PerL Wrote:

> As the Injection pump delivers an even pressure for the injectors, the
> electronics control the injectors timing, when to open, how much to
> open and how long they should stay open. Chip tuning alters the timing
> for the injection and let more fuel into the cylinder.

This is how it works on new common rail or unit injection systems.
However the current TDI is based on the good old VE pump and timing
is adjusted by turning the cage the cam rollers are mounted in to
effectively change the pumping timing of the plunger. On old style
1.6l pumps this is proportional to internal fuel pressure which
in turn is proportional to rpm. On new styly VE pumps (Like mine
in the 1.9l TD and TDI) there is also a solenoid that allow you
to leak fuel back and lower the pressure and thus retard the timing.
The details of how to control this is sketchy in the factory
fuel injection manual and I currently have mine unhooked.
If any one have more info on this I'd appreciate, (or could salvage
a "glow plug control unit and brain" ftom a 1.9l TD for me cheaply)

Drawings and a detailed description of the injection pump
is on my WWW page.

/Martin
--
Westy 1.9l Turbo Diesel
Quantum 1.6l Turbo Diesel

Martin Jagersand                 email: jag@cs.yale.edu
Computer Science Department             jag@cs.rochester.edu
Yale University

        Slow down and visit the VW diesel Westy page:
          WWW: http://www.cs.rochester.edu/u/jag/vw
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