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RE: S4
errr, i'm not sure you'd want a f1 power unit in your car. 9k rpm before
you have any torque is not usable. certainly not in real life. as to the
bore and stroke dimensions of f1 power units, there are *none* published for
the last few years. the only published specs of which i am aware are the
honda v12 ra122b/e in 1993. have the modern units anything in common with
this unit? those that know, certainly aren't telling.
and there is very very little in common between a porsche boxer motor and a
f1 mill, other than the fuel and air bit. i certainly would't put porsche
boxer engines on a performance pedestal. as i'm sure you know, bmw, ferrari
and honda have been getting higher specific n/a horsepower for years...
as far as usuable power is concerned and the hypothetical optimal
bore/stroke relationship, there's nothing wrong with the rs2 unit. 86mm
stroke and 9:1 static cr as well. 315 reliable hp from 2.2litres is fine by
me. it really has very little to do with the "textbook" bore and stroke
dimensions, and mostly about materials and manufacturing and the "q" word:
quality. look at the 5v audi v8 unit for another example. it's specific
hp/cc rating (74bhp/litre for the a8, 86bhp/litre for the s8) is very good
for a production engine . certainly much better than porsche have managed
with a production v8 - don't forget that porsche needed 5.4 litres of euro
32v 928gts to produce 345bhp, and that the s8 is also managing better per
litre than the new 3.6l 996 boxer motor. in fact the n/a a8 is comfortably
ahead of the 20v turbo ur-quattro in power to weight @180bhp/tonne vs
158bhp/tonne.
anyway, generally speaking a longer stroke will allow more torque. there is
increasing recognition that this is a very positive component in a good
engine. for example, i find it interesting that the bmw 4.4 v8, while
having a lower hp rating than the 4.2 audi unit, has a higher torque
rating...
actually to my mind, it is more about cost and efficiency. for example, the
audi 3.7 v8 has a bore/stroke of 84.5/82.4, while the 4.2 has a bore/stroke
of 84.5/93.0. why? clearly because both can be manufactured using the same
milling operations with the only difference to the crankshaft.
interestingly also the old i5, and the new 2.4 and 2.7 v6's and the 1.8 i4,
all have bores of 81.0mm. and the i5, the 2.8v6, the 1.8 and the 2.7 all
have strokes of 86.4mm.
so, i'm not sure what your point is. porsche a performance car company and
audi not? not sure that i follow you. here in nz, i can get a subaru wrx
sti to shade a new c4 dynamically, be faster and be $150k nzd cheaper as
well (source australian wheels magazine). i can get a better performing ttq
for less than the boxter. now, who is the performance car company?
dave
'95 rs2
'90 ur-q
-----Original Message-----
From: Michael Williams [mailto:urquattro@surfree.com]
Sent: Friday, 9 April 1999 14:19
To: Dave Eaton; quattro@coimbra.ans.net
Subject: RE: S4
Dave Eaton decided to speak these words:
>yes, but my point is that the (reputed) increase in stroke and cr will
>*increase* the low-down torque of the motor, which isn't too shabby in the
>1st place....
Oh, i know this. But while it may help initial torque, it limits the
potential of the engine to produce massive amounts of power without MAJOR
modifications.
Basically, i dont like the theory of small bore long stroke engines. It
puts alot of stress on the lower end, and limits redline and power
potentials...
For example, audi engines have what, 86mm strokes lets say, thats about 3
inches or so. An F1 or Porsche boxer engine has a stroke of maybe 1.5-2
inches...sometimes less...
that is the way to go...large bore, short stroke....interesting way for
audi to go...but i guess they really arent a performance car
company.....hmm
later...
Michael Sheridan Williams
ICQ# 11740998
1983 UrQuattro, MC--1.8 BAR, borla, 16x7.5 OZ Mito's w/ SP8000's, K&N
1985 4000S Quattro miles, Koni Yellows/Coilover (2B), strut brace, Sport
8000 Tires, K&N
http://members.aol.com/daserde2