I suspect that is that this related to the same = reason that my 2.1L Syncro gets worse gas mileage that a 235 hp Chevy = 327-powered IH Scout I used to have (it averaged about 17-19 on the = highway with military axles and 35" tires, even towing a = trailer). The Syncro is underpowered, and forces you to drive at = WOT a lot of the time. With more horsepower and torque available = at lower RPMs, your driving habits are altered and you end up having to = "push" the car less, resulting in better mileage.
Smooth driving results in better mileage, all other = things being equal.
(I should mention that the aforementioned Scout = started with a Holly 4 barrel 750 cfm carb and only got about 12 mpg = until I switched to a Rochester 2 bbl unit, which gave better low-end = performance)
Brent Christensen
'89 GL Syncro Westy
Santa Barbara, CA
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.C=
OM]On Behalf
> Of David Marshall
> Sent: Sunday, March 26, 2000 10:22 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Why did this mod increase my fuel =
economy?
>
>
> Volks,
>
> First a little background on my vehicle:
>
> - 1988 Syncro Transporter (Double Cab)
> - 225/60R16 tires (~27")
> - 2.0L 1995 Jetta engine
> - 1.8L Cylinder head from 1986 Jetta
> - 266 degree cam
> - Timing set to 10deg BTDC
> - CO set to 1.5%
> - 87 Octane fuel
> - CIS Fuel distributor from 1979 Audi =
Fox
> - CIS-E knock sensor (ignition timing) from =
1987 Jetta GLI
> - Scirocco 16V fuel injectors
> - Audi 5000 turbo warm up regulator
> - No cat, free flow exhaust
>
> Proior to my modification I was getting ~15L =
per 100km (16 US
> mpg) in town
> and ~13L per 100km (18mpg) on the highway doing =
a constant 100km/h.
>
> The modification that I did was very =
simple. Ever since I
> installed the
> ABA (formerly 3A) engine I have been too lazy =
to modify the
> throttle pedal
> linkage so the throttle valve would open fully =
when the pedal
> is all the
> way down. Performance was good and fuel =
economy was nothing to be too
> concerned about. The problem with this =
setup is the 2nd
> butter fly (larger
> of the two) in the throttle valve would open =
only part way (75%). The
> solution to this was to install a small bolt =
and nut in the
> linkage of the
> throttle valve so 2nd butterfly would open =
sooner and all the
> way open when
> the pedal was fully depressed. Normally =
the smaller
> butterfly open 75% of
> the way before the larger starts to open - with =
the bolt in
> place it starts
> to open at 50%. The result was a much =
more snappy drive with
> a noticable
> "push you into the seat" feeling when =
you are accelerating as
> the thottle
> would go wide open a lot sooner and in a non =
linear fashion.
> The first
> fill up I did after the mod I got about 8L per =
100km... I
> figured I must
> have missed recording a fill up so I thought =
nothing of it.
> On saturday I
> drove from Quesnel to Prince George on 11L of =
gasoline - this
> was a 125km
> trip through rolling hills at a leasurly 95 to =
100km/h - this
> translates
> into 8.8L per 100km (26.7 US mpg)- the trip =
back we did a
> little more speed
> ranging from 100km/h to 115km/h plus really =
pushing hard in
> 3rd going up
> some of the steep hills - we consumed 14L of =
gasoline or
> 11.2L per 100km
> (21 US mpg).
>
> So, why did things get better with a throttle =
that opens
> quicker? Not that
> I am complaining!
>
> -- David Marshall =
- =
; - Quesnel, BC, =
Canada --
> -- 78 VW Rabbit, 80 VW Caddy, =
84 VW Westie, 85 VW Cabriolet --
> -- 87 Audi =
5000 Quattro, 88 2.0L VW Syncro Double =
Cab --
> -- David's Volkswagen Home =
Page http://www.volkswagen.org --
> -- Fast Forward Autobahn Sport Tuning http://www.fastforward.ca --
> -- david@volkswagen.org (pmail) or =
vanagon@volkswagen.org (list) --
>