Tag Archive for IS-F auto swap

Transmission ECU – Brake Sense Circuit

GPI4 (Brake sense)

This circuit is located behind the center of the Ampseal connector. This circuit is built as a digital input, but we must bring the nominal 12V brake light voltage down to the 5V that the processor pin can handle (~6.5 Volts absolute maximum). R33 forms one leg of the voltage divider, and also limits the current through the Zener diode if the voltage is greater than 5.6 Volts.

  1. Install and solder a 15K Ohm, 1/8 Watt resistor {brown-green-orange, 15KEBK-ND} in R33.
  2. Install and solder a 10K Ohm, 1/8 Watt resistor {brown-black-orange, 10KEBK-ND} in R34.
  3. Install and solder a 5.6 Volt Zener diode {1N4734ADICT-ND} in place of C20, with the banded end towards heat sink. You will have to space it up off the board by about ½” (12mm) to get the leads to fit.

Thats you done!

Megashift brake sense circuit

12v brake sense circuit




If the input voltage is 14.5 Volts, the voltage divider will reduce this to 14.5 * 10K/(10K+15K) = 5.8 Volts, and the Zener diode further bleeds this off to 5.6 Volts (nominal) with a current of 14.5/15×103 = 0.97 milliamps (the Zener is rated for 1 Watt, which is much higher than we need which is ~1 milliamp * 0.2 Volts = 0.0002 Watts).

If the input voltage is 11.5 Volts, the voltage divider reduce this to 115 * 10/(10+15) = 4.6 Volts, and the Zener diode does nothing. 4.6 Volts is till plenty to trigger the input pin (the acceptable voltage range for ‘high’ on a HCS12 input pin is 3.25 Volts or higher), which means the supply voltage from the brake signal could drop as low as 8.1 Volts and still trigger the input successfully.


2URGSE + AA80E + ISF DIFF now fitted to the Supra

Well, the supra now has all the major main mehanical work almost complete. The rear end runs with the ISF torsen differential with ISF shafts and Modified outter joints. Custom Prop setup links to the AA80E. Lots of room around the trans tunnel, and with Carefull planning by Colin ment we retained stock trans mounting points, just a few tweaks to be done now to the motor mounts. We have plenty of room to play with for the exhaust manifolds too.

Auto to manual….


Well in Prep for a manual Conversion the first step is to find a suitable bell Housing, and the one below may be the answer. The IS-F 8 speed is a one piece design case so looking at other similar ‘ur series’ engined vehicles the TOYOTA SEQUOIA 4600CC 32-VALVE DOHC EFI, AUTOMATIC 6-SPEED SR-5 Model seems to be a good candidate.

Part no. 351110C030