550cc Injector Upgrade

The Japanese imported Supra TT comes fitted with 430cc injectors compared with 550cc injectors on the UK model. After several stages of modification you may find you need more fuel. One way is to fit a rising rate fuel pressure regulator or another is to upgrade the injectors from 430cc to 550cc

You can obtain most parts second hand from a scrapped UK spec Supra. All you need extra is a couple of new 7 way automotive connectors and a length of multicore (7) automotive cable.

The method of injection control is the same between the models except the UK spec injectors are of a different impedance and the final drive circuitry of the Jap ECU is different. This means that when fitting the UK spec 550cc injectors you have to also fit a ballast resistor in series with the injectors.

Here are the wiring diagrams.....

UK Injector Wiring

Jap Injector Wiring

Jap Injector Wiring (state2)

Modified Jap Injector Wiring

Pictures of the EFI resistor.....

Side View

Top View

In Situ

Pictures of the wiring loom modifications.....

Broken into wiring loom attached to firewall.

New connections to EFI resistor.

Finished, tapped into wiring loom.