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Old 08-16-2003, 09:43 AM
stevebfl stevebfl is offline
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
You would be getting a timing adaptation code if you were detonating.

Your values for timing seem appropriate except for the minus sign, but expressing timing is a matter of how you look at it. Timing is usually expressed as degree before top dead center BTDC. Since all cars advance timing the value is considered plus.

But, the actual value if expressed mathmatically would be expressed as a point before a time or t-x or just -x with x being the degree of timing.

One thing I might point out is that timing is individually controlled per cylinder to stop knocking. The actual cylinders are identified by general position (cam and crank sensors) and specifically by the knock sensors.

Also that motor has dual plugs and the relative timing of each plug is adjustable as there are two coils also per cylinder. There are various firing strategies and the plugs usually don't fire together. If the plugs can be identified as "A" and "B" they are usually fired this way: A then B, B then A, A then B, B then A etc etc with the point being to sweep the flame front back and forth and keep even temps to avoid detonation from hot spots (while keeping it as hot as possible - probably). The length of time from A to B also can change and it can be set to zero so that they fire together. I don't think there is anyway to verify any of this other than through on-board diagnostics.

So the value you are seeing is only a generalized expression of what is really happening. if you were to view this with the Star Tester you could get a reading of the knock control timing correction per cylinder. You could even alter the timing in 7deg increments till knock affects one cylinder thus allowing a degree of built in help for technicians.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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