On Wed, 11 Oct 2006, Jason Bleazard wrote:
> Actually, come to think of it, I seem to remember reading that the VW TDI
> models have some kind of pressure relief system for this exact problem, so I
> guess there is some amount of expansion possible. At least for diesel fuel.
>
You're close Jason, really close. I'm actually shocked to hear anybody
but me mention this :-)
All VW models actually have this air gap in the top of their fuel tanks,
and it is "vented" when the fuel door is shut. Once that vent is held
open by the fuel door being closed, it gives the fuel room to expand. The
little lever that "vents" the tank can also be pressed by the fuel nozzle
when filling up. On a gasser, if you "vent" and then park in the sun
without burning enough fule to give it room to expand, you WILL spill
fuel - so the only time it's not a bad idea to vent a gasser is when
you'll be driving a good 20-30 miles right away to burn up the fuel in
the filler neck. Ignoring of course the contamination of the evaporative
emissions recovery system when "topping off" a gas burner...
On a TDI, since diesel is less volume-volotile, it doesn't get pushed out
when the fuel warms up. Doing a 'venectomy' is very common on the TDIs
but a bad idea on a gasser Dub.
"Venting," as it is called in TDI circles, makes a big difference - about
2-2.5 extra gallons of capacity. Which with a "15 gallon" tank makes the
difference between 600 and 750 miles per tank in my TDI. A huge tank and
fantastic mileage just downright rocks for range. I hate driving the
Dakota and having to stop to fuel every 250 miles, whether I want to or
not....
-- +-- Mike Maskalans ---------------- Rochester, NY ----------+ | '98 Dakota CC, SAS on 40s '84 RamCharger 4x4, plow truck | | '02 Jetta TDI 5sp, daily '97 Intrepid, not on the road | +-------------------- <http://mike.tepidcola.com/trucks/> --+
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