From lynx.unm.edu!umn.edu!msc.edu!sgiblab!munnari.oz.au!uniwa!DIALix!metapro!bernie Tue Dec 28 10:34:22 PST 1993
Article: 24758 of rec.autos.vw
Newsgroups: rec.autos,rec.autos.vw,rec.autos.tech
Path: lynx.unm.edu!umn.edu!msc.edu!sgiblab!munnari.oz.au!uniwa!DIALix!metapro!bernie
From: bernie@metapro.DIALix.oz.au (Bernd Felsche)
Subject: Re: Audi V6 / VW VR6
Message-ID: 
Followup-To: rec.autos.tech
Organization: MetaPro Systems, Perth, Western Australia
References: <10463@blue.cis.pitt.edu>  <1993Dec22.183440.23157@engr.washington.edu>  
Date: Tue, 28 Dec 1993 04:23:44 GMT
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Xref: lynx.unm.edu rec.autos:131514 rec.autos.vw:24758 rec.autos.tech:69879

In  schneide@world.std.com (Eric G Schneider) writes:

>In article ,
>Kenneth M. Finnegan  wrote:
>>
>>I'm baffled as to why Audi and VW spent the money and time to develop
>>two different V6 motors of very similar displacement and HP.  I mean,
>>the Audi V6 is a different motor from the VW VR6, right?  But their
>>HP and torque ratings seem to be very similar.  Thoughts?
>>

>The Audi's torque curve is even flatter than that of VW's VR6, but the
>Audi V6 takes up quite a bit more room under the hood (too much for a Golf
>anyway).  However, I believe the decision to go with two seperately
>developed engines was also marketing related (Audi would have a tough time
>competing with BMW and Mercedes even in its home market with "only" a VW 
>engine).

One of the reasons was certainly that of the limited under-bonnet
space on a Golf. There's simply not enough space for an Audi V6.

The Audi V6 produces more torque because it has a dual-length inlet
manifold. The VW VR6 can be fitted with a different inlet manifold
which does just about the same thing - available from VW Motorsport.
Marketing accountants apparently kept the variable inlet manifold
from the standard production engine due to the higher cost.

Overall, the VR6 should be cheaper - it has only one head.

I posted the following article some months back:

>From bernie Sun Sep 26 21:06:10 1993
>Newsgroups: rec.autos,rec.autos.vw
>Subject: VR6 torque boost option
>Summary: VSR after-market option provides more mid-range torque
>Keywords: VR6, VSR, Motorsport, Golf, Passat, Corrado

I've had three requests so far since my first mention of the
VSR for VW VR6 engines, so I'm posting some more details.

The following information is from the May 1993 issue of
Gute Fahrt. It's a paraphrased translation (if you could
imagine such a thing :-)).

-------------

To produce an acceptable product, tuners must nowadays pay close
attention to what they are doing. Top-end performance is no longer the
only requirement. Potential clients are also seeking wider power bands
and high drivability standards. A synergy of utility and enjoyment of
driving. [Americans hear "Fahrvergnuegen."] Only those tuners who
achieve those goals are highly regarded.

Limited by the transverse mounting of the engine, there isn't much room
for generous inlet manifolding. In order to achieve a good compromise
between maximum power output, and adequate torque in day to day use, the
inlet manifold runs across the top of the head. This has circumvented
the shortage of space and allowed the use of an oscillating-flow tuned
inlet manifold. Each cylinder has its own inlet tract that is tuned to
such a length as to ensure positive inlet pressure. As engine output is
proportional to the airflow, this scheme means that the VR6 doesn't have
to be ashamed in the face of competitors. The 2.8 litre produces 174 PS
[ DIN hp] and a maximum torque of 240 Nm at 4200 RPM, and the 2.9 litre
engine in the Corrado achieves 245 Nm at the same engine speed. But this
achievement wasn't enough to satisfy the Wolfsburg developers. To
achieve even more torque, lower down in the rev range, the 6 cylinders
were to breathe even more freely. The idea of the variable inlet
manifold [ german "variables Saugrohr" ] was born and developed in
parallel with the now standard version, with assistance from the
Pierburg GmbH in Neuss, a company which has a high reputation with
things relating to mixture control. The VSR [ abbreviated from the
german ] system did not go into, falling victim to the red pens of
accountants shortly before the VR6 started production.  That this piece
of motor technology was not condemned to the depths of the Wolfsburg
catacombs, is thanks to the interests of Volkswagen Motorsport, based in
Hannover. This VW company took the VSR and now offers it as an after-
market conversion kit for 2888 Marks. The kit may be fitted to all VR6s
with 2.8 and 2.9 litre engines.

Even though the VSR achieves similar aims to those of the switching
inlet manifold of the 2.8 litre V6s from Audi, the operating principle
is different. In the Audi engine, a long, narrow inlet tract achieves
high torque at low revs; 245 Nm at 3000 RPM. The maximum power is
achieved using a short, wide inlet tract, producing 174 PS at 5500 RPM.
For the engine to be fed through the appropriate channels, depending on
engine speed, inlet manifolds are switched using six individual, vacuum
operated flaps at 4000 RPM. In both stages, the technology is based
purely on tuned oscillating-flow inlet manifolds, with the necessary
switching.

The VSR in contrast, two diverse technologies are applied. It is
designed so that at low engine speeds, resonance is used to improve
cylinder charging efficiency -- at higher RPM, oscillation- tuned,
individual, broad tracts are used. Switching from one to the other is
achived by a single flap, also vaccuum operated at 4000 RPM. The tuned
inlet tract operates by the low pressure caused between the throttle
valve and the inlet valve, by the suction of the descending piston,
Through inertia of the air in the tract, the airflow tends to keep
moving towards the inlet, even after it's closed, causing a slight
over-pressure when the inlet valve next opens. This ensures high charge
efficiency even during early stages of the induction stroke. Of course,
further during the same stroke, inlet pressure falls followed by a high
pressure but not before the inlet valve closes.

In order to achieve optimal control of the oscillation and reflection of
the column of air in the inlet tract, it needs to be closely coordinated
with valve timing, but this is not possible due to variation in engine
speed. Even at mid-range-rpm, the valve opening and the are out of
synch. The second pressure wave arrives much too early before the inlet
valve closes and a backflow reduces fill efficiency. Now to achieve high
torque under these conditions, resonance-fill is utilised. This is done
by closing the connection flap between a small resonance chamber which
is immediately before short inlet tracts above the inlet valves. This
transforms the 6 cylinder ending into effectively two 3 cylinder engines
with uniform firing times, and which do not have overlapping inlet
strokes. Resonance pulses of up to 0.4 bar [approx 6 psi] above
atmospheric are achieved, leading to remarkable fill efficiency and
torque increases.

Even though fitting the VSR requires not great skills, it should be
undertaken by a professional with the right tools. For example, fitting
the new EPROM and the new control harness requires dexterity and special
tools. The new chip doesn't alter the previously-programmed behaviour of
the engine management, it only adds an additional control output for the
electrically- controlled, vacuum operated flap. The kit includes
instructions as to complete installion, including connections to the
vaccum circuit and electrical connections.

[ photos of chip in engine maganement unit,
 VSR inlet manifold being fitted,
 and side-by-side VSR with original manifold. ]

Further engine modifications are not required, so one is permitted to
anticipate the VSR transformation. A marked improvement in torque at
mid-range is advertised with 255 Nm available at 3600 RPM on the 2.8
litre engine. This corresponds to an 11% increase at that engine speed.
In the 2.9 litre incarnation, 260 Nm is available, providing more
performance in the most-used rev range.  There is no promise of more
power in the higher RPM range.

To illustrate the performance improvement in a VSR Golf, one doesn't
need any test equipment! Almost right from the start, at below 3000 RPM,
a new urge is sensed. Up to 4000 RPM the engine provides markedly better
acceleration, yet above, the previously expected manners appear because
the torque curve corresponds to that of the standard engine. Even more!
After the impetuous acceleration, the switchover feels almost reserved.
The steeply increasing torque curve up to 3600 RPM also shows a rapid
fall back to the norm between 3600 and 4000 RPM. The torque improvement
is an excellent fit to the Golf VR6.

In fourth gear, the torque boost corresponds to 90 to 120 kmh, in fifth
to 110 to 150 kmh. This turns the Golf into a sprinter, that none of the
near-200 PS professionally tuned chariots comes near. Testign showed
that acceleration from 90 to 120 kmh in fourth gear only took 5.4
seconds. The standard VR6 Golf took 6.1 seconds and a near-200 PS
Oettinger VR6 Golf taking 6.4 seconds, and a Wendland special taking 6.2
seconds. No wonder because their maximum torque happens at much higher
RPM.

Unremarkably, the VSR trick didn't improve peak acceleration or top
speed, both of these being exclusively in the higher rev range.

The VR6 opens up a new field for Volkswagen Motorsport tuning.  This is
appropriate when one expects high torque for comfortable and sporty
driving. It's even more attractive because testing showed reduced fuel
consumption by half a litre [ per 100 km ].  On the other hand, the VSR
offers professional tuners an innovative platform for development - as
some of them have already indicated.

----------------
[End extract]

Even in the home market, VW is highly respected as an engine maker.
It's well understood that Audi and VW are synonymous as engines from
both marques appear in each other's marques, except for the V6 and V8

[ minor diversion follows ]

The "827" engine was developed shortly after Auto-Union (Audi) 
was sold to VW by Mercedes - so one would assume that many Mercedes
qualities were inherited.  It appeared first in the Audi 80 in 1972,
later the VW Passat, then the Scirocco and Golf. It grew an extra pot
to be fitted into the Audi 100 and got blown to be put in the Quattro.
Derivations of the same line are shared amongst the VW group, including
SEAT. The engine is so popular that there was a shortage of it early
this year, presumably because VW was retooling for a cross-flow head.

[ paraphrased from an article in March 26ths "auto motor und sport" ]

Due to production backlogs, VW has been putting 75 DIN hp (55kW) 1.6
litre engines in some Golfs instead of the 75 DIN hp (55kW) 1.8 litre.
Pretty much equal and not much of a story, some would say. I say, read
on.

The 1.6 litre features a cross-flow head design, based on the 111-series
engine design, originally (1974) for the Polo in 0.9 litre form with 40
DIN hp.  A larger capacity version of 1.3 litres powered the Golf II,
and more recently, a 1.4 litre variant is in the entry-level Golf III.
Almost everybody who bought an entry-level Golf III, opted for a larger
1.6 litre engine of the 827 series.

Many modifications have been made to the original 111 engine design,
including the direct-acting overhead cam and a conventional combustion
chamber design, instead of the hollow piston-top.  In capacity, it's
grown from being over-square at 900cc capacity and is now long-stroke
with a stroke of 87 mm and a bore of 76.5 mm to achieve 1.6 litres
capacity.

The 827-series originally powered the Audi 80 of 1972. The 827 has inlet
and exhaust on the same side of the head has been most popular with 1.8
litre capacity, giving good torque over a wide rev range.  There have
been few changes to the design of the engine, mainly isolated to
measures to increase capacity for more power.

Along with the 75 hp, the 827 offers 140 Nm of torque compared to the
111's 126 Nm.

On paper, it doesn't look that different, until one realizes that the
1.8 litre will pull away with 1500 rpm, whereas the 1.6 litre engine
requires 2000 rpm for the same "grunt".

Although the 1.6 litre loves to rev, and the Golfs which get the engine
have gearing to compensate, it means more gear changes for the same
motivation to be achieved, and one can be comparatively lazy with the
1.8 litre engined Golfs.

---------------

Have a pleasant new year.
-- 
+-----+ Bernd Felsche, MetaPro Systems Pty Ltd   ,,,     Phone: +61 9 362 9355
| | | | bernie@metapro.DIALix.oz.au             (o o)      Fax: +61 9 472 3337
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