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FCD mod for 93+ Supra Turbo

(not recommended to use by

Purpose: to remove the fuel cut that occurs when boosting over 14psi. This mod doesn't actually increase the boost, but it allows you to do so via further mods such as adding a boost controller/bleeder valve, downpipe, exhaust.
Tools/parts required: (2) 1/8" vacuum caps (see Fig. 3) available at auto parts stores,  10mm socket (optional).
Time required: 5 minutes.
This modification has several shortcomings. I recommend you install a Greddy BCC (about $100) instead of the FFCD unless you have converted to parallel turbos (TTC mod). The FFCD fools the computer into thinking it's not making any boost. While this works great in disabling the fuel cut to run high boost, it also interferes with other important operations such as:
- 9V to 12V fuel pump operation (perform the 12V fuel pump modification to fix this, otherwise, you are risking detonation when the #2 turbo kicks in).
- Prespooling the #2 turbo properly. There is a large boost drop just prior to the #2 turbo kicking in. The Greddy BCC lessens the boost drop. The TTC mod fixes this.
- EGR operation (Disable the EGR system to fix this).
- idle control (doesn't seem to be a problem).
1. Locate the turbo pressure sensor (green sticker at 'C'), which is located near the throttle body.
2. Remove one end of 4" vacuum line at 'A' (see Fig. 1).
3. Unbolt the turbo pressure sensor for easy access to the bottom of the sensor.
4. Remove other end of same vacuum line (at 'B') that connects to the bottom of the turbo pressure sensor.
5. Place one 1/8" vacuum cap at 'A', and one at 'B' (where the vacuum line was previously connected). See Fig. 2 (from different angle). When installing the vacuum cap on the turbo pressure sensor, squeeze the air out of the cap before installing to prevent a constant over-boost condition from being reported to the CPU (this may cause strange behavior such as the engine stalling when the traction control control kicks in). Note that the turbo pressure sensor is unbolted on one side in the picture.
I highly recommend connecting a boost gauge at 'A'. If you don't have a boost gauge yet, use a hose clamp or tie wrap to make sure the vacuum cap at 'A' doesn't blow off (not shown) or remove the metal "Y" and replace it with a single line from the "gas filter" to the fuel pressure regulator VSV. This will prevent a possible engine-damaging lean condition if the vacuum cap blows off and the car is run hard for an extended period.
6. Bolt the turbo pressure sensor back in place.

stock setup

Fig. 1 (stock)


after FCD mod

Fig. 2   (after mod)


1/8 vacuum caps

Fig. 3  (1/8" vacuum caps)

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