Blackwell Electronic True Twin Conversion ON/OFF Kit Installation

Product development/production and write-up/pictures by Jeremy Blackwell. Special thanks to Derek McCollough for helping take the pictures!

If you would like to purchase this ‘E-TTC Kit’, you can BUY IT HERE!

Introduction:’s Electronic True Twin Conversion ON/OFF Kit (‘E-TTC Kit’ for short) allows you to change your Supra’s stock twin turbo operation between normal ‘sequential’ mode and ‘parallel/true twin’ mode by simply flipping an ON/OFF switch! This modification is great for road racing, racing from a roll, and at the strip (with drag radials) for the following reasons:

-Reduces the chance of bearing/shaft failure in the #2 turbocharger since it’s always working instead of going from a near stop to full boost within a few hundred RPM’s (which eventually warps the shaft.)
-Provides more power between 3300 and 4300 RPM’s, and allows the car to hit peak boost a couple hundred RPM sooner.
-Power delivery is much more smooth, and causes less wheel spin in comparison to standard sequential operation delivering power all at once. It makes your car feel like it has a tiny single turbo on it.
-Gives your exhaust that DEEP throaty sound at idle and at lower RPM’s!!
-Looks nice and tasteful mounted on your Supra’s dash!

Installation and appearance have also been simplified by running the wires directly to the ECU in comparison to the old method of running wires through the fender and into the engine bay as with most home-made E-TTC kits. This kit uses high quality 3M quick-disconnect male/female spade connectors that also allow you to return your wiring to factory in minutes if you need to! All 6 connections on the back of the switch are first fluxed and soldered to ensure a tight and clean connection, then waterproof silicone is added around the terminals to prevent corrosion and shorting out. The wiring is then covered with heat shrink wrap for a clean installation.

Here’s how it works: your second turbo comes online when the stock ECU lets the Intake Air Control Valve’s vacuum switching valve (IACV VSV) and Exhaust Gas Control Valve’s vacuum switching valve (EGCV VSV) ‘see’ a constant ground for the circuit. This usually happens around 3700 RPM, which is when your #2 turbo normally comes online. The ‘E-TTC Kit’ allows you to let the circuit ‘see’ a constant ground simply by flipping a switch ON, thus making your #2 turbo stay online until you flip the switch back OFF!

Time Required: 30-60 minutes

Tools Required:
– rachet with short extension
– 10mm socket
– shorty phillips head screw-driver
– flathead screw-driver
– wire cutter, stripper, and crimper

LEGAL DISCLAIMER: Install this modification at your own risk! ‘Speed For Sale LLC’ will not be held liable for any damage that occurs to you or your car while/after installing this modification!

Installation Steps:


1. Disconnect the battery’s negative cable using the 10mm socket. Be careful not to touch the positive and negative terminals at the same time with the rachet!

2. Remove the passenger side kick panel: We’ll start the install by getting the wiring at the ECU ready, and then move on to taking apart the dash to install the switch. First, remove the passenger side floormat and the 2 small holder clips at the very top end of the carpet that holds it down (many Supras are missing these.)You can do so by removing the push-clip on the kick panel near the floormat (push the center of the clip IN, then pull the entire clip OUT…see picture 1 below.)

Then, simply remove the kick panel by firmly pulling UP on it to release the 4 or 5 retainer tabs holding it down (see pictures 2 and 3 below.)

3. Expose ECU: Pull back the carpet to expose the ECU cover (see picture 4 below.)

Using the 10mm socket and extension, remove the 2 10mm nuts at the bottom of the ECU cover and gently take the cover out and set it aside. Now you should see the main ECU and smaller traction control ECU (see picture 5 below.)

4. Find and cut proper wires & install male spade connectors: Be very careful on this step!

FOR USDM SUPRA WIRING HARNESSES, locate the 2 wires that are Pin B-40 GREEN with BLACK stripe (IACV VSV) and Pin B-39 GREEN with YELLOW stripe (EGCV VSV).

FOR JDM SUPRA WIRING HARNESSES, locate the 2 wires that are Pin B-40 GREEN with BLUE stripe (IACV VSV) and Pin B-39 GREEN with YELLOW stripe (EGCV VSV).

CAREFULLY cut back some of the electrical tape/wrap that bundles the entire wire harness together so that the wires have more ‘slack’ to work with (see picture 6 below.)

Once you have done this and have the 2 wires located, cut them both about 2" from the ECU so that you have some extra wire to work with in case you mess up! After you cut both wires, strip all four ends that are left, and crimp the MALE connectors that are included with the kit in the following manner:
Put the BLUE connectors on the 2 cut ends of the Pin 40/IACV VSV wire, and the RED connectors on the ends of the Pin 39/EGCV VSV wire (see picture 7 below.)   The MALE connectors go on the cut ends of the wires going to the ECU, and the FEMALE connectors go to the cut ends of the wires going out to the VSV’s in the engine bay.
This is easy to remember because the blue connectors go on the IACV VSV wire (cold=blue) and the red connectors go on the EGCV VSV wire (hot=red.) This kit has male/female connectors so that you can quickly and easily unplug the ‘E-TTC Kit’ and plug your stock wires back together should you ever wish to put the car back to stock.

5. Now that the ‘hard’ part is over, you can move on to removing the dash, mounting the switch, and connecting the wires. If you did NOT purchase your ‘E-TTC Kit’ pre-mounted in a factory trim piece that mounts beside the traction control, then mount the switch whereever you like (as long as the wires reach), put the ring terminal to a constant chassis ground, and skip to STEP 10. If you DID buy the Kit already pre-mounted in the factory trim piece, please continue to STEP 6.

6. Remove your dash: Pull out your ashtray, and then GENTLY pull up on the dash piece around your shifter until it pops loose (see picture 8 below.)

Using the ‘shorty screw-driver’, remove the 5 phillips head screws that hold the dash piece above your gauges in place (the one with the small various warning lights…see picture 9 below.)

Pull the piece out, then disconnect the 3 wire harness connectors from it (be sure to disconnect your negative battery cable or your AIRBAG warning light will stay on until you reset it!) The next piece to remove is the trim piece around your gauges. Grasp the top part of it at each end and gently but firmly pull. The top will pop loose, then pull the bottom loose. Next, remove the one single screw that holds the MAIN dash piece in place (the one with the air conditioning controls…see picture 10 below.)

Pull the dash from the top and you will feel it pop loose, then pull from the bottom near the ‘TRACTION CONTROL’ button and the entire piece will pop loose. After it’s loose, you need to remove all the connectors on the back of the dash piece. These connectors are: 2 air conditioning wire harnesses (orange, press clip and pull), lighter wire harness (pull off), lighter illumination (bulb, turn counter-clockwise and pull), traction control wire harness (press clip and pull), and clock wire harness (press clip and pull.) Now you should have the MAIN dash piece loose, and now have easy access to the back side of it.

7. Install the switch/trim piece in the dash: Using a flathead screwdriver, pry the side tabs of the current rectangular trim piece that is located to the left of the TRACTION CONTROL button (when looking at the dash from the front side) so that the piece comes loose and pops out the back side of the dash (see picture 11 below.)

Now, simply insert the trim piece/switch portion of the ‘E-TTC Kit’ where the other trim piece was located on the backside of the dash until it pops into place (see picture 12 below.)

8. Route wires: Pull back the carpet going along the passenger side of the console. Run the main bundle of 4 wires coming from the ‘E-TTC Kit’ under the radio head unit and down through the passenger side of the console so that the 4 red/blue connectors are ran under the carpet and down to the stock ECU…do not hook them up yet! (see pictures 13 and 14 below.)

Next, run the ring terminal/ground wire from the ‘E-TTC Kit’ underneath the black plastic piece that is directly in front of the shifter (if you don’t run the wire under this black dash under-piece, it will be pinched bewteen the dash and the under-piece!) Using the 10mm socket and extension, first remove the ‘front passenger-side’ bolt holding the shifter dust boot down, then put the ring terminal/ground wire on this bolt, and finally screw the bolt back in (see pictures 15 below.)

9. Put dash back together: Follow STEP 7 above going backwards to reinstall the dash. When you are done it should look like picture 16 below:

10. Hook up ECU/VSV wires to the ‘E-TTC Kit’ wires: THE 2 LONGEST WIRES WITH MALE CONNECTORS COMING FROM THE ‘E-TTC KIT’ GO TO THE CUT FACTORY WIRE ENDS GOING TO THE VSV’S/ENGINE BAY, AND THE 2 SHORTEST WIRES WITH FEMALE CONNECTORS GO TO THE CUT FACTORY WIRE ENDS GOING TO THE ECU/COMPUTER!!! Double check to make sure you have this connection correct, or the kit will not work! Plug the blue connectors together, then plug the red connectors together. Please note that these connectors will be tight, and will take a good bit of force to connect them! Once you have connected the wires, use a zip-tie to bundle the wires together so they don’t get caught on the plastic ‘retainer hook’ on the back side of the ECU cover when reinstalling.  Once you have done this, the wires will look like they are in picture 17 below:

11. Reinstall the ECU cover, carpet, and passenger side kick-panel by following STEP 3 in reverse order, and then STEP 2 in reverse order. Now, your car should be fully put back together. It’s time for a test drive!!

12. You may turn the switch ON at any time you wish, but I recommend turning it on at idle. On ’96-’98 Supras, you need to make sure the ETTC switch is turned OFF when your car is turned off, if not you will get a check engine light when you start your car back up.  Once you turn the switch on, you must build boost before it will be active, because pressure must be trapped between the stock ‘pressure tank’ and the IACV and EGCV actuators for them to open. You will notice a bit more lag below 2800 RPM, but more power between 2800-4000 RPM as well as a smoother power band and peak boost a couple hundred RPM sooner. HAPPY BOOSTING!!

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