[Vwdiesel] INCREASING AND DECREASING FUELING
Libbybapa at wmconnect.com
Libbybapa at wmconnect.com
Mon Dec 12 10:46:33 EST 2005
Okay, I got very clearly that an engine just pumping air will not produce
boost and so dropped the idea of underfueling when accelerating with boost in a
TD. But the idea just wouldn't play dead in my head. The fact is we're not
just pumping air. Obviously the volume of gasses leaving the engine compared to
that entering the engine is far greater. That volume of gasses is what spins
the turbine. Even at idle with an extremely minimalal fueling for the amount
of air, the turbine will spin. The VNT turbo with vanes closed will actually
produce boost at idle on a 1.6. Although there is no throttle plate, there
still would be pumping losses when pushing that air in and pushing the gasses
out especially considering the losses of some of the gasses passing the rings.
I understand that fuel makes boost, but still feel that a condition could
exist where the amount of boost air entering the engine is above that where any
benefit in work is achieved and therefore a detriment to fuel economy.
I understand Svend's claims to high economy in "ECO mode". I also have
talked to others that tried "ECO mode" with a significant drop in fuel economy
accompanying the abysmal drop in performance. I have also heard from several
folks that the 1.9TD ECO (not sold in North America) had resultant lower fuel
economy. That is second hand and unconfirmed by me. Also, if I remember
correctly, the most recent Fuel Economy numbers produced by Svend resulted in mid to
high 40's (US gallons), figures that my '86 N/A Jetta could easily beat with
300,000 miles on the engine, horrendous compression (400, 320, 320, 230) and
200,000 miles on the injectors.
Andrew
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