nissan200sx.dk Posted September 28, 2013 Report Share Posted September 28, 2013 When i adjust for bigger injectors, should i chance the master or just %.. Quote Link to comment Share on other sites More sharing options...
smelly Posted September 29, 2013 Report Share Posted September 29, 2013 Here is the answer I received when I asked this question. I went from 17lb injectors to 72lb injectors. "72lb is about 4 times more fuel than 17lb so if you have only changed the injectors then you want only about a quarter (25%) of the original pulse width. Also be aware in the Vi-pec the 'master fuel trim' is an adder, not a multiplier like most ecu's, so if you put a value of 50% into the 'master fuel trim' field that will actually add 50% to the current pulse width which give you 1.5 times more fuel (i.e 150%). So, you are best set the 'master fuel trim' back to 0% and instead use the 'master fuel' setting - change this to about a quarter of its original value (i.e if it is currently 10ms, change it to 2.5ms) i.e 17/72 = 0.236 = 23.6%. So to inject the same amount of fuel with the new injector you will need approx 24% of the original pulse width." Hope that helps. Quote Link to comment Share on other sites More sharing options...
Simon Posted September 29, 2013 Report Share Posted September 29, 2013 Start by adjusting the master. The trim can then be used if needed as a fine adjustment. If your doing a full tune the master fuel will be enough and the trim can stay at 0. Tuning will take care of the rest. Quote Link to comment Share on other sites More sharing options...
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