What is the difference between diesel pistons and normally aspriated petrol pistons?
Answers:
The biggest difference is the hardness and thickness of the material they are made from. Diesel piston are usually a harder and thicker material in order to be able to with stand the extreme heat and pressure in the combustion chamber. Also, diesel pistons are going to be bigger in diameter and in length noit only for strength but also to be able to creater enough pressure to fire each cylinder.
you tell me please?
A naturally aspirated engine receives its air source "naturally" like a detroit deisel. It has sloted sleeves that pull air from the air boxes each time the piston goes into the intake stroke.
An engine that is not naturally aspirated uses a "mechanical" source to provide it with air such as a turbo or blower forcing the air in through intake valves.
The different specification of piston is not the only difference between petrol and diesel engines.
Petrol engines create power by igniting vapourised fuel within the combustion chamber. This is done by a spark plug.
Diesel engines do not have spark plug: because diesel is much less flammable than petrol, diesel engines make power by compressing the vapourised fuel mixture to such a high pressure that enough heat builds up to ignite the mixture in the combustion chamber.
Because of the higher pressures involved in a diesel engine it has to be much stronger. Therefore all the components are made of stronger materials. For example; most modern petrol engines have a block (the big bit of metal which the pistons go up and down in) made from an alloy metal for low weight, but a comparative diesel engine will require a block made from iron, for strength. Likewise the pistons, valve gear, conrods etc, all have to be stronger to deal with the extra strain.
This is why diesel engines are heavier than their petrol cousins.
By outward appearance they look pretty much the same. Diesel pistons are under much higher pressures, so they are built of better stronger material, and are somewhat "thicker" castings- which of course makes them heavier! The big difference between the diesel and the gas engines is how the fuel is burned! Combustion on gas engine is done with an electeric spark,-- diesel is compressed so much that it has "spontaneous combustion", -- in other words it is compressed so much that it explodes! Whenever anything is compressed into a smaller space the by-product is heat, the smaller the space the greater the heat. Piston clearance (from head) on a gasoline engine may be as much as a half inch (very low compression engine), --but clearance on diesel engine is down to thousanths of an inch in some cases!
Becaue of the high pressures and stresses of diesel combustion, the rest of the engine is "beefed up" also! The pistons are heavier to prevent them from bending or breaking easily, the bearing surfaces are larger, and the crank is heavier material also. Even the block itself is heavier, and has heavier "webs" for the crankshaft bearings. The heads are always cast iron, always much heavier casting thickness etc.
So you can see that the diesel engine is a "whole different animal" !!
Im afraid some of the answers on here a slightly incorrect, a couple of them say that the diesel is compressed until it reaches combustion temperature, that is incorrect it is AIr only that is compressed at a much higher rate than the petrol engine where the fuel air mixture is compressed, the diesel or CI engine (compression ignition) compresses air to such a point that when the atomized fuel is injected the heat is such that it causes the fuel to ignite. A typical petrol engine will have a compression ratio if around 14:1 so in theory the air is been squeezed unitl its 14 times smaller, where as a diesel engine will have a compression ratio of anything up to and over in some cases of 23:1
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