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I am relatively new to the electrical/tuning aspects of an engine, but I've built and rebuilt several motors, and I understand most of the principles behind what makes a motor tick. And I've been learning a lot more watching the webinars and taking the EFI Fundamentals course. But, it seems I am a little stuck on this topic. A little background first: I'm using the Link G4+ software for a Vi-PEC i88 ECU. The motor is a heavily modified 1.8L 4-cylinder Audi engine. This motor uses coil-on-plugs and a camshaft position sensor.
I understand what to do and why we are doing it, but I have some questions related to concepts.
1. What determines the degree of rotation on the crankshaft that is used for the base ignition timing? For example, the base file for my car's engine states that the base ignition timing is 279.
2. What factors can cause the number stated earlier to change? Does timing of the camshafts have any effect on this since the camshaft position sensor determines where in the sequence the cylinder is at?
I think this is what you're after if I understand your question correctly
The number used inside the ECU to calibrate the base timing is dependent on the orientation or location of the trigger inputs relative to TDC #1. In general terms you can think of this as the number of degrees of crankshaft rotation between the synchronisation event and TDC on #1 cylinder. The number itself isn't particularly relevant or important to us though - Simply adjust the number until the timing lines up correctly with a timing light and the actual ignition timing matches the timing the laptop is displaying.
Thanks for the replies.
So, in Webinar 095, you mention issues with the camshaft sensor wheel can vibrate causing the sensor to potentially count the same tooth (or more). Is this still a concern with a 1-window trigger setup?
Also, if the base ignition timing needs to be adjusted, would you add the same amount of degrees to the injection timing number?
And, finally, since the trigger wheel for my camshaft position sensor is fixed to my intake camshaft, if I advance or retard that camshaft, would that cause the base ignition timing to change, and I would then have to recheck the timing with a timing light?