Selecting an Engine Control Computer (ECU): -

Date	Discussion
Feb 2023	Fuel Injection systems used to be all mechanical. This is particularly true for diesel engines. The mechanical fuel metering systems were generally clumsy and not able to provide the finesse, and nuanced operation, of their more modern and very efficient electronic counterparts. Furthermore, they had to be built to very fine tolerances, which made them not only very expensive to manufacture and, therefore, to repair but made them very susceptible to malfunction as their component parts began to wear. Electronic control systems have now, largely, replaced their mechanical forebears. Engine Control Computers (ECUs) have evolved into very complex devices that monitor a huge range of information, from every part of the engine, to ensure the best possible performance. An engine can now easily be tuned for maximum power, or minimum emissions or optimum fuel economy, whatever best suits the current application, by simply changing the ECU program. Car companies probably spend millions of dollars on researching ECU techniques, and settings, that best suit their vehicles. However, there is also a thriving DIY market for people who want to build racing cars, enhance motorcycles and quadbikes, or simply convert their boats to electronic fuel injection. Many of the ECUs offered to home builders are offered by established racing component suppliers that provide well researched kits for specific vehicles. Some ECUs are provided to the "plug and play" hobby community to develop for themselves. Naturally, the pricing of ECUs, for the DIY market, can vary enormously , depending on the level of investment made toward their creation. Another corner of the market is aimed at DIY people who have an electronics background, (or who are prepared to learn), and that is where the ECU for Rhapsody has been sourced. A significant development in the hobby electronics world, that has made this possible, has been the arrival of the Arduino computer from a development company in Italy. The Arduino is a complete, working, programmable computer, with a significant memory facility, that is able to store and execute complex computer programs. There are various models but think in terms of a printed circuit board about the size of a packet of cigarettes, (remember them?), and costing about $30. There are a number of competing products doing similar things, the "Raspberry" comes to mind and Rhapsody has one of those already, to send status information such as House battery voltage, LPG tank levels, and details of any bilge pump activity, to my mobile phone via the Internet. (Of course!) An Arduino is a complete baby computer, however it is not able to drive heavyweight engine hardware, like injectors or spark plugs, directly. It needs to be provided with a specially designed interface board to make its outputs, and inputs for that matter, compatible with the various parts of the engine. Again, there are a number of competitive products on the market to fulfill this role. "Megasquirt" is a very popular unit, as is the one I have chosen, which is called "Speeduino". To put the pricing of these units into perspective, the cheapest complete ECU, from someone like Haltec Conversions, starts at around $2,500 and rises rapidly depending on the options selected. The price of the Speeduino is just $230. Yes, you have to build the printed circuit board yourself. Yes, you have to download the software yourself. Yes, you have to perform the final tuning yourself, but the end result should be exactly what you want it to be. In addition, Speeduino is designed and developed in Castlemaine in Victoria and the software is provided via the Public Domain and is free. The Speeduino Kit, version 0.03.4, was duly ordered, and it arrived as a printed circuit board (PCB) with a large number of plastic bags full of components. The PCB was very clearly silk screened, with all the component details shown, that made building the whole thing a very straightforward, albeit four-hour, job. The kit did not include the actual Arduino computer itself but specified that the so-called "Mega 2650" was required. As with all things, there are the original units and there are copies. I elected to buy the "real thing" from Arduino, which cost $21.95, whilst there are a number of cheaper "copies" available from China - naturally. The assembled Speeduino board, with the Arduino processor plugged in, worked perfectly and its software downloaded and installed without any issues. There is a separate setup and tuning program, called "Tuner Studio", and it was also downloaded. Tuner Studio has a no-frills version that is free, however, if you want to use its various advanced facilities, there is a one-time charge of $69.95. For the Speeduino to operate correctly, it needs to be connected to the engine to be able to monitor its "vital signs", such as coolant temperature, air pressure, throttle position, oxygen content of the exhaust gasses and current air temperature. Most petrol car engines are so-called "4-strokes", which means that one complete cycle of the engine occurs every two revolutions, or 720 degrees. The Speeduino needs to know where the engine is in that 720 degree cycle at any given instant because it needs to be able to time the operation of the injectors correctly. This is done by taking a continuous timing signal from the engine to the Speeduino and there are a number of ways in which this can be done. Rhapsody's engine has mechanical points in the distributor, which fire the appropriate spark plugs at the correct time within the engine cycle, for each of the six cylinders. This type of ignition system was designed in 1904 by Charles Kettering as was used almost exclusively in every petrol engine car built in the following 75 years. Although Rhapsody is fitted with an "after-market" electronic ignition system that both reduces the load on the points and produces a much more reliable spark. The whole system is well developed and works very well, so I decided to keep it. It is true that the Speeduino unit is quite capable of replacing the old system with an electronic version and there would be some tuning advantages in doing that. However, enhanced performance is not the goal here, and it's not worth the extra effort and expense. The principle role of the distributor points is to drive the ignition system, of course, however, since they occur at specific times, in the engine's 720 degree cycle, they can be used by the Speeduino unit to drive the fuel injection system as well. In a six cylinder, four-stroke, engine the pistons always arrive at Top Dead Centre (TDC) in pairs. One piston will be starting its power or firing stroke and the other will be starting its induction stroke. Or, put another way, one will be ready for a spark and the other will be ready for fuel to be injected. This is very convenient because it means that for every spark pulse, a fuel injection pulse is required as well and the Speeduino can use that fact to correctly time the fuel injectors. All the Speeduino needs is access to the pulse from the points. Easy! Well, not quite. The car ignition system operates on 12volts and the Speeduino operates on 5 volts. Also, because the point's regular role is to drive a highly inductive load, it becomes, electrically, very "noisy" and far too messy to be used by the Speeduino directly. The pulse signal from the points has to be reduced to the right voltage and heavily filtered to remove the extraneous noise pulses before it can be used, and a separate filter circuit has to be built to do that.

Date

Discussion

Feb 2023

Fuel Injection systems used to be all mechanical. This is particularly true for diesel engines. The mechanical fuel metering systems were generally clumsy and not able to provide the finesse, and nuanced operation, of their more modern and very efficient electronic counterparts. Furthermore, they had to be built to very fine tolerances, which made them not only very expensive to manufacture and, therefore, to repair but made them very susceptible to malfunction as their component parts began to wear.

Electronic control systems have now, largely, replaced their mechanical forebears. Engine Control Computers (ECUs) have evolved into very complex devices that monitor a huge range of information, from every part of the engine, to ensure the best possible performance. An engine can now easily be tuned for maximum power, or minimum emissions or optimum fuel economy, whatever best suits the current application, by simply changing the ECU program.

Car companies probably spend millions of dollars on researching ECU techniques, and settings, that best suit their vehicles. However, there is also a thriving DIY market for people who want to build racing cars, enhance motorcycles and quadbikes, or simply convert their boats to electronic fuel injection. Many of the ECUs offered to home builders are offered by established racing component suppliers that provide well researched kits for specific vehicles. Some ECUs are provided to the "plug and play" hobby community to develop for themselves. Naturally, the pricing of ECUs, for the DIY market, can vary enormously , depending on the level of investment made toward their creation.

Another corner of the market is aimed at DIY people who have an electronics background, (or who are prepared to learn), and that is where the ECU for Rhapsody has been sourced. A significant development in the hobby electronics world, that has made this possible, has been the arrival of the Arduino computer from a development company in Italy. The Arduino is a complete, working, programmable computer, with a significant memory facility, that is able to store and execute complex computer programs. There are various models but think in terms of a printed circuit board about the size of a packet of cigarettes, (remember them?), and costing about $30. There are a number of competing products doing similar things, the "Raspberry" comes to mind and Rhapsody has one of those already, to send status information such as House battery voltage, LPG tank levels, and details of any bilge pump activity, to my mobile phone via the Internet. (Of course!)

An Arduino is a complete baby computer, however it is not able to drive heavyweight engine hardware, like injectors or spark plugs, directly. It needs to be provided with a specially designed interface board to make its outputs, and inputs for that matter, compatible with the various parts of the engine. Again, there are a number of competitive products on the market to fulfill this role. "Megasquirt" is a very popular unit, as is the one I have chosen, which is called "Speeduino". To put the pricing of these units into perspective, the cheapest complete ECU, from someone like Haltec Conversions, starts at around $2,500 and rises rapidly depending on the options selected. The price of the Speeduino is just $230. Yes, you have to build the printed circuit board yourself. Yes, you have to download the software yourself. Yes, you have to perform the final tuning yourself, but the end result should be exactly what you want it to be. In addition, Speeduino is designed and developed in Castlemaine in Victoria and the software is provided via the Public Domain and is free.

The Speeduino Kit, version 0.03.4, was duly ordered, and it arrived as a printed circuit board (PCB) with a large number of plastic bags full of components. The PCB was very clearly silk screened, with all the component details shown, that made building the whole thing a very straightforward, albeit four-hour, job. The kit did not include the actual Arduino computer itself but specified that the so-called "Mega 2650" was required. As with all things, there are the original units and there are copies. I elected to buy the "real thing" from Arduino, which cost $21.95, whilst there are a number of cheaper "copies" available from China - naturally.

The assembled Speeduino board, with the Arduino processor plugged in, worked perfectly and its software downloaded and installed without any issues. There is a separate setup and tuning program, called "Tuner Studio", and it was also downloaded. Tuner Studio has a no-frills version that is free, however, if you want to use its various advanced facilities, there is a one-time charge of $69.95.

For the Speeduino to operate correctly, it needs to be connected to the engine to be able to monitor its "vital signs", such as coolant temperature, air pressure, throttle position, oxygen content of the exhaust gasses and current air temperature. Most petrol car engines are so-called "4-strokes", which means that one complete cycle of the engine occurs every two revolutions, or 720 degrees. The Speeduino needs to know where the engine is in that 720 degree cycle at any given instant because it needs to be able to time the operation of the injectors correctly. This is done by taking a continuous timing signal from the engine to the Speeduino and there are a number of ways in which this can be done.

Rhapsody's engine has mechanical points in the distributor, which fire the appropriate spark plugs at the correct time within the engine cycle, for each of the six cylinders. This type of ignition system was designed in 1904 by Charles Kettering as was used almost exclusively in every petrol engine car built in the following 75 years. Although Rhapsody is fitted with an "after-market" electronic ignition system that both reduces the load on the points and produces a much more reliable spark. The whole system is well developed and works very well, so I decided to keep it. It is true that the Speeduino unit is quite capable of replacing the old system with an electronic version and there would be some tuning advantages in doing that. However, enhanced performance is not the goal here, and it's not worth the extra effort and expense.

The principle role of the distributor points is to drive the ignition system, of course, however, since they occur at specific times, in the engine's 720 degree cycle, they can be used by the Speeduino unit to drive the fuel injection system as well. In a six cylinder, four-stroke, engine the pistons always arrive at Top Dead Centre (TDC) in pairs. One piston will be starting its power or firing stroke and the other will be starting its induction stroke. Or, put another way, one will be ready for a spark and the other will be ready for fuel to be injected. This is very convenient because it means that for every spark pulse, a fuel injection pulse is required as well and the Speeduino can use that fact to correctly time the fuel injectors. All the Speeduino needs is access to the pulse from the points. Easy!

Well, not quite. The car ignition system operates on 12volts and the Speeduino operates on 5 volts. Also, because the point's regular role is to drive a highly inductive load, it becomes, electrically, very "noisy" and far too messy to be used by the Speeduino directly. The pulse signal from the points has to be reduced to the right voltage and heavily filtered to remove the extraneous noise pulses before it can be used, and a separate filter circuit has to be built to do that.