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MegaSquirt questions from a noob

3K views 10 replies 6 participants last post by  Slave2theBunny 
#1 ·
I've been looking into ditching the Bosch fuel injection system on my '83 GTI "JH" 8V engine and replacing it with MegaSquirt. I've got some decent mechanical skills, but haven't done a lot of work on fuel injection and ignition systems, so I've got a few beginner questions, so bare with me...

1. I'm assuming the mechanical injectors need to be replaced with EFI injectors. What injectors will work with my engine? Or what specs should I be looking for?

2. It looks like I need to add a fuel rail since I'll be taking out the Bosch fuel distributor. Any recommendations on what fuel rail to use? Can a used one from a later model VW be retrofitted? Or should I shop for an aftermarket rail (if so, where?)?

3. Going to MegaSquirt, is the stock "5th injector" no longer needed? If not, what do you plug up that port with?

4. Where is the MegaSquirt ECU usually mounted? In the rain tray?

That's all I can think of for now; I'm sure I'll have more questions as I dig deeper into this.

By the way, here's what the folks at DIYAutoTune gave me as a suggested parts list:

MicroSqrt8: Assembled ECU (includes 8 ft / 2.4 m harness & tuning cable)
GM3bar-map: MAP sensor
GM3bar_piggy: Pigtail connector for MAP sensor
CLTIATwPiggy: Coolant / Oil temperature sensor
IATwPiggy: Intake Air Temperature Sensor
38NPT-Bung_A: Aluminum bung for IAT sensor (Also available in stainless steel)
USB-2920: (Only needed if your laptop doesn't have a true DB9 port)
 
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#2 ·
There is nothing that you will use on the stock CIS fuel system. Maybe the fuel pump and the lines from the tank.

If you got suggested parts list, why not take their advice? If I were to dive into a EFI conversion, I would stick with one vendor. Once you start shopping around, you're likely to get a lot of finger pointing when things do not go right.

Stick with one vendor and buy everything from them.
 
#3 ·
I do intend to take their advice on the parts list they given me. However, after asking them about injectors and fuel rails, they said they do not carry the ones I need for my engine.

I haven't had my car on a dyno, so I don't know the exact HP, but I would estimate it is somewhere in the range of 100-120HP. DIYAutoTune said that at 120HP they would recommend 19-21 lb/hr injectors, but they do not carry them that small.

For a fuel rail, they suggested I look into compatibility of using an 8V Digifant rail from a later model VW.

So my questions still stand. Anyone else got any answers to my questions?
 
#6 ·
I'm not interested in doing a carb conversion (and don't want to get into a tired discussion about the advantages/disadvantages of each). I am only interested in getting feedback from people who have done or know how to do a MegaSquirt conversion so I can understand what it takes.
 
#7 · (Edited)
mount the ecu in the car or under the rain tray ..away from rain and heat

no you dont need a 5th inj

ive just done it on a vw polo which is similar ...pretty much need a wideband kit as well , then some knowledge or $$$$ to get it driving well

probably best to keep asking around and copy someone elses set up , theres not a huge amount of wires to connect really
 
#10 ·
i purchased the microsquirt ecu with 3ft harness , aem wideband kit , added a air temp and map sensor to the car

kept the stock distribuor and coil ,coolant sensor etc , ecu is powered by the stock relay

depends how picky you are with the install , you could throw it on and have it running in an afternoon , but taking care with the correct style crimps and making it look nice takes alot longer

ive just got it starting and idling now , need to spend some time on the road tuning it , started pretty easy though
 
#11 ·
Did what you're planning to do back in 2006ish, JH block, converted from CIS to full megasquirt standalone, used a volvo tps, GM sensors for air temp, turboed my JH, digi injector cups and a giant allen key to unscrew them if you're lucky, I used corrado g60 injectors to start off with then move to Ford red tops iirc, you can use a digi fuel rail but you will need to make custom brackets to hold it down since the CIS head does not have the attachment points for the fuel rail, You can see most of my old build here https://forums.vwvortex.com/showthread.php?9309503-MK1-turbo-(re)build-3-0, the more detailed one on vintagewatercooleds is long gone now. You can try tuning it yourself but if you want to get the most out of it, bring it to a tuner with a dyno. But if you're not gonna go forced induction it's a lot of work just to ditch the CIS. probably easier to just do another type of swap like a 2.0 aba and bring the electronics with it.
 
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