Interview with CV Raman, Sr. Executive Director, Engineering, Maruti Suzuki India Ltd.
Raman san answers 23 critical question for car owners. Questions are varied: what happens if your brakes fail, what happens if you fill a wrong fuel in your car by mistake, what happens if... Questions asked by Roy P. Tharyan, Editor, Motown India magazine. www.motownindia.com
A1)When we are developing a car, we set the tyre pressure
keeping in mind ride comfort, handling performance, fuel efficiency, safety and
NVH (Noise, Vibration & Harshness).
As to how the tyre will perform during an emergency is also kept in
mind. The tyre pressure recommendation as given by the OEM is very important to
follow as far as the customer is concerned. It will give you optimised
performance. Driving with low pressure tyres will compromise ride comfort,
handling and responsiveness of the car. The vehicle will be sluggish to drive.
The vehicle will also deliver a lower fuel efficiency.
Q 2) You drive a car on a long
stretch with the right air pressure. Theoretically, the tyres heat up and the
air pressure inside increases. WHAT
A2) There will be absolutely no issue because the tyres will
heat up a bit but it will get stabilised as it will get cooled simultaneously
because of the wind. I don’t think there
should be a concern here if the ambient temperature is high and the tyre
pressure is right.
Q3) You drive your car with the tyre
pressure more than the prescribed limit. WHAT
A3) There will be an
impact in terms of ride comfort; it will become bumpier and bouncier. The ride
will also be a lot harsher. Of course, the handling will improve because the
tyre pressure has increased. Sometimes, two separate tyre pressures are given
by the manufacturers, depending whether a full load is sitting. The pressures
need to be adjusted. Those are things
which are very important for a comfortable journey. It is a way of doing the
tuning of the tyres and the suspension for giving this comfort feel to the
Q4) While driving one of the car
tyres gets punctured and gets deflated. You insist on driving on. WHAT HAPPENS?
A4) The tyre will get cut and you will hear a lot of noises
as it is flattened. In case of front tyre deflation, the driver will be able to
immediately make out from the responsiveness of the steering wheel. And if one continues driving for some period
of time, the tyres get cut.
Q5) Can this situation get
A5) Yes, in the sense, the control sometimes can become
difficult, especially if you are driving at high speeds. If the tyres blow out
when you are driving, you do realise the instability in the vehicle. But at
medium speeds, one can continue and not feel the difference because of various
reasons, for example if the music inside is loud or especially if on rear
Q6) During dune bashing in SUVs, the
tyre pressure is lowered. WHY DO THEY DO
THIS? WHAT HAPPENS when you do not lower the tyre pressure while dune
A6) Since sand is very soft, with the specified tyre
pressure, the tyres will start digging into the sand. In order to reduce that,
they lower the tyres pressure. It allows you to get the traction on a softer
surface. That makes it easier for the vehicle to move around.
Q7) In a petrol car you fill in
diesel fuel by mistake, and vice versa. WHAT
A7) We do make sure that we put a sticker on the fuel cap,
whether it is diesel or petrol. And today in accessories also, we have a full
decal which says petrol or diesel which can be put right on top of the fuel lid
so that they are very careful. But sometimes there is a mistake by the customer
or the guy filling the fuel.
In case diesel is put in petrol car, it will not atomise
like petrol resulting in insufficient combustion of fuel,excessive soot
generation or misfire, which may lead to engine damage. Conversely, in case
petrol is put in diesel engine, the air fuel mixture will not burn as there are
no spark plugs and hence will not start. It will operate till the diesel fuel
in line is over. Also lubrication of some key parts like High Pressure fuel
pump will not happen with Gasoline fuel resulting in permanent damage.
Q8) The coolant / engine oil in your
car leaks completely while you are driving. WHAT HAPPENS?
A8) If coolant leaks, it may not show up if there is no
coolant in Engine (sensor may be measuring air temperature in the coolant
jacket). Customers should be careful, if there is an accident or coolant
leakage is observed under the vehicle.
However, if coolant temperature increases for any reason, it will show
up on the instrument cluster. If that happens, one needs to take it to the
service centre. In case you miss reading the temperature warning it will lead
to some kind of stress which can lead to the engine seizing. If there is a loss
of lubricant (engine oil) or loss of coolant, the engine could seize. If the engine oil is lower than low level, it
could lead to the engine seizure.
Q9) Can water be substituted for
coolant in an emergency situation?
A9) That does work. But the heat removal will be lesser. It
can’t be used for long. It could lead to some kind of a seizure of the engine
if one continues with it for long. The boiling point will be lower since this
is a presurrised system. Heat removal will become an issue. It does have an
impact on the thermal efficiency. Using water is also not recommended as it
could lead to scaling inside engine causing heat up and slow damage to the engine.
Q10) There is no brake oil and you
keep driving. WHAT HAPPENS?
A10) Usually, there is a secondary circuit which is there
and even if there is leak on one circuit, we will still be able to stop the
vehicle. It should not get impacted. But if both the circuits are completely
drained, which is a very unusual situation, and I do not think it will ever
happen, at slow speeds you can always stop with the hand brake. If one circuit
leaks, then there is a tertiary circuit which will allow the brakes to function. That’s how the system works.
Q11) While changing a flat tyre
onefits the jack in a wrong place under the vehicle body. WHAT HAPPENS?
A11) It’s not a right thing to do, because jacking points
are usually specified by the manufacturers in the owner’s manual. It can lead
to an imbalance in your jack. The lift up may not happen to the extent where
you want the tyre to come out. People should read the owner’s manual and
understand that there are jacking point for the front and the rear. And if this
is not done properly, it can imbalance the vehicle and this may not be safe. It
could also damage the underbody.
Q12) The driver yanks out the car
key while driving his vehicle. WHAT
A12) If you do that, the engine will stop. The first impact
is on the braking system because the vacuum will get lost.Steering also will
get hard. It is not a very sane thing to do. It is dangerous.
Q13) In a push button start / stop
car, you press the button while driving.
A13) In the case of push button, if there is an emergency he
has to continuously press for two seconds or Press the button three times in
order to stop the vehicle. Otherwise it will not respond when the vehicle is
Q14) You are driving at a good speed
and suddenly someone pulls the hand brake. WHAT
A14). The rear wheels are braked and front wheels are at the
same speed which causes imbalance and the vehicle can spin.
Q15) You are driving around with
your hand brake lever pulled up partially and it is not completely disengaged. WHAT HAPPENS?
A15) If the hand brakes are engaged, it reflects on the
instrument cluster. The light for parking brake will come up. If this is still
ignored and people keepdriving, you will feel a bit of sluggishness and it will
of course impact the friction material of the brake lining. The material will
get eroded. This will also cause excessive fuel consumption as you are putting
more load on engine.
Q16) You are driving normally and
you suddenly try to slot the reverse gear. WHAT
A16)In a 5 speed gear transmission, normally the reverse is
just below the fifth gear. Any deliberate attempt to move to reverse gear from
5th gear is prevented by the mechanical inhibitor system in the
transmission.Sometimes such an inhibition is provided in Gear shift lever
(usually in 6 speed transmissions) where you have to lift the knob up and push
into reverse gear. But if you forcefully try to move from a third or fourth
gear to reverse, there will be a loud clashing noise and sudden load increase
feeling on the gear knob due to high inertia of reverse gear. You will
definitely realize there is something wrong.
Q17) In an automatic transmission
car, one tries moving from Drive mode “D”to
Reverse “R”while driving. WHAT
A17) Automatic transmissions are electronically controlled.
While deliberately trying to shift it to “R”, it will not engage in reverse
gear, even if the Gear Lever is in R position, till the car comes down to a
threshold speed. This speed of reverse gear engagement is normally less than 10kmph.
Q18) You are driving a manual car
with the clutch pedal half depressed. WHAT
A18) Clutch riding used to be a common issue in the past.
But nowadays most customers understand that they do not have to ride the
clutch. . Clutch life is severely compromised if the car is continuously driven
with half depressed clutch pedal. The customer will also feel loss of power and
Q19) It is a warm day and you are in
a stationery car with the engine running. You put on the AC and take a nap. WHAT HAPPENS?
A19) It is not recommended. There should be some level of
air circulation. The internal air (cabin air) in re-circulating mode can get
contaminated and this can lead to suffocation because of lack of oxygen. If at
all one does it, they need to lower the windows a little bit so that some fresh
air keeps coming in. Or you can put it in fresh mode for fresh air to come in
but then the cooling gets impacted. I will not recommend running your ac for a
long period in a stationery car with your engine running and your windows
rolled up. It has its impact, one definitely from the health perspective,
second from the fuel efficiency point.
Q20) Your AC is on and your engine
is running. You car is in a closed garage. WHAT
A20) The situation will be worse. I will definitely not
recommend it because it is a closed space. The exhaust is on, the pollutants
are getting circulated with the fresh air and that’s worse. This is not at all
Q21) You are driving your car fitted
with air bags, without a seat belt. You meet with a frontal accident and your
air bags are deployed. WHAT HAPPENS?
A21) Wearing seat belts help you to reduce injuries during
accidents by as much as 55 to 60 per cent. Airbags help you by another 5 to 10
per cent. Without wearing a seat belt, the air bag alone will not help you
reduce the severity of the crash. The seat belt is the primary safety mechanism
which restrains the occupants. The secondary
system is the air bag which helps in reducing the injury to the
occupant. If you are not wearing a seat belt, the impact is going to be very
high if the airbag gets deployed.
Similarly, where vehicle manufacturers are concerned, we
give seat belts for all five seats in a 5-seater. Generally it is noticed that
only people in front wear the seat belts, while at the rear nobody does. I
would recommend that everybody should wear a seat belt. If the person in the
rear is not wearing a seat belt, he can be thrown in front in the case of an
accident. And if the person in front is also not wearing a seat belt, the
situation can be really worse. It is generally seen that not wearing a seat
belt results in large number of fatalities in road accidents. That can be
really prevented if one were to wear seat belts. Of course, the more important
thing is driving safely and below recommended speed limits.
Q22) Ankit Bhardwaj: You fit bigger sized tyres in your car, bigger that
what is recommended. WHAT HAPPENS?
A22) By fitting bigger sized tyres, you tend to change the
offset of the knuckle or where it is fitted. The large / wide tyre will also
interfere with the wheel housing. So, when you are turning the vehicle, you
will not get the full turn and it will intrude into the wheel housing or clash
or rub with the wheel housing.
Q23) Lastly, when you have larger
and smarter looking tyres, will it be able to clear the requirements for wheel
balancing and wheel alignment?
A23) No, it won’t because the offset is there. When you are
putting a larger tyre, what they do is at the knuckle side they will put an
additional offset, usually a steel component, to put the tyre out. Most of the
times you will get to see these large tyres sticking out of the body. That is
because, one, when it is turning you need to create some space in the wheel
housing. Two, the kinematics of this is obviously not the desired kinematics,
it is different and definitely there will be some issues with that in terms of
durability. Fitting larger tyres to your vehicle is more of a fad and it should