[Mike@N54Tuning.com]

Hey Everyone,

Sorry for the delays in posting data, as I just got back from my honeymoon and wanted to be heavily involved in this testing procedure.

As most have seen we've been discussing CPS as a form of timing control, and unfortunately much of those threads have digressed to the point of personal insults and have become rather useless. So I am making a new thread to share this data, and hopefully engage in a more informative and professional discussion. I would hope that members with no technical knowledge but strong opinions (on either side) would refrain from posting.

Also keep in mind I am not claiming to be a tuning expert. I can read logs and understand the principles, and I want to engage in this discussion. If you disagree with me then do so in a professional way.

The following logs were captured from a fully modified well adapted 135i during two days of testing. One day with the V3 using the latest Stage 3 maps, the next day with the JB3 using the latest map 7. Same tank of gas, same weather, etc. The same roads were used, and efforts were made to keep testing conditions as close as possible. All testing was done on 91 octane in 90 degree weather, at around 15psi boost, which represents the worst possible conditions for "knock" (high heat and high boost). During both tests the cars were loaded with 550# of passenger and driver to ensure the results were comparable to a 335i. Starting IAT temperatures were matched.

The original objective was to recreate Shiv's previously posted V3 logs under similar circumstances so that CPS offsetting could be tested. The problem that immediately has came up is run to run variance. These runs have huge timing variances between them.

In addition here are two JB3 logs for reference. They exhibit similar timing behavior, only an overall lower timing curve (as no offset is applied). They also reflect better boost targeting and less throttle closure but that is beyond the scope of this discussion.

So here are two questions:

1) Why do these V3 logs captured not match the ones Shiv posted?

2) How should we analyze CPS offsetting when run to run variance eclipses the CPS offset being applied?

Finally an observation:

Backing out the CPS offset, the overall timing curves do not look very different to me. Especially given the run to run variance. I can't look at any of these charts and say they indicate a happier or safer engine. Which supports the point that CPS offsetting is not an effective timing control. I will also add that this JB3 map combination is not officially supported by BMS. Map 7 is supposed to be used on 93 or higher octane.




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