[xj-s] SPAL Fan redux

Hi Again Chris: I am sorry that I didn’t see that you were trying to save a
few bucks and you were looking for a good deal even if it might be a little
less in
quality than the SPAL fans. I have looked and looked through all, and I mean
all, the websites for both SPAL and Perma-Cool. I think that under the
circumstances your choice is exactly the right one. You are right about the
draw of the SPAL fan. It is healthy and indeed I saw it under certain load
conditions up to 18 amps. I am not an engineer but I do know that a more
powerful electric motor will have a larger draw (it is elemental.) However,
I don’t know what the conditions are that place the load on the fan. If I
were an engineer I would be able to tell you…I read about the curved fans
and the glass filling of the harder outside shell. I read how it was all
balanced. I read about the curved blades moving less air but they were
quiet. I did find some clues to the power of the elec. motor in the
description of the two fans. The Perma-cool fan has a CFM rating of 2,100
rpm to 2,950 rpm instead of the one rating of 2,700 rpm. That may be it. It
plays out in my circumstance. I never hear or see any variation in the rpm
of the fans.
I guess that I am also impressed at some of the cars that I have seen the
SPALs in, Ferraris, Mercedes-Benz, Diablos etc. and that is a thing I often
follow.
But…and I do mean But…your choice is exactly the right one because it
gives you the most bang for the buck…and that is a clever and appropriate
choice. So…Good Choice. When you do the mounting be very careful it does
look as though the mountings are not all that secure. But, again, I do agree
with the choice of the Perma-Cool manufacturer of not running a shroud. Air
flow, as you know, is the most important thing of all to help the radiator do
its best. When all the people think that adding a fourth tier into the
radiator is the way to go when all it is doing is blocking the air from
coming through the radiator. The newest radiators are, as in mine, two tiers
with internal tubes that are 1" in diameter. The newest ones going into the
NASCAR cars are a single tier. And that does it.
You know Chris, sometimes I forget what it was like when I was in my 20s
or 30s and every dime had someone’s name written on it. That was a time in
New York City when not only did I now have a car to drive I didn’t even have
the 50 cents I needed to ride the bus to work. I got my bike from my
family’s New Jersey home and rode it to work until its frame broke and then I
walked to and from my job at 12 am and home at 9 am.
So…forgive me for my insensitivity and the best of luck with your fans.
Bradley Smith

Hi.

Can somebody please explain why electric fans are so preferred to
mechanical belt-driven ones? I am not going to pretend that I know
anything about the efficiency losses in the systems of this type, but
are the losses incurred in a belt driven system really greater than those
of an electrical system? The alternator is still belt driven, and
there are losses incurred in generating the electricity, wiring and
the fan motors.

Thanks.

Gordan

Gordan Bobic wrote:

Can somebody please explain why electric fans are so preferred to
mechanical belt-driven ones?

Sure! You need to move enough air to cool the engine under all
conditions, including idle. With an electric fan, you install the
fan that moves enough air, and it runs at that speed all the time.
With a belt-driven fan, you install a fan that moves enough air when
the engine is idling at 750 rpm, and at 2500 rpm on the highway it’s
moving many times what you need, robbing power, wasting fuel, and
making noise. At 6500 rpm it’s moving many, many times what you
need, robbing lots of power, wasting gobs of fuel, screaming like a
banshee, and thinking about coming apart and putting big dents in
your hood.

Most manufacturers, including Jaguar, include a fan clutch to reduce
these effects, but they don’t reduce them anywhere near as much as
simply having an electric fan. And some people like to go the
OPPOSITE way and replace the fan clutch with a spool!

Add a couple of other benefits. The electric fan can be operated
after the engine is shut off if needed. The electric fan doesn’t
even need to come on until the engine has warmed up. Also, in the
specific case of the Jaguar XJ-S, installing an electric fan can be
the CHEAPER fix when the OEM belt-driven fan and clutch goes south.

I am not going to pretend that I know
anything about the efficiency losses in the systems of this type, but
are the losses incurred in a belt driven system really greater than
those of an electrical system?

By a bunch.

The alternator is still belt driven,
and there are losses incurred in generating the electricity, wiring
and the fan motors.

It’s not the efficiency that’s the problem; it’s the fact that the
belt-driven fan is providing so much MORE airflow than you need under
the vast majority of operating conditions. If you could magically
convince a belt-driven fan to run at a constant speed regardless of
engine RPM, it’d be the system of choice – but a fan clutch doesn’t
work well enough in this regard, often slowing the fan too much at
idle and not enough at speed.

– Kirbert

[Kirbert’s big explanation snipped…]

OK, I’m convinced. What is the best electric fan conversion kit that’s
available that will fit the V12 XJS (preferrably the XJ40 as well)?
Provided that it will keep the V12 sufficiently cool under just about all
conditions (idling in a traffic jam in 110F in the shade summer heat with
the air-con blasted all the way up), I’d like something that “just” “bolts
on”.

Speaking of which, the bonnet’s not on the car at the moment (yes, I will
post some pictures of the bonnet with the vents as soon as the car is
painted properly), so I’m tempted to replace the radiator as well (160K
miles, never been replaced or cleaned AFAIK). Hence two questions:

  1. What radiator should I be looking into acquiring? OE, or is there
    something better available from the aftermarket suppliers? Preferably
    available in UK…

  2. Are any decent cooling system filters available in UK? Is there a TEFBA
    reseller here that anyone knows of?

Cheers.

Gordan

I was going to post a lengthy response about why electric fans are better,
but then I saw Kirbys and there was no need. However one added point:
electric fans are also fun because you can combine them, as I would suggest
you do if you have ample clearance. What do I mean? Have an electric fan (or
pair of fans, even better) sitting behind the radiator which are “puller”
fans, and then have another one in front of the radiator as a “pusher” fan.
Puller fans are more efficient in terms of how much air they can transfer
through the radiator at a given speed (fan speed), however if you put the two
together that should keep your big V12 nice and happy.

I heard a tip that for a stock Jag radiator you can take the electric fans
off a late model Camaro and they fit pretty well, however if you feel you
should replace your radiator you might as well go for a package deal from an
aftermarket supplier who can give you a good set.

Good luck, and stay cool!

-Ted
-82 XJS – Radiator? Who needs a radiator without an engine?

Gordan

go for a Perma-Cool 18" high performance (reversible) fan, part no. 19117,
U.S. $ 103.95. It will fit the existing
fan shroud (XJ-S) by just drilling four holes into it. Available from
www.summitracing.com (and don’t forget
to order a wiring kit in case you are less inclined to do electrical
homework)
(I am indebted to Brynal H. for the suggestion of this particular model of
fan.)
Keep the OEM electric fan so that
you don’t have to fabricate a new fan shroud.
As for a radiator, Stephen Gibson has supplied me with an OEM radiator at a
very
good price that has already enthralled several list members, try Stephen
Gibson
at Info@supercatjaguarspares.freeserve.co.uk or
www.supercatjaguarspares.freeserve.co.uk

No affiliations et cetera …

Good luck.
Frank

Frank Gerber, Wetzikon, Switzerland
XJ-S V12 Le Mans 1988 special ed. no. 50

Gordan Bobic schrieb: > 1) What radiator should I be looking into acquiring? OE, or is there

something better available from the aftermarket suppliers? Preferably
available in UK…

  1. Are any decent cooling system filters available in UK? Is there a TEFBA
    reseller here that anyone knows of?

Cheers.

Gordan