How to: ETCC mod JZA80

How to: ETCC mod JZA80


  • A Double Pole, Double Throw (DPDT) rocker switc
  • 6 x 2m lengths of cable in 3 colour’s (black, blue and white). I say 2m because you can always cut it later – and 3 colour’s for identification but the colour’s are up to you.
  • 6 female spade connectors
  • 4 male and female bullet connectors
  • 1 ring connector
  • Crimping tool
  • Wire cutters

This is an involved method, as you have to cut into part of the ECU wiring loom, so if you’re unsure, DONT DO IT. It could be an expensive mistake!


The theory of this method works in a similar way to the TTC method, but instead of bypassing the VSV’s that control the sequential operation, the system stays locked in parallel mode due to the fact that the VSV’s are electrically held open. When Sequential is selected, the system operates as normal, however, if ETTC is selected, the VSV control signal is sent to earth, as a result the VSV’s are held open. 


NOTE: Before you start this, best to point out that if you try this, and kill yourself or your car in anyway, it’s not my fault.

There are 2 methods in carrying out this mod.

  • The one described below
  • Instead of cutting in the ECU loom, you cut into the VSV wires in the engine bay. I believe the method below is easier as you do not have to run wires through the bulk head, everything is contained within the car

But in terms of switch connections, everything is the same.

  • Take the 6 lengths of wire, and crimp the female spade connectors on.
  • On the black wires, crimp the ring connector on, so that the wires are joined together
  • Take the rocker switch and connect the black wires to the bottom 2 contacts
  • Connect the blue wires to the center 2contacts
  • Connect the white wires to the top 2 contacts






It’s up to you on where to install the switch – I personally have mine in the armrest storage area so the switch is “hidden”






Now the “messy bit” – cutting in to the ECU loom.

  • Disconnect the battery!
  • Locate the ECU – Passengers foot well, under the carpet and a plastic cover.
  • Remove the multi plug connector from the ECU
  • Locate Pins 39 (Exhaust Gas Control Valve) and 40 (Intake Air Control Valve) on Connector E9
  • Follow ONE wire at a time the wire away from the ECU 6 – 8″ and then cut, then do the following

This bit is important!

  • Take pin 39 FROM THE ECU and connect it to the top left contact on the rocker switch by use of the bullet connectors
  • Take the corresponding wire TO THE Exhaust Gas Control Valve and connect it to the center left contact on the rocker switch by use of the bullet connectors
  • Take pin 40 FROM THE ECU and connect it to the top right contact on the rocker switch by use of the bullet connectors
  • Take the corresponding wire TO THE Intake Air Control Valve and connect it to the center right contact on the rocker switch by use of the bullet connectors
  • Finally, connect the black wire and connect it to an earth. I personally used one of the big bolts by the gear stick.

Now you can

  • Reconnect the ECU multi plug
  • Put the plastic cover back on
  • Put the carpet back down
  • Hide the wires up in the trim, out of the way
  • Take the ring connector with the black wire crimped on, and connect it to an earth point. (there are several on top of the transmission tunnel, by the gear stick)
  • Admire your handy work




You have now completed the ETTC mod!
Well, actually, not quite yet. You see until the system is pressurized, it won’t be in parallel mode. So take the car for a drive, and get it to boost. When it first boosts, it’ll funny, because as it comes on boost, it’ll cause the second turbo to come on line as soon as you start making boost. After the first time, you should notice three things. Firstly, the car sounds a lot beastier!! That’s because you’re no longer shutting off half the exhaust when you’re under 4000 rpm. Second boost comes on MUCH more smoothly. Third, it doesn’t come on fully until about 4000 rpm. You will get some boost from about 3000rpm, but not all of it.

Your immediate impression might be “this is crap, the car seems so sluggish”. But give it some time (a few days to a week, depending on how much you drive), a few things will happen. You will get used to the car needing a few more revs to really boogie, the computer needs some time to learn that there’s no boost down low, so it can advance ignition timing (you may notice some black smoke from severe over-fueling at first too). It’ll also take a while to realise that the car is noticeably more fuel efficient, and once the computer has sorted itself out, you realise that this is not some poxy little 2 litre 4 cylinder, the NA supra makes as much torque as a WRX, so it doesn’t need the turbo down low for normal driving. But mostly, I love the linear turbo response – the 3000-4000 rpm range is useful again, and the Supra seems a whole lot more fun to drive.



When switching between ETTC and Sequential, its important not to switch when the engine is under load/under boost, as this can cause damage to the pressure tank/sequential system

Its advisable to “switch” when the engine is at idle – this does not mean you have to stop the car every time to switch – use the clutch! – I have been using this method for 6 months and everything is fine!