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Chapter 16 The Digital Pulse Adjuster (left) is shown here with its Hand Controller (below). Here the system is in LOCK and RUN modes. LOCK means that no tuning changes can be input, while RUN mode displays the load being experienced in real time when the Digital Pulse Adjuster is monitoring a pulsed input signal. Digital Pulse Adjuster Take control over any of the pulsed solenoids in your car. You can increase or reduce turbo boost, change power steering assistance (weight) or even alter auto transmission gear-change characteristics! T HE DIGITAL PULSE ADJUSTER is our companion project to the Digital Fuel Adjuster presented in Chapter 19. Like the Digital Fuel Adjuster, the Digital Pulse Adjuster is a breakthrough design in car modification. You can now do things which could never be done previously – not without spending a helluva lot of money on a commercial interceptor, anyway. And even then, in many cases you still couldn’t do all that this project can. With the Digital Pulse Adjuster You Can Use This Circuit To . . . •  Modify the action of the factory boost control valve to create a custom boost curve •  Modify the action of the auto transmission pressure control valve to give better shift firmness in late model transmissions •  Modify the action of the power steering control valve to give better weight on speed-controlled systems •  Modify the action of the idle speed control valve to alter idle speed •  Control an extra fuel injector, water injector or toluene injector 92 PERFORMANCE ELECTRONICS FOR CARS (DPA) you can change control signals being sent to solenoids like injectors or flow control valves. This is an immensely powerful function because it allows you to directly control an extra injector or the way the factory flow control valve operates. You can alter the turbo boost curves, change power steering weight, alter idle speed, or even tighten up the auto transmission gear-change characteristics! The DPA literally redefines the way in which car modifications can now be made. And the cost is only about $80, with its companion LCD Hand Controller (necessary for programming) about $60. The kit is also straightforward to assemble and easy to tune. What It Does The DPA can be used in two ways: (1) Driving an extra injector: the siliconchip.com.au Digital Pulse Adjuster taps into the signal coming from the ECU that drives the fuel injectors. The DPA is then used to drive a new injector, using the values provided by the original ECU signal and also any changes that have been programmed in by the user. Fig.3 (p.100) shows this approach. (2) Changing flow control valves: the DPA intercepts the signal coming from the ECU that originally drove a flow control solenoid valve (eg, a boost control valve). The DPA then takes over the function of driving the existing valve, using the values provided by the original ECU signal and also any changes that have been programmed in by the user. Fig.4 shows this approach. So you can either add an injector and drive it with the DPA, or you can take over the driving of an existing solenoid (eg, a boost control valve). Extra Injector Let’s have a quick look at how you’d drive an extra injector with the DPA. For example, you might have a heavily modified car that is running out of fuel at high loads – at full power, the injectors are flat out (ie, at or near 100% duty cycle) and the mixtures are dangerously lean. So you install an extra injector – but how do you control it? With the DPA, it’s dead-easy. First, the input of the DPA is connected to the drive wire of one of the original injectors. The new injector is then connected to the output of the DPA. Without making any plus/minus tuning changes to the output signal, the new injector will perform just like the original injectors – so when the original injectors are at 50% duty cycle (ie, open for half the time), so will the new injector. Each time the original injector fires (the one that the signal has been taken from), the new injector also fires. But this means that at low loads the air/fuel ratio will be too rich – the new injector will be adding fuel when it’s not needed. With the DPA it’s easy to fix that – you simply reduce the output at low loads (ie, low injector duty cycles). The load points being accessed by the car are shown on the LCD Hand Controller, so it’s easy to see where the changes need to be made. By varying how much you pull back the operation of the new injector, you can: (1) bring it on very progressively; siliconchip.com.au Main Features •  Programmed using the LCD Hand Controller (no PC needed) – see Ch.17 •  Only one LCD Hand Controller needed for multiple units •  Can be used to drive extra injectors •  Can be used to intercept flow control solenoids, including boost control •  128 duty cycle steps – adjustable in 127 up or down increments •  When no changes are made, input duty cycle equals output duty cycle •  Interpolation between adjacent load points •  Real time and view modes and (2) tune the full-load and part-load mixtures very finely. Flow Control Valves Changing the way that flow control valves work is nearly as easy. Consider, for example, a speed-sensitive power steering system that uses a pulsed valve to control how firm the steering is. You feed the flow control valve signal to the DPA input and then wire the valve to the DPA output. With the DPA’s tuning changes set to zero, there will be no change to the weight of the steering. But what you want is heavier steering at higher speeds. Again it’s easy to make the changes. Drive the car at the speeds where you feel the steering is too light and watch what load numbers are coming up on the hand controller at those speeds. For example, they might be over the spread of 40-80 (the maximum range is 0-128). Taking it a step at a time, try increasing or reducing the output at the numbers between 40 and 80 and see what happens to the steering weight. (In fact, in most cars the In this Lexus LS400, a prototype of the Digital Pulse Adjuster is being used to re-tune how the power steering weight varies with speed (the full map is shown in Fig.9). The display is in RUN mode, showing that at the INPUT load point of 18, the OUTPUT tuning adjustment is -1. Except when viewing the map or making changes to it, the controller doesn’t need to be plugged into the main module. PERFORMANCE ELECTRONICS FOR CARS 93 By using two microcontrollers, both the component count and the cost have been kept low. The multi-pin plug at the top of the board connects to the Digital LCD Hand Controller which is used to make the mapping changes. output will need to be reduced to make the steering heavier.) Once you have achieved the steering weight that you want, go back through the map and smooth the shape of the changes that you’ve made. Because you can make changes in real time when the car is undergoing the condition that you actually want to change, tuning the DPA is quick and easy. The Design (1). RUN, VIEW and LOCK Modes: as briefly indicated above, the DPA allows both real-time and non-real- Specifications Maximum solenoid load..........................................................3A (5-ohm load) Input signal..................................................... injector or solenoid drive signal Output signal......... switch to ground to drive solenoid connected to 12V supply Offset adjustment..................... ±127 steps corresponding to 0.787% per step Maximum offset adjustment......... 100% for either a fully on or fully off solenoid Input adjustment points........................1-128 corresponding to 0.78% per step Maximum input frequency.................................... 600Hz for full 0.78% control Input to output response time for offset change............................ around 5ms Display update time............................................................................ 250ms Normal offset adjustments.........step up and down with 1 step per button press or at 4 changes per second if button held Skip offset adjustments........... step up and down with 4 steps per button press or at 16 steps per second if button held 94 PERFORMANCE ELECTRONICS FOR CARS time adjustments. This means that you can be running the car and change the signal going to a flow control valve, immediately seeing how this affects the system’s behaviour. This real time mode is called RUN. You can also use the DPA in VIEW mode; that is, without the car system operating. In VIEW mode, you can scroll through the load points, change the up/down adjustments that have been made or put in new adjustments. VIEW mode is good for smoothing the adjustment “curve” or for quickly getting major adjustments into the ballpark before fine tuning occurs. Both RUN and VIEW modes are selected from the Hand Controller. A third mode – LOCK – is selected by a switch on the main unit. It is used when you want to prevent inadvertent changes being made to the map, so LOCK needs to be turned off before you can make any tuning changes. (2). The Hand Controller: this compact unit uses a 2-line LCD, eight “direction” buttons, a recessed RESET button and a RUN/VIEW button. The siliconchip.com.au Fig.1: follow this diagram and the photos to build the PC board. Be sure to install all polarised components correctly and don’t get the two microcontrollers mixed up (they run different programs). functions of the Hand Controller are shown in Fig.6. As briefly mentioned, the different duty cycle adjustment points are called “load points”. When the DPA is set to RUN, you can see which load point is being accessed in real time; pressing the up or down keys will modify the signal at that point. To speed up the tuning process, you can jump up or down by four load points at a time by 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 voltage modification keys are also available in fine ). range () and coarse range (  Holding down the black pushbuttons alters the values by four steps 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 made the up/down changes to the load points, these changes are automatically stored in memory. After you have finished tuning, set the siliconchip.com.au switch on the main unit to LOCK and then disconnect the Hand Controller – the tuning map will be retained, even if power is lost. You can also leave the Hand Controller connected all the time if you wish but again, the switch should be set to LOCK so that inadvertent tuning changes cannot be made. In LOCK, the RUN mode continues to work normally, allowing you to watch the action of the map when the car is driven. A single Hand Controller can be used to program multiple DPAs, so if you are using extra units, only one Hand Controller needs to be built. This same Hand Controller is also used to program the Digital Fuel Adjuster and the Independent Electronic Boost Controller projects (see Chapters 19 & 21). When the DPA is set so that input = output (that is, no tuning adjustments have been made up or down to the duty cycles at those load points), the output follows the input exactly, without any step changes in duty cycle. When you have made up or down adjustments in the duty cycles, you should program in a smooth curve – you don’t want a sudden spike or dip as that load point is reached. While the system does interpolate for you, there’s no need to make its job especially hard! A recessed reset switch is provided on the Hand Controller. When reset is pressed with a pointy tool for around four seconds, all output values are returned to zero change – therefore, pressing this button will result in the loss of all tuning values! A successful completion of the reset process is indicated by RESET momentarily appearing on the display. Construction Given its capability, the DPA doesn’t have a lot of components to mount on the PC board. However, as usual, it’s vital to follow the parts overlay diagram and the photos extremely carefully, taking particular care with the orientation of the polarised components (electrolytic capacitors, ICs, transistors, diodes and LEDs). Note also the positions of the wire links, PERFORMANCE ELECTRONICS FOR CARS 95 How It Works The Digital Pulse Adjuster (DPA) is based on two microcontrollers, IC1 and IC2. IC1 monitors the incoming pulse signal and in its default condition, produces an output which exactly follows the input. It also monitors the RA3 and RA4 outputs of IC2 via counters IC3 and IC4, to determine whether it is required to alter the duty cycle. The output can be altered from fully off (0% duty cycle) to fully on (100%), regardless of its original duty cycle. It can also be set anywhere over the full duty cycle range even if the input signal is showing a steady-state on or off signal (ie, no pulsing). In this case, the output pulse frequency is that which was stored in memory. This frequency can be stored permanently or updated each time the DPA is used. Second Microcontroller The second microcontroller (IC2) also monitors the input pulse signal, calculates its present duty cycle and displays it as a value from 1 to 128, on the Hand Controller. The required output value is also shown on the display, ranging from 0 where no change is required to plus or minus 127. The change required is then sent to IC1 (via the counters) which changes the 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 down or up by the RA3 and RA4 outputs in response to the duty cycle offset required at each of the 1-128 PWM duty cycle settings. The outputs of counters IC3 and IC4 are in turn monitored by IC1 which changes the duty cycle accordingly. Linking Options The circuit includes several linking options to determine whether the output pulse signal is locked to the negative (falling) or positive (rising) edge of the input signal (link LK1); whether the input value reads from 1-128 or from 128-1 for the input signal (link LK4); and whether the output variations alter the pulse duty cycle up or 96 PERFORMANCE ELECTRONICS FOR CARS down for a plus (+) or minus (-) setting (link LK2). Note that when the DPA is used to intercept the solenoid output signal from the car’s ECU, the original solenoid load may need to be simulated. More on this later. The input signal is fed through a 1kΩ resistor and is clamped between +16V and - 0.7V using zener diode ZD1. The 100nF capacitor filters voltage transients. The signal is then used to switch transistor Q1 via a 1kΩ base resistor and 500Ω trimpot VR1. VR1 is adjusted so that the transistor switches on at a few volts to ensure reliable triggering. When Q1 switches on, the output of Schmitt trigger IC5f (pin 12) goes high (to +12V). Conversely, when Q1 is off, pin 13 of IC5f is held high via a 1kΩ pull-up resistor. IC5f inverts this signal and it is inverted again by IC5e. The output of either IC5f or IC5e is selected by link LK1 and applied to the RB0 input (pin 6) of IC1 via a 3.3kΩ resistor. Similarly, LK4 selects either of these two outputs and feeds the selected signal to the RA0 input (pin 17) of IC2. These two links select the edge locking for IC1 & IC2, as mentioned above. Duty Sense Selection LK4 selects the Duty Sense. This selection displays 128 for a fully low input pulse signal and 1 for a fully high input signal. The (+) selection will show the reverse (ie, 1 for a fully low input and 128 for a fully high input). Since these are just numbers relating to the PWM duty cycle, LK4 is normally installed in the (-) position. Link LK5 (output sense) has a similar function and is also normally set in the (-) position. Conversely, positive sense will give a longer low drive when the duty offset is positive and shorter low drive when the duty offset is negative. Link LK2 selects either the positive (+) or negative (-) output signals from pin 7 or pin 8 of IC1. The selected output drives transistor Q2 and this, in turn, drives four paralleled inverters (IC5a-IC5d). These then drive Mosfet Q3 (MTP3055) and this switches the extra injector solenoid or whatever else you decide to control with the DPA. Diode D1 clamps the transient voltages that occur each time the solenoid is pulsed off. The 100nF and 100μF capacitors across the supply prevent transients being introduced on the supply line, while fuse F1 protects the Mosfet if there is a short between the output and the +12V supply rail. LED3 is turned on whenever the Mosfet is switched on, giving a useful indication when you are doing the input threshold adjustment with trimpot VR1. Any flicker in the output due to an incorrect setting is immediately seen on the LED. Input pulse indication is provided by LED2 which is connected across transistor Q4. This transistor is driven by the output of IC5f, which in turn follows the input pulse level. When Q4 is off, current flows through LED1 via a 2.2kΩ resistor and also though LED2. Conversely, when Q4 is on, LED2 turns off while LED1 stays on to indicate that power is connected. Apart from monitoring the pulse signal at its RA0 input, IC2 also drives the LCD module in the external Hand Controller and monitors the switches. Note that IC1 operates at 20MHz while IC2 operates at 10MHz. Switch S1 provides a lock feature, to prevent any adjustment changes after set-up is complete. S1 connects the RA5 input of IC2 to +5V to disable the lock feature. Power Supply Power for the circuit is derived from the switched +12V ignition supply via reverse polarity protection diode D2 and a 10Ω resistor. Zener diode ZD2 protects the circuit from transient voltages and the 1000μF capacitor provides decoupling and supply ripple smoothing. Regulator REG1 provides the +5V supply. Fig.2: there are relatively few parts in the circuit because most of the work is done by microcontrollers IC1 & IC2. Microcontroller IC2 also drives the LCD module in the external Hand Controller via a DB25 socket. siliconchip.com.au siliconchip.com.au PERFORMANCE ELECTRONICS FOR CARS 97 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 panels 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 500Ω horizontal trimpot (code 501) (VR1) 1 2-way pin header 2 3-way pin headers 3 jumper shunts 2 M3 x 6mm screws 2 M3 nuts 4 No.4 x 6mm screws 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 Semiconductors 1 PIC16F628A-20P microcontroller programmed with pwmmod.hex (IC1) 1 PIC16F628A-20P microcontroller programmed with pwmadjst.hex (IC2) including the two very small links (see Table 1 and “The Links” section). These links should be installed first. Make sure that you don’t form any solder bridges between adjacent PC tracks and double-check the board against the parts list, overlay and photos before powering it up. Note: the two microcontrollers run different software programs, so don’t get them mixed up. Testing It’s very important that you test the operation of the DPA before installing it. The very first step is to connect 98 PERFORMANCE ELECTRONICS FOR CARS RESISTOR COLOUR CODES Value 10kΩ 3.3kΩ 2.2kΩ 1kΩ 22Ω (10W) 10Ω 4-Band Code (1%) brown black orange brown orange orange red brown red red red brown brown black red brown not applicable brown black black brown 2 74HC193 4-bit presettable 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 1 22Ω 10W 2 10Ω Note: this parts list does not include the LCD Hand Controller (necessary for programming) – see Chapter 17 the DPA to power and earth. With the Hand Controller plugged into the main module, the LCD should then come to life. (1). VIEW mode: in this mode, each of the load points and its corresponding tuning adjustment can be seen. The display will look something like this (values may be different): OUTPUT 0 (dD) INPUT 0 <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 point value (from 1-128) and the Up/Down buttons 5-Band Code (1%) brown black black red brown orange orange black brown brown red red black brown brown brown black black brown brown not applicable brown black black gold brown make the tuning adjustments to the output. [(dD) means “delta duty cycle”; ie, change in duty cycle.] Using the Left/Right keys, move to Load Point #29 and then use the Up/ Down keys to dial in an output of -14. This causes the output duty cycle to be reduced by 14 units at this load point (the maximum is ±127). VIEW mode is easily used to smooth the changes. For example, having a sudden jump like this: Output Input 0 27 0 28 -14 29 0 30 0 31 is likely to lead to a problem with whatever you are controlling, because the output changes so dramatically at INPUT 29. Instead, it’s better to make the changes smoothly like this: Output Input -5 27 -8 28 -14 29 -8 30 -5 31 This blending is most easily done in VIEW mode. (2). RUN Mode: Run mode only becomes active when the DPA is actually monitoring an input duty cycle. To test the device in this mode, it’s therefore necessary that you supply a variable duty cycle input. The easiest way of doing this is to monitor the duty cycle of a fuel injector in a car. Again, connect 12V and earth to the DPA, then connect the input terminal to one side of an injector. That done, set trimpot 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. Note also that some cars use peakhold injectors. In that case, you will need to connect the DPA to the injector siliconchip.com.au The parts on the back panel, from left to right, are: (1) the Lock switch (which prevents tuning changes being made); (2) the DB25 connector for the Hand Controller cable; (3) the entry hole for the signal input and output connections; and (4) the entry hole for the +12V and ground connections. via the Peak-Hold Adaptor described in Chapter 18. LEDs 2 and 3 vary in brightness according to the input and output duty cycles, respectively. When these duty cycles are 100%, the LEDs are at full brightness. Conversely, when the duty cycles are at 0%, these LEDs will be off. Between these two extremes, the LEDs show intermediate brightness levels accordingly. If you find that the output LED flickers erratically when the output duty cycle should be steady (eg, when you haven’t made any changes to the output map and the input duty cycle is constant), adjust trimpot VR1 on the PC board anti-clockwise a little to give cleaner switching. Note that if the trimpot is adjusted fully anticlockwise, the transistor will never switch, so always keep the setting above this minimum. Depending on the duty cycle being monitored, the displayed Load Point number can vary from 1 to 128, while the up/down adjustment value that you set can vary from 1 to 127 for siliconchip.com.au The Hand Controller (see Chapter 17) displays the load points and allows tuning changes to be made. It’s compact and easy to operate. increases and -1 to -127 for duty cycle decreases. When no tuning change has been made (ie, input duty cycle = output duty cycle at that Load Point), the display OUTPUT shows a “0”. Any changes made to the OUTPUT value are also delivered to the output. You can see the action of the DPA by using the Hand Controller to change the duty cycle adjustment and then watching LED3 alter its brightness. For example, if when the car is idling PERFORMANCE ELECTRONICS FOR CARS 99 Fig.3: when being used to control an extra injector, the Digital Pulse Adjuster taps into the signal feeding the standard injectors. The DPA then directly drives the new injector. Fig.4: when being used to change the operation of a factory solenoid (eg, a boost control solenoid), the Digital Pulse Adjuster intercepts the signal coming from the ECU and then takes over the function of driving the existing valve. The resistor simulates the load of the solenoid so that the ECU doesn’t register a fault code. When using the DPA to control an existing a solenoid, it’s likely that a large resistor will need to be wired across the ECU output so that the ECU still thinks it is operating the solenoid. Shown here are 5, 10 and 25-watt resistors. The resistance value that you need can be found by measuring the solenoid coil resistance and a 10-watt resistor will usually be sufficient. Included in the Jaycar kit is a 22Ω 10W resistor which will be suitable in many cases. the Hand Controller is showing a Load Point of 29, adjusting the output at this Load Point upwards should increase the brightness of LED3. In this RUN mode, the , , and  buttons do not operate, as the unit is displaying the actual load being experienced real time. In both RUN and VIEW modes, the DPA continues to provide the output variation – this means that values can be altered while the car is running. 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. Fitting Fig.5: most pulsed solenoids in a car have one side of the solenoid connected to +12V and turn on the solenoid by earthing it through the ECU. However, in some cases, the solenoid has one side earthed and is switched by being connected to +12V through the ECU. If that’s the case, the approach shown here should be used to connect the DPA and link LK2 will need to be moved – see text and Table 1. 100 PERFORMANCE ELECTRONICS FOR CARS Whether you are driving an extra injector or taking over the driving of an existing solenoid, in both cases you will need to work out which is the signal wire that the ECU uses to switch the device rapidly on and off. Nearly all cars feed a constant +12V to one side of the injector or solenoid and then earth it through the ECU. In other words, to turn it on, the ECU’s switching transistor connects one side of the device to earth (ie, chassis or 0V). It’s this wire that we use as the signal wire for the DPA. The easiest way of finding out which wire is which is to unplug the solenoid or injector, turn on the ignition (but don’t start the engine) and use a multimeter to measure the voltage between each terminal and earth (ground). In siliconchip.com.au Fig.6: this diagram depicts the functions of the Hand Controller, shown here in VIEW mode. In RUN mode (ie, real-time display and tuning mode), “RUN” is displayed on the Hand Controller and the scroll left/scroll right keys no longer operate. nearly all cases, there will be battery voltage on one wire and zero voltage on the other. The signal wire is the one with zero volts (0V) on it. Alternatively, if you have a multimeter with a duty cycle or frequency function (and you really should have – they’re cheap and vital for this sort of work!), the signal wire is the one on which you can measure a frequency or duty cycle when the solenoid or injector is plugged in and running. As a final alternative, you can do as you did above when testing the DPA and simply connect one side of the solenoid to the DPA and see if the INPUT load points shown on the Hand Controller change as the valve operates. (Note that you may need to drive the car to get some solenoids – eg, the boost control solenoid – to work properly.) If there’s no signal, try connecting to the other side of the solenoid. How you proceed from there depends on what you are doing with the DPA. Running An Extra Injector (1). Connect the DPA input to the signal wire of an existing injector. (2). Connect ignition-switched power and earth to the DPA. (3). Wire the new injector between the siliconchip.com.au DPA output and the +12V rail. Fig.3 shows this wiring. Easy, huh? Intercepting A Solenoid (1). Locate the signal wire of the solenoid. (2). Cut the signal wire and connect the end coming from the ECU to the DPA input. (3). Connect the end of the signal wire coming from the solenoid to the DPA output. (4). Make sure that the other side of the solenoid has a constant +12V on it when the ignition is turned on. (If it doesn’t, cut this wire and connect the solenoid end to +12V, as shown in Fig.5. Note that link LK2 will then need to be positioned differently What The Jargon Means Using the Digital Pulse Adjuster is dead easy and understanding it is mostly just a case of sorting-out a few terms. Here they are: DPA – Digital Pulse Adjuster, the signal interceptor described here. Interceptor – a device that takes a signal and changes it before sending it on its way. View – the mode where you can scroll your way through the whole map, making changes as you proceed. Run – the real-time mode where you can see which load point is being currently accessed by the running car and what changes have been made at that point. Lock – the mode (activated by the toggle switch on the main unit) that prevents tuning changes being made. Load Point – the 128 available points that cover the full range that the signal is working across; eg, from 0-100% duty cycle. Input – shows the load point. Output – shows the up/down adjustment made at that load point. Interpolation – this refers to the way that the DPA smoothly changes its output between adjacent tuning points. Earth, Ground, 0V, Chassis – these terms mean the same thing in all vehicles with a negative chassis; ie, the negative battery terminal connects to chassis. Ignition Switched 12V – this is the wire that has +12V on it when the car’s ignition key is turned on. PERFORMANCE ELECTRONICS FOR CARS 101 The Digital Pulse Adjuster can take over the factory turbo boost control solenoid, allowing changes in maximum boost and alterations to the shape of the boost curve while retaining all the factory hardware. – see the “Links” section and Table 1 below). (5). Connect ignition-switched +12V and ground (GND) to the DPA. (6). Measure the resistance of the solenoid. (7). Place a 10-watt wirewound resistor of the same resistance as the solenoid across the ECU output, then Entering The Numbers While it may initially seem that a lot of button pushing is needed to construct the tuning map, the actual task of punching in even a full 128-point map still only takes five minutes or so. Make sure when entering a large map that you use the “express” black buttons and when you have finished your map, go through all load points to make sure that you haven’t inadvertently entered a completely wrong adjustment at any point. Scrolling through all the load points is easy – just hold down either the  or  white scroll button. At the end of a successful tuning session, it’s recommended that you jot down the map on a piece of paper – primarily so that you can find your way back to the original values if you decide to do some more tuning later on. 102 PERFORMANCE ELECTRONICS FOR CARS check it doesn’t get overly warm when the car is driven. If it does, double the resistance value and use two such 10watt resistors in parallel. Fig.4 shows this wiring. Note: the wirewound resistor simulates the solenoid load to the ECU, so that a fault condition isn’t triggered. In some cases, the ECU won’t even output a signal without a resistor in place. If the resistor fails to cancel the Check Engine light, try using the coil from a 12V relay or solenoid in place of the resistor. The resistor provided in the kit is a 22Ω 10W unit and this will typically work fine. The Links There are five configurable links on the PC board. Links LK1-3 are moveable in service while Links LK4 and LK5 are soldered into place. The links allow for many options when the DPA is used in unusual installations, however the link positions shown in Table 1 can be used in the vast majority of applications. Their functions are as follows: Link LK1 – Movable: this link selects whether the DPA looks at the rising or falling part of the input signal square wave. When you select “negative”, it watches for a negative or falling edge and with “positive” selected, it looks for a rising or positive edge. Where edge lock is not important, you can select either setting but link LK2 must then have the same setting (ie, positive or negative) or the output will be inverted. For most operations, negative edge locking is required since the injector or solenoid is usually driven by being connected to ground. Link LK2 – Movable: this link either sets the output to the same polarity as the input or, alternatively, inverts it. In some situations (eg, when you have converted a solenoid that was once switched to 12V to being switched to earth), this link will need to be in the opposite position to link LK1. Link LK3 – Movable: once the system is working correctly, link LK3 can be removed from the board. When it’s in place, it causes the DPA to store the frequency of the solenoid pulsing each time power is switched on and it first detects a frequency. This is so that the DPA can still pulse the solenoid correctly when there is no input frequency (ie, you want to change an input of 0% or 100% duty cycle to another duty cycle). Link LK4 – Soldered: this selects Table 1: Linking Options Link Type Normal Placement Link 1 Movable Negative Link 2 Movable Link 3 Movable Link 4 Soldered Link 5 Soldered Notes See text Set this link to opposite configuration to LK1 when a solenoid that was originally Negative switched to +12V has been converted to being switched to earth (0V) to sense pulsing frequency only Removed once system Used when a duty cycle of 1 or 100 needs to is working properly be modified Change this to positive if you want the Negative Load Number sequence on the Hand Controller reversed Change to positive if you want the up/ Negative down adjustment on the Hand Controller reversed in action siliconchip.com.au the relationship between the waveform of the duty cycle and the load point number shown on the Hand Controller. When the link is set in its negative position, the display will show a load point of 1 for fully high and 128 for fully low. When the link is placed in the positive position, the display will show 128 for fully high and 1 for fully low. Link LK5 – Soldered: this selects whether making an increase or decrease in adjustment on the Hand Controller results in a longer low drive or high drive to the output duty cycle. Positive sense will give a longer low drive when the duty cycle adjustment is positive and less low drive when the duty cycle adjustment is negative. Negative sense will give shorter low drive when duty cycle adjustment is positive and more low drive when duty cycle adjustment is negative. Tuning So you have the DPA wired into place, controlling a solenoid or an extra injector. Now what? First, we’ll cover the interception of an existing solenoid signal; eg, a boost control or power steering solenoid. Press the reset button for at least 4 seconds and confirm that RESET appears on the Hand Controller. This ensures that all tuning changes are returned to zero. Test the car in this form – it should behave exactly as standard. If it doesn’t, you have a problem. Try swapping the position of Link LK2 in case you have inadvertently inverted the signal. Also check by observing LED3 that the output signal doesn’t have any erratic behaviour. If it has erratic flashing, adjust trimpot VR1 as described above. Finally, make sure that you haven’t blown the onboard fuse. If all is well, put the DPA into RUN Mode and have an assistant in the car check the INPUT numbers on the Hand Controller as the car is driven. They should alter in a logical fashion; eg, changing over the range from 40-100. In some applications, the range may stretch right from 1-128, which corresponds to a 0-100% duty cycle input signal. Every load range number – even 1 and 128 – can be tuned. The next step is to make some plus or minus tuning changes within the range of load points (the INPUT numbers) being accessed. Make the siliconchip.com.au Fig.7: the Digital Pulse Adjuster was used to control boost on a modified Subaru Impreza WRX. The signal to the factory boost control solenoid was intercepted and the changes shown here made to the duty cycles going to the valve. Because of intake and exhaust mods, boost was originally spiking to over 100 kPa (14.5 psi), then falling back to 80 kPa (~12 psi) before declining even further on its way to the engine redline. To get rid of the spike, less air was initially bled from the wastegate line (righthand side of graph), then smoothly the settings transitioned to more air being bled from the hose than normal, causing the boost to maintain a higher level. All this tuning was carried out on the road – there’s no need to try to calculate it all out beforehand! (Note that this tuning used an earlier prototype version of the DFA which had only 64 load points, not the 128 of the current model). Fig.8: here are the boost curve results of intercepting the Subaru Impreza WRX boost control valve with the Digital Pulse Adjuster. The original boost curve (blue line) included an overshoot, followed by a declining level of boost. The boost curve achieved with the DPA is shown in red – the overshoot has been dialled-out while the boost level has been maintained rock-steady through the rest of the engine rev range. Remember that using the DPA to alter boost lets you retain all of the factory boost control hardware – you don’t need to buy any more valves or solenoids. Furthermore, the ECU can still pull back boost if problems are detected (although it can’t pull it back too far). adjustments up or down by only a few increments and drive the car again, to check the effects. The idea is to slowly feel your way, assessing how much the altered load point values change the way the car drives. For example, if you are intercepting the boost control, closely monitor the boost gauge and see which way your tuning adjustments are causing the boost curve to move. The key point is to make changes PERFORMANCE ELECTRONICS FOR CARS 103 Uh, Oh . . . A Few Downsides So what are the downsides of this unique interceptor? (1). When intercepting the action of existing solenoids, the original signal needs to have sufficient information in it. For example, if the ECU operates a valve with only (say) 40% and 70% duty cycles – and nothing in between – then all you will be able to do is change those 40% and 70% figures (which will show up as INPUT load numbers of 51 and 90 respectively). However, this is very rare – manufacturers use varying duty cycle valves because of the fineness of control that is then possible. But the wider the range of duty cycles (INPUT load numbers on the DPA) that the ECU sends to the solenoid, the better the end result of your interception will be. (2). You can’t cause the solenoid to have a duty cycle greater than 100% or less than 0% (in these cases, the valve is either fully open or fully closed!). So, for example, if you’re increasing the duty cycle of the boost control valve to bleed off more air and the boost is rising nicely during this tuning process, you could reach a point where no matter how much more you increase the output on the DPA, the boost stops slowly and smoothly and carefully assess the results. Having an assistant in the car to watch gauges (eg, boost) and operate the Hand Controller is vital to this process. Depending on what you are intercepting, how cautious you are and rising any further. This is because the valve is now operating with a 100% duty cycle. In this case, you can insert a restriction in the boost air supply to the valve, which will make the same level of bleed more effective. In fact, you’ll probably have to come down in duty cycle! (3). If you are radically increasing duty cycles, make sure that the solenoid doesn’t become too hot. The higher you take the duty cycle, the more power it will need to dissipate. But this shouldn’t be a problem except in rare cases where duty cycle was originally nearly always low and you have intercepted it to make it nearly always high. (4). If you are using the DPA to run an extra injector and if the duty cycle of the original injectors is 100% at only (say) half load, using the DPA won’t work very well – you’ll have lost the ability to make further tuning changes at higher loads. (It’s much the same point as #1 above – there isn’t enough variability in the input signal). In this case, you really need much bigger injectors – easy to achieve in air-flow meter cars with the Digital Fuel Adjuster described in Chapter 19. how smooth you want the end results, it might take a few hours of on-road tuning to get the modification perfect. Michael Knowling, contributor to the on-line automotive magazine Auto-Speed, had never previously seen the DPA but was soon using one of the prototypes to alter the boost solenoid behaviour in his modified Impreza WRX. He took two half-hour road sessions to completely dial out the boost spike that was previously occurring and then hold boost at a higher than standard value steady and strong to the redline (see Figs.7 & 8). If you are running an extra injector or two (the DPA will quite happily run two injectors with a minimum resistance of 10-ohms each), start off with the map pulled back right across the whole range of INPUT load numbers. Make these changes in VIEW mode. Set up like this, the extra injector should not be operating at all at idle – check that this is the case by listening to it (use a piece of discarded hose as a stethoscope to listen to the injector). Drive the car on the road or on a dyno and using an air/fuel ratio meter, assess at what load number on the Hand Controller the mixtures start to run lean. At that point, you can decrease the amount that the injector has been pulled back in duty cycle – gradually bringing it into play. Getting the mixtures right is then simply a case of further tuning the DPA. Conclusion Extensive testing of the prototype Digital Pulse Adaptor shows that the unit allows cheap and effective car modifications that couldn’t previously be achieved. When you realise that you can now intercept and modify the action of any pulse-width controlled flow valve or solenoid in the car, or run a very finely-mapped extra fuel injector, the modification possibilities  are brilliant. Fig.9: this is the map of changes made with the Digital Pulse Adjuster to alter the power steering weight in a 1998 Lexus LS400. The DPA was used to control the action of the solenoid that regulates steering weight. The steering was made lighter when the car was stopped and moving only very slowly (load sites 33-44), then progressively heavier as vehicle speeds (and the original system’s duty cycles) rose. The result was stunningly good, with the car having vastly better high speed stability and giving increased handling confidence. (To imagine the effect, think of the opposite – an arcade game with super-light steering that has no feel.) 104 PERFORMANCE ELECTRONICS FOR CARS siliconchip.com.au