Stock 914 Fuel Injection Pulse Widths Options

[JeffBowlsby]

I stumbled on this chart of pulse widths courtesy of Brad Anders...Hopefully it is a starting point for anyone tuning an aftermarket FI ECU who also use stock injectors and fuel pressure.

0.1ms resolution is necessary.

The charts give data for PW based on manifold vacuum and RPM.

Stock 914 FI pulse widths

[lapuwali]

QUOTE (SLKWrx @ Jun 23 2005, 04:59 AM)

I really wish I understood this stuff. Anyone have a page that helps explain how all this works?

A web page, no, but an excellent introduction to how ALL electronic fuel injection systems work is Bosch Fuel Injection and Engine Management, Charles O. Probst, Bentley Publishers. He covers all of the major flavors of Bosch fuel injection, including those used on the 914 (D-Jet for most, L-Jet for the US 1.8). Highly recommended.

Very briefly, the pulsewidths are the length of time the injectors are held open. The injectors are simply valves, the injection is done by holding the fuel pressure on one side of the injector fairly high (usually about 2-3 Bar, or 30-45psi), and simply opening the valve into the intake manifold, where the pressure is relatively low (0.3-0.9 Bar). Holding the injectors open longer sprays in more fuel, thus enrichening the mixture. So, you can control mixture across a wide range by just changing the pulsewidth from short (lean) to long (rich).