Dauner

Do you know if Audi/VW wrote an SAE paper on the 20-valve engine, it's improvements over the 16V, and thoughts behind the turbocharging decision?

Thanks!
Mark 98.5 A41.8TQM

Alf Arkin

Yes they did, but as you can see this is the "tint and clear corners" forum.

Another Drew

This is from one of their US patents

"........ BACKGROUND OF THE INVENTION

Inlet and outlet valve rows alternate in a state-of-the-art internal
combustion engine, that is, in the direction transverse to the longitudinal, a
row of outlet valves is followed by a row of inlet valves, a row of outlet
valves again, and lastly a row of inlet valves. Two camshafts are provided, an
inlet camshaft and an outlet camshaft, which are positioned above the outer
valve rows, and each of which actuates the valves of the outer valve row and
the valves of the nonadjacent inner valve row. The valves of the inner valve
rows are inevitably inclined at a steep angle to the longitudinal axes of the
pertinent cylinders, this resulting in an unfavorable shape for the combustion
chamber. Moreover, since the length of the inlet and outlet channels of the
two cylinder rows varies, there is no certainty that the same admission and
combustion conditions are present in all cylinders.

In order to prevent these unfavorable conditions, DE-A 38 31 333 discloses
the mounting of inlet valve rows on both sides and near the plane of symmetry
extending between the cylinder rows, but the outlet valve rows on the outside
of the inlet valves, and provision of a common inlet camshaft for the two inlet
valve rows in the plane of symmetry between cylinder rows and provision of an
outlet camshaft for each outlet valve row.

As a result, all cylinders have combustion chambers, as well as inlet and
outlet valves, of identical design, so that uniform admission and an identical
combustion process for all cylinders are ensured. It has been found, however,
that cylinder-selective fuel injection, essential for good mixture preparation,
cannot be achieved with this internal combustion engine. In addition, intense
heating of the intake mixture and the resulting admission loss are unavoidable.
Lastly, this design cannot be used for an internal combustion engine with more
than two inlet valves, since there is no room on the inlet camshaft common to
all the inlet valves for more than two cams per cylinder. Because of these
cramped space conditions, the inlet valves can be actuated only by tappets, not
by rocker arms.

SUMMARY OF THE INVENTION

An object of the invention is the development of a generic internal
combustion engine in which the combustion chambers and the inlet and outlet
valves of all cylinders may also be of identical design, but in which
cylinder-selective fuel injection may be provided and heating of the mixture
admitted kept low without any problem, and, lastly, in which more than two
inlet valves may be provided per cylinder.

In the present invention, Since the inlet valve rows are mounted externally
to the outlet valve rows, the inlet channels provided may extend obliquely
inward from the outside.

This presents the option of providing an injection valve which injects into
the appropriate inlet valve or valves. In that the inlet channels are
positioned on the outside, heating of the mixture admitted is prevented or, at
any rate, reduced. External positioning of the inlet valve rows yields the
additional option of providing long inlet channels with little space required,
so that torque is increased in the lower engine speed range. Lastly, since
each inlet camshaft actuates the inlet valves of only one cylinder row, more
than two cams per cylinder may be mounted on each inlet camshaft, so that, for
example, an internal combustion engine with three inlet valves per cylinder can
be developed without difficulty. Moreover, in the proposed arrangement of the
inlet camshafts there is enough space for actuating the inlet valves even by
way of rocker arms. This is a consideration of particular importance, in that
the possibility is created of mounting a variable valve control unit, for
example as is claimed in DE-A 42 05 230. The present invention also offers the
possibility of developing an internal combustion engine optionally with tappet
control or control by tappets or rocker arm control for inlet valves.

In order to achieve high output and high torque over the entire engine speed
range, the state of the art provides for rotating the inlet camshafts as a
function of engine speed in order to achieve optimum admission conditions in
all engine speed ranges. While up to the present each inlet camshaft has been
provided with an adjustment device of its own, in accordance with another
feature of the present invention only a single adjustment device is provided
for both inlet camshafts, preferably on the outlet camshaft, which is then
powered directly by the crankshaft as the only driven camshaft. Camshaft
adjustment devices generally have a drive element powered by the crankshaft and
a driven element rotatable relative to the latter. Consequently, the drive
element is connected to the outlet camshaft and the driven element to both
inlet camshafts, preferably by way of a chain gear, the driven element of the
adjusting device and the inlet camshafts having chain gears of the same
diameter. The diameter of these chain gears may be considerably smaller than
that of the drive gear seated on the outlet camshaft and drive-connected to the
crankshaft, as a result of which the overall width of the cylinder head, in
determination of which the diameter of the chain gears seated on the inlet
camshafts is decisive, is reduced. This is, of course, of particular
importance in installation of such an internal combustion engine in the engine
compartment of a motor vehicle........................"<p>Andrew Lee
00 S4 Silver/alcantara
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valium

LOL! And the "I beat a Lamborghini in my stock 1.8t!"