Thursday, 29 October 2015

MEMS 1.6 / 1.9 Ignition timing map adaptation


As mentioned previously, the real meaning of the so-called "unknown variable" was not really clear, it has been suspected to be either ignition offset or open-loop fuel enrichment (a kind of acceleration pump).

Thanks to the data logging option, it's possible to compare the ignition timing advance vs RPM vs MAP for two separate runs, each of them performed with minimum and maximum allowable setting (116 vs 140).

Then, with a simple perl script a data matrix can be build and visualised (gnuplot):

Of course more averaging, filtering by coolant temp or IAT is clearly needed, but this is how it looks:

 (2D map variant)

(3D version)


Not having access to a dyno it's not really possible collect all possible combinations of  timing vs rpm vs map values required to plot complete ignition map, also the low rpm/load area is bit noisy due to idle speed control interventions, nevertheless it gives a good overview of timing differences.

In short, the timing adaptation variable influences the amount of advance (or retardation) in the area of MAP pressure above 60 kPa.

For example, in case of  K-Series 1.8 16v (Freelander I) it's possible to to adjust timing advance (only for loads above 60 kPa) withing the range of -4.5 to +4.5 degrees. Each increment or decrement equals to difference of 0.5 degree, however it's not possible to exceed 4.5 deg (140-116 = should be -6,+6 deg.).

Default value: 132 (timing retarded by 2 deg.)

Min value: 116 (timing advanced by +4.5 deg)
Max value: 140 (timing retarded by +4.5 deg)

tbc...

7 comments:

  1. Well for some reason the idle tuning and unknown values behave like afr values to me being I.e 13.2 as and afr for idle and 12.6 afr for wot but that's what I think it is, I got some decent performance out of those values thus far I gets a little better @ 12.5 but I don't want to waste too much fuel, try these settings on your car leg me know how they perform.

    ReplyDelete
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  4. What value is for mems 1.6 +2-2.5 min value is 108 max if i remember 158

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  7. Have you had chance to try this timing adaptation on the MEMS2J? There's some speculation that Rover was a little conservative with their ignition timing maps. So it could prove interesting to those with VVC engines.

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