Re: Electronic to Mechanical Pump

Posted by RodInNS on April 04, 2006 at 15:17:47 from (142.177.113.219):

In Reply to: Re: Electronic to Mechanical Pump posted by jdemaris on April 04, 2006 at 11:32:44:

The new Cummins system is fully electronic, with electronic unit injectors. The old PT systems had mechanically activated/timed, pressure/orifice metered injectors. The new systems simply have a crank position sensor feeding the brain box, and that tells the injectors when to jump. So it allows for variable fuel timing, as far as I'm aware. The old NTC's were notoriously known as hard cold starters. I think it's fairly well accepted that electronics smartened up the starting on most Cummins and Detroit engines.
As far as the Jetta's go, I think some people's mileage will vary. I know one guy who's getting I would say probably mid to high 50's (mpg US). He was getting the advertised 64 miles per Imperial gallon, which is somewhat larger than yours, and I haven't done the exact conversion. This was from an '03 Jetta TDI. My mother has an '04 Jetta TDI, and it's probably doing low-mid 50's (US), but I've had it down to low 30's on some low level flights (80 mph). It can certainly burn fuel on a hard pull. I think most of the decrease that some people see is basically just dragging a bit more car around than the old models. New jetta's are a bit heavier than the old boxes. There is no theoretical reason for an IDI engine to be more efficient than a DI engine.
You are quite correct though, that the new emissions requirements for Tier III, including EGR will decrease a diesel's mileage. I haven't looked at the specs on that lately, but I seem to recall it as being quite significant. for what it's worth...

Rod

Replies:

• Re: Electronic to Mechanical Pump jdemaris 20:08:02 04/04/06 (0)

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