This post will hopefully contain wiring and installation info specific to the 3sgte in the near future. Please PM me anything useful.
How to mount a trigger wheel
A lot of this info can be found at www.trigger-wheels.com www.diyautotune.com
and similar sites.
This is something which pays to be done carefully as you have the opportunity to destroy your crank bearings and require a bottom end rebuild. Excessive weight and an unbalanced crank should be avoided at all costs. Use as little material to get the job done properly and ensure it is fully semetrical.
For the 3sgte you can consider welding a hollow wheel around the outside of the crank by tacking it, using the crank wheel centre bolt with a flat trigger wheel, making a custom mount or drilling/tapping holes into the crank pulley if you are brave.
To mount a flat wheel you will need to bring the crank bolt out from the recess of the crank pulley. This can be done with a properly lathed balanced steel spacer or simply with a correctly sized stack of washers. The crank bolt will need to be replaced with a longer one to make up for the length lost by the spacers. It needs to be of the same grade to take the correct torque.
Alternatively a mount similar to pit_celica's can be used to bolt the wheel to the crank using the original crank bolt which will only lose a minimum amount of its in contact threaded length. I cannot see exactly what pit_celica's looks like under the wheel but I would think a design like this could easily be made by someone with a lathe/tig welder. If the trigger wheel bolt holes were elongated, the wheel could be rotated slightly relative to the crank similar to adjustable cam gears.
To answer my own question, it is usually a better idea to use the crank to mount a trigger wheel than use the distributor to give you a cam angle signal to be converted to crank angle. The reason being it seems is because the cam rotation resonates somewhat and it gets worse with higher rpm. It fluctuates either side of the real crank rpm which of course will lead to extra problems. The most reliable way therefore seems to be the crank method. As a bonus you get to seal up the stock distributor hole and have a bit more room, no more leaking distributor seals.
This site has some very good pictures
http://www.turbomr2.com/MR2/HowTo/Engin ... GTE-03.htm
This shows the Tec3 crank wheel mount and VR sensor mount on an mr2.
How to mount VR sensor
Obviously the VR sensor needs to be bolted to the engine somewhere as engine movement relative to the chassis will alter its position otherwise. The bracket should be very rigid and resistant to vibration. Being adjustable both in an angular plane around the trigger wheel and towards and away from the wheel is an excellent idea as it allows you to fine tune the sensors location. The VR sensor should be 0.75 -1.5mm from the trigger wheel. Washers can be used to alter these distances as well.
When mounting the whole lot have the engine at top dead centre. As long as it is at TDC it doesn't matter what rotation the trigger wheel missing tooth is in relation to the crank. It also doesn't matter where the VR sensor is. All that matters is that while the engine is at TDC the VR sensor reads 9 teeth (ie 90 degrees) ahead of the missing tooth. There is additional info on setting it up including the software settings here http://www.diyautotune.com/tech_article ... _index.htm
and in the megamanual. If you buy a premade megasquirt II it will already come configured for EDIS.
Spark plug leads
I do believe pit_celica had his professionally made by magnecor for $300. I have also read of people simply using the stock ford ones and swapping the boots from the 3sgte ones to make them weather proof. This is moderately difficult. An easier approach is to crimp the ford coil ends onto the 3sgte leads. This means you have a 100% stock spark plug lead which seals the head correctly and functions as stock. Unless you have the $20-150 tool to crimp them, I suggest taking it to a qualified auto electrician and pay a few $ to have it done right.
How to wire megasquirt to the stock harness
This can be done in other ways also ie- make a jumper cable between megasquirt and the stock harness. It is also possible to get a second stock ecu, gut it and stick megasquirt inside it, solder the connections correctly internally and have a fully plug in system should you decide to revert back to stock for any reason. You can also make an entirely new harness using the kits sold by vendors such as DIYautotune.
It is important to realize that there are many wires throughout the engine loom which go to/from the ecu or the engines sensors but not necessarily to both the ecu and sensors. For example the 12V power supply to the idle up valve does not come from the ecu but goes through the loom. Cruise control is another system whereby the throttle body switch wire travels through the loom to the cruise control ecu but will not go to megasquirt once installed. The point of this pararaph is to state that making a new loom from scratch is fairly complicated and is not covered in the wiring diagram although if you use the BGB it should be easy to work out exactly what you need to give consideration to. It will take a lot longer and making sure other systems still function will be challenging.
From my research the easiest option is to cut the stock ecu plug off the loom and use a pre-made 18" loom using the DB37 plug to wire into it or make a patch harness (DB37 is the style of plug megasquirt uses ie 37 pins)
Here is a basic schematic of megasquirt from the megamanual.
Here is the wiring for EDIS showing its 2 wire interface with megasquirt.
Here is the stock ecu pin outs for a 1990 st185 taken directly from the BGB.
They can be matched up quite simply. I have made a list of the supposedly stock pins/wires with their colours and basic function. I have tried to match this to the megasquirt schematic above. I do not know if this is 100% correct.
Wiring Diagram's Download
st185 Wiring Diagram
pit_celica's wiring diagram
pit_celica's 2nd wiring diagram in .dwg format
This first wiring diagram is entirely made up by me. Please help with any corrections. I made it using the BGB electrical diagrams, the megamanual diagram above and what I think is common sense. Please PM all corrections or better alternatives to things. It is my third and last attempt before trying it myself to find any corrections the hard way. A basic principle behind my diagrams is to use wires already in the stock harness which have now become redundant. Examples are stock AFM wiring, MAP sensor wiring, cold start injector wiring etc etc. Since these items can now be removed the plugs/wires are there to be used for new purposes such as air temp sensor, edis etc. Obviously this means it cannot be returned to stock but certainly makes the installation a lot easier, cleaner and stock reliable.
The second diagram was kindly made by Sam (pit_celica) who is running a gen 4 caldina 3sgte and would be better for anyone without a gen 2 st185 ie st165/205 or using a different generation engine. It has all the megasquirt, edis and all stock electrical connectors labeled so you can work out how to do it yourself. Simply match the megasquirt and edis names with the same name of the apropriate plug. This way wire colour etc is irrelevant.
The third diagram is in .dwg format which is similar to CAD etc, you can download free dwg viewer here http://www.infograph.com/products/dwgviewer/
Extra 3sgte wiring info
The idle up valve we use is not a stepper motor. Gimpster was kind enough to explain how to use megasquirt to control this function. You will need PWM add-on to the V3.0 megasquirt board or otherwise this comes already installed on the V3.57 board.
"Quick overview of how the stock idle control valve works. Our IAC's arent stepper motors. It gets a constant +12V when the keys on, and with no input it rests in the "center" of its adjustment. The ECU has two lines, ISO and ISC. O = open and C = closed.
Assuming you're using the PWM idle kit and install it per the MegaSquirt Assy manual, you will hook it to the "ISO" pin at the ECU plugs to pin 30 on the DB37. ISC you will put on a high quality 40ohm / 50 watt resistor. I highly reccomend using a quality metal body/heatsink'd resistor for this. At this point the MS will be "fighting" the close side and you'll tune your idle accordingly. This is exactly how the V6 IAC works, and my old V6 car idles great!"
Please note: the alltrac BGB uses the tags RSO and RSC instead of the ISO/ISC as found in the mr2 BGB.
This is the wiring diagram from www.diyautotune.com
As you can see pin 2 is used in the later boards for reducing noise using shielded wire. All connections to and from both the EDIS ignition module, the VR sensor and the tacho should be done with properly grounded shielded wire. This will reduce any electrical interference and ensure good quality signals.
Air temp sensor
You will need a new air temp sensor to run with MS. An open element GM style sensor is ideal. Without running new wires the best thing I can come up with to easily wire it in to the stock harness is as follows
- use the map sensor wiring since it will no longer be there
- tap the ground of the sensor into the brown E2 sensor ground wire of the stock MAP sensor
- use the red and white PIM wire as the signal wire
- remove pin 15 from the IG1 connector in the footwell as the PIM wire also goes to the stock boost gauge on the dash which will no longer work anyway. I do not know if the gauge would interfere with the wire at all but just to be sure.
- obviously use these wires on the ECU end to wire to MS accordingly. The ground will already be taken care of ie pin 19 on the DB37 harness going to E2 and the red and white PIM wire will need to go to pin 20 on the DB37 harness.
- the AFM wiring would be perfect also except that it is located a long way from the intake manifold. The EGR temp sensor would also be great for those with non-JDM cars who do not care about emissions.
Our stock tacho will not work with EDIS since we are now using two coils instead of one. The following circuit as can be found in the megamanual is the solution.
Taken from http://www.megamanual.com/ms2/EDIS.htm
The two wires from the coils are the outside wires on the 3 connector plug which goes from the EDIS ignition module to the coil pack.
These are the standard part specs used in the tacho circuit if you purchase them locally.
2x Diodes Inc Standard 400V 1A, 1V @ 1A, 5µA @ 400V
1x DIODE ZENER 18V 1W 5%, 18V @ 14mA 1W, 20 Ohm @ 14mA, 1.2V @ 200mA, 5µA @ 13.7V
When ordering from DigiKey make sure you order the idle up valve resistor at the same time.
It makes the most sense to make the circuit in the engine bay and then run one shielded cable through the firewall into the cabin to the tacho. An alternative is to cut the plug off the ignitor loom. The black wire goes directly to the instrument cluster for the tacho and means you do not have to run any additional wires yourself.
So I am sure everyone has worked out that once this is removed there is going to be a 27mm hole in the head for crap to fly in and oil to fly out. One option I was persuing was using a 5sfe distributor plug from toyota however it came in 37mm and so will not work for the 3sgte unfortunately.
This is a picture of how Bill Strong solved this problem on his 4age.
As you can see the distributor is on the side in these engines but the hole is filled with a rubber freeze plug (rubber on the inside).
They can be purchased in a variety of unexpanded and expanded sizes so they can exactly match the hole before tightening. Make sure they are definitely oil resistant but beware they can pop out. I will not use one unless I make a metal brace using the 2 distributor bolt holes to ensure it cannot come out.
Metal expansion plugs can also be used such as on most engine blocks. The size of these needs to be a very accurate match. They are supposed to be very slightly bigger than the hole they are filling so as to be a tight fit. It is a good idea to use locktite when inserting them. This is a good resource for freeze plugs. Always use brass ones.
http://www.circletrack.com/enginetech/c ... index.html
I am currently working on another of my own indestructible solutions.... which as of now consists of a 27mm brass
freeze plug (do not use other materials). It fits the hole perfectly with some force required to get it in. More info on this is located further into the thread.
Here is the MS unit itself with db37 plug and MAP sensor port
And everything you will need
Top right is 30ft of shielded wire for signals (shouldn't need more than 10ft), followed by the megasquirt assembled unit if you buy it complete, then is my trigger wheel and spacers which will depend on the setup you choose, bottom left is the GM air temp sensor with pigtail, above that is the db37 loom to splice into the stock engine harness and finally a serial cable at the top (db 9) for tuning and usb adapter if you do not have a computer with a serial port.
Last edited by tw2
on Sat Nov 28, 2009 3:25 am, edited 14 times in total.