HKS Fuel Cut Defencer (FCD)

    At about 10-12 psi (depending on air temperature) of boost pressure the Supra's ECU will cut fuelling to the engine for about 1 second. This is because the ECU thinks that the wastegate has gone faulty and it cuts fuel to protect the engine from too much boost.
    When fuel cut happens the Engine warning light will come on and the car's speed will plummet. The engine will carry on turning so oil is still being supplied to the engine and fuel cut does not hurt the engine at all. After a second or so the fuel will return and the car will carry on. A few seconds later the warning light will go off.
    The HKS FCD is designed to raise this Fuel Cut limit. It does this by interrupting the boost pressure signal from the turbo and reducing it by a variable amount depending on the RPM signal. This means that the Fuel Cut limit is raised, but still provides protection.

To fit an HKS FCD

• Locate and unplug the ECU (Electronic Control Unit), this is above the glove box.
  • Unscrew the the three screws holding on the plastic covering piece below the glove box (just above where a passengers feet would be).
  • Unscrew the two screws holding the glove box hinges on and remove the glove box.
  • Unscrew the two screws holding the glovebox lock catch on
  • Unscrew the two screws holding the top of the glove box to the underside of the dash
  • Unscrew the two screws holding the ECU in place. This will have three plugs as shown below and be labeled either ECU or TCCS (Toyota Computer Control System). (The other box is the ABS Control Unit)
  • Remove all three plugs from the ECU
• Locate the wires shown below (plugs changed in August 1988, but it will be obvious which ECU you have from the plug sizes)

February 1986 to July 1988 ECU Plug Layout

August 1988 and newer ECU Plug Layout

• Splice wire I (RPM Signal, Light Blue with Red Stripe in 1991) into green wire on FCD
• Splice wire E (Earth, Thick Brown  in 1991) into Black wire on FCD
• Splice wire B (Battery 12V, Black with Red Stripe in 1991), splice into Red wire on FCD
• Cut wire P (called Turbo Pressure, but is actually Air Volume signal from Air Flow Meter)
• Join the ECU end of wire P to the Yellow wire on the FCD
• Join the wiring loom end of wire P to the White wire on the FCD
• Put everything back together
• The engine will run very roughly for the first few miles as the ECU re-learns its fuel mappings etc.

There are two types of FCD, The Standard type which has an adjustable dial on the front and the K type which has the rpm wire and no adjustment. I have installed a K-type on my 1991 Automatic MkIII with no problem. Martin Bradshaw had lots of problems with his standard type on a 1990 Automatic and has switched to a K type.

My advice would be to get a K-type and if it doesn't work (i.e. you get fuel-cut on gear changes then swap it for a Standard type, without more information I can not say for definite which type suits which cars better.

The following advice is given by Nathan Ley at TDi.

As a rule, we always use 'K' Type FCDs on Mk3 Supras. However, sometimes they do not work on all cars, and sometimes STD types work. There does not seem to be any pattern to fitment, and HKS Europe cannot shed any light on why this happens. Suffice to say, in our experience, the K type works on about 95% of vehicles. I would not say that in all cases STD types are used on autos either!