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Chapter 21 Independent Electronic Boost Controller Imagine being able to flick a switch on the dash and change between two boost maps. Nope, not two boost levels but two complete boost maps! I F YOU’VE GOT a high-powered turbo car with traction problems, one boost map can bring up boost slowly and gently, peaking at a low psi level. That can be your “wet weather” or “partner driving” map. Your other boost control system map? It can bring on boost as hard as possible, allowing a boost over-shoot if you want and then maintaining high boost right to the red-line. That’s a lot different to just changing the maximum boost value! In effect, you’ve got a dual-personality boost control system at the flick of a switch. The Independent Electronic Boost Controller (IEBC) can be fitted to any EFI turbo car. It doesn’t matter if the car originally ran electronic boost control or a purely pneumatic system (although if the latter’s the case, you’ll Why Have A Boost Control? A turbocharger consists of a turbine (through which the engine exhaust gas flows) and a compressor (which blows air into the engine’s intake). The two are mounted at opposite ends of a shaft, so that when the turbine rotates more quickly, so does the compressor. The air-flow output of a turbo compressor rises as the square of its rotational speed. This means that doubling the turbo’s shaft speed increases the air output by a factor of four. This characteristic is quite different for an engine, where a doubling of engine speed will (theoretically, at least) double the engine’s appetite for air. A turbo that can develop 5 psi boost at 3000 RPM engine speed may therefore develop 20 psi boost at 6000 RPM! In practice, varying engine breathing and turbo efficiencies mean that the action of the turbo and engine need to be matched all the way through the load range. For example, to maintain a constant boost level, the waste-gate may need to be shut (causing the turbo speed to be as high as possible) at both ends of the engine rev range. The IEBC allows precise matching to be carried out at all engine loads. 134 PERFORMANCE ELECTRONICS FOR CARS have to source a boost control solenoid from a wrecker). The action of the boost control solenoid can be mapped right across the engine load range – in fact, a maximum of 64 different engine load sites can be mapped for the boost levels, both on the high and low maps. This allows excellent control over the rate of boost increase. Waste-gate creep can be completely dialled-out, if that’s what you want. The “knee” of the boost curve can also be tweaked as much as you like (that’s the section of the curve where the boost needs to start flattening out – ie, at the selected maximum level). In fact, the boost curve can be fine-tuned at any engine load. For example, if you have a small intercooler, you can taper the boost off at high engine loads. Alternatively, if you have excellent intercooling, you can lift turbo boost even further to take advantage of the higher speed forced-cooling (if the turbo can supply the air, that is). Big turbos that are slow to spool up can be brought on as hard as is physically possible, while turbos that tend to arrive with a gearboxdestroying rush of torque can be tamed to be gentle and progressive. In short, this boost control gives you unrivalled flexibility in determining siliconchip.com.au Auto Transmission On cars with an automatic transmission, there may be a small boost spike on each full-throttle upward gear-change. This occurs because the amount of air that the engine is breathing suddenly decreases with each gear-change and it takes a moment for the air flow through the air-flow meter to respond. This in turn leads to a reduction in injector duty cycle and consequently, boost solenoid duty cycle. You may be able to overcome this by using the Frequency Switch (covered elsewhere in this book) to momentarily switch to the low boost curve just before the revs at which full-throttle up-changes occur. the shape of two user-selectable boost curves. Fig.1: the simplest boost control method uses a waste-gate actuator which is a diaphragm backed by a spring. Movement of the diaphragm opens the wastegate, causing the exhaust flow to be bypassed around the turbine, thereby limiting turbo speed and boost pressure. The System The IEBC circuit is virtually identical to the Digital Pulse Adjuster described in Chapter 16. It uses the same digital Hand Controller for programming and is even built on the same PC board. However, it has completely new software and uses a significantly differently approach to controlling the output. Rather than acting as an interceptor (ie, changing a signal that is already going to a solenoid), the IEBC is a complete control system. So even if you are familiar with the Digital Pulse Adjuster, you should regard the IEBC as a whole new ballgame. The IEBC monitors a single signal input – ie, a fuel injector duty cycle. Injector duty cycle refers to the proportion of time that the injectors are open, expressed as a percentage. It’s easy if you think of injector duty cycle as being another way of expressing engine load (that is, engine power), with this figure taking into account throttle angle, actual intake airflow, temperature and so on. In fact, by measuring injector duty cycle, we’re looking at a signal that has lots of information about the operating status of the engine. Low injector duty cycles (ie, low engine loads) appear on the Hand Controller INPUT screen as low load siliconchip.com.au Fig.2: an electronic boost control system adds a pulsed solenoid to bleed air from the waste-gate actuator hose. This solenoid valve is controlled by a variable duty cycle signal. When the duty cycle is high, more air is bled from the solenoid, less pressure is seen by the waste-gate actuator, the waste-gate opens less and the boost rises. Conversely, when the solenoid duty cycle is low, less air is bled from the solenoid, more pressure is seen by the waste-gate actuator, the waste-gate opens more and the boost falls. Note that a restriction is normally placed ahead of the solenoid T-piece to reduce the air flow required through the solenoid valve for a given boost pressure change. PERFORMANCE ELECTRONICS FOR CARS 135 which you pulse the boost solenoid, so you can see that you have a lot of control! The Hoses Fig.3: the Independent Electronic Boost Controller uses a solenoid that’s installed between the boost pressure source and the waste-gate actuator. This means that instead of the pulsed solenoid valve altering the amount of air that is bled from the waste-gate hose, the IEBC’s solenoid directly controls the amount of boost pressure that the waste-gate actuator “sees”. To relieve pressure after a boost event (the pressure would otherwise remain trapped between the waste-gate actuator and the closed solenoid), a small vent is plumbed into this line. Varying the size of this vent also allows the chosen solenoid to be matched to the system. site numbers, while high injector duty cycles (high engine loads) show as high INPUT load numbers. In a typical car which has injector duty cycles that vary from about 2% to 80%, the load number range that appears on the INPUT screen of the Hand Controller will vary from 1-51 (the maximum possible is 1-64). In round figures, you will usually have something like 50 engine load sites over which you can set the boost level. But how do you set the boost level at each engine load site? By using the Hand Controller, you have complete control over the duty cycle of the boost control valve. At each load site, you can set the duty cycle of the boost control valve to be anything from 0-100%. At 0% duty cycle, the boost control valve is completely shut and at 100% duty cycle, it is completely open – “in between” duty cycle values will give “in between” flow. (See under “Testing” for more on the individual characteristics of boost solenoids.) The boost that is developed depends largely on the duty cycle with RESISTOR COLOUR CODES Value 10kΩ 3.3kΩ 2.2kΩ 1kΩ 10Ω 10Ω, 10W 136 4-Band Code (1%) brown black orange brown orange orange red brown red red red brown brown black red brown brown black black brown not applicable PERFORMANCE ELECTRONICS FOR CARS 5-Band Code (1%) brown black black red brown orange orange black brown brown red red black brown brown brown black black brown brown brown black black gold brown not applicable The IEBC uses a unique approach to controlling boost pressure, so don’t just skip this bit, even if you’re familiar with turbo boost controls. Boost control systems rely on a valve (called a waste-gate) that bypasses exhaust gases around the turbine, thus slowing the rotating speed of the assembly and reducing the amount of air being supplied by the turbo’s compressor. Because waste-gates handle high temperature exhaust gases, they are operated remotely by means of a waste-gate actuator. A rod connects the waste-gate actuator to the waste-gate. In cars without electronic boost control, the waste-gate control system consists of a hose that senses boost pressure from a connection close to the turbo compressor’s outlet. Boost pressure travels down the connecting hose to the waste-gate actuator, deflecting the actuator’s diaphragm against the internal spring. If the factory wastegate actuator is set for 7 psi boost, the diaphragm will be deflected (and the rod moved) so that the waste-gate valve will bypass enough exhaust gas to hold boost close to 7 psi. This boost level is called “waste-gate spring pressure”. Fig.1 shows this approach. Electronic boost control normally adds a pulsed solenoid to bleed air from the waste-gate actuator hose. This solenoid valve is controlled by a variable duty cycle signal. When the duty cycle is high, more air is bled from the solenoid, less pressure is seen by the waste-gate actuator, the waste-gate opens less and so boost rises. Conversely, when the duty cycle is low, less air is bled from the solenoid, more pressure is seen by the waste-gate actuator, the waste-gate opens more and so boost falls. Fig.2 shows this type of system. Note that a restriction is normally placed ahead of the solenoid T-piece, which reduces the air flow required through the solenoid valve for a given boost pressure change. Well, that’s how it’s normally done – but the IEBC is different. Instead of the pulsed solenoid valve altering the amount of air that is bled from the waste-gate hose, the IEBC’s solenoid directly controls siliconchip.com.au Fig.4: take care when positioning the polarised components and make sure that you follow this parts layout diagram closely when configuring the link positions. In particular, note that links LK1 & LK3 are left out of circuit for the IEBC. The circuit board is almost identical to the Digital Pulse Adjuster (DPA) described in Chapter 16 and in fact, it is the DPA board that’s pictured here. However, there are major software changes for the two PIC microcontrollers and the linking options are different. In particular, note that links LK1 & LK3 are shown installed in this photo but, in reality, they must be left out of circuit for the IEBC. siliconchip.com.au PERFORMANCE ELECTRONICS FOR CARS 137 Fig.5: wiring the IEBC into place is straightforward. The input is connected to the switched side of an injector and the solenoid is wired between the output terminal and an ignition-switched +12V source. Connect power and earth and the wiring is completed! the amount of boost pressure that the waste-gate actuator sees. That is, the solenoid is connected in-line between the boost pressure source and the waste-gate actuator. When the solenoid is shut, the actuator sees no boost pressure at all. When the solenoid is open, the actuator sees full boost pressure. To relieve pressure after a boost event (the pressure would otherwise remain trapped between the wastegate actuator and the closed solenoid), a small vent is plumbed into this line. Varying the size of this vent allows the chosen solenoid to be matched to the system. Fig.3 shows the plumbing arrangement of the IEBC. In Action Let’s have a look at how this part Main Features •  Uses digital Hand Controller (no PC needed) for programming •  Only one Hand Controller needed for multiple units •  Drives any boost control solenoid •  Switch allows instant selection of two completely different boost curves •  Full waste-gate anti-creep function •  Boost curves can be mapped at up to 64 different points •  Duty cycle of waste-gate valve can be set in 1% increments •  Interpolation between adjacent load points •  Real time and view modes •  Boost level always matched to throttle-requested power 138 PERFORMANCE ELECTRONICS FOR CARS of the system works. In this example, we want the engine to come up to 15 psi (~1 Bar or 100kPa) boost as fast as possible and then hold it at that level to the redline. Previous experiments with a bleed-type boost control on this car have shown that boost normally falls away over the last few thousand revs – a trait that isn’t wanted. (1). To make the boost increase as fast as possible, we keep the solenoid valve completely shut at low loads. Yes, that’s right – the solenoid valve is kept closed (ie, 0% duty cycle) and so no boost pressure at all can get to the waste-gate actuator. As a result, there is absolutely no waste-gate creep. (2). When boost level reaches (say) 13 psi we begin pulsing the wastegate solenoid, allowing boost to start reaching the actuator and so opening the waste-gate. (3). As the boost level rises further we pulse the solenoid at greater and greater duty cycles, allowing the boost level to transition from rapidly rising to holding a constant 15 psi. We then find that – in this example – a 60% duty cycle keeps the boost pressure nicely at 15 psi across the midrange. (4). As revs rise further, boost starts to drop, as it did with the previous bleed system. With the IEBC, that’s easily fixed by reducing the duty cycle values applied to the solenoid at these high loads, to again reduce the wastegate opening. OK, that’s how the pneumatics of the system work but how to do you go about dialling-up all these settings? Before we get into that, let’s look in more detail at the Hand Controller. The Hand Controller The Hand Controller (described in Chapter 17) is used to input all the tuning information and to also view the resulting tuning maps, both real time and non-real-time. It uses a 2-line LCD, eight “direction” buttons, a recessed RESET button and a RUN/VIEW button. Fig.8 shows its functions. Once the IEBC has been set up, the Hand Controller can be unplugged. The Hand Controller displays both engine load and output boost solenoid duty cycle. As stated previously, engine load is taken from the measured injector duty cycle which is shown as INPUT load numbers, from 1 to a maximum of 64. At each of these engine loads, the OUTPUT duty cycle siliconchip.com.au of the boost control solenoid can be set anywhere from 0-100%. To speed the tuning process, you can jump up or down by four load points at a time using the black    and   keys. The whiteandkeys allow you to move up or down the load range one site at a time. In the same way, the boost control solenoid duty cycle adjustment keys are also available in fine range () ) and ( ). and () and coarse range ( Holding down the black pushbuttons changes the values by about 4 changes per second. Alternatively, by pressing the switch at a rapid rate, the values can be altered more quickly. There is no “Enter” key: once you have entered the boost control duty cycles at the different load points, these changes are automatically stored in memory. Two completely different boost control maps (High and Low) are available and these are selected by a toggle switch on the main unit (this switch can be mounted on the dash if you want). Normally, of course, you’d program the High (“H”) map for high boost levels and the Low (“L”) map for low boost levels but you can make the two maps provide any boost curves you want. Note that a single Hand Controller can be used to program as many IEBCs (and also Digital Fuel Adjusters and Digital Pulse Adjusters) as you like. This means that if you are using extra units, only one Hand Controller needs to be built to program them. A recessed Reset switch is provided on the Hand Controller. When Reset is pressed with a “pointy” tool for around four seconds, all OUTPUT duty cycles values for that map are returned to 0%. A successful reset process is indicated by RESET appearing momentarily on the display. There are two very important points to note about the Reset button: (1). Pressing it will result in the loss of all tuning values! – ie, all the duty cycles that you have entered at the different load sites while constructing that boost map will be lost. (2). Pressing it will result in no boost control! This is because the default reset is 0% duty cycle – ie, the boost control solenoid is shut. (There are good reasons for having the system set up like this – if you decide you don’t like this approach, you can alter the position of a link which will reset the siliconchip.com.au The IEBC can be used with any 12V solenoid. However, proper boost control solenoids (like the ones shown top left and bottom) will work best, especially at low duty cycles. You should always test the solenoid on the bench before installing it in a car. This allows you to check that it’s working and to determine its working duty cycle range. solenoid to fully open and so set boost at the minimum across the full load range. Refer to the “Link’s” section below for more details.) Solenoids The IEBC is not supplied with a boost control solenoid. Any 12V solenoid is suitable, although those originally used to control boost in a turbo car are best because they will be able to cope with high under-bonnet temperatures and with being pulsed. Boost control valves are readily available from wreckers, especially those importing used Japanese engines. Before installing the solenoid, you should test that it works correctly. This is very important as it can be difficult to trace the cause of a problem if you have a solenoid valve that malfunctions during boost tuning. Additionally, most boost control valves are directional and will leak if connected the wrong way around – testing on the bench will show which port is which. Testing requires a 12V power supply (a bench supply or car battery) and a source of air pressure (either an air Specifications Maximum solenoid load............................................................. 3A (5Ω load) Input signal...................................................................... injector duty cycle Input adjustment points........................ 1-64 corresponding to 1.56% per step Output signal....... switch to ground to drive solenoid connected to 12V supply Output duty cycle adjustment............................................................ 0-100% Default output frequency....................................................................... 10Hz Learning option for output frequency ........................ 2Hz min. to 600Hz max. Input to output response time for offset change........................... around 5ms Display update time............................................................................250ms Normal offset adjustments.........................step up and down with one step per button press or at four changes per second if button held Skip offset adjustments.......................... step up and down with four steps per button press or at 16 steps per second if button held PERFORMANCE ELECTRONICS FOR CARS 139 How It Works The circuit is based on two microcontrollers, IC1 and IC2. In operation, IC1 produces a pulse width modulated (PWM) signal (at its RB1 & RB2 outputs) that can be varied from fully off (0% duty cycle) to fully on (100% duty cycle). The values between these two extremes can be adjusted in 1% steps. IC1 also monitors several inputs to determine whether it is required to alter its output duty cycle. This is done according to a map that’s programmed in using the Hand Controller. The frequency of the PWM output signal is 10Hz but this can be altered by “teaching” the processor a new frequency (see separate panel). However, for a turbo boost application, this shouldn’t be necessary. The second microcontroller (IC2) monitors the input PWM signal from one of the fuel injectors and calculates its current duty cycle, assigning it a value from 1-64. This value or “load site” number is shown on the Hand Controller display. The output PWM duty cycle required from IC1 at each load site is also displayed and values can range from 0-100%. The change required is then sent to IC1 (via counters IC3 & IC4) and IC1 then sets its output pulse duty cycle accordingly. It works like this: IC2’s RA3 and RA4 outputs drive the down and up inputs of IC4 which, in conjunction with IC3, comprises an 8-bit up/down counter. As a result, this 8-bit counter is cycled by the RA3 and RA4 outputs in response to the duty cycle offset required at each load site setting. The outputs of IC3 and IC4 are in turn monitored by IC1. Linking Options The circuit includes several linking options. Among other things, these set Peak/Hold Injectors? If, no matter how you adjust trimpot VR1, you cannot read a load site on the Hand Controller, or the load site number changes erratically with varying engine loads, your car may have Peak Hold Injectors. In this case you’ll need to build the Peak Hold Adaptor described in Chapter 18. 140 PERFORMANCE ELECTRONICS FOR CARS the PWM output sense (link LK2) and whether the input signal value reads from 1-64 or from 64-1 (link LK4). In practice, link LK2 is normally set in the (-) position. This means that IC1’s PWM output provides no drive to the solenoid when the Hand Controller display shows 0% and full drive when the display shows 100%. Moving the link in the (+) position reverses this – ie, the solenoid will be fully on when the display shows 0% and completely off when the display shows 100%. LK4 (duty sense) is also normally in the (-) position. In this position, a load site value of 1 is equivalent to the monitored injector being off (ie, not driven), while a load site value of 64 means that the injector is being fully driven (ie, 100% duty cycle). Conversely, if LK4 is in the (+) position, the injector is off at load site 64 and fully driven at load site 1. The selected duty sense signal is applied to IC2’s RA0 input (pin 17). Switch S1 selects between two different boost curves. When it’s open, IC2’s RA5 input is pulled to 0V via a 10kΩ resistor and the high curve is selected. Conversely, when S1 is closed, RA5 is pulled to +5V and the low curve is selected. Input Signal Processing The pulsed input signal from the fuel injector is fed through a 1kΩ resistor and is clamped between +16V and -0.7V using zener diode ZD1. The associated 100nF capacitor reduces voltage transients. The signal is then used to switch transistor Q1 via a 1kΩ base resistor and 500Ω trimpot VR1. In practice, VR1 is adjusted so that the transistor switches on at a few volts, to ensure reliable triggering. When Q1 switches on, pin 13 of Schmitt trigger inverter IC5f is pulled low and so its output (pin 12) goes high (to +12V). Conversely, when Q1 is off, pin 13 of IC5f is pulled high via a 1kΩ pull-up resistor and pin 12 goes low. IC5f thus inverts its input signal and this is inverted again using IC5e. IC1 produces two PWM signals (at RB1 & RB2) and one of these is selected using link LK2. The RB1 output is the non-inverted signal, while the RB2 signal is inverted. Link LK2 selects either the (+) or the (-) signal polarity and this determines how the boost control solenoid is driven. The selected PWM output drives transistor Q2 (via a 1kΩ base resistor) and this, in turn, drives four paralleled inverter stages (IC5a-IC5d). Basically, Q1 inverts the selected output from IC1 and also converts this 0-5V signal to a 0-12V signal to drive the inverters. IC5a-IC5d in turn drive Mosfet Q3 and this switches the negative terminal of the solenoid to ground. Diode D1 clamps the transient voltages that occur each time the solenoid is switched off. The 100nF and 100µF capacitors across the supply at this point prevent transients being introduced on the supply line, while fuse F1 protects the Mosfet in the event of a short between the output and the +12V supply rail. LED3 turns on whenever Mosfet Q3 is switched on to drive the solenoid. This gives an indication of the relative duty cycle output, as its brightness varies according to the duty cycle of the PWM signal. Input pulse indication is provided by LED2 which is connected across Q4. This transistor is driven by IC5f which in turn follows the input level. When the input signal is at ground, transistor Q4 is off and LED2 is lit via current flowing through LED1 and its series 2.2kΩ resistor. Conversely, when the input is at 12V, transistor Q4 is switched due to the base current flowing through its 10kΩ resistor. This effectively “shorts” out LED2 and so it is off. LED1 lights when the power is connected. It has a current path through Q4 when Q4 is on and through LED2 when Q4 is off. Driving The Hand Controller As well as its other duties, microcontroller IC2 also drives the LCD module in the Hand Controller and monitors the switches. This controller is identical to the one used for the Digital Fuel Adjuster and the Digital Pulse Adjuster. Power Supply Power is derived from the switched +12V ignition supply and is applied via reverse polarity protection diode D2 and a 10Ω resistor. Zener diode ZD2 protects against transient voltages, while a 1000µF capacitor provides decoupling and supply ripple smoothing. Finally, regulator REG1 provides the +5V supply. siliconchip.com.au siliconchip.com.au PERFORMANCE ELECTRONICS FOR CARS 141 Fig.6: most of the work in this circuit is done by microcontrollers IC1 & IC2. IC2 also drives the LCD module in the external Hand Controller via a DB25 socket. Fig.7: this graph shows the boost control map used in a Maxima V6 Turbo. The waste-gate solenoid is kept shut (ie, a 0% duty cycle) until load site 28, giving zero waste-gate creep and so quick boosting. Over load sites 2834, the waste-gate solenoid begins to open, to start control boost. From load sites 35-46, a waste-gate duty cycle of 44% gave the required constant 11 psi boost. However, to maintain this boost level right through to maximum power, it was found that the duty cycle had to be reduced at higher loads and by load site 64, the waste-gate has again been completely closed. On this car, this boost map gave very quick boosting then held boost level right across the rest of the load range (see Figs.9, 10, 11 & 12). compressor regulated to 15-20 psi or a large syringe, obtainable cheaply from a chemist shop). All you have to do is apply air pressure to each port in turn until you find one where the pressure is held by the un-powered Switching Boost Maps The High (H) or Low (L) boost map is selected by the toggle switch on the main unit. This is configured so that when the switch is closed, the “H” curve is selected and when the switch is open, the “L” curve is selected. This switch can be easily remote-mounted (eg, on the dash), allowing on-the-fly boost map selection. If you want to get even trickier, you can use the Delta Throttle Timer (see Chapter 15) to switch from Low to High boost map when you start to drive hard. To do this, first configure the Delta Throttle Timer so that the relay closes when you drive with quick downward throttle movements and set the timer to say 30 or 60 seconds. That done, wire the adjacent normally open and common terminals of the DTT’s relay in parallel with the boost curve selection switch. That way, you can leave the switch set to the Low boost map but whenever you drive hard, the system will automatically dial up the High map! And of course, you can still manually select High when you want to. 142 PERFORMANCE ELECTRONICS FOR CARS solenoid. Mark this port with a “P”. If you now apply power to the solenoid, it should open and allow the air to flow through it. However, instead of opening when power is applied, some solenoids do the opposite and close. These solenoids are called “normally open” (NO). A normally open solenoid can be used in this system but a normally closed design (ie, one that opens only when power is applied) is preferable. This is because the solenoid will be shut most of the time that you are driving the car, preventing waste-gate creep when you do start to come onto boost. A normally closed solenoid will therefore run much cooler because it will usually be switched off (ie, 0% duty cycle). If you have to use a normally open solenoid, keep the solenoid poweredup on the bench for 5-10 minutes and check that it doesn’t get hot – most solenoids will get warm but one rated for continuous use shouldn’t get hot. If it does get hot, connect a 10Ω 10-watt resistor in series with it. This will drop the power dissipation of the solenoid so it will run cooler – or more precisely, the heat load will be shared by the resistor and the solenoid. A 10Ω 10-watt resistor is supplied in the kit. When using a normally open solenoid, Link LK2 must be installed in the positive position – see “Links” below. Construction The IEBC doesn’t have a lot of components to mount on the PC board. However, as usual, it’s vital to follow the parts layout diagram (Fig.4) and the photos carefully, taking particular care with the orientation of the polarised components. These components include the electrolytic capacitors, ICs, transistors, diodes and LEDs. Note also the position of all the wire links, including the two very small links – the links should be installed first. Make sure that you don’t form any solder bridges between adjacent PC board tracks and double-check the board against the parts list, overlay and photos before powering it up. During construction make sure that you follow the link positions covered under the “Links” section below; these defaults are shown on the component overlay. Ensure you follow the overlay and text – rather than the photo of the PC board – when configuring these links. Finally, don’t get the two PIC microcontrollers (IC1 & IC2) mixed up, as they run different software programs (see Parts List). Testing It’s very important that you test the operation of the IEBC before installing it. The very first step is to connect the IEBC to power and earth (at this stage, you don’t need to connect anything to the input or output terminals). That done, plug the Hand Controller into the main module – the LCD should immediately come to life. (1). VIEW mode: in VIEW mode, each load point and its corresponding boost control solenoid duty cycle can be seen. The display will look something siliconchip.com.au like this (although the values may be different): OUTPUT 2% (H) INPUT 5 <VIEW> This mode allows the manual viewing of each INPUT value (ie, load point) and the corresponding OUTPUT setting. The left/right buttons allow selection of the load site values (from 1-64) and the up/down buttons make the tuning adjustments for the boost control solenoid (from 1-100%). A “H” on the LCD means that you have the “High” boost curve switch position selected, while “L” will appear if the “Low” boost control curve is selected. As an exercise, use the left/right keys to move to load site 29 and then use the up/down keys to dial in an output of 25%. This causes the boost control solenoid to be pulsed at a 25% duty cycle at this load point. VIEW mode is easily used to smooth the changes. For example, in order to give the quickest boosting, you might want to have the solenoid valve closed until load site 29. Your tuning map might therefore have a sudden jump like this: Output (%) 0 0 0 75 75 75 75 75 26 27 28 29 30 31 32 33 Input However, this is likely to lead to a problem where boost will surge. This is because when the engine load Learning A New Pulsing Frequency Extensive testing of the prototype IEBC showed that the relatively slow pulsing frequency of 10Hz worked well with a wide variety of 12V solenoids. At this frequency, the solenoid is oscillating fully open and shut while controlling the flow. However, the use of higher operating frequencies permits the solenoid pintle to “hover” in mid-positions, which will result in reduced solenoid wear. If this approach is taken, the frequency has to be exactly matched to the mechanical and electrical characteristics of the individual solenoid design – ie, there is no universal frequency. It is possible to “teach” the IEBC a different solenoid operating frequency. To do this, a frequency generator is needed, or the output of a PC soundcard can be used with frequency generator software running on the PC. This software is available free from a number of web sources – do a search under “free frequency generator software”. Follow this procedure to teach the IEBC a new solenoid operating frequency: (1). Install link LK1 in the positive position. (2). Install link LK3. (3). Turn trimpot VR1 fully clockwise. (4). Connect the frequency generator (or sound card) output to the IEBC (positive to the “Input” terminal and negative to the ground terminal). (5). Select the desired frequency on the generator and set the generator output to about 1V RMS. (6). Apply 12V and ground to power-up the IEBC. (7). Wait a few seconds, then switch off and remove Links LK3 and LK1. (8). Connect the solenoid and re-apply power. (9). Using a digital multimeter set to frequency, measure the pulsing frequency of the solenoid. It should now be the new value. Frequencies from 2–600Hz can be used, with those in the 50–150Hz range working well with many solenoids. Once you have set a new frequency, manually adjust the output duty cycle across the whole range and confirm that the valve operates appropriately. Fig.8: the functions of the Hand Controller, shown here in VIEW mode. In RUN mode (ie, real-time display and tuning mode), the word “RUN” is displayed on the LCD and the scroll left/scroll right keys no longer operate. siliconchip.com.au PERFORMANCE ELECTRONICS FOR CARS 143 An easy way of providing a test boost pressure is to use a large syringe, available from chemist shops. This allows you to quickly find which port is which – most valves are directional and contrary to popular opinion, will hold boost on only one port. reaches point 29, the waste-gate will suddenly open, causing boost to fall. In turn, this will drop the engine load, taking the system back to load site 28, whereupon the waste-gate will fully close, causing boost to suddenly rise . . . and so the cycle will repeat. For this reason, it’s better to make the changes smoothly like this: Output (%) 0 0 25 35 45 55 65 75 26 27 28 29 30 31 32 33 Input This blending is most easily done in VIEW mode. (2). RUN Mode: RUN mode becomes active only when the IEBC is actually monitoring an input duty cycle. To test the device in this mode, it’s therefore Setting The Vent Size The function of the vent which is placed between the solenoid and the wastegate actuator is mainly to relieve pressure. This pressure relief occurs after boost has been high and then drops – eg, following a gear-change, when the mapping requires a boost decrease, or when you lift your foot. If the vent hole is too small, boost will be slow to rise again after a decrease. Conversely, if the vent is too large, the minimum boost level will be limited – ie, you won’t be able to drop the boost to the level you want, even with the solenoid fully open. Because it acts as a small bleed, the vent hole also affects the operating range of the solenoid. If you find that the duty cycles that you are using are all very low (eg, 20–30%), increase the size of the vent. If you find that the duty cycles that you are using are all very high (eg, 80–90%), reduce the size of the vent. In much of the testing, we used a 2mm hole and a Nissan Skyline boost control solenoid valve – the combination working very well. However, testing a Goyen industrial ¼-inch valve showed that the vent size needed to be larger to suit this unit. If you want a vent that’s easily adjustable in size, use a ¼-inch needle valve in place of the small hole. Needle valves are available quite cheaply from industrial pneumatics suppliers. 144 PERFORMANCE ELECTRONICS FOR CARS necessary that you supply the IEBC with an injector duty cycle signal. Again, connect 12V and earth to the IEBC, then connect the input terminal to one side of an injector. Set the pot on the PC board (VR1) fully clockwise. Start the car and select RUN mode. A load point number should appear which changes when the engine’s throttle is blipped. If the load point number on the display doesn’t change, try connecting to the other side of the injector – no damage will result if you initially connect to the wrong side. LEDs 2 and 3 vary in brightness according to the input and output duty cycles. When the input and output duty cycles are 100%, these LEDs will be at full brightness. When the duty cycles are at 0%, these LEDs will be off. Variations in duty cycles between these two extremes are indicated by variations in the brightness of the LEDs. LED2 shows the input duty cycle and LED3 the output duty cycle. If you find that the output LED flickers erratically when the output duty cycle should be steady (eg, when you have all the OUTPUT duty cycles set to say 50%), adjust the pot (VR1) on the PC board anticlockwise a little to give cleaner switching. Note that if the siliconchip.com.au pot is adjusted fully anti-clockwise, the transistor will never switch, so always keep the setting above this minimum. (If you have a car with peak/hold injectors, refer to the “PeakHold Injectors?” panel.) Depending on the duty cycle being monitored, the displayed load point number can vary from 1-64, while the OUTPUT duty cycle value for the boost control solenoid can be set from 0-100%. Any changes made to the OUTPUT display are delivered to the output of the IEBC. You can monitor the action of the IEBC by using the Hand Controller to change the duty cycle and then watching LED3 alter its brightness. For example, if the Hand Controller shows load point 1 when the car is idling, increasing the solenoid duty cycle output at this point should increase the brightness of LED3. Note that, in RUN mode, the left/ right buttons (, , and ) do not operate, as the unit is displaying the actual load in real time. Note also that the IEBC provides the output duty cycle in both RUN and VIEW modes. This means that the boost valve control values can be altered in real time while the car is under load. You can alter the current value that is displayed in the RUN mode or you can alter selected values in the VIEW mode. Either way, any changes will be included in the output. Parts List 1 microcontroller PC board coded 05car131, 130 x 103mm 1 plastic case, 140 x 111 x 35mm (Jaycar HB 5970) – supplied fully machined with screened lettering 1 20MHz crystal (X1) 1 10MHz crystal (X2) 1 DB25 PC-mount socket 2 DIP18 IC sockets 2 2-way PC-mount screw terminals 1 mini-U heatsink, 19 x 19 x 10mm 2 M205 PC fuse clips 1 3A M205 fast blow fuse 1 2-way pin header 2 3-way pin headers 3 jumper shunts 6 M3 x 6mm screws 2 M3 nuts 1 400mm length of 0.8mm tinned copper wire 1 1m length of red automotive hookup wire 1 1m length of green automotive hookup wire 1 1m length of black automotive hookup wire 1 1m length of yellow automotive hookup wire 1 500Ω horizontal trimpot (code 501) (VR1) Semiconductors 1 PIC16F628A-20P microcontroller The easiest way of making the vent that relieves any pressure build-up between the solenoid and the waste-gate actuator is to solder up one arm of a brass T-piece and then drill a small diameter hole through the solder plug. siliconchip.com.au programmed with pwmcntrl.hex (IC1) 1 PIC16F628A-20P microcontroller programmed with pwmadjrl.hex (IC2) 2 74HC193 4-bit up/down counters (IC3,IC4) 1 74C14 (40106) hex Schmitt trigger (IC5) 3 BC337 NPN transistors (Q1,Q2,Q4) 1 MTP3055 Mosfet (Q3) 1 LM2940CT-5 5V regulator (REG1) 3 16V 1W zener diodes (ZD1-ZD3) 3 5mm red LEDs (LED1-LED3) 1 MUR1560 15A 600V diode (D1) 1 1N4004 1A diode (D2) Capacitors 1 1000µF 16V PC electrolytic 1 100µF 16V PC electrolytic 1 10µF 16V PC electrolytic 6 100nF MKT polyester (code 104 or 100n) 1 47nF MKT polyester (code 473 or 47n) 1 1nF MKT polyester (code 102 or 1n) 4 22pF ceramic (code 22 or 22p) Resistors (0.25W, 1%) 7 10kΩ 2 3.3kΩ 3 2.2kΩ 6 1kΩ 2 10Ω 1 10Ω 10W This boost control valve was fitted to mid-late 1980s Nissans and is available from “Japanese-importing” wreckers. It is a normally closed design which works very well with the IEBC, having an effective duty cycle range of 5-80%. PERFORMANCE ELECTRONICS FOR CARS 145 •  Link LK2 – Movable: link LK2 is MANIFOLD PRESSURE (kPa) 60 40 20 0 -20 -40 -60 0 1 2 3 4 5 6 7 SECONDS Fig.9: the boost curve of the guinea pig auto-trans Maxima V6 Turbo at full throttle in first gear, from a standing start. The Maxima (always slow off the line!) took just over three seconds to reach the peak boost level of 75kPa (just under 11psi). You can see that there is a very slight boost overshoot of about 5kPa (about 0.75psi) before the boost settles at the designated level. After six seconds, the redline has been reached and the throttle is closed. MANIFOLD PRESSURE (kPa) 150 100 50 0 -50 -100 -150 0 1 2 3 4 5 6 7 8 9 SECONDS Fig.10: the boost curve of the Maxima V6 Turbo is shown here in second gear, from a rolling 60km/h start (the slowest speed at which the auto trans car wouldn’t kick-down to first gear when floored). As you can see, the boost level takes only about two seconds to reach the full value and then holds it straight as an arrow right through to the redline. Once you have got used to the way the Hand Controller works, connect a solenoid. As shown in Fig.5, the solenoid is fed ignition-switched +12V on one side and the other side connects to the IEBC output terminal – ie, the solenoid is earthed through the IEBC to switch it on. With the solenoid connected to the IEBC and the Hand Controller set in RUN mode, start the car and dial up a 50% duty cycle OUTPUT on the load site being shown. You should now be able to hear or feel the solenoid chattering on and off at 10 times a second. Change the duty cycle and you should hear the solenoid’s behaviour change. Now is a good time to vary the OUTPUT duty cycle over the full range while you listen to the solenoid. 146 PERFORMANCE ELECTRONICS FOR CARS Typically, a boost control solenoid will work over the duty cycle range from about 15-80%. If your solenoid stays silent except over a very narrow range of duty cycles (eg, from 4050%), the valve is not suitable for this application. Take note of the range over which your chosen solenoid works – your boost curve tuning must be within that range. The Links There are five configurable links on the PC board. Links LK1-3 are movable in service while links LK4 and LK5 are soldered into place. The links allow for several options, as follows: •  Link 1 – Movable: this link should be removed from the board (note: this link is used only to program in a new pulsing frequency – see panel). normally set to the negative position for a normally closed solenoid. In this position, the solenoid will be shut when the boost control solenoid duty cycle is set to 0% and fully open when the duty cycle is set to 100%. If you want this reversed (so that the solenoid is fully open at 0%), move LK2 to the positive position. This will also cause the boost to revert to the lowest possible value when the reset button is pushed. However, on-road tuning will take longer as it’s likely that every tuning value will need to be altered. This link will also have to be moved to the positive position if you are using a normally open solenoid (ie, one that shuts when power is applied). •  Link LK3 – Movable: this link should be removed (note: as with LK1, it’s used only to program in a new pulsing frequency). •  Link LK4 – soldered: this link is normally set to the negative position. Change it to positive if you want the load number sequence on the Hand Controller reversed. •  Link LK5 – soldered: this link must be kept in the positive position. Fitting If you have followed the test procedure outlined above, you will already have done all of the wiring. To recap, Fig.5 shows the wiring connections. The hose layout for the IEBC is shown in Fig.3. However, we have not yet described the construction of the vent. The easiest way of making this is to buy a ¼-inch brass T-piece and block the vertical arm of the “T” by soldering it closed. Once the solder plug has cooled, drill a 2mm hole through it. In some systems, the size of this vent hole will need to be altered – you will find out if this is the case during initial testing (see the “Vent Size” panel). Enlarging the vent is easy just drill a larger hole. Reducing the vent size involves resoldering it and then drilling a smaller hole. Aspects to be careful of when organising the plumbing include: (1). Minimise all hose lengths within the system. (2). Protect the hoses and solenoid from exhaust heat (this may include using a high-temperature insulating wrap). siliconchip.com.au The system will not work without appropriate tuning. To do this tuning, you will need an assistant, a boost gauge, a reasonably quiet road (preferably a race circuit) and at least an hour of time. The first step is to use the switch on the main unit to select the particular map (High or Low) that you want to tune first. That done, press the Reset button with a pointy tool and check that RESET appears on the screen. Note that only one map at a time is reset – ie, either High or Low, depending on which is selected. Next, use the VIEW/RUN button to select RUN mode. Assuming that the system is configured as recommended, there is now no control over boost. Now select a test gear (eg, second gear) and put your foot down. The boost will rise quite rapidly (probably much more quickly than you’re used to) and when it gets near to the peak value that you want, your assistant should call out something appropriate (like “now!”). At this point, immediately lift your foot. So, for example, if you’re setting the boost control for 15psi, your assistant would call out at around 13psi and then you’d quickly back off the throttle. The load site that appears on the Hand Controller when the assistant called “now!” shows where you need to start increasing the solenoid duty cycle, to bring the waste-gate into action. For example, the “now!” might have occurred at load site 31. At that point, switch back to VIEW mode and set the values to something like this: Output (%) 0 0 25 35 45 55 75 100 26 27 28 29 30 31 32 33 Input Set remaining higher load sites to 100% Note how the duty cycle starts increasing before load site 31, so that the boost curve changes smoothly at this point. Test drive the car in the same gear. Now boost should rocket up to somewhere close to your designated level and then drop right back once siliconchip.com.au MANIFOLD PRESSURE (kPa) Tuning 150 100 50 0 -50 -100 -150 0 1 2 3 4 5 6 7 8 9 SECONDS Fig.11: here the boost curve (what curve?!) is shown for the Maxima V6 in third gear. Again, this is from the slowest speed at which the transmission wouldn’t downchange to second gear when floored – about 100km/h. From there to 160km/h, the full-throttle boost curve is amazingly level, varying by only a few kilopascals (say under 0.25psi) right to the redline. 150 MANIFOLD PRESSURE (kPa) (3). Use good quality clamps or spring clips on the hoses so that no unintended boost leaks can occur. (4). Make sure that the boost control solenoid is plumbed with its pressure port (the one you marked with a “P” in testing) connected to the boost pressure source. 100 50 0 -50 -100 -150 0 1 2 3 4 5 6 7 8 9 SECONDS Fig.12: even a full-throttle kickdown from second to first gear causes no boost flare problems, with boost taking about 1.5 seconds to rise to its maximum designated value and then staying there. Note that these graphs are all at full throttle but in some ways the linearity of the part-throttle behaviour is even more impressive. load site 33 has been reached. This is because from load site 33 onwards, the solenoid valve has been set to fully open – 100% duty cycle – and so at loads above this, the boost will decrease to waste-gate spring level. Gradually alter the solenoid duty cycles (upwards to reduce boost, downwards to increase boost) until you achieve the boost curve you want. You can then flick the switch and do the other map, which will be quicker to set up now that you have a “feel” for the required settings. Fine tuning will involve concentrating on the transients, especially in controlling the “knee” of the curve in different gears. For example, you may get more boost overshoot in first gear than in third. The chosen duty cycle settings will be a compromise that retains good control in all gears and situations. If you have a car with an automatic transmission, then refer to the “Auto Transmission” panel at the start of this chapter. It might all sound complicated but it’s not. It’s much harder to describe how the tuning is done than to actually do it! Conclusion There are a number of very positive aspects about this boost control system. First, the absence of any restrictions in the boost path between the boost source and the waste-gate actuator means that when the solenoid is open, very fast control over the waste-gate can be gained. This is important during transients like quick throttle movements, especially with a small and responsive turbo. In many other systems, restrictors on the boost supply causes waste-gate PERFORMANCE ELECTRONICS FOR CARS 147 The Hand Controller is the same as used for the Digital Pulse Adjuster and the Digital Fuel Adjuster. It’s used to input all tuning information and to view the resulting tuning maps, both in real time and non-real-time. In this project, it displays both engine load and output boost solenoid duty cycle. control lag, leading to overshoots and poor control. Second, when on boost, the relationship between throttle and boost is uncannily good. For example, you might have the peak boost set to 15 psi, a level gained at full throttle. However, in most electronic boost control systems, you’ll also get 15 psi boost even when the throttle is at only 75% opening. That puts a higher load on the intercooler and the turbo than is really needed – the partly closed throttle is limiting the air flow, so why develop full boost? But with the IEBC, you get the maximum boost needed to develop the power that’s being requested by your throttle position. On the road, it’s easy to see this – at full throttle (eg, 4000 RPM), the boost gauge might show 15 psi. Close the throttle slightly and the boost falls back to 12 psi. Close it a bit more and you have 10 psi. With this system, boost isn’t always trying to be set to the maximum – instead, it is being matched to the power that the engine is actually developing. This gives excellent throttle control without limiting the power available when you actually do bury your foot! Third, full control over waste-gate anti-creep is built into the system – you can completely prevent waste-gate movement until the engine is well on boost. Conversely, you can cause the waste-gate to gradually open, to give a very linear boost rise. Fourth, the High/Low boost switch doesn’t just switch between two peak boost levels. Instead one of two complete boost maps is available – including full control over waste-gate anti-creep, rate of boost increase, peak boost level and the shape of the boost curve to the redline. Finally, there’s the cost. The Independent Electronic Boost Controller kit costs only about $80. If you have already built the Hand Controller (say to control mixtures through the Digital Fuel Adjuster), you’ll only need to build the kit and find a surplus boost control valve and a T-piece to complete the system. Even if you need to buy the Hand Controller kit, you’ll still be looking at a saving over commercial equivalents of something like 75% . . . and do any of those designs have two completely configurable boost maps to choose from?  You make the call. But Is It Closed Loop? The IEBC doesn’t measure boost and then try to maintain it at a designated level. We could have designed a system that did this but at a much increased cost. Unfortunately, there’s no such thing as a cheap, high-quality boost pressure sensor. And having experienced the IEBC, we’re not even sure now that it would be a major advantage. Anyway, strictly speaking, this isn’t a closed loop boost control. However, if an increase in boost results in more engine air flow, the described system does actually have major “closed loop” elements in it. This is because if an 148 PERFORMANCE ELECTRONICS FOR CARS increase in boost pressure causes an increased intake air flow (and the engine doesn’t run lean), the injector duty cycle must rise to reflect this increased air flow. Since we’re monitoring injector duty cycle as the main input, the IEBC takes this increased boost into account. However, there are two caveats: (1) that the injectors are not already flat out at 100% duty cycle; and (2) that an increase in boost pressure actually does result in an increase in engine air flow. In the latter case, on some engines, exhaust back-pressure from the turbine is so high that increasing boost from (say) 15 to 17 psi makes nearly no difference to engine power – you should always use the lowest boost pressure that gives you the desired power level. This also saves exhaust manifolds and turbine housings from high temperatures that can melt them and keeps the intercooler load to a minimum. So when used on a car which varies the duty cycle of the injectors to take into account the increased airflow, and on cars where the increase in boost pressure actually does result in an increase in air flow, the IEBC’s action is largely a closed loop system. siliconchip.com.au