Slomove's Birkin Pictures and Files
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Injection Mapping

The new throttle bodies (Summer 2005) required complete mapping of the fuel injection. This was done on numerous road trips using an LM1 wideband lambda meter from Innovate Motorsports. The result was quite satisfactory, however optimal fueling at minimal throttle was difficult to achieve due to a linear throttle position sensor (TPS) and relatively coarse resolution of the Emerald ECU. A parallel resistor on the TPS (seel following graph) resulted in significant improvement. Of course the entire fuel map had to be shifted and re-optimized. Good reason for another few blats :)

tps_graphsm.jpg
A similar effect can be achieved with a log scale TPS but this is much cheaper.

Map with Linear TPS Only
injmapnoresistsm.jpg
Very steep slope at low revs and throttle makes for difficult fuel map optimization

Map with 2kOhm Parallel Resistor
injmapwithresistsm.jpg
After the change the map was further optimized, leading to the distinctive ridge at 2500 rpm

As a result the car drives really nice now in cruising. Smooth acceleration right from idle, no "holes" and decent fuel economy (28USGPM highway). Still the same "snap" response at part throttle and full chat.

Dyno Run 6/15/2008 on Chassis Dyno
slomovepwr.jpg
Not too bad....The flat between 6k and 7k rpm is probably due to ring flutter