Updated Aug, 2012
One of the leading tech questions that we get here, regards questions with mounting the Hall sensor and magnets on our E and F systems, so here are some more ideas on this topic.
Many people seem to have problems understanding the diagrams in the manuals regarding Hall sensor placement and magnet mounting. The diagrams are intended to be viewed as if they are transparent and that you can "look through" the components such as crank pulleys. Magnets and sensors can be mounted on either the front or back face of the pulley. Rear face mounting is more popular as this generally puts the mount closer to the timing cover. The fact that the Hall sensor is flipped 180 degrees is unimportant.
Magnets and Hall sensors do not need to be mounted at TDC. The procedure in the manual is clear if it is followed step by step. This is VERY important . We recommend that the Hall sensor location be chosen first to avoid any interference problems with fan belts, alternators, water pumps etc. The Hall sensor may be located anywhere around the crank pulley that is convenient. Once the Hall sensor is mounted, turn the crank to TDC #1. Put a mark on the pulley where the middle of the Hall sensor intersects the pulley. From this mark, go 80 degrees in the direction of crank rotation and make another mark. This is where the first trigger magnet is placed. The other trigger mag(s) are placed either 180 degrees from this one on 4 cylinder engines, 120 degrees on 6 cylinder engines or 90 degrees on 8 cylinder engines. On F systems, the synch mag is placed 40 degrees past the first trigger mag, in the direction of crank rotation on the outer radius circle.
It is important to note that the Hall sensor location determines magnet mounting position around the pulley. Before glueing magnets into position, use the follwing procedure to check that you have done things correctly:
1. Turn the crank to TDC #1
2. Now, turn the crank backwards 180 degrees, until the crank is at BDC, coming up to fire on #1 cylinder
3. Turn the crank in its normal direction, slowly by hand until about 120 degrees before TDC. At this point, the synch magnet on F systems should be crossing the synch element on the Hall sensor.
4. Keep turning the crank in its normal direction until it is about 80 degrees before TDC. At this point, the first (#1) trigger mag should be crossing the trigger Hall element
5. When the first trigger mag crosses the trigger Hall element, it tells the ECU to do the calculations based on RPM and manifold pressure and fire the spark at some amount before TDC which is now coming up. The ECU needs some time to be able to do the calculations and still fire the spark 20-40 degrees before TDC. This is the reason for mounting the magnets so that they cross their sensors 80 degrees before the pistons reach TDC.
This update includes step by step photos of the correct way to install the magnets and Hall sensor for a 4F system. This may help potential users.
Step 1- Position crank pulley at TDC #1. Draw arrow on pulley for direction of engine rotation.
Step 2- Position Hall sensor for best location around pulley to clear belts etc. and for mounting bolt proximity. Mark pulley where center of sensor crosses.
Step 3- Scribe inner and outer circles as per manual and measure with calipers.
Step 4- Place 80 degree protractor against orginal mark from step 2 and other edge in direction of rotation arrow from step 1. Mark pulley here for 1st trigger magnet on inner circle.
Step 5- Place 40 degree protractor (F systems only) against the 1st trigger mark from step 4 and direction of rotation arrow from step 1. Mark pulley here for synch magnet on outer circle.
Step 6- Magnets shown in position on rear pulley face
Step 7- Make up Hall sensor mount from 1/2 inch T6 plate, 3/4 bar stock spacers to span two timing cover bolts. Spacers should allow 1.5 to 2.5mm clearance from magnets to Hall sensor plate face.
Step 8- Hall bracket in position
Step 9- Pulley and Hall in position
Step 10- Closeup of Hall installation
Step 11- Front view of complete installation on Toyota 2TC
Step 12- Installation on 4AG Toyota
Be sure to carefully follow the installation process described in the manual. This article is intended as supplemental help to the manual, not as a replacement.