Bipes ACU Auxiliary Control Unit for Timing and Knock Control. 2.6" W x 4.25" L x 0.875" H Timing control for '90-'97 Miatas

Transcription

1 Bipes ACU Auxiliary Control Unit for Timing and Knock Control 2.6" W x 4.25" L x 0.875" H Timing control for '90-'97 Miatas 1

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3 Table of Contents Introduction... 4 ACU Features... 5 Compare for yourself... 6 How the Bipes ACU Works... 7 ACU Installation Instructions... 9 Programming the ACU Programming Instructions Jackson Racing Supercharger 1.8L Fuel Enrichment Option JR Fuel Enrichment Option Wiring Diagram ACU Programming Tips Airflow Retard RPM map Air Temperature Application Notes L Moss/Jackson Racing/Sebring supercharger L Moss/Jackson Racing BBK (big boost kit) Nitrous Oxide In-dash timing adjustment MAP sensor External Temperature Sensor Software revisions Version Version 1.2-3/24/ Version 1.3-5/11/ Version 1.4-8/14/ Version /20/

4 Introduction The Bipes ACU (Auxiliary Control Unit) dynamically retards the timing of your engine to protect it from detonation or knock. The unit works on either normally aspirated or forced air (turbocharged or supercharged) engines. Normally aspirated Probably the easiest and most inexpensive power modification to the Miata engine is to advance the base timing. This technique is well known and documented. A problem can arise if you advance the timing more than a few degrees: detonation. The ACU allows you to enjoy the power gains that advanced timing offers while protecting your engine from detonation or knock. Turbocharged or supercharged If you followed supercharger installation instructions and set the base ignition timing back, you helped protect your engine from detonation but you robbed it of power. Changing the base timing affects timing under all conditions, not just the conditions at which your engine is susceptible to knock. The ACU retards timing only when needed. Nitrous Oxide To protect your engine, you may need to retard timing when you switch on your nitrous oxide. The ACU can be configured to automatically add a user-selectable amount of retard when the nitrous is engaged. 4

5 ACU Features 3-input timing map: RPM, airflow (boost), and air temperature. Retards up to 20 degrees of timing. User programmable. Easy to program. Self-contained - no PC, keypad, or other additional device required to program. Integrated diagnostic display. Precision tachometer display mode. Software upgradable by replacing a chip. Best value (most features, low cost). Bipes ACU Exclusive Feature The Bipes ACU is the only add-on timing device to offer timing control mapped to intake air temperature. The Link, a replacement ECU priced at over $1000, only recently offered the option of air temperature mapping. This Link option requires the addition of a special temperature sensor that costs another $100! The Bipes ACU uses the Miata's own temperature sensor to provide air temperature mapping at no extra cost. 5

6 Compare for yourself Programmed retard Retard based on engine load Retard based on RPM Retard based on temperature MSD JR J&S Reprogrammed J&S Yes Yes No Yes Bipes ACU Yes Yes Yes No Yes Yes No Yes Yes Yes Yes No No No No Yes Knock sensor No No Yes Yes No Adjustments Diagnostic display None None Knock Sensitivity Retard monitor (optional) Price $150 $400 $435 - $595 Knock Sensitivity Max retard (4 choices) 10 or 20 on knock Retard monitor (optional) $435 - $595 None Retardto-boost Retard-toairflow Retard-to- RPM Retard-totemperature Multi-function (optional) Retard monitor Air flow Air temperature RPM $200 - $250 MSD is the Sebring Supercharger Mazda Miata Boost Control by MSD Ignition, available from several sources. JR is the Jackson Racing Boost Timing Control Unit from Moss Motors J&S is the Safeguard unit by J&S Electronics, available from several sources. Programmed J&S is the Safeguard unit with Miata reprogramming by the manufacturer. 6

7 How the Bipes ACU Works The Miata's Engine Control Unit (ECU) controls ignition timing. The ECU uses a Crank Angle Sensor (CAS) to determine the position of the crank at any given time. It then fires the spark plugs at exactly the right moment. When is the 'right moment'? That depends on a number of factors, such as the engine RPM, the amount of air and fuel being drawn into the engine, and engine and air temperature. The ECU uses internal maps and algorithms to constantly compute the 'right moment'. The ACU is inserted into the electrical path from the CAS to the ECU. The ACU can retard ignition timing by delaying the signal from the CAS to the ECU. Delaying the signal accomplishes the same result as rotating the CAS, as is done when setting the base timing. Of course, by doing this electrically rather than mechanically, the amount of delay or retard/advance need not be fixed. The ACU, like the ECU, constantly computes the amount of retard to add based upon engine conditions. 7

8 The ACU uses three input parameters to map the correct timing (two are illustrated below): Engine load (airflow). RPM Intake Air Temperature 8

9 ACU Installation Instructions Connect the ACU by splicing into 4 wires (ground, +12 volts, air temperature, and airflow) at the ECU. A fifth wire (CAS) is cut, and each end of the cut wire is connected to the ACU. Refer to the connection diagram. Connection Diagram - 1.6L engine 9

10 To attach wires to the ACU, first remove the terminal plug from the header. Strip about 1/4" of insulation from the wire. Insert the bare end into the terminal plug and tighten the screw. Reinsert the terminal plug into the header after all wires are attached. We recommend that you cut the CAS wire and install a male connector (such as a spade lug) on one end and a female connector on the other end. Then attach the proper mating connectors to wires attached to the ACU. This will permit the ACU to be removed from the circuit and the stock configuration restored by unplugging and replugging a few connections. (The other 4 spliced connections can remain.) It is important that you select a switched +12V source of power for the ACU. The ACU resets itself and reads the switches when powered on. For this function to take place as intended, the ACU must be connected to a proper switched power source. 10

11 Locate wires at the ECU by both position on the connector and the wire's color code. Don't rely on the color code alone. The ACU should be located somewhere in the passenger compartment, such as next to the ECU, under the dash, or in the glove box. Don't mount it in the engine compartment. It is not sealed against moisture and contaminants. Locating connections at the back of the ACU ECU Connections Signal '90-'93 1.6L '94-'95 1.8L '96-'97 1.8L Ground 2A or 2B black 2A or 2B black 4C or 4D black +12V 1B white/red 1B white/red 4B white/red Air temp 2P red/green 2P red/black 3K red/black Airflow 2O red 2O red 3B red/white CAS 2E white 2E white 4F white 11

12 ECU connector pinout - 1.6L engine ECU connector pinout - '94-'95 1.8L engine ECU connector pinout - '96-'97 1.8L engine 12

13 Standard Mazda Wiring Color Codes Code Color B Black BR Brown G Green GY Gray L Blue LB Light Blue LG Light Green O Orange P Pink R Red V Violet W White Y Yellow 13

14 Programming the ACU Programming the ACU is easily done by setting a few switches. You can program the following parameters: Operate with either a 1.6L or 1.8L engine. (The engines use different airflow sensors. The ACU can work with either.) Amount of retard to apply under full load. (The ACU will automatically map actual retard to smaller amounts under less than full load conditions.) Amount of retard to add under high temperature. (The ACU will automatically scale retard back in cooler air.) Conservative or aggressive RPM map. Input or output variables to display. (Optional on models equipped with a display only.) Jackson Racing Supercharger 1.8L air temperature fuel enrichment option (see following section) Specifications are subject to change. Programming Instructions Locate the switches at the back of the unit. 1. Select the engine type: Switch 1 Engine open 1.6L closed 1.8L 14

15 2. Select the amount of timing you want to retard under maximum engine load (the ACU will scale the timing back under lighter loads): Switch 2 Switch 3 Switch 4 Full AFM retard open open open 4 open open closed 5 open closed open 6 open closed closed 7 closed open open 8 closed open closed 10 closed closed open 12 closed closed closed 14 Airflow to Retard Map 15

16 3. Set the amount of additional retard to apply at high intake air temperature (the ACU will scale back at lower temperature): Air Temperature to Retard Map Switch 5 open Switch 6 open open closed closed open closed closed Retard-totemperature ratio (values are approximate) 1 degree retard for each 65 degrees F (40 degrees C) 1 degree retard for each 50 degrees F (30 degrees C) 1 degree retard for each 30 degrees F (20 decrees C) 1 degree retard for each 30 degrees F (15 degrees C) 16

17 4. Set the RPM map that you want, from conservative to aggressive: RPM Map Switch 7 Switch 8 Start Retard RPM Full Retard RPM open open open closed closed open closed closed Set the display (on models so equipped) to monitor the desired parameter: Display Options Switch 9 Switch 10 Display Function Description open open Retard Each LED = 2 degrees of timing retard open closed Airflow All LEDs on = maximum airflow closed open Air Temperature Each LED = 20 degrees F closed closed RPM Each LED = 100 RPM (above 500) Note The display option can be changed at any time, even while the ACU is operating. The other switches may be set anytime, but they will only take effect after the unit is reset. You must turn the ignition (power to the ACU) off to reset the ACU and change parameters. Jackson Racing Supercharger 1.8L Fuel Enrichment Option Some Jackson Racing supercharger kits for the 1.8L engine include a wiring harness that inserts a 15K ohm resistor into the air temperature circuit. ACU units shipped after June 13, 2001 provide an option to accommodate the Jackson Racing modification. If your kit included an 'Idle compensator module', you can only use this option if you have disabled the module by disconnecting the pressure switch (some owners have found 17

18 that disconnecting the switch fixes a hesitation or stumble problem). Please note that we are not recommending or endorsing any change in installation of the supercharger. We are not accepting responsibility for any alterations that you make to the fuel delivery system. Here's how to enable the ACU option: 1. Remove the four screws from the bottom of the ACU. 2. Remove the bottom cover. 3. Locate the jumper near the center of the board. Jumper in the 'normal' position. 4. Remove the jumper from the two posts towards the back (connector end) of the unit. Re-install the jumper on the two posts towards the front (LED end) of the unit. 18

19 Jumper in the '15K' position 5. Replace the bottom cover. 6. Reinstall the 4 screws. 19

20 JR Fuel Enrichment Option Wiring Diagram To use this ACU option, you must connect your ACU as shown below: Note that the air temperature connection to the ACU must be made from the air temperature sensor, and not the ECU. Your supercharger kit may have included any or none of the components (resistor, idle compensator module, pressure switch) illustrated in gray. If your kit has a pressure switch and an idle compensator module, this ACU option will only work if you have disconnected the black wire between the pressure switch and the idle compensator module. Please note that we are not recommending or endorsing any change in installation of the supercharger. We are not accepting responsibility for any alterations that you make to the fuel delivery system. 20

21 ACU Programming Tips If all those switches on the back of the ACU appear a bit intimidating, take a look at these programming tips. The tips offer some step-by-step guidance Airflow Retard To set airflow retard, it s helpful to think in terms of a timing target. Let s use the case of a 6 psi supercharger application. The nominal base Miata timing is 10 degrees. Our supercharger instruction manual tells us to set base timing to 8 degrees if we are using 93 octane gasoline and 6 degrees base timing if we are using 92 octane. Alas, we can only find 92 octane. Our base timing, then, must be 6 degrees. This also becomes our timing target. We want to restore the low-end torque that we loose if we were to move base timing from the nominal 10 to the 6 degrees recommended by our supercharger manual. Moreover, suppose we actually want to improve low-end torque over nominal by bumping the base timing up to 12 degrees. To figure out where to set the ACU s airflow-based retard, compute the difference between the target timing and the desired base timing. In our case, this is 12-6, or 6 degrees. Set the ACU airflow-based retard to 6 degrees. Let s take another example. Suppose we move to California, and can only find 91 octane gasoline. That might lower our target timing from 6 down to 4. To maintain our desired base timing of 12 degrees, we compute 12-4 = 8. Set the ACU airflow-based retard to 8 degrees. RPM map At low RPM we can safely run with greater advance than we can at higher RPM. This means that we want to retard the timing at high RPM. The ACU uses an RPM-timing map to adjust timing appropriately. Think of this function as blocking or inhibiting retard at low RPM. Retarding when the RPM is quite low, we risk losing power needlessly. The ACU allows you to select one of four timing maps. A good place to start is the moderately aggressive timing map of 2500/3800 RPM. (With this map selected, the ACU will not add any timing retard below 2500 RPM. Above 3800 RPM, it will permit the full airflow-based timing retard, provided the airflow conditions warrant it). If the difference between your base timing and your timing target is not large, you will probably be safe with the more aggressive RPM maps. As you increase this difference, you might need to move to a more conservative RPM map. Air Temperature Standard engine control units adjust timing based upon intake air temperature. As air temperature increases, timing is retarded slightly. A typical rate is 1 degree of retard for each 7 to 9 degrees C (12 to 16 degrees F) increase in intake air temperature. In a turbo or supercharged application, more timing retard may be required than what the stock ECU 21

22 provides. The ACU can be set to add air temperature-based retard to the amount of retard provided by the stock ECU. Choices range from 1 degree of retard for every 40 degrees C increase in temperature to 1 degree of retard for every 15 degrees C increase in temperature. Remember, this retard is in addition to what the ECU is already doing. When programming your ACU for temperature, a good place to start is 1 additional degree of retard for each 30 degrees C increase in temperature. If that is not sufficient in hot weather, try 1 degree of retard for each 20 or 15 degrees C temperature increase. The adjustment in timing by the ACU in effect changes the base timing that you or your mechanic set by rotating the crank angle sensor. For example, with base timing set to 12 degrees, and using the recommended ACU setting, the ACU in effect resets the base timing to 11 degrees when the intake air temperature rises 40 degrees C above the temperature at which base timing was set on the car. Remember that at typical shop or garage temperatures, the ACU will add some temperature-based retard (typically one or two degrees at nominal ambient air temperatures). Two degrees of temperature-based retard will show up as one LED lighted if you have the display set to show retard. If the intake air temperature drops significantly from the garage-shop temperature, the LED will extinguish and the ACU will advance timing slightly. (The above description applies to ACU software revision 1.4.) 22

23 Application Notes 1.8L Moss/Jackson Racing/Sebring supercharger To alter fuel delivery, SOME 1.8L Moss/Jackson Racing/Sebring supercharger kits use a modification to the intake air temperature sensor. This modification tricks the Engine Control Unit (ECU) into thinking that the air temperature is much colder than it actually is. The ECU responds by adding fuel, which is needed because of the extra air provided by the supercharger. Neat trick. A problem with this setup is that too much fuel may be delivered at idle, when the supercharger is not adding air. Some 1.8L supercharger kits use an 'Idle compensator module' to address this situation. This compensator basically disabled the resistor that is switched into the air temperature sensor circuit when not under boost. Several owners have experienced drivability problems with the 'Idle compensator module' as it switches in and out of boost. Many have disconnected the boost switch. Others have replaced the module with a fixed 15 K ohm resistor. Unfortunately, the 'resistor trick' will trick the ACU as well as the ECU. This will render the ACU air temperature compensation inoperative. (The ACU will otherwise function normally.) Although you might think that you could remedy the situation by connecting things in the proper order, it's not that simple. Explaining why is a bit involved and requires some basic understanding of electricity and Ohm's Law and is beyond the scope of this manual. Further complicating matters, not all Moss/Jackson Racing/Sebring 1.8L kits use the same air temperature setup. Some use the 'Idle compensator module' and some don't. Later versions of the base kit do not use a modification to the air temperature input at all, but use an Auxiliary Fuel Pressure Regulator instead. But, it is our understanding that the Big Boost Kit (BBK) uses both! To properly connect the ACU, you will need to know if your kit uses a fixed resistor and/or an idle compensator module or not. 23

24 If your kit uses an AFPR only, make the air temperature connection to the ACU as per the standard wiring diagram. Do NOT use the 15K option. There are three work-arounds for the 1.8L Moss/Jackson Racing/Sebring supercharger application with modified air temperature circuitry. Choose one: 1. Don't enable ACU air temperature compensation. Leave the air temperature terminal on the ACU disconnected. You may need to dial in an extra degree or two of airflowmapped timing retard to compensate. You will still get all of the other benefits of the ACU. 2. If your kit uses a fixed resistor, set the ACU's 15K option (see the programming page). The ACU will then operate with this modification. The ACU's temperature resolution will not be quite as good as with the stock Miata setup, but it will be adequate. You will need to connect the ACU's air temperature input at the temperature sensor, before the fixed resistor, not at the ECU. See the wiring diagram. 3. If your kit uses an 'Idle compensator module', install a separate temperature sensor for the ACU. Determining if a fixed resistor and/or an 'Idle compensator module' are installed It is not easy to determine if your 1.8L supercharger kit included a fixed resistor or 'Idle compensator module' by visual inspection. You can however determine this via an electrical inspection. You will need a voltmeter for this procedure. 1. Allow the car to reach ambient temperatures under the hood. 2. Connect a voltmeter to the air temp input signal at the ECU. (Use the ECU Connections chart to locate the correct pin.) If using a voltmeter probe, you can probably make contact with this pin without splicing into the wire. 3. Turn the ignition on. 4. If the voltmeter reads about 4 volts or more, then there is a 15K or similar resistor and no idle compensator module installed (or the idle compensator module is disabled). Connect the ACU air temp input at the thermistor and set the jumper to the 15K position. Done. 5. If the voltmeter reads about 2 volts, then EITHER there is no resistor installed OR there is a resistor installed along with an idle compensator module. Continue. 6. A helper may be needed for this step, and the voltmeter connection may need to be spliced. Drive the car and observe the voltmeter under boost. 7. If the voltage remains at about 2 volts or lower, then there is no resistor installed. Connect the ACU at the ECU and leave the ACU jumper in the normal position. 8. If the voltage jumps up to 4 volts or more under boost, then returns to 2 volts or less, then there is a resistor and an idle compensator module installed. Choices are to leave the ACU air temperature input disconnected or install an external thermistor. 24

25 Note: We are not recommending or endorsing any change in installation of the supercharger. We are not accepting responsibility for any alterations that you make to the fuel delivery system. 1.6L Moss/Jackson Racing BBK (big boost kit) The 1.6L BBK (big boost kit) uses an AFM Module (in addition to an AFPR) to manage fuel. The AFM Module is well-behaved and does not alter the air temperature sensor's output. The ACU will work properly with the AFM Module, but you must connect the ACU air temperature input to the junction between the air temperature sensor and the AFM Module, not at the ECU. The ACU is also well behaved and will not affect AFM Module operation. Nitrous Oxide If you are running nitrous oxide, you may want to retard timing when the nitrous is on to avoid knock. The ACU can be set up to add 3, 4, 6, or 8 degrees of retard across the board when you engage the nitrous. You can easily do this by using a common automotive relay. Refer to the wiring diagram below. This illustration references the 1.6L ECU pins and wire colors, but the application works equally well on the 1.8L engine. 25

26 Here's how it works: The airflow and RPM retard maps are disengaged by connecting the airflow input to ground. The air temperature input is connected to a set of relay contacts that switches to ground when the nitrous is engaged. When the nitrous is not on, the ACU thinks the air temperature is very cold, and it adds no retard. When the nitrous is on, the ACU thinks that it is very hot, and it adds the total amount of air temperature retard. You program the amount of retard via the air temperature switches. Switch 5 Switch 6 Nitrous retard open open 3 degrees retard open closed 4 degrees retard closed open 6 degrees retard closed closed 8 degrees retard In this application, set switch 1 to the 1.8L setting (closed position), even if you have a 1.6L engine. Switch 1 Engine open closed 1.6L - n/a 1.8L - Nitrous In-dash timing adjustment If you're willing to forego air temperature compensation, you can easily connect a control to your ACU to adjust timing up to 8 degrees right from the driver's seat. This can be a useful temporary connection. It allows easy adjustment of base timing to help experiment with just the right amount of timing retard that is needed in a particular application. Once you've determined your car's particular needs, you can set the programming switches appropriately, reconnect the temperature compensation, and disconnect the in-dash control. To install this control, you'll need to obtain two components - a 10K ohm potentiometer (linear taper preferred) and a 13K ohm resistor, rated at 1/4 watt or more. These components are readily available from electronics stores such as Radio Shack Connect these components as shown in the wiring diagram. Note that the ACU air temp input is not connected to the Miata's air temp sensor in this application. This input is connected to the center lead of the potentiometer. Wire to the outside leads of the potentiometer and the resistor as shown. 26

27 In-dash timing adjustment wiring diagram. This illustration references the ECU pins and wire colors for the 1.6L engine, but the application works equally well on the 1.8L engine. To use the control, rotate the potentiometer fully counterclockwise. Set the display to indicate retard. Set the air temperature switches to 1 degree of retard for every 15 degrees C temperature change. Start the engine and let it idle. You should see no LEDs lighted. If you see four LEDs lighted, and these extinguish as you rotate the control clockwise, reverse the connections to the outer leads of the potentiometer. With the engine idling, adjust the control back and forth. You should be able to light 0, 1, 2, 3, or 4 LEDs. This represents from 0 to 8 degrees of added retard (2 degrees of retard for each LED). Don't be alarmed if the engine idles poorly or even stalls at the 8 degree setting. Set the control so that 2 LEDs are lighted. Now, adjust your base timing manually (using a timing light and rotating the CAS) to your desired base timing value. You should now be set up to add or subtract base timing via the control. For example, if you set base timing to 12 degrees, then rotating the control fully counterclockwise to extinguish the two LEDs that were lighted will leave you at an effective 16 degrees of base timing. Rotating fully clockwise to light four LEDs will put you at 8 degrees base timing. You should be able to verify this with a timing light. The control adjusts timing across the board. As airflow and RPM increase, the ACU will add more retard to this base value. The display will show the total amount of retard that is being applied by the ACU at any time. (This application requires software version 1.4.) 27

28 MAP sensor For those not satisfied mapping airflow to retard, you can map boost to retard instead by connecting an external manifold air pressure (MAP) sensor to the ACU. A standard GM 2 bar MAP sensor will trigger the ACU to start pulling timing at about 2 psi of boost and will pull maximum timing at about 9-10 psi of boost. Refer to the table below. Boost/vacuum ACU LEDs Vacuum psi boost 4 2 psi boost 5 4 psi boost 6 7 psi boost 7 10 psi boost 8 13 psi boost 9 15 psi boost 10 ACU action No retard Variable retard Maximum retard ACU boost-to-retard map with external MAP sensor. (The ACU LEDs column is with the ACU set to display Airflow.) Information on GM MAP sensors may be found at the DIY-EFI web site ( To purchase a 2 bar GM MAP sensor, I went to my local Checker auto store and asked for a MAP sensor for a '90 Pontiac Sunbird. I got a GM equivalent part for $68. Vacuum/boost Signal 20" vacuum 0.7 v 0 psi boost 2.3 v 15 psi boost 4.8 v To check that you have the correct MAP sensor, measure the output voltage with the manifold pressure port disconnceted. You should see about 2.3 volts. To use the external MAP sensor, connect it per the wiring diagram below. Basically, you just connect the airflow input of the ACU to the MAP sensor instead of to the Miata's airflow meter. To power the MAP sensor, you must connect it to +5 volts. Fortunately the Miata can supply this voltage at the ECU or at the airflow meter assembly. For example, on the 1.6L engine, +5 volts is available at ECU pin 2K, which is connected to the airflow meter assembly via a green with red stripe wire. 28

29 MAP sensor wiring diagram. This illustration references the ECU pins and wire colors for the 1.6L engine, but the application works equally well on the 1.8L engine. In this application, set switch 1 to the 1.8L setting (closed position), even if you have a 1.6L engine. Switch 1 Engine open closed 1.6L - n/a 1.8L - External MAP sensor Use switches 2-4 to select the boost-to-retard map that you desire. For example, if your turbocharger develops up to 6 psi of boost, and you would like to pull 5 degrees at maximum boost, select 0.8 degrees of retard per psi of boost (6 psi times 0.8 degrees/psi = 4.8 or about 5 degrees). Remember that in this application the ACU will reach maximum boost-mapped retard at about 10 psi. More than 10 psi will not result in additional retard. 29

30 Boost-to-retard map (approximate) with GM 2 bar MAP sensor Switch 2 Switch 3 Switch 4 Degrees of retard per psi of boost open open open 0.4 open open closed 0.5 open closed open 0.6 open closed closed 0.7 closed open open 0.8 closed open closed 1.0 closed closed open 1.2 closed closed closed 1.4 External Temperature Sensor Some Sebring/Jackson Racing/Moss supercharger kits for 1.8L Miatas use a resistor in the air temperature sensor line to the ECU and an "Idle compensator module" to adjust fuel delivery. This setup makes it impossible for the ACU to read the correct intake air temperature. The cleanest solution to this problem is to install a separate air temperature sensor (thermistor) for the ACU. 30

31 To install an external thermistor for the ACU, you need to add the three external components as illustrated in gray. These components may be obtained from the electronics distributor Digi-Key for under $15 including shipping. The thermistor value is 2K ohm at 25 degrees C (Digi-Key part no. KC001T-ND). The resistor values are 2.7k ohm (Digi-Key part no. 2.7KQBK-ND - the minimum order quantity is 5) and 5.6k ohm (Digi-Key part no. 5.6KQBK-ND). Visit Digi-Key online at digikey.com to place an order. The thermistor should be mounted in or near the intake air stream (near the air filter would be suitable). The resistors may be mounted anywhere convenient. You may be able to mount them right at the ACU connector. The thermistor may be connected to ground almost anywhere, including most metal parts of the car or engine. Take care to properly solder wires to these parts and insulate the connections (shrink-wrap tubing is recommended). 31

32 Software revisions Version 1.1 This software version uses the following RPM map choices: RPM Map Switch 7 Switch 8 Start Retard RPM Full Retard RPM open open open closed closed open closed closed Version 1.2-3/24/01 Changed to a slightly less aggressive set of RPM maps: RPM Map Switch 7 Switch 8 Start Retard RPM Full Retard RPM open open open closed closed open closed closed

33 Version 1.3-5/11/01 Added the Jackson Racing/Moss/Sebring 15K resistor trick option. Version 1.4-8/14/01 Changed the RPM display to precision tachometer. Modified the air temperature-to-retard mapping. Now, as air temperature increases, the ACU adds more retard independent of airflow and RPM. Previously, extra retard at high temperature was added only at higher RPM and airflow. Version /20/01 Adds a percentage of timing back in (via less timing retard) at higher RPMs, based on the amount of total retard the ACU is programmed for. This is of benefit to both forced induction and naturally aspirated cars. 33