Map Rescale

GEMS engine calibration software

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Map Rescale

Post by R!C0 » Mon Jan 21, 2008 3:58 pm

Often with boosted engines it is necessary to increase the maximum load in the fuel ignition and wastegate calibration maps. This requires MAP max, or Air Flow max, to be increased. To minimise dyno or tuning time, it is often possible to liberate lower load lines.

Say the bottom 3 load lines are nominally identical then, 2 more full load lines may be generated thus:

With a 14 load site system. Copy the top 12 lines into the bottom 12 lines of the 3 load based maps: Fuel Ignition and Wastegate Duty maps.

Now load must be corrected. Assuming linear step sizes, each step in load axis is about the same say 24kPa. So old load scale ran from 0 - 300kPa, new scale will need to start at 48kPa and run to 348kPa.

So MAP max, or Air Flow max will need to be increased by (348/300) = 1.16 = +16%. So if old max was 72 new value will be 84, the user Load scalar option will also need adjusting accordingly so old scalar was 300 new scalar needs to be 348.

The 2 new load lines should be filled extrapolated values based on the 2 map cells immediately below (the two old highest load sites). So if there was a decrease in ignition of 3 degrees between rows, then continue this retard into the two new rows. Or as a simpler guess, the two top lines may be multiplied by 117% using the block percentage change for fuel map. Except if the cell value in raw units exceeds 255, then the bottom 10 rows should be percentage changed by 85% and MicroSec/bit increased by 117%. Now the Injector duty should be checked to see if any critical sites exceed 100%, if so then fuel pressure may be adjusted rather than larger injectors fitted.

Open a 2nd copy of GWv3 with the original calibration and compare the new maps to check your recalling. The check for other options that may be effected by re-scaling such as: Rad Spray Load, OX FB Load, Log Load, IC Spray Load.

Rename and Save recalled calibration, in notes add those changes you made and the source for those changes.