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VintageWatercooleds.com Technotes :: Fuel System :: EFI Info :: Megasquirt Harness

Megasquirt Wiring Harness

Table of contents
Wiring Basics
Connectors
Fuel Pump Relay and the Fuse Panel
About the optional Megasquirt Relay Board
The importance of proper Grounding
Wiring Diagrams for Megasquirt Conversions
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Wiring Basics

Most of the wiring you will do will be with 20 or 18 gauge wires. It is unnecessary to "step up" to larger gauge wires - that will only cause you problems and take more time. Even the fuel injectors under full load use barely any power.

Make sure to use high quality multi-stranded automotive wiring. Automotive Primary is the minimum requirement. SXL or TXL wire is of higher quality, and will last longer. DO NOT use solid core wire, or household THHN wire available from hardware stores. Your wires will have internal breaks and fail you and cause troubleshooting headaches.

GPT wire is the lowest quality - it is sold in autoparts stores as "Automotive Primary Wire" - it uses a PVC jacket and is rated for 85 degrees C. It's great for lighting and general wiring.

TXL is the next one up, it's the thinnest and lightest underhood wire. This type of wire is insulated with crosslinked polyethylene, and is much stronger than GPT. This is rated to 125 degrees C.  TXL is the ideal wire to use for megasquirt.

GXL is the medium thickness wire, the only difference between this and TXL is the thickness of the insulation. This type of wire is insulated with crosslinked polyethylene, and is much stronger than GPT. This is rated to 125 degrees C. You can use this in high abrasion or stress areas such as injector wiring.

SXL and SGX are the heaviest insulation available in this type of wire. This type of wire is insulated with crosslinked polyethylene, and is much stronger than GPT. This is rated to 125 degrees C.

You can order wiring kits from some of the Megasquirt suppliers that are pre-labeled and color coded with standard connections. Make sure that they use high quality wire!

Connectors

The most important connectors are the Fuel injection connectors for Bosch fuel injectors. Many cars use these, and there are several different variations, mainly in the way they are attached to the injector.

I use connectors from 1990s Audi cars in the salvage yard. They have nice accordion boots, two piece connectors, and easy-off wire fixings that don't need tools to remove them from injectors.

You can also easily order fuel injection terminals from Megasquirt hardware suppliers, or other standalone suppliers.

The other important thing is crimping. You will need a double barrel crimper to make proper connections to these type of terminals. These crimpers are available online, and VERY rarely in autoparts stores.

Fuel Pump Relay and the Fuse Panel

When I add megasquirt to a car, I just plug right into the fuse panel to get power (DIN 30), the Ignition on signal (DIN 15) and the fuel pump out (DIN 87) which goes through the stock fuel pump fuse. This makes it simple to add those 3 connections.

About the Optional Megasquirt Relay Board

UNDER CONSTRUCTION (August 15, 2007)

The Importance of Proper Grounding

Wiring Diagrams for Megasquirt Conversions

Here's my main diagram, Click it to enlarge!

Here's the new diagram for MSnS-e with Distributor ignition...

Some selected pictures from the harness (WAY, WAY more to come!)

EFI Diagrams

Bosch type Fuel Injector
	Diagram of an EFI Fuel System
	Standard Injector Dimensions
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Stock Fuel Injection system Diagrams

	Diagram of the CIS Jetronic System
	Diagram of CIS-E Jetronic System
	Diagram of the Digifant II system
	Digifant II Fuel Rail
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Parts for the Megasquirt or other EFI conversion

	Throttle Position Sensor (Digifant I, or 2.0 16v CIS-Motronic with Auto Transmission)
	Megasquirt EDIS-4 Wiring Diagram
	Stock VW ignition System Diagram
	VW with EDIS-4 and Megasquirt + Spark
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MORE TO COME SOON !!!

Sources: Megasquirt Website; VWVortex Forums Post "The Megasquirt from CIS-E and Motronic Official Post!"

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