Megasquirt FAQ, writeup (Updated 30/10/09)

Hi, I take a look at your .msq. Now, plz make a datalog of your engine idling. I want to see how smooth it is. Be sure to log IAT, CLT, Batt voltage, RPM, MAP, PW, VE, AFR.

Thanks

Good luck with your tuning!

Sam
 
Hi, thanks a lot for the datalog. I will say like you : very smooth!

I have some question for you :

1- How do you wire the IAC valve (pins RSC, RSO with Fidle)
2- How do you wire your ground system. Would you plz make a kind of diagram of how your ground system is wired, where it is bolted? Intake manifold? Head? Firewall? Here's mine for your information :

MSground.jpg


I'm asking this because I have big voltage drop and I want to cure it!

Thanks
 

Quark

New member
I just got a little daughter.. 2400 grams, I will get back to you later... But I can tell you to look at the V3 wiring, and connect all you sensors to E2 ground on the orignal wiring. All the rest of the grounds should be connected to E1. You have a voltage drop because you have a difference between you senor ground, and what the sensors actually get of ground. E2 is the direct ground wire for the sensors. So connect E2 to pin 19 (db37)
http://www.megamanual.com/ms2/v3ext_wiring.gif
 

Quark

New member
Thank you..

I had time to look for it now..

You need to take your CLT, EGO, IAT to pin 19 on db37. Bacisly CLT, EGO, IAT runs throug E2.

Edis you should connect to engine ground, remember a noise capasitator on that ground wire.

RSC is ground and rso should be connected to fidle pin 30 on db37. Remember to upgrade for PWM idle valve.

I dont know how you get to the wires, if you just tab into them on the ECU plugs?

If you do, take the ground from the original wiring "E1" and connect pin 8-9-10-11 and 18 (db37) to it.
 
Hi, thanks for your reply.

I don't know what wiring diagram your are using, but mine do not have any E1 or E2 ground points.

My grounding points in my manual are :

-EA = front right fender
-EB = front left fender
-EC = intake manifold

Anyway, the only difference between your setup and mine about the grounding point is that instead of running 5x20gauge wires to intake manifold, I run 5x20ga wires for 8" long joining togheter to a 14 ga wire to firewall (look at my diagram in my previous post).

Maybe 5x20ga wires all the way to the grounding point will divide the resistance in the wire and make a better current flow.

BTW, I used a RSautosport universal wiring harness and I soldered my connectors on it, simply. I didn't use the stock harness for the whole part.

For the PWM idle upgrade, i think I have it installed on my V3.0 board. How can I verify it? Can you post a picture of it or a link to the megamanual.

Are you running a wideband sensor or the stock O2 sensor?

Thanks again for the help! I want to do my new wiring harness the perfect way!
 

Quark

New member
I am sure that you have E1 and E2 in your stock toyota wiring, they use these codes in all their models (I am talking about the original toyota ECU connectors). In general keep sensor ground on pin19 (db37) and keep all other ground as short as possible, this is very importent. (remember that current runs from minus to plus, and not from plus to minus, like alot of people thinks)

PWM_Idle.JPG


http://www.msextra.com/manuals/MS_Extra_Hardware_Manual.htm#Fidle

ST185ECU.JPG

Here you can se E1 and E2 location on original wiring.

You do have an alltrac, right?
 
Ha, ok, you are talking about the E1 and E2 pins on the stock ecu connector. I was confused... I thought you were talking about the grounding points location (intake manifold, left and right fender, those are named EA, EB and EC).

My car isn't a ST185, it's a ST184 with a ST215 3sgte engine.

Thanks for the info!

Sam
 

tw2

New member
pit_celica":1urda8ah said:
Ha, ok, you are talking about the E1 and E2 pins on the stock ecu connector.
Wow you guys have been busy. I think that is how I have done my wiring diagram. So you shouldn't have to run your own grounds for anything except maybe the EDIS stuff since it is in the engine bay.
 
I'm not an electrical expert, but according to Quark25 superb flatline battery voltage datalog, I would say that he did it the right way. I'll follow his tip and I'll do my grounding like he did :

CLT, EGO, IAT, TPS to pin 19 on db37. Those were on pin E2 on stock ECU connector

ECU ground to intake manifold to pin 8-9-10-11 and 18 on db37. Those were on pin E1 on stock ECU connector.

As for EDIS, IAC, cruise control grounds, I'll run them all to the intake manifold with a separate ground strap.
 

tw2

New member
Ok I have had another look at it.

I have in my diagram 18 and 19 to E2 which is the stock sensor ground which I have done wrong since I didn't notice 18 was not a sensor ground. I will have to change that.

So the correct way is 19 to E2 and 8,9,10,11,18 to E1?

E01, E02 and E1 ground in the exact same place (intake manifold) according to the st185 electrical diagram I have so it shouldn't matter which one of those you use for 8,9,10,11 and 18.


Why did you have to run grounds for cruise control? They use the interior kick panel and brace for grounding already according to the electrical diagram.
 
Look at my last post, this is how it should be done :

All sensor grounds to pin 19 on DB37.
Pins 7-8-9-10-11 on DB37 to the ground location on the intake manifold.

For IAC and EDIS grounds, I'll send them all to the same bolt on the intake manifold.

For the cruise control, his ground pass by the IG1 connector pin 11. This connector is located near the stock ECU. IG1 and IG2 connect the engine wiring harness to the dash harness (in cabin).
 

Quark

New member
Solved the Idle valve problem, and now have a 100% perfect running wasted spark 3sgte.. :-D

The fix for the Idle valve is a 25ohm 50 watt resistor in line before RCS goes to ground... :-D
 

tw2

New member
Quark25":1cx6qf6h said:
The fix for the Idle valve is a 25ohm 50 watt resistor in line before RCS goes to ground... :-D
Congradulations! I have on page one a 40ohm 50 watt resistor listed as a good option so good to know it doesn't really matter too much. Feel free to put up as many of the software settings you have used, it would be much appreciated. All the fuel values, dwell time etc can get a bit overwhelming reading through the manual.

Thanks pit_celica I understand most of that now. I am not totally certain about the cruise control but I don't have any wiring diagrams with me at the moment but I will work it out when I have a look in the car today.
 

tw2

New member
pit_celica":ksfneira said:
For the cruise control, his ground pass by the IG1 connector pin 11. This connector is located near the stock ECU. IG1 and IG2 connect the engine wiring harness to the dash harness (in cabin).

ECUplus.jpg

Sorry to be annoying but are these two circled green IG1 and IG2? If I leave them plugged in when I have megasquirt then I have nothing to worry about right?

The only thing that needs to be done to IG1 is to splice the new tacho signal into it?

Do you know what the box cicled pink is for? Do I leave that in place when I install megasquirt?

Thanks for your help.
 
Ok, you are right, those both connectors are IG1 and IG2. You will need to keep them because there are some wires that you may need like :

-tacho
-oil press switch
-coolant sender
-ground cruise control
-cruise control input
-back-up light swith
-etc

Give me your email address and I'll send you my wiring harness diagram revised. You'll understand what I'm talking about!

And this black thing is the circuit opening relay, keep it there, do not touch it.

Sam
 
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