Fw: New VR6 stuff (long)

["Christopher Morgan" <cmor@home.net>]

Ooops, I forgot to send this over here.  All you GTI co-listers got this a
few hours ago.

>So I have here in front of me the VW Service Training book for the New
Golf,
>Jetta, and GTI.  There's lots of neat stuff and no, I don't know how you
can
>get a copy of it.  I can't even get a copy of it.  The one I have is
>borrowed and has to be back in a couple of hours.
>
>To quote a topic of interest:
>
>"The VR6 engine has a new intake manifold that increases low RPM torque and
>high RPM power.  It does this by taking advantage of the self-charging or
>ram effect that exists at certain RPMs.
>
>"By 'tuning' the intake runner length, engineers can produce this ram
effect
>for a given RPM range.  A manifold that has two different lengths of
runners
>can produce the ram effect over a broader RPM range.
>
>"The VR6 engine uses two lengths of runners but not in the same way as the
>dual path manifolds used on other engines.  Instead of using high velocity
>air flow in a long narrow manifold runner to ram more air into an engine at
>low RPM and then opening a short large diameter runner for high RPM, the
VR6
>engine takes advantage of the pressure wave created by the pressure
>differential that exists between the combustion chamber and the intake
>manifold.
>
>"All air enters the intake manifold plenum, referred to as the Torque Port
>and is drawn down the long intake runners to the cylinders.  A second
plenum
>called the Performance Port, which is attached to a set of short manifold
>runners, joins the long intake runners near the cylinder head.  A Rotary
>Valve separates the Performance Port from the short runners.
>
>"Note that the Performance Port does not have any other passages to the
>intake manifold other than through the Rotary Valve.  It does not have
>access to the Torque Port and does not admit any more air into the
cylinders
>than what is already drawn down the long intake runners."
>
>There are a few more pages with illustrations and a more detailed
>description of how the pressure wave stuff works (Physics 122).  The
>interesting thing is how the two plenums work.  One is at the end of a long
>set of intake runners and is called the Torque Port.  It is also connected
>to the throttle body (which lets air in of course).  The second plenum,
>called the Performance Port, is attached to a set of short runners and has
>no other connections to let air in or out.  It is basically an empty
chamber
>that lets a pressure wave bounce around and exit out the same runners from
>where it entered.  The Performance Port is closed off to the rest of the
>intake tract between 900 and 4300 RPM by the Rotary Valve, which is a long
>cylinder with six holes cut through it perpendicular to its axis.  The
>Rotary Valve rotates 1/4 turn to open or close and is operated by a vacuum
>solenoid and change-over valve that in turn is regulated by the ECM.  If
you
>look here http://home9.swipnet.se/~w-90969/vr6_4v.jpg (this isn't the same
>engine that is shown in the book, but you'll get the general idea) you can
>see the bulge across the front of the intake manifold that houses the
Rotary
>Valve.  Seems pretty cool to me, and apparently it works.
>
>Other things mentioned are a dual mass flywheel, an electronic throttle,
and
>the new Bosch ME7 Motronic system.  The first item reduces NVH in general
>and gear clatter when idling in neutral.  As for the electronic throttle,
it
>also reduces NVH transmissions and allow the ECM to pick the optimum
>throttle setting (regardless of what your right foot may be saying).  I've
>driven a few TDIs that also have the drive-by-wire set-up, and I'm not
>exactly sold on it.  The pedal feels dead.  I prefer the direct feedback
>that a cable gives.  As a side note, because the ECM can now control the
>full range of the throttle, the functioning of the cruise control was
>integrated into it.  Thus, there are no more vacuum lines, pump, and servo
>like on the A3.  The ME7 system if left to a separate training manual that
I
>haven't seen yet.  It may not even be out yet.
>
>That's all for now, gotta go.
>
>-Chris