27. Install C1 {399-4329-ND, 0.1 µF, 104) and solder. This is located near pin #20 of the CPU socket.

28. Install and solder C20 {399-4361-ND, 0.033 µF, 333 marking}. It is located in a row of three capacitors above the L1 inductor you installed (above ".info" in the copyright notice)

29. Install and solder C21 {399-2075-ND or 399-4326-ND, 0.01 µF, 103 marking}. It installs beside C20.

30. Install and solder C24 {399-1911-ND, 47 pF, 470 marking}. This installs on the other side of C20.

31. Install and solder C25 {399-1908-ND, 22 pF, 220 marking}. This installs near the Y1 square silkscreen pad.

32. Install and solder R1 {10KEBK-ND, 10K, brown-black-orange}. This installs near pin #18 of the CPU socket.

33. Install and solder R3 {51KEBK-ND, 51K, green-brown-orange-gold/silver). This installs near pin #21 of the CPU socket.

34. Install and solder R6 {10KEBK-ND, 10K, brown-black-orange}. This installs near L2, by the 'Boot' jumper hole.

35. Install and solder R21 {10KEBK-ND, 10K, brown-black-orange}. This installs between C20 and C25.

36. Install and solder R22 {100KEBK-ND, 100K, brown-black-yellow}. This installs between the pad for Y1 and the components you have already installed nearby.

37. Install and solder R23 {10MEBK-ND, 10M, brown-black-blue}. This installs between the Y1 pad and the CPU socket.

38. Install and solder Y1 {300-1002-ND, 32768 Hz crystal, the very small silver can with the two tiny wires}. Note that Y1 is physically fragile, do not drop it. The crystal will fail to operate if it touches other components, so be sure it is clear of these. Bend the leads at a 90-degree angle so that the crystal lies parallel to the PCB. Note: You may want to “glue” the crystal to the printed circuit board with a cushion of silicone rubber adhesive (RTV) or 'hot glue'. A small "blob" on the under side of the crystal will cushion the crystal and dampen any mechanical vibrations. A small metallic ground pad is provided for this purpose.

39. Insert the CPU U1 {the 68HC908 for MegaSquirt). For the 68HC908 (MegaSquirt) processor the notch faces downward (line up with silk screen and socket notch). You may have to bend the leads inward a bit to get it into the socket - be careful not to break one off. Note that bending the CPU leads can be tricky. Your objective is to have the width of the CPU leads exactly match the width of the socket pins, before you attempt to firmly push the CPU into the socket. Ideally, you want to bend all pins at the same time. One technique is to hold the CPU with your thumb and index finger of each hand, so that one side of all the pins are against a rigid flat surface. Your thumbs are on the top of the CPU at each end and your index finger is underneath between the pins. By firmly tilting the CPU against the flat surface you will bend all the leads on one side of the CPU. Go slowly, a mini bend of a few degrees each time. Be careful not to bend the pins too far. Make several checks for fit in the socket as you go along. If you are having a difficult time visualizing this technique, place the CPU on a flat surface as if it were in the socket. Now turn the CPU up 90 degrees so that it is standing on the flat side of half its pins. A second method to bend all the CPU pins at once is to use an extra long needle nose pliers and grab all the pins at once. A twisting motion applied to the pliers will bend all the pins simultaneously. With care, this will also work if the needle nose pliers are only long enough to grab half the pins. Just make the bends in two steps.

40. You are now ready to test the operation of the processor. Plug in the DB-9 serial cable into the board and to the PC. Next we will ensure that the software is in place, on both the processor and the computer.

Note that the 68HC908 processors (for standard MegaSquirts and MSnS-E) already have the code loaded. Simply install MegaTune with all the default settings, and you should be ready to run.

To perform the tests at this step, you will also need to have MegaTune installed on your computer (this is also the program you will use to tune the fuel injection in the vehicle). To install the latest version of MegaTune on your computer:

1. Click this link to go to the MSnS-E release site,
2. Select "MS1-Extra's MegaTune, includes latest firmware WITH the complete manuals", download it and install it.
3. It will create a folder called 'C:\Program files\MegaSquirt\MegaTune2.25' and subfolders 'mtCfg' and 'carMtCfg'.
   The install program also creates an icon on your desktop with the name MegaTune, DON'T click it yet, you need to set up MegaTune (see 'Using MegaTune225').
4. The install program will also create a folder in 'C:\Program files\MegaSquirt\' called 'Car1', this is where all your vehicle specific information will go.
5. You need to tell MegaTune which version of MegaSquirt you have (MSnS-E, etc.), as well as the EGO type, etc.
   To do this, use the mtCfg program, which can be opened directly from the MegaTune folder. Look for the CODE_VARIANT variable, it will be in 'Car1/settings.ini/Settings/CODE_VARIANT' in the directory tree on the left side of the mtCfg window. Click on CODE_VARIANT. You can then use the drop box in the upper right section of the window to select your code variant.
   

Click the link to find more information on MegaTune.

On the PC, run MegaTune by clicking on the icon on your desktop. Go into the "Communications" window and select the proper COM port (the "Verify ECU operation" does not operate, so do not be fooled). Exit this screen (back to the main window).

41. Plug the stimulator into the ECU. On the PC, click the "Realtime Display" under "Tuning" on the main menu, which brings up a new screen. Look at the "Time(s)" near the top left corner of the Realtime Display - it should be counting up, incrementing every second (it will roll over at the value of 255, back to zero). If the seconds count is there, you are running! If not, check the cable, make sure there is power, and check the COM port. The only other value on the screen which is working correctly is the "Batt V" box - it should be displaying the battery voltage (from about 7.0 - 8.5 volts, depending on the 9-volt battery condition). All other boxes will have nonsense for numbers.

Input Section Construction & Testing

42. Remove the processor from the 40-pin socket - use a thin screwdriver and pry it from the socket, first one end, then the other - place it back on the foam pad it was shipped with. Now, you are going to install all of the input sensor components.

43. Install and solder C3 {399-4329-ND, 0.1 µF, 104 marking}. This is located in the bottom right section of the board (near the DB37, furthest away from the heat sink) between the U2 column of holes and the SPR2(CANL)/SPR1(CANH) holes.

44. Install and solder C2, C9 and C10 {399-2083-ND or 399-4353-ND, 0.22 µF, 224 marking}. These install in the column of capacitors just above "Grippo" in the copyright notice on the silkscreen at the bottom of the board.

45. Install and solder C4, C6, and C8 {399-4202-ND, 0.001 µF, 102 marking}. These install in the column of capacitors just above "Grippo" in the copyright notice on the silkscreen at the bottom of the board.

46. Install and solder C5 and C7 {399-2102-ND or 399-4389-ND, 1.0 µF, 105 marking}. These install in the column of capacitors just above "Grippo" in the copyright notice on the silkscreen at the bottom of the board.

47. Install and solder R2, R9, and R10 {1.0KQBK-ND, 1K, brown-black-red}.  These install in the column of resistors just above "&" in the copyright notice on the silkscreen at the bottom of the board.

48. Install and solder R5 and R8 {2.2KQBK-ND, 2.2K, red-red-red}.  These install in the column of resistors just above "&" in the copyright notice on the silkscreen at the bottom of the board.

49. Install and solder R11 {1.0MEBK-ND, 1M, brown-black-green-gold).   This installs in the column of resistors just above "&" in the copyright notice on the silkscreen at the bottom of the board.

Note: R11 and R10 are part of the EGO input circuit (with C10). It is very important that you do NOT install a capacitor across the sensor input before R11 (C10 comes after R10 and R11 and is fine). Some people have recommended adding such a capacitor to 'smooth' the sensor input. This will cause problems, especially with wide band analog outputs such as you find on Innovate's LC-1.

Also, if you have a wideband sensor/controller, be sure to ground the controller to the same point as MegaSquirt!

50. Next you need to make a decision. There are two input circuits for the tach signal:

• The Hall/optical/etc. circuit takes the square wave input from a Hall sensor, optical sensor, or points. It can also be used for triggering off the coil (but only if you are not controlling ignition timing).
• The VR circuit takes the AC signal from a variable reluctor sensor and converts it to a square wave for use by MegaSquirt.

The VR circuit is install in step 51, if desired.

In most cases, you should install both circuits, and make the selection between them with jumpers. However, if you do not want to install the Hall/optical/points circuit, skip ahead to step #51.

Read the MS EXTRA TRIGGER INPUT MANUAL --> http://www.msextra.com/manuals/MS_Extra_Ignition_Hardware_Manual.htm#hall

1. To install the Hall/optical input circuit (or points without a coil connection):
   1. Install and solder R12 {390H-ND, 390 Ohm, ½ watt, orange-white-brown}. This is installed between the resistors you have just been installing and the CPU socket. This resistor should be mounted roughly 2mm above the surface of the PCB. Also, the value of this resistor may have to be changed if you trigger from the negative side of the coil depending on application - start with the supplied value, and if gets hot while the engine is running, then increase the value, in steps, up to 10K (like 470 Ohms, 560 Ohms, 680 Ohms, 1K, ...), or even more in some applications (consult the MegaSquirt Forums list for advice). However, do not adjust this resistor on assembly, unless you have a good reason to do so.
   2. Install and solder R13 {4.7KEBK-ND, 4.7k, yellow-violet-red}. This is located 3 places close to the heat sink than R12 (which you just installed).
   3. Install and solder C11 {399-2075-ND or 399-4326-ND, 0.01µF, 103 marking}. This installs at the top of the row of 'vertically' oriented capacitors above "Bowling" in the copyright notice.
   4. Leave the C30 location empty - DO NOT jumper it.
   5. If you have a Hall sensor or optical sensor, do not install D1, put a jumper in its place. It is located beside R12, further from the heat sink.
   6. For most installations, diode D2 {1N4001DICT-ND, the marked 1N4001} is not needed. Do not install D2, install a jumper in its place (made from a snipped off lead). It is located beside D1, closer to  the heat sink.

      Note: this diode (D2) is needed only if the ignition system has a large offset bias - most systems do not have such a bias. So, to start, you can either solder in a jumper wire in this location, or, you can install the diode D2, and then install a jumper around the two leads of the diode - in effect shorting it out. The latter will allow you to snip the jumper later on if needed, putting the diode back in circuit. Solder the diode in observing the banded end as on the board, then solder a wire jumper across the diode itself.

   7. Install/solder opto-isolator U3 {160-1300-5-ND, 4N25). This is located near the center of the PCB. If you have bought a socket (AE7300-ND or AE10021-ND ) for this component, solder it in place instead, then insert U3 into the socket. Observe the proper orientation (notch matches PCB - towards the heat sink, or dot for pin #1 which is the square pad on PCB at the notched end of the silk screen). If neither are there, hold the chip so that the writing is facing you and the right way around. Pin #1 is on the bottom left.
   8. Leave the C12 location empty - DO NOT jumper it. This is located above "Bowling" in the copyright notice. This capacitor may need to be installed and/or the value increased if there are noise problems with the tach signal - values up to 0.1uf will work. The 0.001uf value is a good starting point.

   If you later find you have an intermittent tach signal on the vehicle, but it doesn't work at all speeds or all temperatures in the car, check the Hall circuit modifications here: Hall input circuit mods

   This input circuit is also used - with the modifications below - if you want to trigger off the negative side of the coil, since the points control the negative side of the coil's primary circuit. However, you can only trigger off the coil's negative terminal if you are NOT trying to control ignition timing. Do either 50a or 50b, not both.

2. For triggering off the coil negative terminal/points:
   1. Install and solder R12 {390H-ND, 390 Ohm, ½ watt, orange-white-brown}. This is installed between the resistors you have just been installing and the CPU socket. This resistor should be mounted roughly 2mm above the surface of the PCB. Also, the value of this resistor may have to be changed if you trigger from the negative side of the coil depending on application - start with the supplied value, and if gets hot while the engine is running, then increase the value, in steps, up to 10K (like 470 Ohms, 560 Ohms, 680 Ohms, 1K, ...), or even more in some applications (consult the MegaSquirt Forums list for advice). However, do not adjust this resistor on assembly, unless you have a good reason to do so.
   2. Install and solder R13 {4.7KEBK-ND, 4.7k, yellow-violet-red}. This is located 3 places close to the heat sink than R12 (which you just installed).
   3. Install and solder D1 {1N4001DICT-ND}. This is the famous Wing Diode - you will want this if you are triggering off the negative side of the coil - such as with points (reduces tach signal false-triggering).
   4. In the place of D2, install a 22V or 24V Zener diode {1N4748ADICT-ND}, in the reverse of the indicted orientation (i.e., put the band at the other end rather than that indicated on the silk screen). Note that the stim will not be able to send a signal through this diode. If you have installed it, jumper it for operating on the stim.
   5. Install/solder opto-isolator U3 {160-1300-5-ND, 4N25). This is located near the center of the PCB. If you have bought a socket (AE7300-ND or AE10021-ND ) for this component, solder it in place instead, then insert U3 into the socket. Observe the proper orientation (notch matches PCB - towards the heat sink, or dot for pin #1 which is the square pad on PCB at the notched end of the silk screen). If neither are there, hold the chip so that the writing is facing you and the right way around. Pin #1 is on the bottom left.
   6. Install and solder C11 {399-2075-ND or 399-4326-ND, 0.01µF, 103 marking}. This installs at the top of the row of 'vertically' oriented capacitors above "Bowling" in the copyright notice.
   7. If you are going to use the negative side of the coil to trigger MegaSquirt (I.e., you are not using ignition timing control), then install and solder C30 {399-2083-ND or 399-4353-ND, 0.22µF, 224 marking}.
   8. If you are going to use the negative side of the coil to trigger MegaSquirt (I.e., you are not using ignition timing control), then install and solder C12, the Ed capacitor (399-4202-ND, 0.001 µF, 102 marking}. This is located above "Bowling" in the copyright notice. The value of this capacitor may need to be increased if there are noise problems with the tach signal - values up to 0.1uf will work. The 0.001uf value is a good starting point.

51. As we noted in step 50, there are two input circuits for the tach signal. One takes the square wave input from a hall sensor, optical sensor, or points.

In most cases, you should install both circuits, and make the selection between them with jumpers.

However, if you do not want to install the variable reluctor (VR) circuit as well as the Hall circuit, skip ahead to step #52.

1. Install and solder R42 and R55 {1.0KEBK-ND, 1K Ohm, brown-black-red}. R42 is located near the DB37 side of the Y1 pad. R55 is beside it, about 25mm above the 'dash' in the copyright notice (the R55 label may be partly obscured by a via).
2. Install and solder R44, R53, and R54 {10KEBK-ND ,10K Ohm, brown-black-orange}. R44 is between U1 and U7 near the center of the board. R53 is near L1, above ".info" in the copyright notice. R54 is located directly above the dash in the "www.msefi.com/msefi - (C) 2005" notice.
3. Install and solder R45, R46, and R48 {10KQBK-ND, 10K Ohm, brown, black-orange}. R45 is located beside R12 (the large resistor you spaced off the PCB), closer to the heat sink. R46 is located beside R45, above the "2005" text in the copyright notice. R48 is located very near the center of the PCB.
4. Install and solder R47 {47KEBK-ND, 47K Ohm, yellow-violet-orange}. R47 is located very near the center of the PCB.
5. Install and solder R49, and R50 {100KEBK-ND, 100K Ohm, brown-black-yellow}. R50 is beside R47, R49 is to the right (and slight below these - closer to MOV1),
6. Install and solder R51 {1.0MEBK-ND, 1M Ohm, brown-black-green} near the center of the PCB.
7. Install and solder R52 {CT94W104-ND} and R56 {CT94W103-ND}. These are the trimmer potentiometers used to 'tune' the VR circuit. The longest lead (and/or the one nearest the "1" imprinted on the case, depending on where you got your components) on each pot should go in the square pad closest to the heat sink. R52 is used to adjust the hysteresis, R56 is used to adjust the zero-crossing point. For VR sensor operation, the pot on the transistor base (R56) needs to be turned to zero volts and the pot on the op-amp feedback (R52) needs to be turned to maximize resistance (i.e. give 100K feedback resistance). This should be with both screws turned fully counter-clockwise. For more on adjusting the VR pots, see this link.
8. Install and solder C31 {399-4329-ND, 0.1µF, 104 marking}. This is located  as the 4th cap in the row of "vertical" capacitors above "Bowling" in the copyright notice.
9. Install and solder C32 {399-2075-ND or 399-4326-ND, 0.01µF, 103 marking}. This is below C31, further from the heat sink.
10. Install and solder D24 {1N4001DICT-ND}. Be sure to match the band on the diode to the band on the silkscreen. This is located immediately above the "2005" in the copyright notice, beside R56.
11. Install and solder Q22 and Q23 {ZTX553-ND}. These are located beside D24 (which you just installed), closer to the heat sink. The side of Q22 & Q23 with the rounded edges (i.e., the shorter of the two flat sides) is referred to as the 'rounded side', and it goes away from the CPU for both Q22 and Q23. If you imagined the side that had rounded corners was completely round, then it would match the PCB silkscreen. Be VERY careful when soldering these, the pin spacing is very tight. It is a good idea to clean your solder tip before attempting this. If you do accidentally bridge the leads with solder, you can use a piece of solder wick (which is a fine braided copper ribbon) and a hot soldering iron to remove the excess solder. Note: if you got your kit from a distributor, be sure to follow any instruction they have supplied for these parts!
12.  Install and solder U7 {LM2904NFS-ND}. This is located beside the CPU socket, closer to the DB37 connector. If you have bought a socket for this component (AE7208-ND or AE10011-ND), install and solder it instead, then insert U7 into the socket. The notched end (or the end with a dot in one corner), goes to the end closest to the heat sink.

52. Select the tach input circuit with jumpers:

For the VR sensor: Jumper VRIN to TACHSELECT on the bottom side of the PCB (near the DB37, opposite the heat sink.) Jumper TSEL to VROUT (Or VROUTINV if you want the VR input to be inverted) on the bottom side of the PCB, near the center.

OR(Do NOT install both sets of jumpers, chose one set or the other!)

For the Hall sensor, optical sensor, coil negative terminal or points: Jumper XG1 to XG2 on the bottom side of the PCB, near the 40 pin socket, Jumper OPTOIN to TACHSELECT on the bottom side of the PCB, near the DB37 connector, opposite the heat sink. Jumper TSEL to OPTOOUT on the bottom side of the PCB, near the center.

Note for the Hall/optical/points circuit: The LED inside of the opto-isolator is fired by a signal provided by the ignition system. The pulses existing on an ignition, especially when pulled directly off of the coil primary, can spike to very high voltages. The return path of the LED is terminated to jumper pad XG1. This return path can either go directly to the board ground (by placing a jumper from XG1 to XG2), or, the return can be brought out of one of the jumper slots on the DB-37 connector (like SPR4 for pin #6), and then grounded with a separate wire on the DB-37 connector, thus isolating the ground. Note: for the ECU to work on the stimulator, then the XG1 terminal needs to be hooked to XG2, and right now we are doing stimulator testing, so install a jumper from XG1 to XG2.

When you install the ECU, if you need isolation because the tach signal is resetting the ECU (for those installs tapping right off of the ignition coil (-) terminal), then you can remove this jumper and connect XG1 to SPR4, and ground this pin (#6 for SPR4) with a separate return wire. Note: if you are using a tach output from an aftermarket or many OEM setups, the tach signal is a nice +12V pulse - these will work fine with the XG1 terminal jumpered to XG2 in the install. Again: for testing right with the stimulator, hook XG1 to XG2. Later, after you install this on your vehicle, if you have reset problems, then remove this jumper and jumper XG1 to SPR4, and bring out a separate return ground wire to the ignition module/distributor on DB37 pin #6.

You may also need to do this if the Hall sensor input is noisy in the vehicle. To reduce noise, run the ground from the Hall sensor to one of the jumper slots on the DB-37 connector (like DB37 pin #6 for SPR4), then connect SPR4 to XG1. Remove the jumper to XG2. (Note that you will have to ground XG1 with a jumper wire to run on the stim.) Twist the signal wire (DB37 pin #24) and ground wire (DB37 pin #6) together all the way to the ignition module, this will further reduce noise in the signal.

53. The MAP sensor, U2 {MPX4250AP), is next. It mounts on the under side of the PCB, with the vacuum port facing the DB37 connector end of the PCB, and the markings on the sensor facing away from the PCB so you should be able to read the "MPX4250AP" marking when the sensor is installed. The leads are bent toward the PCB, and soldered on the top-side. The notch on the lead indicates pin #1 - this corresponds to the square pad on the PCB.

The MAP sensor is held to the PCB with two nylon screws - do not tighten the MAP sensor too tight, this will distort the case and introduce an offset in the readings by flexing the load cell inside the device. And, yes, solder the leads on the top side of the PCB. You will have to devise a scheme to run a tube from the barbed MAP fitting to your intake manifold.

54. Install and solder R4 and R7 {2.49KXBK-ND, 2.49K, red-yellow-white-brown-brown). These are the temperature sensor "bias" resistors. They install above the "&" in the copyright notice.

If you want to use other sensors, you can change the transfer-function files in the MegaSquirt 68HC908 processor by using EasyTherm to change MegaSquirt's code to match your temperature sensors.

55. Time for a little testing. Install the processor, hook up the stimulator, hook up the DB-9 to the board and PC, fire up MegaTune, and bring up the "Realtime Display" window. You should be able to see responses when you move the knobs on the stimulator.

First, look at the RPM - it should change when you move the RPM pots on the stimulator. Note that if you have installed the VR input circuit jumpers in step #52, the stim is not currently designed to put out the sort of signal (AC) the VR circuit expects. However, by adjusting the pots at R52 and R56, you might be able to get a useable signal into MegaSquirt. The RPM may not be stable at each end of 1000-6500 range, but it should be workable over that range, at least. Then you'll know that the rpm input circuit is functioning at it should.

All sensors should react to the corresponding pots on the stimulator. When the O2 pot is moved, the O2 voltage moves irrespective of the other settings. On the other hand, the EGO correction bar (or equivalent gauge on the tuning screen) WILL NOT move away from 100% unless you have the EGO correction parameters set properly and MegaSquirt senses the proper inputs to activate EGO correction. Note that if you have not connected a TPS to your MegaSquirt, (testing in car, for example) the TPS value will slowly creep up to a maximum value, and O2 correction will be disabled. You should check that MegaTune reads approximately the correct barometric pressure when no vacuum is applied. Below is a chart of the 'normal' barometric pressures for various elevations above sea level. MegaSquirt should generally be within 4 or 5 kPa of the values below at your elevation.

If you don't pass the above tests, recheck all of the assembly steps in this section, verifying the correct components are installed with the correct orientation. If everything appears fine, check the troubleshooting tips at the end of this assembly manual

Output Section Construction & Testing

56. Install and solder R14 and R17 {10KEBK-ND, 10K Ohm, brown-black-orange). These are located near the center of the PCB, in the column of components roughly aligned with Q9 on the heat sink.

57. Install and solder R16, R19, R26, R27, and R29 {1.0KEBK-ND, 1K Ohm, brown-black-red}.(Note - R26, R27 and R29 only for LED's.) R16 is near the MOV1 (a bit further away from the DB37). R19 to the right (closer to the DB37) of the resistors you installed in the last step (R14 & R17) on the other side of C13 and C14. R26, R27, & R29 are located near the LEDs at the DB9 end of the PCB.

58. Install and solder D3 {1N4001DICT-ND}. This is located near the center of the PCB, near R14 and R17. Observe the proper polarity.

59. Install and Solder D4 and D8 {1N4748ADICT-ND} - observe the proper polarity. These are located beside MOV1, a bit further away from the DB37 connector. (Note - do not install D8 if you are using a PWM idle valve.)

60. Install and solder R15 and R20 {22QBK-ND, 22 Ohm, red-red-black}. R15 is located below the Q1 location on the heat sink, R20 is located below the R38 location on the heat sink.

61. Install and solder R24, R25, and R28 {330QBK-ND, 330 Ohm, orange-orange-brown). (Note - only for LED's.) These are located very near the LEDs on the DB9 end of the PCB.

62. Install and solder the transistors Q2 and Q4 {ZTX450-ND}. (Note - do not install Q4 if you are using a PWM idle valve.) These are located to the left of the MOV1. The side of the transistor with the white label faces the DB37 connector. If you got this transistor from a distributor (as part of a kit) then they likely have special instructions for it (search the packaging or contact the distributor). Distributors sometimes make substitutions for various reasons, and thus their notes are important. If your Q2/Q4 are the standard Digi-Key part {ZTX450-ND}, but don't have a white label, then the side with the rounded edges is the 'curved side', which is oriented to be closest to the DB37 connector.

Be VERY careful soldering these small transistors, clean your tip, and make sure not to bridge the closely spaced pins.

If you use any other transistor other than PN2222AD26ZCT-ND or ZTX450-ND from the MegaSquirt/Digi-Key parts ordering page, you MUST check the pin orientation, as the order can be different for apparently identical parts!

For PWM Idle Valve Users Only Note - if you are using a PWM idle valve (Ford or Bosch 2 wire valve), these valves can not be operated with a relay. As a result, they need a higher capacity transistor installed. Remove Q4, Q20, D8 and R39. Solder the (E) emittor to the DB37 side of position R39. Solder the (C) collector to the DB37 side of position D8. Solder the (B) base to the heatsink side leg (upper) of R19. DO NOT install Q4 for use with PWM idle valves - it cannot handle the current directly for PWM idle valves. ('On/Off' type idle valves used with a relay are fine with the default Q4.) Instead, for a PWM idle valve, use a TIP120/121/122 transistor (such as Digi-Key 497-2539-5-ND, 74¢ ea.) mounted on either the heat sink (if you have a spare spot) or the case. You should use a mica insulator (4724K-ND, 93¢) with heat sink grease as well. Run wires to the Q4 connections as shown below: Do not install Q20, do not install D8, and jumper R39 as well. You will also have to put a 1N4001 diode across the PWM Idle valve itself - the banded end goes to the 12 Volt supply, the non-banded end goes to the lead that goes to MegaSquirt (this diode is for flyback purposes on the idle valve).

63. Install C13 {399-4329-ND, 0.1 µF, 104) - and solder. This is located a bit closer to the heat sink, and a bit closer to the DB9 than Q4.

64. Install and solder C14 {399-3559-ND, 4.7 µF). This is located just a bit further away from the heat sink than C13, which you installed in the last step. Observe polarity. Recall that the positive lead has a small + near it on the body of the capacitor.

65. It is choice time again. In this case, you will decide whether to populate the high-current ignition driver circuit. This circuit can be used to drive a single coil in a distributor application. In conjunction with an appropriate input signal (from a VR, Hall, or optical sensor, or even points), it allows you to eliminate a separate ignition module, such as a GM HEI 7 or 8 pin module, and run the coil directly from MegaSquirt.

Read the MS EXTRA SPARK OUTPUT MANUAL --> http://www.msextra.com/manuals/MS_Extra_Ignition_Hardware_Manual.htm#msdout

66. Install and solder U4 {IXDI404PI-ND}, the FET driver. This is located near the Q3 location on the heat sink. If you bought a socket {AE7208-ND}, solder it in place and insert the chip. Be sure to orient it correctly, the notch or dot on the chip goes to the notched end on the silkscreen; this end is closest the heat sink.

67. Install D17 and D18 {1N5819DICT-ND}, the Schottky diodes. These are located on either side of the FET driver (U4) you just installed. Make sure the band on the diode matches the silkscreen.

68. Install and solder D21 {1N4753ADICT-ND}. This is located just a bit further away from the heat sink than D17. Make sure the band on the diode matches the silkscreen.

69. Once again you have a choice to make about whether to install certain components. In this case, you need to decide if you wish to install the PWM flyback damping circuit as well as the standard flyback circuit. The PWM flyback damping circuit is useful primarily for those running pulse width modulation (PWM) with low-impedance injectors. However, it will work fine if you install it with high impedance injectors. If you prefer to install only the standard flyback circuit, skip ahead to step #70: To install the PWM flyback damping circuit:

1. Install R30, R31, R34 and R35 {270QBK-ND, red-violet-brown}. R30 and R31 are near R37 on the heat sink, R34 and R35 are near Q9.
2. Install R32 and R36 {1.0KQBK-ND, 1K Ohm, brown-black-red}. These are located besides the resistors you installed in the last step.
3. Install Q9 and Q12 {TIP125TU-ND}. Bend the leads to fit in the holes so that the hole in the tab lines up with the hole in the heat sink. These transistors mount to the heat sink, but they MUST have an insulator between the transistors and the heat sink. Use the insulator kits for this {4724K-ND}. You may have to trim the mica insulator somewhat to avoid hitting the transistor leads - use a sharp pair of scissors. Use heat transfer compound between the component, mica insulator, and the heat sink.
   
   After assembly, check that you have very high resistance between the metal tab of both Q9 and Q12 and the heat sink. If you get less than about 60K Ohms (± 20K Ohms) resistance, you MUST correct it. Usually chamfering the bolt hole and sanding the heat sink lightly will solve the problem. Once you have ~60K Ohms or more resistance between the tab and heat sink, solder the leads to the PCB.
4. Install Q10 and Q13 {2N3904FS-ND}. The flat side of the transistors face the heat sink. These are located near Q9 and R37 on the heat sink. The pins are very close together, use a clean tip, and be careful not to bridge the joints.
5. There are no jumpers to install.

70. To install the standard flyback circuit:

1. Install R18 and R33 {270QBK-ND, red-violet-brown}. These are located below R38 and Q1 on the heat sink.
2. Install D6 and D20 {1N4753ADICT-ND}. These are located beside the resistors (R18, R33) you just installed. Make sure the band on the diode matches the silkscreen.
3. Install Q3 and Q11 {497-2629-5-ND}. These mount to the heat sink. No insulator kit is necessary, the tab can contact the heat sink. Use heat transfer compound between the component and the heat sink.
   
4. There are no jumpers to install.

71. It is choice time yet again. You have to decide whether to install the current limit circuit for driver FET protection. This clamps the current to ~14 Amps, and it is recommended that most people install this. To install the current limit protect circuit:

1. Install R37 {TAH20PR050JE-ND}. It goes on the heat sink, however it does not have a mounting hole. You can use double sided thermal transfer tape {BER158-ND} to fasten it to the heat sink, however this is quite expensive if you are just doing two resistors.
2. Install R38 {TAH20PR050JE-ND}. It goes on the heat sink as well, however it does not have a mounting hole. You can use double sided thermal transfer tape {BER158-ND} to fasten it to the heat sink, however this is quite expensive if you are just doing two resistors.
3. There are no jumpers to install.

72. IF you installed R37 and R38 in the previous step, install Q14 and Q15 {2N3904FS-ND} - otherwise you can leave then out. It does no harm to install them in every case, however. Use a clean tip, and be careful not to bridge the closely spaced pins.

73. Install D5 and D7 {FR302DICT-ND}. These diodes should be mounted about 2-4mm off the board. Make sure the band on the diode matches the silkscreen. These are located near R38 and Q3.

74. Install Q19 and Q20 {2N3904FS-ND}. These are located in line with the existing transistors (Q2 and Q4) to the left of the MOV1. Be very careful when soldering them, use a clean tip, as the pin spacing is very tight. (Note - if you are using a PWM idle valve, do not install Q20.)

75.Install R39 and R40 {1.0H-ND, 1 Ohm, brown-black-gold}. These are located on either side of the transistors (Q19 & Q20) that you installed in the last step. (Note - if you are using a PWM idle valve, install a jumper in place of R39).

76. Install Q1 and Q5 {IRFIZ34GPBF-ND}, the FETs (field effect transistors, used to drive the injectors). These are bolted to the heat sink, be sure to use heat transfer compound between the FET and the heat sink. These are insulated case variety, so they mount directly on the heat sink.

77. Install and solder Q6, Q7, and Q8 {2N3904FS-ND}. (Note - only for LED's.) Follow the silkscreen to orient the flat side of these transistors, which faces the DB9 end of the PCB.

78. We now have everything installed, other than the LEDs - these mount on the case ends.

79. Now, take one of the case halves, and install the PCB in the second-down slot down from the top. Note: The wider lip of the case side is near the heat sink side of the board. This is to allow the top lid case to close. The aluminum should fit against the case lip for a little extra heat transfer.

80. Next, mount the LEDs - D14, D15, and D16 {P301-ND} to the case font, and bend the leads down to the board and solder. The flats on the LEDs (the side with the short lead) faces the DB9 connector. First, install the LED holders on the front panel, through the front. Next, the LEDs press into the rear of the holder. Mount the case front panel to the case half (which has the PCB). Orient the FLAT on the side of the LED lip (the side with the shorter lead) towards the DB-9 socket (each LED). You will see that the PCB silk screen also has a "dash" above the LED circle symbol indicating the side of the flat. Bend the LED leads down to enter the PCB holes for them - you will have to do a trial fit, then trim the leads down a bit. See the illustrations below. Then solder the LEDs to the PCB from the top of the PCB. It is a little tricky - take your time.

• D14 (closest to the DB9 connector) will light each time an injector is fired .
• D15 (in the middle) is warm-up enrichment (WUE). It will light if your in a warmup situation (i.e. if the coolant pot on the stim is set to a value where the warm-up enrichment is greater than 100%).
• D16 (furthest from the DB9 connector) is accel enrichment (AE). It will light briefly if you turn the TPS pot on the stim from idle to full throttle.

If you don't pass the above tests, recheck all of the assembly steps in this section, verifying the correct components are installed with the correct orientation. If everything appears fine, check the troubleshooting tips.

Note: normal MAP readings in kPa for the MegaSquirt when the engine is not running (or is on the stimulator) should be somewhere around 85-103, depending on your elevation. You can check the tuning section of this manual for the details of how pressure varies with elevation. This is a good time to clean the excess flux from the board. A common problem with boards that were working and quit for no apparent reason is flux residue. Remove the processor. Wash your board with:

• 99% isopropyl alcohol (isopropyl alcohol is rubbing alcohol, any drugstore will have it - don't use the 70% isopropyl alcohol, it is much less effective), or
• acetone.

Compressed air can speed the drying process, but be aware that some of the commercial compressed air cans have a solvent that can saturate any remaining flux and cause problems.

If you want to seal the finished board, use a conformal coating. Wait until you have tested the board thoroughly though. If you do not think you will be doing much repair work on the board, you can not beat silicone conformal coating. It does require some digging to get it off for repair, however. Avoid the urethane coatings, as they are considered permanent and are a pain to try to work through.

This should slow down or prevent "solder bloom" and other deterioration of the PCB. Condensation is a fact of life for an outdoor component undergoing temperature changes. You can solder right through the stuff and the residue cleans well with pure grain alcohol.

Slide the completed PCB into the case. The wider lip of the case side is near the heat sink side of the board. This is to allow the top lid case to close. Put a bit of heat sink compound between the heat sink and the case to enhance the cooling of components by using the case itself as part of the heat sink.

Your next job is to mount the unit in the car, tune, and go!

You cannot install the MegaSquirt box under the hood. Engine bay temperatures are just too high. The recommended place to install the MegaSquirt box is in the passenger compartment (like under the seat, kick panel, etc), this is where many OEM boxes are located. In addition, you will need access to the RS-232 serial connector for tuning, which is hard to access under the engine hood. If you put the MegaSquirt box in the passenger compartment, you will not have heat-related problems (unless you mount it directly in the path of the air stream of the car heater).

MegaSquirt should be connected with a pass-through hole (and grommet) to the engine compartment for the wiring to the injectors, sensors, fuel pump, etc. If you have put your MegaSquirt together, but it does not work, don't panic, just follow the troubleshooting instructions.

External Wiring

Note that MegaSquirt is a bank fire injection system, you connect half the injectors to the driver for one bank (pins 32/33), the other half to the other driver (34/35) [4 are shown]. See: the FAQ. You can connect them in any order. For troubleshooting ease, having each bank on a separate driver might help. However, you might want to separate them into alternates in the firing order, which some people have claimed is theoretically slightly beneficial. As an example, on V8s with bank fire systems, manufacturers typically run one bank off one driver, regardless of the firing order. The advantage of doing it that way is it makes troubleshooting easier.

All MegaSquirt installations must have an input (tach) signal to determine engine speed. This signal comes in on pin #24 of the DB37. A variable reluctor (VR) input (tach) sensor is shown (above) for the input. To use a Hall sensor, optical sensor, or points trigger, you connect the signal to the same input pin (DB37 #24) as the VR sensor. You must ground the VR other lead of the sensor as well, and pin #7 is shown for this. However, pin 7 is not a 'dedicated' or specialized ground for the VR sensor, it just happens to be a ground. The VR sensor can be grounded to any pin that connects to the board's ground, and it can be connected externally (I.e., in the DB37 connector for the harness, or even in the wiring loom).

The DB37 pin #36 is an output, used to control an ignition module, or control a coil directly (if the high current ignition driver circuit is installed). It only needs to be connected if you are controlling ignition timing and dwell.

If you are using PWM Idle control, you cannot use the FIdle relay on the relay board, and have to jumper the relay socket. The jumper goes from the relay socket hole nearest the CB1 polyfuse to the relay socket hole nearest DB37 pin #4.

This provides a direct signal from the MegaSquirt to the PWM idle valve. Note that the transistor on the V3 main board is NOT sufficient to drive a Ford PWM Idle valve (as well as many other makes) directly. You MUST use the another transistor (such as a TIP120/121/122) that control the valve. You can use the proto area to connect this circuit, or you can build it externally.