Knowledge Base

How to gain 4-5BHP by modifying the MR2T fuel pump wiring to run the pump permanently at full speed.

3S-GTE Fuel Pump Modification
by David J Black

Disclaimer

What you do to your car is your business and responsibility, not mine. The steps outlined here are a general guideline and are provided as-is, without any form of warranty or guarantee. If you do not know what you are doing, please leave this modification to someone who does!!

This article has been created to provide MR2 turbo owners with the necessary information to do the well known Celica GT4 fuel pump modification to their cars.

The modification is common among owners of the GT4, but few MR2 owners have ventured this far!

The fuel pump within the MR2 runs at two speeds, controlled by the ECU. It has been found that running the pump permanently at the faster rate will yield 4-5BHP plus an increase in torque. To change the speed of the pump, there is a relay that switches in a resistor to reduce the voltage across the pump. This document describes the procedure to remove the relay, allowing full voltage at all times.

Please refer to the URL below for the original details. If you are not aware of this modification, please do follow this link, as this document does not provide the full description as to why we are doing this!

http://www.gtfour.com/article.asp'ID=AAAAHA

A full copy of the ECU wiring can be found at http://mr2manual.teq.org/images/ewd_03.gif

The above diagram shows the fuel pump relay and the resistor. These components are mounted on the rear engine firewall on the MR2. In the GT4, they are in the engine bay fuse box.

The picture below shows the standard pump relay and resistor location in the MR2.

The round connector below the relay is hard wired to the relay. I removed the relay totally from the car, as it is no longer needed.

The modification is a simple wire jumper, to connect two of the pins on the relay plug, thus keeping the pump at full pressure at all times.

The diagram below shows the relay connector pins, and identifies them as they are indicated in the circuit diagram on page 1 of this document. This is provided for reference only.

The picture below shows the relay, now removed from the car, along with the simple wire link that will be installed in its place. I soldered the spade connectors on the wire link, rather than crimp. I thought this may prove more reliable in the longer term.

The wire link can now be installed in the car. Please make sure you insert it as shown in the picture below!!

The circuit diagram reference pin numbers are shown in the above picture for clarity.

To finish the job, I sealed the above connector with silicon sealer. This will keep the water out, and can be removed in the future if necessary. I tucked the connector out of harms way, below the fuse box.

: Wed Apr 27, 2005 7:06 am

Just to add a word of warning - it does smooth out the power curve, but a number of GT-4 owners had their fuel pumps burn out early as the pump is running at full speed all the time. Replacing the fuel pump on the MR2 is a labour intensive task ..

: Wed Apr 27, 2005 9:43 am

Is this similar to the Supra fuel pump mod whereby its running at 12v all the time instead of switching between 9v & 12v?

: Mon Jun 06, 2005 7:30 am

Yes !

: Tue Jun 28, 2005 5:46 pm

i disagree chaps,the fuel pump running at full speed all the time will not cause it to wear prematurely...a mk1 fuel pump runs full speed all the time and they rarely expire early,as does mk2 NA and NA celicas i believe...in my opinion just coincidence a fuel pump has packed in.If you think about it the pump only drops onto the lower speed circuit at idle only,when driving very little time is spent at idle so its practically on the high speed circuit all the time anyway.

: Tue Jun 28, 2005 5:48 pm

so what are the benefits? how does it create the extra power? and detrimental effects?