As the summer
months approach, the advertising scene is full of claims and counterclaims
of how much better at cooling a product is. Never to be left behind, car
manufacturers woo the car buying public with the comfort their car offers
in the heat of the Indian summer.
But there is no sure-shot way of knowing which of their claims is true and
to what extent. People are often fooled by high blower speeds and the seemingly
tremendous cooling prowess of the air conditioning system with low ambient
temperatures. But have you ever left the car parked under the midday sun
for a couple of hours in a place like Delhi or Jaipur and then driven around
all day without the air-con system seeming to make no difference to the
sweat pouring down your back? Wasn't this the air conditioning system that
chilled you in a couple of minutes at the dealership and made you feel as
if you were in a deep freeze just three months back when you were buying
the car?
There is no easy way to judge which one of them has the best air conditioning
system. We at OVERDRIVE spent months consulting various air conditioning
experts including the biggest names in the business to arrive at the best
way of finding out which is the car that cools the best, has the fastest
rate of cooling, cools evenly throughout the car and at the same time makes
the least amount of noise.
We worked out a detailed test procedure and did the test during the period
when summer was at its hottest in Pune. During the days when we tested the
cars we made sure that the ambient temperatures were over 40 degrees Celsius.
Luckily for us Pune has had one of the hottest summers in this first year
of the new millennium; and we were able to complete our testing within the
15-day period we had earmarked for it with testing being called off only
on a very few days because of the ambient temperature being less than the
stipulated one. We tested only between 1200hrs and 1500hrs on sunny days
and on a circular city course that was 20km long and drove at speeds so
that it took us between half an hour and thirty-five minutes from start
to finish.
 Each
of the vehicles was parked in the sun with all doors and windows closed
and the test was started only when the temperature reached 60 degree Centigrade
or 90 minutes had elapsed, whichever was earlier. In most cases the cars
got up to 60 degrees before the 90 minutes elapsed. Each car was kitted
out with eight quick response thermocouples monitoring the temperature both
at the air-con vent grilles, at the centre and at the sides and also at
the back if there were vents at the back (if there is need) and also at
various places inside the cabin so as to get the comfort levels of each
of the passengers. Then data from these eight points was monitored and recorded
every minute for the duration of the 30min drive with a complement of four
passengers in every car. Each air-con was kept at the full cold mode and
the air flow set to recirculation with the blower speed at maximum and the
air vents pointing straight in front. All the cars were driven by one person
on the same route at similar times of the day to avoid a difference in driving
styles affecting the performance of the air-con.
We made it a point to avoid black (except in the case of the Opel Corsa
Royale which was available in black only) or white or silver cars and chose
pastel shades wherever possible. All the cars we used for the air-con mega
test were relatively new and had clocked similar number of kilometres. We
also made it a point not to include cars with sun film or tints unless they
were part of standard equipment. Though we were advised to test the performance
of the air-cons for efficiency on the highway too, we felt that the city
test was adequate to find out what we wanted to know as well as being most
suited to the requirements of our readers.
Along with temperatures from eight points in the car we also checked the
noise levels in the car with the air-con switched on and the blowers turned
to maximum with engine at idling speed. This noise level mainly reflects
the noise of the blower since most of the outside noise is filtered out.
And though the cabin insulation lets in some engine noise it is mainly the
noise from the blowers that our ratings reflect. Apart from the final rankings
which are based on average cabin temperatures during the last five minutes
of the test weighted for the speed of cooling during the first ten minutes
of the test, we also rated each car on the basis of the speed at which it
brings the temperature down from unbearable levels to bearable ones (Cooling
Speed), the average temperature inside the cabin during the last 20 minutes
of the test (Cabin Temperature), the average grille temperatures during
the last five minutes of the test (Grille Temp) as well as on how good the
circulation inside the car is (Circulation). Circulation has been derived
by monitoring the difference between the grille temperatures and the temperatures
for the front passengers and for those at the rear.
The results of the air-con mega test have been tabulated segment-wise with
a comment on each car. While the tested vehicles have been put into either
the small car segment, the mid-size segment and the multi-utility vehicle
segment, the Mercedes-Benz cars are in a league of their own and do not
stand up to segmentation. In the S-class for example, we put all the fan-speed
on full (no 6) and the temperature setting to low and then tested the car.
I am sure though that the system would have been much more effective had
we just left it on auto mode.
The other interesting observation is the compromise between the noise levels
and circulation. With blowers and vents upfront, the better the circulation
has to be, the higher the rpms they have to work at and the louder the noise.
The problem is circumvented slightly by having vents for the rear passengers.
The best solution is to have more blowers, preferably for each of the occupants
which can then operate at optimum noise levels while maintaining good circulation.
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June 2001