In reply to a message from Jags+30jugs sent Thu 30 Nov 2006:
Sorry, don’t know your name, but your post partly supports my case
doesn’t it? In theoretical terms at least? If not, it wouldn’t be
the first time my supposed ‘logic’ has confused good people.
Sorry 
If you asked me for two markets - one European and one Rest of
World - where these cars would be most likely to be driven hard
as a matter of course, I’d cite Germany and certain Middle East
countries. I think that’s just a matter of record. If I were
planning cars for those markets I’d put high-speed endurance (and
full-flow cooling) higher up the agenda than for North America
where speeds are generally lower than even our crowded UK, and
sludging up is a real issue for city cars.
Of course there’s no such thing as a single fixed oil cooling set-
up that’s perfect for all possible conditions/climates. So
somewhere along the line you either make the system adaptable by
using an oil thermostat, or you choose full-flow or bypass which
will suit one set of usage circumstances better than another,
depending on the choices you make and build into the design. For my
money, on a high-end engine such as a V12, which was used in both
luxury sedans for city-slickers and a sporting car for enthusiasts,
Jag would have done well to use a thermostatic full-flow system so
the engine could work closer to the optimum in both settings, but
it seems instead they tailored this apsect of the car to suit
various markets, just as they did many other aspects. I assume that
suited most of the customers most of the time or Jag wouldn’t have
done it. Even if there were V12s which never got driven fast in
Germany, or others which were habitually pushed hard in the USA, I
(and Jag presumably) was looking at the general case.
All I was suggesting (no stronger) was that since oil temps are
highest (higher than water) when water temp is not usually a
problem (fast highway) and water temps are highest when oil temp is
lower (slow traffic) there is some logic in bypass and linking the
two via an oil/water intercooler (as in the E-type V12). I accept
that strictly-speaking this goes beyond the original full-flow/by-
pass question for an XJS oil/air cooler, but some of the logic
applies, and this is the V12 engine list not the XJS.
Not sure what ‘overheated’ oil means. I didn’t mention it and you
haven’t defined it, so we may have quite different views and
therefore be talking at cross-purposes?
As for no XJS running too cool, since I don’t have mine yet I can’t
really comment. But I can say that I know of several XJ-S cars
within a few miles of me (including a late 6.0L) which IMHO have
suffered from being babied and run too cool, on average, over short
trips. I may end up buying one of them and rectifying that :-).
This kind of city driving is in many ways a much harsher service
environment for a big engine than highway use, since as you know it
is easy for products of combustion to accumulate and damage the
engine. I suspect many V12s die prematurely from it.–
Peter Crespin 66 2+2 E-type, 74 Daimler 4.2
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
