924Board.org

[ideola]

[ideola]

I've received a couple of email inquiries requesting installation instructions, so I thought I would "memorialize" them here for future inquiries and reference:

Installing the trigger wheel is pretty basic, there's not much of a trick to it. It's the pickup sensor installation that is important.

You need to know where your pickup sensor is going to be located, and you need to know what the offset from TDC is for the ignition system you plan to run.

For example, a standard Ford EDIS setup by default requires the VR sensor to be 90 degrees BTDC relative to the missing tooth. Many aftermarket engine management systems allow you to adjust the "offset", but you will need to consult the installation instructions of the system you plan to use to find out how to figure that out.

For the sake of discussion, let's assume you are going to stick with standard EDIS with a 90 degree BTDC setting. You need to identify where your sensor is going to go. Then what you need to do is install the trigger wheel such that the missing tooth is 9 teeth BEFORE the sensor in the direction of crank rotation (on a 924, when facing the motor, it rotates clockwise). To accommodate as many permutations as possible, my trigger wheel is indexable so you can install it in any one of six positions when you bolt it on.

The trigger wheel is designed to be "sandwiched" between the main crank v-belt pulley and the Gilmer pulley to which it bolts.

• Use a 24mm socket and ratchet to rotate the engine to TDC.
  
• Remove the six Allen head bolts that hold the v-belt pulley to the Gilmer pulley. NOTE: You do NOT need to remove the large 24mm bolt that holds the Gilmer pulley in place.
  
• Determine the optimal orientation of the trigger wheel relative to your crank position sensor
  
• Put the trigger wheel in place (note there are smaller holes in each position to accommodate the TDC centering nub on the Gilmer pulley).
  
• Re-bolt the v-belt pulley using the original Allen head bolts, being careful to ensure the TDC marker on the v-belt pulley is oriented correctly
  
• Torque the Allen head bolts to factory spec.

Also note that you will need to space out the other v-belt pulleys by .125", as this is the thickness of the trigger wheel. For the water pump pulley, use my spacer. On a 931, the alternator and A/C compressor are both attached to the same bracket, so you simply need to remove the three large bolts that attach that bracket to the block, and put washers/spacers between the bracket and the block. For a 924 naturally aspirated, you have to do this for the A/C bracket, and then also add washers to the upper and lower pivot points on the alternator mounting ears. (Note that the 924/931 alternator uses a funky multi-piece pulley, and the shaft to which it mounts is not long enough to merely shim the pulley...unfortunately!
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erstwhile owner of just about every 924 variant ever made

[Joma]

two months ago i bought a trigger wheel from your shop
and it works fine but my timing belt is running against it,
causing it to make a squeaking noise.
have you heard of this problem before?
and do you know of a possible fix for it.

many thanks

Joma

[ideola]

I've sold at least 30 of these, and this is the first report of any issue.

I've noticed on some cars that the timing belt has a tendency to "walk" toward one or the other of the edges of the cam sprocket. I'm wondering if there is somehow wear on your sprocket that is causing the belt to walk toward the front of the sprocket, which might cause it to rub on the trigger wheel.

Cam sprockets are cheap and plentiful, you might consider swapping on an alternate sprocket. If you can't find one, I have several spares.
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erstwhile owner of just about every 924 variant ever made

[3forall]

I have a 36-1 wheel from ideola and the same thing happens but I don't blame the wheel. My belt does move around a bit, when the engine is cold it sits right along the edge of the cam sprocket towards the front of the engine and rubs on the trigger wheel. It made a bit of a squeal but as far as I can tell it doesn't cause any damage. As the engine warms up the belt settles right on the middle of the cam sprocket and no longer rubs.
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1981 924 Weissach edition
1982 931 - Megasquirt and liquid intercooler
1969 911

[Joma]

i dont blame the triggerwheel it is perfectly cut and flat,
but i changed the sprocket and the belt stays in the middle of the sprocket now.
and no longer makes a noise
thanks for the fix.