VW Vortex - Volkswagen Forum banner

Wiring it up - My First Megasquirt System

29K views 64 replies 18 participants last post by  need_a_VR6 
#1 ·
I got my MS ecu so its time to get started with my first megasquirt install. I'll have a lot of questions along the way and your feedback is welcome. Since all these wires except maybe 2 are going to the engine compartment anyway, I decided to put the ecu in the rain tray instead of running all those wires from the inside of the car to the engine. There was a already a threaded stud and a post there from the original Digi II ecu bracket mounting, I enlarged the hole in the MS ecu flange for the stud, and then popped a rubber grommet over the post that the original ecu bracket used, and filed that corner of the MS ecu flange down just enough to slide it into the slot in the grommet. I just hate drilling holes when I don't have to. I going to fabricate a small triangular bracket to connect the 2 holes on the other end of the MS ecu to the post that secured the rear of the orginal DigiI I bracket.





Now I'm trying to figure out if I can tap into the wires in this connector that went to the original module, instead of going to the fuse box for fuel pump trigger and power. This is a 91 GTI Digi II car.



So far I've determined that:

Red/White - Heated Oxygen sensor + 12v supply
Red/Yellow - Fuel Pump Relay signal to ECU
Red/Green - Starter cranking signal
Black/Yellow - +12v from digifant relay
Red/Black - ? Main Fusebox Starter Power? (goes to coil)
White/Red - ? maybe for MFA option

Could I just use red/yellow for fuel pump trigger and black/yellow for power ?
 
See less See more
3
#2 ·
Is your MS box water-proof? if not, the raintray is not a good choice for mounting it. And you still have to run the tuning cable thru the firewall, why not just mount the MS inside the car and only have to deal with the firewall pass-thru on install and not every time you do some tuning?
 
#4 ·
no its not waterproof, but my rain tray cover is good and I don't have clogged up drains. Was the original Digi II ecu waterproof? This will not be a daily driver, more of a weekend street car. And as far as the tuning cable, why can't I just open the hood, plug in the tuning cable, and then pass it through the window to a laptop.
 
#6 · (Edited)
So far I've determined that:

Red/White - Heated Oxygen sensor + 12v supply
Red/Yellow - Fuel Pump Relay signal to ECU
Red/Green - Starter cranking signal
Black/Yellow - +12v from digifant relay
Red/Black - ? Main Fusebox Starter Power? (goes to coil)
White/Red - ? maybe for MFA option

In the Bentley it shows that red/yellow wire connects to fuel pump relay termimal 85, which is exactly where my purple MS- terminal 37 wire needs to go. So is there any reason that I can't just
connect to the red yellow wire in the picture above?

Also the Bentley shows that black/yellow wire connects to Digi control unit relay terminal 87, which is exactly where my red MS 12V+ switched- terminal 28 wire needs to go. So I should be able to connect to the black yellow wire in the picture above for MS power after adding a 2 amp in line fuse, correct?
 
#7 ·
FV-QR

Mount that crap to the passenger side of the center console, route the wires behind that and the kneebar/under dash tray and out of the grommet directly to the left of the steering column...
 
#8 ·
Mount that crap to the passenger side of the center console, route the wires behind that and the kneebar/under dash tray and out of the grommet directly to the left of the steering column...
OK, tough crowd, I'm moving the ecu inside the car, and yes I had already been eyeing up those 2 grommets/holes to the left of the steering column as a good place to route the wires, if I was going to put it inside. So making progress I'll have some pics posted soon.
 
#10 ·
I pulled the firewall plug out that was to the left of the steering column, and I have a assortment of grommets so I grabbed the one that was the closest to the size I needed and I really lucked out, it fit perfect. I did not measure it, just stuck it in. Not only that but the ID is the perfect size for the split loom to slide through, just barely enough room and man it is tight.





I think I'll just mount the control unit on top of the tunnel under the dash with the front of it just flush with the front of the flat euro console cover. That way I'll have easy access to plug the tuning cable right in.

 
#11 ·
Any worry about it being directly under your heater core if you mount it there? I've got mine wire tied around my non-AC heater between the blower and the center console. Even without my knee bar, it can't be seen (keep lookey-loos from noticing that this thing isn't stock and therefore more fun to steal, although boost controller is kind of a give away...). But back on point, if your heater core goes in a bad way, might leak hot coolant all over your MS...
 
#13 ·
sure takes time to get everything you need, to even begin making your own wiring harnes.
I mean we are dealing with 20 gauge TXL wire and you have to have connectors for that
gauge/range of wire, not to mention:

heat shrink
heat gun for the heat shrink
wire covering, I like the split loom, of course you need at least 3 different sizes and make sure you get the high heat nylon not the cheap polyethylene stuff
connectors, metal crimp style for 20 gauge wire, male, female, end to end
crimper, wide range for both crimps on the metal connectors
fuses, 2 amp for switched power, 5 amp for fuel injectors
fuse block panel or in line fuse holders with connectors for 20 gauge.

its almost like a chess game, before you make one move, cut or crimp one wire, you have to look ahead several move to see what the results will be within the big picture of the harness
 
#15 ·
What throttle body are you using? I'm thinking of using the stock to avoid the issue with getting a tps TB. Thoughts from people who have gone this route? I just finished assembling my MS just waiting for my spare VW harness go get here so I can use it for the connectors :)
 
#21 · (Edited)
Very meticulous. Did you ever get your question sorted out to that 6 pin plug in the rain tray or is it no longer relevant since you moved the ECU in the cabin?

G60 Digi used 2 separate plugs similar that yours and you can tie everything in via it/them. w/o looking I am not sure but the other wire may be for ISV power.
 
#22 ·
yes I did, I tapped into those existing wires that I needed instead of messing with going into the fuse box. Thats where they come from anyway, much cleaner.

I used red/yellow for fuel pump trigger and black/yellow for switched power.
 
#26 ·
I am wiring up my tps sensor, which is just ground, tps sig, and 5v ref, simple enough, but wiring up the hall I just jump off the 5v ref also for hall power, and a ground, but I could not find the hall signal wire which should be pin 24 wire. Well, I finally found it. I pulled the DB37 connector apart to get a look at the wires and found it, pin 24 has a solid light gray wire connected to it and pin 24, pin 1, and pin 2, are all together in one of those wires that look those SPR/extra wires that I just left in the car rolled up. Its a has a white case with braided inner liner and the markings on the wire cover are,

WHITE: Crank CKP +/RPM input Black: ckp-E17 1197 22 awg 2c (UL) cmp c (UL) US 150 C FT6 ROHS, but no DIY autotune or Pin 24 ID on it.

I ran the wire out in the engine compartment, but should I just put a connector on the pin 24 gray wire, are just put all 3 in one connector?
 
#30 · (Edited)
#31 · (Edited)
Wiring up the 14point7 Spartan Wideband Lambda Sensor:

First of all a switched power source. I need a power source thats live only when engine is running, vs. one that has power when the engine is spinning over prior to starting.

Don't the main & fuel pump relays supply power while starting also? All the wiring diagrams I've seen show wideband switched power source at main or fuel pump relay terminal # 87.


And on the 5 sensor wires : correct me if I'm wrong

Red - switched 12V power when engine is running, not when spinning over before starting
Black - ground at ECU, pin 1 or 2
White - gound at engine block
green - to ECU pin 23, O2 sig
brown - not used
 
#32 ·
I have my JAW unit powered from a 12v switched relay. Not the same as my pump which is controlled by MS. I have 3 relays, one for the FP, one for MS & WB and KS and the last for coil, IAC and injector power. (W/O looking, I think that is how I have them powered and then fuses for each.)





As for wiring the Spartan, it should have instructions that came with or when his site get back up, the info is available there.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top