The Effect Of Cold Air On The Radiator

[agfs]

A couple of weeks ago I had the misfortune, when traveling over a humpback railway bridge at about 30 mph, to hit a traffic cone that had been placed in the middle of the road, pointing towards me on the downward slope, by some idiot. There were no road works in the vicinity neither was there a wind. The cone was about 30 ft away when I saw it and cracked the front bumper and destroyed the lower air deflector opening up the whole area between the two fog lights to the weather.

Until that air deflector was replaced (yesterday), together with the front bumper, the car averaged only 28 mpg ! Now it’s back to 56.7 m.p.g. It just shows how the effect of cold air can directly affect the radiator and the performance of the car if that deflector is missing.

Might it not be a good idea if air deflectors were operated by a motor to open and close depending on, and being controlled by, the temperature of the ambient air ? Would that not improve the performance and avoid our having to avoid stuffing it up with pipe insulating foam ?

[timberwolf]

What do you mean by the air deflector? I am vaguely aware that there is a least one cover under the front of the engine bay, which would smooth the flow of air going underneath, without that I imagine it would be a real drag

[agfs]

What do you mean by the air deflector? I am vaguely aware that there is a least one cover under the front of the engine bay, which would smooth the flow of air going underneath, without that I imagine it would be a real drag

[agfs]

The air deflectors (dunno what else to call it... grid ?) lie immediately below the front number plate and between the two fog lights and consists of 5 angled 'deflectors'. If thse are removed, the bottom of the radiator becomes visible.

[timberwolf]

Oh, that's called the lower radiator grille.

[agfs]

OK, but its purpose is to deflect air away from the bottom third/half (whatever) of the radiator which is why I referred to them as 'air deflectors'.

[phil4]

My understanding is that the radiator has a control valve that negates some of the effect of cooler ambiant air, than say on a normal car. As such, while I'm sure the cold air does have an effect (more dense therefore more drag for a start), I suspect your huge drop in MPG was due more to hugely changed aerodynamics. I suspect the dislodged front work, probably caused lots of extra drag at the front, and that was likely more of a problem.

Just my 2p worth mind.

[agfs]

Thanks for your input, Phil4. I'm sure you have a point there. With no lower radiator grille the front would look like the mouth of a feeding hammerhead shark there would be quite a difference in the aerodynamic effect. What is surprising to me is the massive drop in the mpg figures.