Method for converting a spark ignition system to an enhanced sequential spark ignition system for a 6-cylinder engine

This article explains a simple method of converting the wasteful spark type ignition system in your car to an enhanced sequential spark type 6 cylinder engine ignition system.

Main Requirements

I was browsing the cars and motorcycles section but couldn't find what I was looking for. I hoped you might be interested in seeing my project.

My car has a straight 6 cylinder EFI engine with a firing order of 1-5-3-6-2-4 (Ford Australia). The ignition is a waste spark type with coils 1 and 6 paired, 2 with 5 and 3 with 4.

I'm looking for a circuit that can take the ignition pulses from the ECU and alternate between 1 and 6, 5 and 2, 3 and 4.

That way you can have individual coil drivers and full sequential firing. On power up the system is reset and a counter monitors the odd and even pulses, I guess maybe there would be some software involved.

There are 3 separate circuits, 1 for each output pulse from the ecu, 1, 5 and 3 always get the first pulse on odd numbers, 6, 2 and 4 get the second pulse on even numbers. Then the circuits just alternate until you cut the ignition.

I hope you find the idea of ​​this project interesting and worth your time and effort to publish the solution on your website.

My response: I will try to design the specified circuit for you, but since I'm not an automotive expert, I'd be interested to know how your existing system wastes spark types and if the new odd/even idea would help improve it?

Nevertheless, according to me the new idea can be implemented using a common IC 4017 divider IC without the need of software.

Mr. Brunton: I plan to supercharge the engine with more powerful individual coils after the ignition upgrade. You are correct that there is no advantage to introducing a sequential ignition system on a standard engine.

The three pulses emitted by the ECU are arranged in sequence, and their timing is calculated by the ECU based on engine speed, intake air temperature, throttle position, etc.

How the circuit needs to work

This circuit does not need to worry about the ECU's work. All it needs to do is route the pulses between a pair of terminals to the same terminal the first time, then alternate between them.

I would just put three identical circuits on one board, with a separate circuit for each ECU output.

When you crank the engine for the first time, the ECU waits for a signal from the crankshaft trigger wheel sensor.

It then waits for a signal from the camshaft position sensor. Once the ECU receives these two signals, it knows where the top dead center of cylinder 1 is on the compression stroke.

It then sends out the first pulse as programmed to start the engine, with the other pulses following in sequence.

I'm glad to hear that you think there is a simple solution, and I appreciate you finding this project worth your time.

For more details, please consider the accompanying sketch.

design

The following diagram shows the processor circuit used to convert wasteful spark ignition into enhanced sequential ignition.

In the diagram, points A and B should be connected to the trigger inputs of the corresponding CDI units for igniting the associated internal combustion engines.

The working principle of the circuit can be understood with the help of the following points:

1) Once the circuit is powered by 12V battery, IC 4017 is reset through C1.

2) Pin 3 of IC now goes high and T2 goes into standby mode with its base biased with the voltage of pin 3. However, T2 cannot conduct yet as there is no voltage on the collector pin.

3) When the first ECU pulse reaches the base of T4, it is turned on and T4 connects pin 14 of the IC to ground. But the IC does not respond to this because it is designed to respond only to positive pulses on pin 14 and not to negative pulses.

4) However, during the conduction of T4, T1 also conducts because its base is negatively biased through D1, R2, and T4. During this process, T1 transfers +12V to the collector of T2 until the voltage is transferred to its emitter and transferred to point A.

5) Next, the ECU pulses off, causing T4 to close, which immediately results in a positive pulse at pin 14 through R1.

6) At this point, IC 4017 responds and causes a logic high level to jump from pin 3 to pin 2.

7) Now, pin 2 goes into standby mode, waiting for the next pulse from the ECU.

8) When the next ECU pulse arrives, the above process is repeated until the ECU pulse is turned off, which in turn causes the logic high level of IC pin 2 to jump to pin 4. At the same time, point B is also transmitted through the transmitter of T3.

9) When a logic high reaches pin 4, the IC is immediately reset, causing a logic high to return to pin 3.

10) The circuit now reaches its previous position and awaits the next repetition.

We will need 3 of these circuits

In the waste spark to sequential spark ignition converter design explained above, only one example was discussed. We will need 3 such circuit modules to configure the appropriate output from the ECU to implement the proposed enhanced high efficiency 6 cylinder engine sequential system.

Fixes:

The design of the wasted spark switch circuit shown above appears to have a serious flaw. The emitter lead of T2 (T3 emitter-follower) will always conduct in response to a high logic on the associated IC 4017 pinout, rendering the operation of the device completely useless.

This problem can be corrected by integrating an AND gate at the output of IC 4017 as shown in the following figure.

Please make sure to connect a 100k resistor between the collector of T1 and ground

Here, we have used IC 4081 quad channel AND gate IC for switching. Only two AND gates are used out of 4 gates and remaining two are not used and terminated to ground properly.

For example, if we look at inputs 1 and 2, we see that 1 is connected to the 4017 output, while pin 2 is connected to the T1 collector. The output of this gate is pin 3, which is always at logic zero. It will not turn on or go high unless both inputs 1 and 2 go high, which only happens when T1 turns on in response to an ECU trigger. The same principle is expected on input pins 6 and 5, and its output pin 4.

Test Results

Mr. Brunton's feedback:

Hello Svagartan, it's been a while since I last contacted you,

I hope all is well with you and your family.

I continued to experiment with the circuit described in "Wasted Spark 2" because it didn't do what I wanted. Output A would go high immediately after powering the circuit. I didn't want that. I wanted Output A to wait for a signal from the ECU before temporarily going high to fire the ignition coil. So I finally decided to connect the BC557 to the ECU signal line instead of directly to 12V and SUCCESS!

My prototype circuit started working exactly the way I wanted it to.

Due to COVID I paused my project but I am glad that I have a working prototype and it is all thanks to you Swagatam. I can't thank you enough.

be safe.

Kind regards, Brenton.

The final working prototype of Mr. Brunton's suggested wasted spark ignition circuit is shown below:

Please make sure to connect a 100k resistor between the collector of T1 and ground

Other specifications provided by Mr. Brunton

If the engine is turned off, the circuit must be de-energized.

Usually, there is only one large positive terminal on the back of the alternator, which is used to connect the power wire.

There needs to be a heavy gauge wire connecting this terminal to the battery so that the battery can be charged by the alternator when the engine is running.

When the engine is stopped, the circuit must be de-energized, so careful consideration must be given to the placement of diodes to control the current.