cbr600

Fuel Injected CBR600 '99 model 


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Motivation

I have a Honda CBR600 that was destroyed in an accident, I kept it initially for spare parts. The engine was in perfect condition although with over 100000Km. It seemed like an exciting challenge to convert its carburettor engine into a fuel injected one, just for the fun of doing it. A lot had to be learned and many implementation problems to be overcame. So I could not resist to give it a try.


Introduction

I have succeed to convert the 1999 CBR 600 engine to fuel injection, ending up with a running engine, mounted on a non-ridable motorcycle. The engine was running so smoothly (without load) that I got really excited about the idea of riding the motorcycle with the new injection system, for that I had to recover the motorcycle to make it ridable again. During a few weekends I have gone through a miriade of short runs for dataloging followed by short stops for adjusting the fuel maps. Since those initial tunning rides I have had the pleasure to drive this motorcycle with the fuel injection system for more than 60000Km and counting without any problems.
 
Have used the motorcycle with the fuel injection on  three long trips:
- trip to Scotland                     - 8000Km long
- trip to Cape Bojador            - 5000Km long
- trip to Nordkapp in Norway - 15000Km

First Ride
The first ride on fuel injection was smooth with a funny problem. While carefully riding (keeping engine revolutions low and monitoring engine parameters), after 10Km the engine stalled and did not start for a while. It was already dark night and I did not carry a flash light so had to push the motorcycle underneath a public illumination light, by visual inspection could not find any cause for the engine stall. After a few minutes tried again and engine started, rushed home to investigate the cause for the engine stall. Back home the first thing I though doing was to remove the fuel tank to have access to all the electrical connections and fuel injection ramp. When double checking the amount of fuel remaining in the fuel tank have noticed the sound of air entering while opening it. It was strange that the fuel tank had reached such a low pressure, it turned out to be the fuel tank respirator hose that was pinched off not allowing air to enter to replace the consumed fuel. This was the only issue the motorcycle had after installing the fuel injection, but was not directly related with it.

For modifying the CBR to fuel injection the following items were implemented/assembled:
1- Electronic control unit (ECU)
2- Fuel injection throttle body
3- Air filter box
4- Exhaust gases oxygen sensor
5- Air filter box and  intake temperature sensor
6- Engine temperature sensor
7- Throttle body position sensor
8- Engine speed information
9- Intake absolute pressure information
10- High pressure fuel pump
11- Fuel return line feed into fuel tank
12- Injection maps switching

In order to understand the operation of the Megasquirt unit and to learn about the basics on fuel injection/spark control please refer to Megasquirt/MSnS Extra documentation that is quite complete.

In this pages you will find mainly the details about the engine modification done, all the basics about fuel injection control using Megasquirt will not be detailed 

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MegaSquirt Electronic Fuel Injection Unit

It would have been very interesting to develop a dedicated ECU from scratch, but such a task would probably be too overwhelming for me and due to time availability would eventually render the project to never finished state.  Anyway an opensource/openwardware ECU was already available in the Internet ready to use. This ECU is the Megasquirt which has been developed initially by two people, Bowling and Grippo, but has evolved with the contribution of many other. The available documentation for Megasquirt is very good, it covers a wide range of possible configurations witch make it suitable for many different engines configurations. I have used the Megasquirt and spark extra version which is a modified original Megasquirt unit to provide spark ignition control  besides the fuel injection control.
In my implementation (at the moment) I am using only fuel injection, the control of the spark ignition is being taken care of by the original Honda ECU.

megasquirt unit megasquirtunit2
Megasquirt spark & extra outside box view Megasquirt spark & extra inside view

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Fuel Injection Throttle Body

The original carburetors had to be replaced by a throttle body with electric fuel injector mounted on it, one for each cylinder. Since both the injectors as well as the throttle bodies are precision parts the safest and less time consuming approach was to acquire a throttle body ramp from another motorcycle already fuel injected from stock production. I found that the throttle bodies from 2001 CBR 600 (first model fuel injected) fitted the 1999 CBR600. The throttle body already had built-in: the automatic air chock actuated by the engine water cooling system; the throttle position sensor; the injectors; and the fuel line pressure regulator.

fulel injection ramp fuel injection ramp
Fuel injection ramp from 2001 PGMFI Honda CBR600 Fuel injection ramp assembled in the enjine

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Air Filter Box and intake air temperature sensor

Have bought an air filter box from the EFI 2001 CBR 600 model. This filter box add to be cut and re-shaped in order to fit into the 1999 CBR 600 frame due to the fact that the fuel ramp is at a much lower position with respect to the carburetors.Have acquired this filter box because I was not willing to change the original one (want to keep all material as original as possible in order to be able to revert the modification at any time) .

air filter box modification inside view air filter box modification external view
Air filter box modification to fit ram air hoses. Internal view Air filter box modification to fit ram air hoses. External view
2001 cbr600 air filter box modification detail assembled modified 2001 cbr600 air filter box
Detail of the modification done to the air filter box of 2001 cbr600 in order to make it fit the 1999 cbr600 frame Air filter box assembled on bike's frame
air filter box fitted to ram air hose air filter box fitted to ram air hose top view
Air filter box assembled into bike frame and connected to ram air hose Air filter box assembled into bike frame and connected to ram air hose. Top view
filter box bottom view
Air filter box seen from bottom side

An intake air temperature sensor was required, again have used the one from the 2001 CBR 600 that is mounted on the top of air filter box (white plug at filter box front side)

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Exhaust Gas Oxigen Sensor

By using an oxygen sensor the initial tunning process of the fuel injection maps can be made quite safe for the engine as well as simplified to the tuner. Have acquired a wideband O2 sensor from Innovative Motorsport, mounted it on the exhaust pipe after the point where the four cylinder pipes are welded together and before the exhaust pipe muffler mounting point.

Lambda sensor assembled sonda lambda assembled
Narrow band lambda sensor assembled (was actually replaced by an Innovate Motorsports wideband unit) Exhaust pipe drilled to fit lambda sensor. Sensor plug nut soldered to pipe

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Water Temperature Sensor

An engine temperature sensor was required, in this case have used the original engine water temperature sensor that became two purpose: provides engine temperature information to the fuel injection ECU and also provides the same information to the original dashbord temperature indicator gauche.

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Throttle Body Position Sensor

Throttle body position sensor, this sensor indicates to the ECU how open are the throttle body valves, this information is used to calculate the amount of fuel to inject into the engine. For this sensor have used also the one form the 2001 CBR 600 that fitted correctly on the throttle body. The sensor is used by the Megasquirt unit was well as by the original ignition control system (spark advance when throutle is opened).

Lambda sensor assembled
Throutle positions sensor


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Engine Speed Information

The engine speed (RPM- rotations per minute) information must be provided to the ECU, in order for it to calculate the amount of fuel to inject. The RPM information was obtained from the original ECU tachometer output signal

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Intake Absolute Pressure

Intake absolute pressure information must also be passed to the ECU in order for it to calculate the amount of fuel to inject. In the case of Megasquirt unit it contains already assembled into its board an absolute air pressure sensor, hence it was only  required to route a small diameter flexible hose from each cylinder intake to the ECU box. The current implementation is using only one MAP (manifold absolute pressure) sensor which does not allow for real time AFR (air fuel ratio) altitude compensation, although a double sensor can be mounted, being one monitoring the intake pressure and the other constantly monitoring the air pressure.

With a single MAP sensor the engine fuel management becomes noticeably miss adjusted when the altitude changes for more than 1000-1500 meters, under this situation a reset to the megasquirt unit will fix it. It can be done while driving in the following way: grab the clutch such that the engine is not moving; stop the engine in the main power switch wait a couple of seconds, the megasquirt unit must also be powered down; turn on the power switch again and start the engine (using the starter or simply by releasing the clutch). 

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Fuel Injectors

The fuel injectors as the name indicates are used to inject fuel into the engine intake manifold, for this operation they need to be connected to a high pressure fuel line. To achieve the necessary fuel pressure "high" pressure fuel pump must be used. Once again I have used the fuel pump from the 2001 CBR600, the main advantage is that it is designed to provide fuel to the injector model being used.
The high pressure fuel pump was designed to be mounted inside the fuel tank for space and cooling considerations. In this case installing the fuel pump inside the fuel tank was not the first option because it would required too many modifications to the original fuel tank, to avoid that, a separated small tank was build to house the fuel pump. This small tank was assembled at the right side of the rear suspension.

high pressure fuel pump fuel pump tank cover view
High pressure fuel pump and fuel filter Fuel pump tank top cover view
fuel pump tank interior fuel pump tank assembled to bike's frame
Fuel pump tank interior coated with anti-rust protection. This coating was not very resistant to abrasion, had to replace it latter by a two components epoxy tank protection from Restom (http://www.restom.net/), that product has a brown translucent color after drying and is hard but still tolerant to physical stress. Fuel pump tank assembled to the bike's frame. Original fuel pump is seen at top left side from rear brake oil container
high pressure fuel pump tank fuel pump tank fixation to bike's frame
Small tank (handcrafted) containing inside high pressure fuel pump. Also shown support for fixation at motorcycle frame Fuel pump tank support (unfinished) assembled to the bike's frame


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Fuel Return Line

A fuel return line from the injectors to the fuel tank was required, this would imply to open an extra hole into the fuel tank. To avoid changing irreversibly the fuel tank, the fuel level sensor mounting was modified in order to still hold the fuel level sensor and also to connect the return fuel line.
fuel return line plug fuel return line plug assembled into the fuel tank
Handcrafted fuel return line plug with coupled fuel level sensor Fuel return line plug assembled into fuel tank

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Fuel Maps Selection

The Megasquirt ECU allows to select between two different fuel maps, the main purpose of this feature is to be used on turbo charged engines. But I found it interesting to be able to switch between two different fuel maps: one optimized for power; the other optimized for fuel economy. The need for dual maps for this reason is highly arguably, because a single well tunned fuel map should suit both purposes at the same time, but in the absence of that premise (well tunned fuel map) having the possibility of switching maps can be very convenient. An electrical switch was assembled at the left handle bar to allow for the real time switching between the two available fuel maps.
Another feature was implemented by means of a multiplexer that allows to scale in real time the current fuel map by the following factors:
-20%; -15%; -10%; -5%; +5%; +10%; +15%; +10%. This is achieved by tricking the ECU in believing that the engine is operating at a different temperature than it really is. The list of fuel injection correction to apply to the engine as function of its temperature is tweaked to correspond to the enrichments presented for very low temperatures. Temperatures no likely to happen in the mildly warm Portugal climate (even at winter).
One of the multiplexer positions is of course the default Megasquirt operation mode. Using the fuel map scaling has a disadvantage related to the fact the the ECU will not be monitoring the real engine temperature neither it will be shown on the dashboard, in the eventuality of an engine problem that raises the temperature it will not be noticeable to the rider.

fuel return line plug
Handlebar fuel maps switching controls
1- Power/economy fuel map selection switch. Old lever for closing carburetors chock. Forward position corresponds to power maps which is VE table 3, backward position corresponds to economy map which is VE table 1.
2- multiposition switch to control fuel map scaling.                     


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Fuel Maps and MegaSquirt Configuration

Temperature sensors calibration files
- Manifold temperature sensor configuration file for original Honda part (cbr 600 2001 fuel injected). Link
- Engine coolant temperature sensor configuration file for original Honda part (cbr 600 1999). Link

MS configuration file. Link

The Megatune software verion used is 2.25, the Megasquirt firmware version is MSnS-extra 026h4.
ve_table3.jpg
Main volumetry efficiency fuel map. Optimized for power
ve_table1.jpg
Secondary volumetry efficiency fuel map. Optimized for economy, to avoid AFR lean situations for high revs or high engine loads the VE entries are the same as the VE map 3.



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First Run




Wiring, Megasquirt box and wideband O2 sensor controller staying under the sit. Wiring, Megasquirt box and wideband lambda sensor controller staying under the site.
final assembly of fuel ingection ramp, air filter box and high pressure fuel pump
Fuel injection ramp filter and high pressure fuel pump assembled and ready to fit fuel tank over it


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