives. Factors such as cost

for end-users, size of the EFI controller small enough to conceal within the motor cycle,

operating voltage within the threshold of the available supply, and easy manipulation of the

parameters in order to manipulate the key functioning variables provide constrains to design an

efficient model of EFI.

Project Plan

     Secondary Research (Engine)    2/5/2009                                                    90
 Secondary Research (Microsquirt)   2/5/2009                                                    90
   Preliminary Problem Definition   2/5/2009               35                       0
            Preliminary Web Page    2/5/2009               35                       0
                        Schematic              2/19/2009            22                  0
                     Board Layout                                                       3/23/2009             44
      Detailed Problem Definition                                                       3/23/2009             44
                Detailed Schedule                                                       3/23/2009             44
           Conceptual Generation                                                        3/23/2009             44                          0
                    Board Testing                                                                                    4/30/2009        6       3
                    Design Review                                                       3/23/2009              44
                         Snapshot                                                                             4/23/2009          13
                    Design Report                                                                             4/23/2009          13           3
                        Web Page                                        3/12/2009                        55                                   3
                          Logbook   2/5/2009                                                    90                                            3
                     Programming                                                                                          5/1/2009    5       3
           Connect to Motorcycle                                                                                          5/1/2009    5       3

                                                           Start Date      Completed         Remaining

Team Responsibilities

Avishesh Dhakal – Accountant, Scribe, Collector of Materials

Brian Patterson – Web Manager, Timekeeper, Scribe, Main Board Layout Editor

Jon Stoker – Leader, Spokesperson, Scribe, Break-out Board Layout Editor

Concepts Considered

        Due to the nature of how this project was presented to us, there was only one concept

considered. From the beginning of the project our team has worked with the Microsquirt due

to overwhelming information available. The processor and circuit components have changed

little from the Microsquirt design because we wanted to better understand how the controlling

software functioned. There have been two additional devices added to the project. These

devices are the breakout board and stimulator.

        The breakout board was considered due to our goal of making the Microsquirt easier for

end-users to add to their motorcycle. Please see A-13. The breakout board serves the purpose

of allowing the Microsquirt and Harley Davidson ECU to be connected to the motorcycle at the

same time. The circuitry on the board will route the input signals from the sensors to both ECU.

The output signals will be routed with mutual execlusion back to the various components of the

motorcycle like the fuel injectors and ignition sparks. Initially the breakout board will only

route the output from the Microsquirt needed to control the injectors, the Harley ECU will

control the rest. As the project matures more functionality will be controlled by the

Microsquirt until it is fully able to control the engine by itself.

        The second device is the stimulator. The stimulator is a device that allows emulation of

signals sent from the engine to test performance of the Microsquirt. The stimulator consists of

multiple pots that can be adjusted manually. The ECU’s output can then be read and compared

for accuracy.

Future Work

       The breakout board planned for this semester was not completed to prototype stage.

This will be completed during next semester. Also the stimulator was assembled but testing of

the microsquirt using this device has been deferred to next semester.

       Additional plans for next semester are programming our Microsquirt to suit the

parameters of the Harley Davidson engine. Testing of the Microsquirt and improving the code

and circuitry will also be accomplished next semester.

System Architecture

       The first version of our conceptual design is the MicroSquirt board built by Bruce

Bowling and Al Grippo [1]. By constructing our first version off of the MicroSquirt, we will learn

the current MicroSquirt board’s construction and discover the difficulties and issues that will

arise when constructing our own controller. This process will also allow testing of a working EFI

controller to give our group a stronger understanding of the expected signal outputs and inputs

for the 2003 Harley-Davidson motorcycle that will allow improved customization of our own


       The MicroSquirt EFI controller can be separated into 10 main circuitry sections. These

include, microcontroller and support, sensor inputs, tachometer input, second tachometer

input, 5 volt power supply, controller area network, serial input, external connection, injector

and ignition coil output, and general output. While much of the circuitry support provided on

the MicroSquirt is not required or used by the motorcycle, the first version of our board will

include all of the circuitry in order to test functionality of the entire system.

       The microcontroller and support fulfills the requirement of a programmable

microcontroller that can store and implement the MicroSquirt’s EFI control algorithms. The

MC9S12C32 microcontroller contains the appropriate number of inputs and outputs to control

the 2003 Harley’s. It contains eight analog to digital converters (ADC) that will be used to allow

the microcontroller to interpret the five analog 0 to 5 volt sensor inputs [2, 8: 5-73-85]. The

controller also contains eight timing module inputs that can output timing square wave signals

to accurately switch the four injector/ignition coils and the idle air control on as well as count

the time between full cycles of the piston from the crank position sensor in order to derive the

RPMs [2]. The MC9S12C32 also contains an SPI that will allow serial data programming of the

controller. The last Harley circuit that this controller must be able to control is the fuel pump

shut off which is done by a simple built in event clock on the MC9S12C32. By containing enough

inputs and output ports to support all of the senor inputs and control outputs for the Harley-

Davidson motorcycle and having 32k of flash, the MC9S12C32 fulfills the requirements of a

programmable microcontroller that can hold and implement control algorithms for the

injector/ignition timing required for proper functionality of the 2003 FLHT as shown in appendix


       All the sensor inputs from the Harley are time varying 0 to 5 volt signals [8: 5-73-85].

Simple RC filtering was implemented on all of the input sensors to allow a clean signal to the

ADC inputs of the microcontroller as shown in A-2.

       Due to the 2003 FLHT having only one crank position sensor, only one of the tachometer

circuits constructed for the MicroSquirt is required for our project. The crank position sensor on

the Harley will output a rough sine wave output where the peaks of the sine wave occur when

the crank position sensor comes into contact with the teeth on the crank wheel [8: 5-95]. By

removing one of the teeth on the crank wheel at initial startup position, a longer time period

when over the missing tooth will occur. By converting this signal into a 0 to 5 volt square wave,

the microcontroller can detect the rising edges and count the time in between the teeth to

determine the RPMs of the engine. In order to create this 0 to 5 volt square wave, a sine to

square wave converter is needed. This can be done using a series of amplifiers as shown in A-3.

        As this EFI controller will be controlling a motorcycle, it is reasonable to assume this

entire controller will function off of a 12 volt battery. Since the microcontroller runs off of a

standard 5 volts, a 5 volt power supply is needed on the board. To construct this power supply,

a LM290LD-5.0 voltage regulator was used with some capacitive and inductive filtering as

shown in A-5. The LM290LD-5.0 was used because of its large voltage input range (to allow for

voltage spikes off battery), operating frequency similar to motorcycle’s engine, and low power

dissipation [5].

        Every microcontroller requires some way to program the flash memory to enable stand

alone systems. The MC9S12C32 uses a serial peripheral interface to program the controller.

This means, a serial transceiver is needed to allow accurate serial data to be transmitted to the

controller. The MAX3221 shown in A-7, was used for this because of its automatic shutoff

feature, RS-232 capability, and 1μA supply current that will minimize power consumption

overall [4].

        The AMP-SEAL 35-pin was chosen for the external connection to the motorcycle for its

waterproof seal around the connector and sufficient pin count as show in A-8. This is an

extremely useful feature when functioning on a motorcycle that is exposed to all kinds of


        Since the microcontroller will output a square wave pulse when the injectors/ignition

coils need to be fired, a simple MOSFET switch can be used. The VND5N07 and VB921ZVFI were

used as the switching MOSFETs for the injector/ignition coil firing as shown in A-9. This was due

to there turn on time, current rating, and required gate to source voltage [6, 7].

       The fuel pump and idle for the Harley require temporary grounding for activation. This

was done with dual MOSFET switches in a single package to reduce the number of component

require as shown in A-10. The IPS1041 was used for its current/voltage protection, low power

dissipation, and dual package feature [3].

       The controller area network (CAN) and second tachometer input were not needed for

the 2003 FLHT but were still constructed in the first version of our board to test functionality.

Since their circuit make up will not be used, the circuits construct for these section are mirrors

of the MicroSquirt circuitry shown in A-6 and A-4.

       Placing all of the circuits shown in A-1 through A-10, a board layout of our EFI controller

was constructed using EAGLE shown in A-11. With this circuit makeup and board construction,

the first version of our EFI controller is done and ready to be tested and improved next



[1]. B. Bowling and A. Grippo, “Introduction to the MicroSquirt EFI controller,” 2005. [Online].

Available: [Accessed: Jan. 22, 2009].

[2]. Freescale Semiconductor. “MC9S12C Family MC9S12GC Family Reference Manual,”

2006. [Online Data Sheet]. Available: [Accessed:

March 12, 2009].

[3].International Rectifier. “Single/Dual Channel Intelligetn Power Low Side Switch,” 2006.

[Online Data Sheet]. Available:

[Accessed: March 12, 2009].

[4]. Maxim Integrated Products. “1μA Supply-Current, True +3V to +5.5V RS-232 Transceivers

with AutoShutdown,” 2003. [Online Data Sheet]. Available: http://datasheets.maxim- [Accessed: March 12, 2009].

[5]. National Semiconductors. “1A Low Dropout Regulator,” 2007. [Online Data Sheet].

Available: [Accessed: March 12, 2009].

[6]. STMicroelectronics. “High Voltage Ignition Coil Driver Power I.C.,” 2004. [Online Data

Sheet]. Available:

P.pdf [Accessed: March 12, 2009].

[7]. STMicroelectronics. “Omnifet: Fully Autoprotected Power MOSFET,” 2004. [Online Data

Sheet]. Available: [Accessed: March 12,


[8]. “Touring Models 2003 Harley-Davidson,” Electrical Diagnostic Manual, Milwaukee:

Harley-Davidson Motor Company, 2002.