What is a Diesel Like?

**sivic** · 16-08-2005 01:06 AM

Originally Posted by wlee2

umm hey gary i might suggest reading up how stuff works and ask about diesel engine..

for 1 all Diesel engines come with TURBO!! yes they need it..

2 diesel engines instead of mixing fuel air then compressing the fuel and air mixture
they compress the fuel first (to insane compression i might add) then use compressed air (yes from the turbo) to ignite the fuel
3 diesel engines have no sparkplugs

the main thing about diesel is that the fuel is compressed before air is mixed in so you sometimes see compression ratings of 18:1
but then again all fuels will never ignite without an and O2 source or air..

ummm a few wrong things there.
1. not all diesels are turbo. the turbo is just there to give it some more pep but are not essential. in fact the 2 diesels i helped do oil changes on today werent turbo
2. they compress the fuel with the air (like any engine). it just happens compression is a hell of a lot higher.
you cant compress just fuel. in fact you cant compress any liquid. its a scientific fact.
the huge compression ratio basically causes it to detonate. its not the air from the turbo otherwise how would the non turbo diesel engines work?

**bennjamin** · 16-08-2005 11:09 AM

Originally Posted by sivic

the huge compression ratio basically causes it to detonate. its not the air from the turbo otherwise how would the non turbo diesel engines work?

afaik its the heat from the huge compression that ignites the usually hard-to-ignite diesel liquid (mixed ofcourse with oil)

Diesel motors are coming along in the world tho - problem is they require iron blocks or more heavy duty ones to take the internal workings. Hence , a diesel block usually weighs considerably more than the same layout on a petrol engine.

**aaronng** · 16-08-2005 11:15 AM

Diesels are different from petrol engine because of a few reasons:

Petrol engines pull in the air-fuel mixture, compress it and then use a spark to ignite. Direct injection petrol engines are similar, just that they inject directly into the cylinder instead of the intake.

Diesels on the other hand pull in air only, compress it til it is very hot (means it requires a high compression ratio) and then spray in the diesel fuel which self-ignites.

The reason why diesels have so much torque is because of the compression ratio. If you want to compare, just take a petrol and diesel engine of same capacity. Divide the petrol's torque with its compression ratio and then multiply with the diesel's compression ratio. The value you get will be very close to the torque of the diesel engine! (actual value is slightly lower, maybe 10%)

The reason why the diesels cannot rev as high as a petrol is because of:
1) It takes time for the injected diesel fuel to spread through the cylinder and self-ignite.
2) Because of the high compression ratios, a diesel engine's internal components are heavier to withstand the stresses. Hence it can't rev as quickly.

**crxzzR** · 16-08-2005 07:21 PM

diesel engines use glow plugs.. =)
they glow to start the combustion process.. after the engine has started the glowplugs are turned off..
the rest of the combustion process occurs by compressing the air [which in turn generates heat] to a point where the diesel fuel ignites...

my 2 cents..

**PhatSol** · 17-08-2005 12:30 PM

Diesel engines are more fuel efficent because they do not have a throttle body, and thus they don't have any vacuum in the intake manifold. Alot of power is wasted on petrol engines creating the manifold vacuum, especially under light load conditions and idle where the vacuum is highest.

Diesel engines can also take rediculous amounts of boost! Have a look at this truck twin turbo kit (notice the turbos are connected in series!):

Plus you have other standard diesel performance upgrades like exhausts, proane injection, chips, and even nitrous.