Hi Guys,
I have been
thinking of writing a post based on multiple topics, but I have been largely
hit by the vast power cuts that have decreased the time I spend in front of
computer.
Recently I have
been discussing topics related to petrol (gasoline) and diesel engine with my
friends. So, I thought of sharing some common questions and answers that may
arise.
Please note that
this post is not for mechanical or automobile engineering guys. Still, you may
find some interesting info here.
1. What is the difference between a petrol and diesel
engine?
Basically Petrol
engines are spark ignition engines, whereas Diesel engines are Compression Ignition
engines.
Petrol engines
have carburetors to suck the fuel. The fuel is atomized (or vaporized) and is
mixed with air. The air helps the fuel to burn. The air fuel mixture is let
inside the cylinder, where it is burned by introducing a spark by means of
spark igniter or spark plug. Thus they get the name Spark Ignition or SI
engines.
Diesel engines don’t
have carburetors, instead they have fuel injectors. Fuel Injectors inject fuel
and supply it directly to the cylinder where burning occurs. Diesel Engines don’t
have spark plugs. The compression ratio of diesel engine is more and also the
auto ignition temperature of diesel is less than that of petrol. So, due to the
compression, high pressure and temperature is created which burns the fuel.
This is the principle of working of diesel engines and hence they have got the
name Compression Ignition or CI engines.
2. Why do motor bikes have petrol engines and not
diesel engines?
Some of the
older model bikes had diesel engines. Diesel engines are bulky in nature.
Carburetors are small, whereas fuel injectors are large and they have to be more
accurate for proper functioning. Moreover higher compression ratio means higher
vibration. Starting CI engines is quite difficult and particularly it’s hard
during cold weather. So, diesel engines are not used in bikes.
3. What happens when diesel is used in petrol engines
and vice versa?
Petrol has
higher auto ignition temperature and it won’t burn at the compression ratio of
a diesel engine without external help. So, the engine won’t run. Whereas when
you use diesel in petrol engine, it’s dangerous. Diesel burns with more power
and it may damage the engine partly or completely.
4. Why are diesel engine cars more expensive than
petrol engine cars? Which is better to buy?
The components
of diesel engine are expensive. As said earlier, they have to be manufactured
with higher accuracy. Diesel engines have more components compared to petrol engines.
This increases the total cost of the vehicle. The taxes imposed on diesel
engine cars are also high.
On a long run
and continuous usage diesel engine cars end up being cheap. This also depends
on a lot of factors like the initial price difference the cars, cost of the
fuel (currently petrol prices are increasing, but diesel prices are flat due to
the extensive usage), cost of maintenance (diesel engines have higher maintenance
costs), mileage, resale value and usage.
Also petrol
engine cars are smoother to drive. You may have experienced it earlier. Bikes
or petrol engine vehicles have lesser vibration whereas diesel engine vehicles such
as buses have more vibration. This is due to the higher compression ratio of
diesel engine. Hence the parts will be worn out soon too. With today’s
technology the vibration effects are decreasing day by day.
5. Why is petrol red in color, whereas diesel
yellowish in color?
Interestingly
both the fuels have nearly the same color, except that petrol is dyed red in
order to differentiate it from diesel. The color depends on countries, though
it is mostly red. In some countries like South Africa, green color is used for
unleaded petrol whereas red is used for leaded petrol.
That’s what I remember
right now. If you have questions related to this or any other suggestions,
please post in the comment section below.
Happy Reading!!!
