With all the discussion on the CPS offsetting lately, I have been delving deeper into this topic and contacting various tuners to get to the bottom of it. Now, we all know the Procede has had and still has misfire problems and the JB has not had this problem. As I have learned more about the impact of this system I have spoken to a couple tuners who pointed me in the right direction.
What is the major difference between the two? CPS offsetting.
Why would CPS offsetting cause misfires? Well, if the CPS offsetting is based on load and not static it will wreak havoc with the misfire detection of the DME. Here is how the Procede does CPS offsetting:
So, the more load the more offset. Why is this a problem? The ECU uses the CPS signal to mesaure the acceleration of the crankshaft. If the acceleration value is outside what the DME expects, it is interpreted as a misfire. So when the ECU goes to measure the crank speed and this signal is changed, boom, misfire.
Why has this been difficult to pin down? Because the Procede varies the offset and it isn't static. CPS offsetting isn't the right way to reduce ignition timing but the only option the Procede really has, as do all N54 piggybacks. Since the number isn't static misfires will happen based on a ton of variables that affect the ECU, load, weather, rpm, VANOS, etc. This is why there is no rhyme or reason to it only the constant of CPS offset.
Further evidence that supports this theory is that Terry of BMS has recently been doing CPS Offset Testing and has been able to induce misfires with the CPS offsetting. So, hopefully this clears things up for people and to be noted a static offset may be best to prevent misfires. Ideally though, tuners we have contacted stated they believe such a vital part of the way the factory DME functions should not be messed with due to its impact on VANOS and the knock detection system.
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