| Preface
In Part-VII of this 'series', I shared with you my thoughts and experience
about the problems one can run into while operating and maintaining one's
Car - as the true 'ownership experience' of any make/model begins and
ends here. With such info at the back of one's mind, let me share with
you some more ..
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1) Erratic Brakes
This is a
problem that arises frequently, especially in cars more than 3-yrs old.
The reasons for such malfunctions can be many. However, the first step
one should undertake is a 'hydraulic' overhaul of the system - by way
of draining out all the old brake fluid and replenishing it with pure/new
and well-branded one of the recommended grade (‘DOT-3 or 4’
as the case may be) - followed by thorough 'bleeding' of all the 4-road
wheel cylinders.
Nowadays,
some advanced A/S/S’s have ‘automatic’ machines for
the purpose and the entire exercise takes just about ½ an hr. In
fact, most OEM’s recommend this procedure once every 2-yrs regardless
of the mileage done and for good reason. However, if this too doesn’t
help, then it's likely that your Brakes' Master Cylinder and/or some of
your Wheel Cylinder ‘Assemblies’ may have to be replaced.
Beware that only ‘re-kitting’ is NOT recommended, as it’s
only a short-term solution.
If this procedure of hydraulic o/h is done as a preventive maintenance
every 2-yrs or so - regardless of the mileage done – one can easily
expect over 75 kkm of trouble free brake hydraulics but unfortunately,
it’s one of the most neglected areas in our scenario.
2) Speed vs 'mileage'
It may be interesting to know that a 1000 cc/Mpfi petrol car today can
easily do 21 kpl @ 60-70 kph and 18+ @ 100 kph. This will drop to ~ 15
kpl if cruising @ 120 kph in its V-Gear.
While one may wonder why should this happen when at higher speeds one
stands to cover the same distance in a shorter time, in reality it’s
not so. For it's a well known fact that wind resistance goes up with speed
in a complex manner - starting with square of it and going up exponentially
to the power of 4 - depending on its magnitude.
In other words, say at a cruising speed of 50 kph, 40% of the engine power
may go towards over coming the rolling resistance and the remaining 60%
to overcome the wind resistance. Assume it's 5 and 7.5 respectively i.e.
total = 12.5 Bhp.
Further assuming that the rolling resistance remains more or less constant
beyond 50 kph, at 100 kph the engine will have to produce 5 + (7.5 x 4)
= 35 Bhp. So as far as the engine is concerned, for 2x the speed, it's
having to produce 3x the power.
Therefore, in terms of 'Specific Fuel Consumption' which is defined as
'grams per Bhp per hr' - that's how the engine sees it - its FC stands
to go up by 3x but then, at 2x the speed, it also has to run for half
the time to cover the same distance or effectively, the FC stands to go
up by 1.5x to cover the same distance. In other words, if it was doing
say 25 kpl @ 50 kph, at 100 kph it stands to do ~ 17 kpl.
And mind you, the 'SFC' that we just talked about above also varies with
the absolute Bhp demanded from the engine coz an ICE's 'fuel efficiency'
drops above and below its peak torque rpm.
Further, since an ICE's max rpm AND Bhp is limited, say typically 60 bhp
for a 1000 cc/Mpfi, it follows that at 100 kph, it's got only 60 - 35
= 25 Bhp left to propel it any faster and going by the above relationship,
this will get used up by another 40 kph or so - leading to its top speed
'capability' of ~ 140 kph.
To sum-up, to get the best 'Fuel Efficiency' (as opposed to absolute Fuel
Consumption/kpl) out of your Car, cruise in its V-Gear as close to its
peak torque rpm as practicable.
3) Choosing the right Spark Plugs
For the Spark Plugs, the most important criteria for their selection is
their ‘Mounting’ thread configuration and ‘Reach’,
followed by 'Heat Value' - typified by their 'type refs/codes' of individual
manufacturers. Most manufacturers have tables of their equivalent codes
of other competing brands but such tables are hard to come by - even with
their so-called 'authorised dealers'. An OEM designs its engine to run
at its best on SP’s of a particular ‘heat-value’ and
if that is altered, then either the plugs may run too ‘cold’/leading
to loss of power/faster fouling or too ‘hot’ – leading
to engine knock – even when other parameters such a thread sizes/reach
etc are ok.
The next important criterion for the SPs is the material and 'configuration'
of their 'electrodes'. Towards the former, Platinum/Copper-Alloy ones
are much longer lasting but at a prorata higher cost. MICO has a suitable
range of such imported ones and one can choose out of them accordingly.
Coming now to their electrode ‘configuration’, i.e. single
or multiple, it's a misconception that the latter, even of the same 'heat-value',
will offer a better performance on a Car that has OE-SP’s as single
electrode types.
This is
for the simple reason that unless such multi-electrode ones have the required
'Spark Energy' available from the OE Ignition System of the Car, they'll
be of little use - such as on the MUL range of present Cars which are
all designed for single gap SP’s only. Infact if each gap is set
to the OE specified one for Single Gap types, they may even malfunction
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