IGNITION TIMING
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This may help:
IGNITION TIMING:
Ignition timing is the point when the spark plug is being fired in relation to the position of the piston and crankshaft. The unit value used is angular degrees. In the VG30, the base timing (or the timing reference at idle) is 15 degrees. This means the ECU is making the engine fire at 15 degrees BTDC, or Before Top Dead Center. This is in relation to the position of the piston and crankshaft. BTDC means that as the piston is in its upward motion on the compression stroke, the plug is being fired when the crankshaft is 15 degrees before the piston reaches top dead center of the cylinder. The object here in setting base timing is to make the ECU and the timing mark on the pulley agree with each other.
Typical timing lights use an inductive pickup to detect when the plug is being fired and when it detects this, it causes a strobe light to fire off. This basic principle allows us to see exactly when the plug is being fired off in relation to the crankshaft position. On the front of the engine just above the crank pulley is a timing indicator which shows a range of degrees on what looks like a ruler. The values go from 0 to 30, from right to left. There is a mark on the pulley that indicates the position of cylinder #1. When the mark is lined up to "0" on the indicator, this means the #1 piston is all the way at the top of the cylinder.
Timing lights also require power in order to fire the strobe light off so be sure to connect the power leads. (Figure 2)
2.
The inductive pickup:
NOTE:! Using this point as the pickup has been found to be the quickest and most accurate method of hooking up the timing light. There is also a black loop on the PTU harness that is supposed to be used for this, however, on a number of occasions it has given vary peculiar results - sometimes getting two points of indication on the pulley and sometimes it being so far off you can't even see it. If you see any oddities like this, use the procedure in Figure 3.
Try this method first. If for some reason you aren't getting a signal, verify that your power terminals are connected and wiggle the pickup around a little on the wire. You should get a pulse. If it still doesn't want to behave, you will need to pull the coil pack out and use a plugwire extension and put the inductive pickup on the high voltage line going to the plug. The inductive loop has been known to do weird things which makes it difficult to trust with something like ignition timing.
3.
Once you have everything properly hooked up, point the light at the pulley and observe. You should see the same as Figure 4.
4.
NISSAN FACTORY BASE TIMING IS 15 DEGREES BTDC.
THE ENGINE MUST BE FULLY WARMED UP DURING THIS TEST
It is not hard to set it dead on 15 degrees and it is highly recommended to get this setting right.
To adjust the timing, the CAM ANGLE SENSOR, or CAS for short, it used to adjust the base timing.
• There are three 10mm bolts that hold the CAS in place. Loosen these with the engine off.
• Since the engine rotates clockwise, turning the CAS clockwise will retard the timing whereas turning it counterclockwise advances the timing.
• Move the CAS in the appropriate direction to adjust the base timing.
• The engine must be running to test it and once you have the CAS loose, you can start the engine and then begin moving the CAS to get the timing mark aligned to 15 degrees.
This process ensures that the timing values in the ignition timing map of the ECU are in fact, correct. All the CAS is for is simply to calibrate the engine with the ECU such that the values in the ECU agree with the actual timing that the engine is running at. The timing light allows you to verify what the actual timing is because it flashes the light off when the plug fires and the markings on the pulley allow you to see what the position of the crankshaft is.
4.
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