On a chrome bumper I'd say none at all as the number plate (on UK cars at
least) is below the apron while the radiator is above it. On rubber bumpers
(going by my V8) its tempting to think that the number plate is obstructing
the scoops in my front spoiler, and the oil cooler and lower 'half' of the
radiator are both below the apron and use the air from the scoops for
cooling. My V8 came with a 'stick-on' number plate inside the scoops which
is technically illegal as it is neither flat nor vertical. When it got too
tatty I replaced it with the pukka item and noticed precious little
difference. It makes no difference at all at a standstill as the fans pass
all the air above the apron, and it is at idle where cooling is least
effective. At normal road speeds i.e. 30 and above there is more than
enough air going through the scoops even with the correct number plate. It
is only at certain speeds below that where the fans will probably be on a
bit longer and more often than if there were no number plate in the way.
But if I didn't need to fit a front number plate I wouldn't.
Because of problems with cooling in hot ambients when idling I fitted a 30%
uprated radiator, but the difference it made was marginal. The 30% relates
to the number of tubes, not the cooling capacity, and when adding tubes the
law of diminishing returns comes rapidly into play. The biggest improvement
to idling cooling was to go through the electrical circuit checking and
cleaning all the connections, supplying 12v directly from the alternator to
the fan relay, and providing local grounds for each fan.
One change I made yesterday was to fit a supporting bar under the
fibre-board shroud between the scoops and the bottom part of the radiator.
Left to its own devices the shroud was arched whereas the scoops and
radiator are rectangular of course. Not only did some of the air from the
scoops 'escape' past the sides of the shroud, a bigger problem is that a
significant amount of air that *did* get into the shroud was free to escape
underneath the radiator. By fitting a brace under the shroud it now
conforms to both the scoop openings and the radiator shape.
Another aspect of rubber bumper cars (at least those with V8 layout) poorer
cooling at idle is the oil cooler being under the shroud it only has air
passing through it when under way, whereas chrome bumper cars will have some
pulled through it by the fan. Oil cooling makes a huge difference on the
V8.
PaulH.
----- Original Message -----
> How much air deflection, if any, do you think the front license plate
> creates that would impede cooling?
|