> According to 'Bosch Fuel Injection & engine Management", by Charles
    >      Probst:
    >
    >      The first continuous injection system (CIS) (1977) was
   K-Jetronic.
    >      Air flow
    >      is measured by a circular plate in the air-flow sensor,
   which is
    >      mechanically linked to the fuel distributor.  Until 1980, fuel
    >      delivery is
    >      strictly under mechanical control in direct relation to air
    > flow;     there are     no electronics.  VW, Audi, and Mercedes call
    > it CIS.
    >
    >      K-Jetronic with Lambda Control is an adaptation of K-Jetronic
   mechanical
    >      control.  The mixture is modulated with a limited electronic
   control
    >      in a
    >      feedback system to maintain a precise air-fuel ratio.
    >
    >      KE-Jetronic combines K-Jetronic mechanical control with total
    >      electronic
    >      modulation of the mixture.  It uses many of the same sensors
    > used in     L-Jetronic (a pulsed fuel injection system).  It's
    > capable of full     mechanical fail-safe if the electronics fail.
    > VW, Audi, and     Mercedes call     is CIS-E.
    >
    >      Andy Hecker
    >      CIS in a '77 Rabbit (RIP)
    >      Digifant II in an '88 Jetta
    >
    >      -------
    >      Paul,
    >
    >         First - I'm sorry for the typos, and 'editing' compliments
    > of MS word     'autocorrect'.  It didn't like 'Jetronic' apparently.
    >  The systems     described     above are all 'Jetronic', not
    > 'electronic(s)'.
    >
    >         Second - the author of the 'Bosch..." book said his
    > production year     references (like the 'first seen in 1977'
    > comment above were for the US     market only.
    >
    >         The chart lists injection in VWs from the Type 3s...
    >
    >         On the history front - also from the Bosch book:
    >
    >        "Bosch passenger-car fuel injection first appeared in 1927 as
    > a diesel     design using engine-driven pumps developing high
    > pressure to deliver     diesel     fuel into the cylinders - direct
    > injection.  In 1937, these pumps were     adapted to aircraft
    > engines, with both diesel and gasoline fuel     applications.  In
    > 19565, similar engine-driven gasoline injection     pumps were
    > developed for the Mercedes-Benz race cars and the 300SL production
    > car,     again injecting fuel at high pressure directly into the
   cylinders.
    >
    >        "The fuel-injection systems described in this book first
   appeared
    >      about
    >      1967.  They are completely different from engine-driven systems,
    >      delivering
    >      fuel at much lower pressures at the intake ports, and are
   generally
    >      electronically controlled.  The early Bosch literature
    > describes these     systems as "non-driven".  Bosch coined the term
    > "Jetronic" to     establish a     common identity for their new
    > designs in most of the 135 countries     in which     they operate.
    >
    >      Andy
    >      -7 from the Russian judge for (lack of) editing...
    >
    > More "me too"..  My '74 Volvo (wagon) had K-Jetronic.  '71's had
    > dual SU side drafts (our first Volvo) - lame.  '72's had electronic
    > FI (I think one year only - maybe the P1800's had more years).  And
    > I think '73 through about '78 had K-Jetronic.  By '82 (our newest
    > Volvo) they had Lambda (O2 sensor).
    >
    > The K-Jetronic ran fine, but had kind of weak throttle response.  As
    > far as throttle response, the sportiest Volvo I've driven is our '67
    > 122S with dual SU HS6's.  Kind of surprising since they don't have
    > an accelerator pump..
    >
    > Matt-
   Matt,
    > The SU uses oil damping of the air piston to slow down the
   opening of the
   throat. This increases venturi velocity and vacuum and thus fuel
   flow when
   throttle is opened, without to much extra air. Thick oil gives a
   rich mixture
   for acceleration. Very thin or no oil generally leads to a stumble
   on quick
   throttle opening. Underbonnet temperature changes the viscosity and the
   effect of the damping and ruins all the careful tuning.

   Colin Smith


Ahah!  Thanks for that little gem Colin..  I had never put that
together.  It makes perfect sense.  I knew that running thin oil made it
run kind of crummy, but mostly at idle.  My theory was that any time
there was any misfire, the thin oil allowed the piston to bounce more,
creating unstable mixture.  I usually ran 20w50 in the dampers, and that
seemed fine.  I also remember that the little circlip/washer assembly on
the end of the damper would get a bit loose which allowed the piston to
move a small amount without the oil being forced through the damper.

SU's are simple, but seem to require constant fiddling.


Matt-

"Seem"? Heck they do! No doubt about it :)

Paul Lamar ...No rotor no motor.

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