feedback

i must admit that i am so pround of being part of this project. it takes us a lot of time and also cost almost $1000. but i have learned so much from doing this project. during the presentation a lecturer asked me what have i achieved from this project. i din't tell him much. but now i can say i have learned how to read a wiring diagram throughly. and i also have learned that how all the wires are wired on a vehicle. it used to be very complicated to me, but now it is so simple and so clear.

also the another thing we have learned is how to program a electronic device. before this i never imaged that it is so simple. we have learned that electromagnetic interference, but before it is just a conpect to me, coz i have never experienced with them. but now i have really had a good touch with it.

presentation day

time goes by so fast and our project also comes to a full stop. we are so excited to present our project to the class. it is the proof of our hard working and knowlege application. when we are doing the presentation we are asked a lot of questions by the lecturers which is not what we expected. may be we are not prepared enough or may be we don't have enough time to explain. but anyway,  we are pround of the project we have done. and it will perform its destiney. this board is gonna used by Unitec to show a student how EFI system works without running the engine.

MAP sensor simuation

A MAP sensor is simply a vacuum gauge connected at the engine’s intake manifold and provides the ECU with engine load information. However, in our project a small DC motor is used to work as an engine to drive the distributor. Without the piston runs down inside a cylinder when the throttle is running at idle or at partly open position, vacuum cannot be produced for the MAP sensor. so a fixed value of 5 volts can only be sent to the ECU which is the atomosphere pressure voltage. so we decided to use a special electronic device to simulate the MAP sensor.

Except the for the PicAxe 08M chip, all the components can be bought as a kit at the price of about $ 10 from Surplustronics. The chip costs another extra $ 4. The kit includes a 22 K resistor, a 10 K resistor, a capacitor, programming unit and also a connector for programming.

without programming this unit is nothing more than a electronic device. this is the first time we acutually get into the touch with programming and it is not hard at all.

motor and throttle body synchronization unit

Since a small DC motor is used to work as an engine, a special designed DC motor and throttle body synchronization unit must be used. When the throttle is closed, the DC motor runs at idle at the speed of 800 rpm. With gradually opened throttle body, the DC motor speed increases correspondingly until reaches to top speed at 4000 rpm when the throttle is fully open. The following picture shows the DC motor and throttle body synchronization unit. It looks like just the same with the unit we have used for the MAP sensor, but the program and is totally different.

The programming of the DC motor and throttle body synchronization unit is the biggest problem we have ever encountered in the project as well as how to wire the unit into the EFI system. The following two pictures show the programs we wrote for the unit but the DC motor did not synchronize well with the throttle. We wrote over 10 programmes from the unit and tried again and again until it really works well.

Electromagnetic Interference

When electric devices are close or interconnected to each other, electromagnetic interference interacts among all these devices. As for our project, the primary source of interference is caused by the secondary ignition cables. When current stops and starts it creates a strong electromagnetic signal wave which interferes with other electronic systems such as crankshaft position sensor, camshaft position sensor and ignitor. The undesirable side-effect of the phenomenon of interference we encounter is that the louder electronic device operating noise and sometimes malfunctions of the electronic devices.  and when we perform scope test, the interference is especially appeared on the waveforms

temperature sensor simulation

there are engine coolant temperature sensor and air temperature sensor included in this project. we thought of two ways to test these two sensors by using a heat gun. and also for the convenience of testing these two sensors, we decided to use a potential meter to simulate the temperature changing. As the potential meter is adjusted the resistance value changes correspondingly which changes the signal voltage to the ECU. howevery, the resistance of engine coolant temperatue sensor can goes from 10,000 ohms when it is cold and drops to a few hundred ohms when it is hot. the potential meter we used can only adjust from 1000 ohms to 3000 ohms, this is why when we use scope to test the sensor there is not much change.

LED for simulating injection pulse

one of the aggreed outcomes of this project is that we should include the fuel system. however when the atomized fuel meet with sparks from the spark plugs, dangerous can happen. under safety concideration, our superviser have agreed to cancle out the application of fuel pump. without the fuel pump runs fuel into the injectors, we have to use LED to simulate injection pulses.

If an LED were connected directly across a 12 volt battery, it would light brightly, but only for a few seconds. Excessive current can destroy the P-N junction. The average LED requires only about 20-30 mA. So a resistor must be connected in series with every LED to control current flow. The method we have used to protect the LED is to connect a 470 ohm resistor in series with each LED. The resistor can be connected to either the anode or the cathode end.