Installing Extra Fuel Injectors


This page describes how to install extra fuel injectors to increase the fuel supply to your engine.  There are a few reasons why you may be doing this, but the primary reason is because you have modified your system such that the ECU does not know or is not able to add enough fuel to maintain a safe air/fuel ratio.  One way to do this is to install one or more cold start injectors near the throttle body.  This concept was developed by Gus Mahon, and is detailed on his web site.  Cold start injectors are used primarily on European vehicles (Saab, Volvo, VW, etc) that are equipped with mechanical fuel injection and the Bosch fuel control system.  Another, more complex way, is to install one or more electronic fuel injectors and control it with a fuel injection control module.  This module pulses the fuel injector the same way that your ECU pulses your current injectors.

Cold Start Injectors

The cold start injectors need to be controlled so that they turn on when needed.  This can be done one of two ways.  If you are only installing one injector, then the easiest way is to use a pressure switch.  This procedure is detailed by Gus Mahon.  If you are installing more than one injector using this method, then you need to install a pressure switchfor each one.  An alternative is to use an Electronic Engine Performance Controller to control up to four injectors.  The downside to this is that you have to have a MAP sensor that can read the manifold pressure up to the level that you need.  This can be done by installing a secondary 3-bar MAP sensor, or by bleeding a stock MAP sensor.  The links below take you to the pages that provide all the details.  Gus's page holds all of his adding fuel tricks, so you should definately look at that.  I have broken down all of the information into seperate pages, which should help you if you are confused.

Adding Fuel, by Gus Mahon (skip to the 5th section)
Controlling Cold Start Injectors With A Pressure Switch, by Russ W. Knize
Controlling Cold Start Fuel Injectors With The EEPC, by Russ W. Knize

Electronic Fuel Injectors

Installing electronic fuel injectors is somewhat more complex.  Aside from figuring out how to mount them, you also have to control them.  There are controllers available for doing exactly this, which even come with the injector(s) and mounting hardware.  I have designed a cheap controller that you can build and use to control your own extra injectors.  This controller can also be used for alcohol and water injection as well.  I have not been able to build or test it yet, so this information will not be available for some time.

Links to fuel injection kits coming soon...
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This page is maintained by Russell W. Knize and was last updated 04/22/99. Comments? Questions? Email

Copyright © 1996-2003 Russ W. Knize