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Interesting Reading regarding 2.9 vs. 2.8 VR6 from C list
Ken Weidmann Jr
GLXTASY@Juno.com
Checkered Flag Automotive Components
95 Black Jetta GLX M3 wannabe
85 Show Scirocco
--------- Begin forwarded message ----------
From: lleff@imisys.com
To: glxtasy@juno.com, jdw8@po.CWRU.Edu
Subject: Interesting Reading
Date: Mon, 12 Oct 1998 10:29:22 -0400
Message-ID: <8525669B.004F6144.00@smtpmail.imisys.com>
Hmmmm... Some of this post (from the C list) is rather interesting.
Especially when you consider that I'm now getting 183hp (wheel) from my
2.9l. Also, it seems as though our 15% driveline loss estimate is pretty
dead-on.
Read on, Bruthas -
Date: Fri, 9 Oct 1998 10:47:53 -0400
From: Vincent Shek <vincent@algorithmics.com>
Subject: [VR6] 2.8l vs 2.9l
I found an interesting post on the vw newsgroup from an engine builder
in England:
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(beginning of original message)
>Subject: Re: VR6 2.8 VS 2.9?
>From: racerbob911@my-dejanews.com
>Date: 02/10/98 19:43 BST
> "dave.leahy" <dave.leahy@mci2000.com> wrote:
> Does anyone know the difference between 2.8 and 2.9? As many specifics
as
> possible please. TIA, Dave
>
> AAA engine - 174 bhp (europe) 81.0 mm bore - 90.3 stroke 2792 cc
> 10.0:1 CR
>
> ABV engine - 190 bhp (europe) 82.0 mm bore - 90.3 stroke 2861 cc
> 10.0:1 CR bigger throttle plate - revised ECU programming.
Some
of
> the horsepower difference is due to a different exhaust system
on
> the synchro.
In my experience and those of colleagues with dynos there is very little
difference in power between the two engines. 2.8s show perhaps high 160s
bhp
and 2.9s show low to mid 170s. At the driving wheels perhaps 140 bhp
from the
2.8 and 145 bhp for the 2.9 with 25-28 bhp transmission losses.
The engines were rated at 174PS (172bhp) 2.8 and 192PS (189 bhp) for the
2.9.
Common sense alone would indicate that 70cc increase in capacity does
not make
an extra 17 bhp when the engines are otherwise identical internally.
That would
be a power gain of 240 bhp per litre of extra capacity.
If anyone has accurate dyno data to either confirm or refute the above I
would
be interested. Preferably engine dyno data unless you have some
particular reason to believe that your wheel dyno is dead accurate.
As an aside the V6 is a horrible engine from the design point of view
with insufficient valve area, poor low rpm torque and weird port design.
Very
hard to get any decent power per litre out of it without spending a
fortune.
Both the 8 valve and 16 valve have always suffered from similar
breathing restrictions. They both have less valve area per litre of
capacity than
nearly all other modern engines and pathetic port design. If any of you
VW
enthusiasts want to see a properly designed engine have a look at the 16
valve
Peugot M16 engine. 160 bhp from 1.9 litres in standard trim back in the
late 1980s.
34.6mm inlet valves compared to 32mm for the VW. Even better is the new
2.0
litre iron block engine in the Citreon Xsara.
275 bhp is possible in road tune with modified head, cams and 4
butterfly throttle body system. Try getting that from a VW.
It's about time VW designed some proper engines with a bigger
bore/stroke ratio and more valve area. Other manufacturers seem to
squeeze larger bore
engines into front wheel drive without problems.
My favourite big capacity engine: the Opel Monza 6 pot 3 litre. 95mm
bore, 69.8mm stroke, 37mm inlet valves. Easily stretched to 4 litres and
300
bhp plus in road trim. Bullet proof bottom end, revs like a banshee, goes
like stink. Bring back rear wheel drive.
Dave Baker at Puma Race Engines (London - England) - specialist flow
development and engine work.
(end of original message)
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>From another of his post:
I'm considering designing and having made a batch of big inlet valves
for the VR6 at 41mm or perhaps 42mm. It depends on what size works best
on the
flowbench in the end. If anyone is interested post on here and if demand
is high enough I'll do it. Most of the valves I see around are not
designed
right for flow or are of poor material quality or inaccurate dimensional
tolerances.
By the way - on the VR6 - I'll put the before and after power figures
too. The customer has already had the car dynoed independently at 145 bhp
wheel
figure (170 flywheel). This is the 2.9 engine and from my (and others)
experience the claimed 192 PS is rubbish. The engines are basically
identical apart
from 70cc capacity and theres no way that makes 20 bhp difference. I
would rate
the 2.8 engine at 165 to 170 bhp and the 2.9 at 170 to 175 bhp.
Transmission losses are about 25 bhp. If anyone has other data I would
be most
interested.
Dave Baker at Puma Race Engines (London - England) - specialist flow
development and engine work.
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Interesting huh?
--------- End forwarded message ----------
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