CrazyEngineers Archive
Old, but evergreen and popular discussions on CrazyEngineers, presented to you in read-only mode.
@ABCD ABCD • 13 Sep, 2012 • 1 like
Why HMV/Trucks only use diesel? Why not Petrol?
Also, why is it more cheaper than Petrol, even though it gives more mileage?
How is CNG different from Petrol and Diesel?
@Amith Gupta • 14 Sep, 2012 because, unlike a commuter vehicle, a truck or HMV is for long distance transportation of goods. And in the long run ..Diesel,which is cheaper than pertol would give the owner an advantage over a similar petrol vehicle !
@Amith Gupta • 14 Sep, 2012 • 1 like CNG occours above crude oil in oil fields and has quite a good calorific value. CNG is compressed natural gas . U should also get some confusion between a CNG and LPG in some cases. CNG is much safer as it would reach the skies incase of accident cuz its lighter than air. Whereas, in a LPG , you would possible be a sittin duck cuz its heavier than air and gives much probability of explosion.
@ABCD ABCD • 14 Sep, 2012 well, what i meant was why diesel is cheaper, and why it gives more mileage.
@white_hat • 14 Sep, 2012 • 8 likes Actually diesel is not cheaper than petrol.It is because of subsidy given here in India.
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Diesel engines are used in HMVs because they have got more torque output.And diesel engines are low speed engines, they run at a much lower rpm than petrol engines.This helps in reducing wear of engine cylinders.Diesel engines are designed to run for months without stopping.Also diesel engines are much more relaible than petrol engines,it does not have spark plugs and ignition circuits, these electrical circuits are vulnerable in moist weather.
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In some countries where diesel price is much higher than that of petrol , heavy duty petrol engines are used in HMVs.
@zaveri • 15 Sep, 2012 white_hat

you have said it.

diesel is preferred because of technical priorities. cost comes later.
@mechky • 17 Sep, 2012 In heavy vehicles, greater traction force is required. Torque of engine is the deciding factor for a vehicle's traction and diesel engines give better torque than petrol engines.
@Anoop Kumar • 20 Sep, 2012
white_hat
Diesel engines are used in HMVs because they have got more torque output.And diesel engines are low speed engines, they run at a much lower rpm than petrol engines.This helps in reducing wear of engine cylinders.Diesel engines are designed to run for months without stopping.Also diesel engines are much more relaible than petrol engines,it does not have spark plugs and ignition circuits, these electrical circuits are vulnerable in moist weather.
.
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In some countries where diesel price is much higher than that of petrol , heavy duty petrol engines are used in HMVs.
+1

One more reason is trucks uses two stroke engine to get more power-to-weight ratio. and two stroke engine are better suited for low grade fuel than 4 stroke engine.
below picture of petroleum refinery you can see that Diesel is 2 grade below than petrol.

[​IMG]
@ABCD ABCD • 29 Sep, 2012 how or why does diesel produce more torque?
why do they have less tax on diesel, though all domestic vehicles are now using diesel? i dont think the speeds of diesel engines are less, as i see they do go in 100kmph+.

ianoop, i think the government has made it compulsory to all vehicles to be 4 stroke engines. i think only old vehicles are of 2 stroke.

no one said about mileage too
@white_hat • 30 Sep, 2012 • 1 like Diesel engines have a higher torque because they have a high compression ratio.
By speed we refer to engine rpm, not the on road speed.
@ABCD ABCD • 01 Oct, 2012
white_hat
Diesel engines have a higher torque because they have a high compression ratio.
By speed we refer to engine rpm, not the on road speed.
But, how can an highly compressed fuel release more power/have high torque?
Speed is proportional to rpm. So, what i said too stands. Right?
@gopi gulivindala • 07 Oct, 2012 1.They burn less fuel than a petrol engine performing the same work
2. Gasoline engines are typically 30 percent efficient while diesel engines can convert over 45 percent of the fuel energy into mechanical energy
@gopi gulivindala • 08 Oct, 2012 3. The absence of coils, spark plug wires, etc.
4.The life of a diesel engine is generally about twice as long as that of a petrol engine[
5. Diesel fuel has better lubrication properties than petrol as well.
6.Diesel fuel is considered safer than petrol in many applications
@Vaisakh Vijayakumar • 13 Jul, 2016 One more reason....If we try to use petrol in bigger-sized engines, it might lead to too much of knocking (because of their pre-ignition).
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