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Re: cooling fan curious; the solution

To: "Jim Hill" <>
Subject: Re: cooling fan curious; the solution
From: Dave Massey <>
Date: Tue, 4 May 2004 08:35:25 -0400
Cc: i44CaTpq005884
Message text written by "Jim Hill"
>Hmmmm . . . does a rear-mounted fan do a better job of "sucking" air
>the radiator than the same fan "blowing" air when front-mounted?
>If someone has done actual testing to show that one method does a superior
>job of cooling the water flowing through a Triumph radiator at low speeds
>and high temperatures (which is when it's needed), I'd love to see the

All good questions.  To which I can only add more.  Such as: why are all
(or at least all the ones I've seen) have the electric fans mounted behind
the radiator?  Is it because the work better there?  Or is it just a
tradition held over from the old days of belt driven fans?  Or perhaps that
is to provide a bit of protection for the fans from objects that may damage
the fan?  It may be important to note that most (if not all) modern cars
have the fan spaced away from the radiator by an inch or more AND a shroud
that will direct air from the entire radiator through the fan.  Given that
we hobbiests are ill equipped to fabricate an effective shroud and we don't
have the space behind the radiator to implement  this and hence we must
mount the fan in intimate contact with the radiator does this "change

Perhaps as a racer you can shed some light on the question of heat
extraction at speed.  Since you typical are on full throttle when you are
not braking you are generating a maximum amount of heat on the track.  Have
there ever been any situations where the cooling systme could not keep up 
under these conditins yet cooled well enough at idle with the fan on?

>Until then: To extinguish a candle flame, would you blow air on it or suck
>air through it?

Interesting anology.  I suppose it is applicable if you were to consider
the consequences of leaks between the fan and the radiator.  In other
words, if the fan were spaced away from the radiator by say 1/4 inch so
that air either spilled out to the side in the case of a pusher or was
sucked in through the gap in the case of a puller, would the loss of air
flow through the radiator be worse in one case or the other?


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