A narrowband O2 (Oxygen) sensor only reads either rich or lean of Stoichiometric. Stoich is the ration to completely combust the fuel. So a narrowband will only read rich or lean. It does not tell you how far away you are from Stoich.
A wideband O2 is designed to read a board range of air fuel ratios. Some widebands will read from 10:1 up to 20:1. Knowing how far we are away from Stoich we are able to calibrate an engine under all conditions. Especially the areas of full power which are critical to performance and longevity.
Top feed fuel injectors are by far the most common, engines like the 4G63 use top feed injectors. Some of our favourite performance engines like early SR20, 3SGTE, 1JZGTE, RB25DET and EJ20 all come standard with side feed injectors.
So what is the difference?
Side feed injectors:
For side feed injectors the fuel enters through slots machined into the sides of the injector. The fuel rail is combined into the inlet manifold or cylinder head.
Top feed injectors:
As the name suggest fuel feeds into the injector from the top.
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