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| Some FAQs and Fundamentals of Automobile Engineering: Part - I | ||
| Home >> Infobank >> Know your vehicle >> Fundamentals of AE - Part I | ||
| We
are all aware that today’s Cars are a far cry from the good old Ambys
and Fiats of the ‘70s/’80s.
The following
‘Q n A’ spread over three ‘editions’ is an attempt
to bring about a greater technical awareness amongst Motorists as to what
makes their Cars tick. A1: It’s the ‘irreparable’ damage to the internal moving parts of an ICE, caused by overheating either due its Lube OR Cooling System failure.
A2: It’s a ‘Factor’ given by the Formula ‘ALF = 100,000/Max RPM x Compression Ratio’ of an ICE. Since it’s a ‘number’ only, it’s devised to ‘compare’ the Life and Reliability amongst comparable ICEs.
A3: Upto the beginning of the ‘Red Line’, an ICE can rev safely/repeatedly without any internal damage. If revved beyond/into the Red Zone, it stands to get damaged due to inadequate Lubrication/Cooling and therefore, Mechanical/Electrical Governors are provided to prevent such a mishap. Q4: Why ‘Multivalve’ Engines are more fuel-efficient than conventional ones? A4: Given the basic Bore/Stroke and Compression Ratio of an ICE, its Power Output is directly proportional to the ‘weight’ of Air/Oxygen that it can draw-in to burn the matching Fuel quantity and inversely to the effort it has to make to expel the Exhaust Gases. Multi-Valve engines therefore have better ‘Volumetric’ efficiency/Specific Power Output than one-in and one-out types. Q5: Why Automatic Transmissions are more thirsty for fuel than their Manual counterparts? A5:
An AT uses a ‘Fluid Coupling’ instead of the conventional
mechanical clutch, to eliminate the need for it’s external manipulation,
in order to make it fully ‘Automatic’. A Fluid Coupling basically
comprises a pair of Turbine-like ‘Rotors’, one of which is
coupled to the Engine which when ‘driven’ by it, develops
pressure in the surrounding ‘Fluid’. This in turn ‘tends’
to ‘drive’ the other ‘Follower’ Turbine Rotor,
which is coupled to the AT. Q6: What are Gear Ratios? A6:
Due to the inherent ‘Torque vs Rpm’ Characteristic of an ICE
i.e. with its Torque rising practically from nil to the max somewhere
midway in the rpm range, one needs ‘suitable gearing’ to ‘match’
the road speed of the Car to the Engine rpm, to enable the Torque required
by the Wheels match the one the engine can develop. A7:
The ‘Size/Power requirement’ of an Auto A/C System is dictated
by the Cabin volume/initial Temp (as high as 70*C for a Car parked in
the Sun) and the Rate of initial Cooling desired – amongst other
factors which are common to most A/C Systems. This results in an Average
Auto System to have a Rating of almost 1.5 Tons 0r 3 bhp when on! Q8: What is ‘Torque Steer’ and what are its disadvantages? A8:
This is a phenomenon peculiar to FWD Cars – the more powerful –the
worse ! What actually happens is : Content generated by S. K. Gupta. - 10/’02. |
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| | Part I | Part II | Part III | | ||
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