What is a Diesel Like?

[**Ghost**]

Can anyone properly explain the workings of a diesel engine to everyone?

1. Torque + KW
I've noticed that on spec sheets diesel engines produce a bucketload of more torque than petrol engines. As far as I understand it, this is due to the way a diesel engine is built. Question is how do they drive?

Firstly, the KW rating is commonly lower than a similar capacity engine, however the torque rating is usually almost double or more the petrol engine. How does this equate out when driven for performance?

Say for example a 1.6L engine that makes 100KW and 160NM at 6000RPM ...

How would this compare with a 1.6 diesel that only makes say 70KW but like 220NM at 3000RPM?

I ask in terms of straightline performance and downgearing response

2. Modifications - Bolt Ons

Petrol Engines, of the naturally aspirated variety, usually carry modifications of intake, exhaust, headers (at least around here)...

is this the same for diesel engines with comparable gains?

3. Driving a Diesel

With Petrol engines, the general idea for NA is to rev it out... but for diesels peak torque arrives pretty much a little bit from idle... so when do u shift for diesel??

i hope that this thread will be useful for all

[tRipitaka]

diesel engines are mainly found in big, heavy vehicles, and for them to start moving, they need high torque..
they don't need high KW as they won't need to be exceeding speeds of 120kmh..

but as for petrol cars, they are no way near as heavy, so they don't need as much torque to get them going.. and KWs.. well if u ever need to go to 180, then i guess it's there :)

[**Ghost**]

I'm more referring to the new diesel engines that are being introduced in small cars... in particular accords and civics

[Felix]

Diesels generally dont rev anywhere near as high as petrol engines. Their redline is usually around 5000RPM. I've driven many diesels, the highest reving one i think was redline at 5500RPM.

[DomenEK]

some modern diesels are pretty well suited to performance motoring, especially in Europe, where the diesel powered car is king. You only have to look at the some of the diesels offered by Mercedes-Benz and BMW. For instance, the tri-turbo SLK (Yes there is a diesel powered SLK - and its quick!) supposedly does the 0-100 dash in a little over 5 seconds. This, along with a diesel powered SL (or SLR - I can't remember) were reviewed in a recent Motor/Wheels magazine.

I've never driven a performance oriented diesel myself, but it's probably safe to assume that they'd have the gearing action down pat. As for when to change gears, I assume it'd be akin to changing gears in a big V8.

[sivic]

most diesels are sluggish but damn good for towing.
the new types of diesels being found in many of the smaller euro cars are aimed towards economy and performance. they are pretty much all turbocharged.
also, they are pretty damn quick. we havent seen the quicker ones make it to our shores but in europe some of the hot hatches have diesels as their top performer and for good reason. good spread of torque with these engines.
prob is, the aim towards economy is wasted to some extent here in oz. while you will have a very eco friendly car it still wont save you heaps because of the ridiculous diesel prices we have. diesel is damn cheap compare to petrol in most other countries.
our govt is just fooked and has put huge taxes on it

[**Ghost**]

wot about modding diesels then\?>

[DomenEK]

Just bolt on a few more turbos, should be sweet!!!! :D

[sivic]

you can mod them.
there is a small scene in japan which even mods turbo diesel 4WD's.
its pretty funny seeing a Landcruiser and Patrol pulling low 14's

[jackosimm]

Most of them come with turbo's stock anyway! However with no intention of increasing power to frightening proportions

[Boost]

the huge diff. in torque and HP is due to the way the engine is designed. A normal high rev. engine has a shorter stroke and lower compression which lets the engine rev. at higher rpm but produce small torque. However a diesel engine has a longer stroke which makes high compression but the engine revs are low but inturn produces more torque. The higher the torque the more force you have available to lug a heavy mass this is the reason why big trucks are diesel rather than gasoline. Plus diesel engines are more fuel efficient than gasoline.
Also dielsel engines dont require spark plugs like convention gasoline engine because of the longer stroke which producces high compression which will produce higher air temperature inside the cylinder. The temp. inside the cylinder is hot enough to ignite the direct inject diesel fuel. Plus diesel engine requires less electronics. thus allowing it to be partially submerged, this is the reason why diesel turbo 4WD (ones with the snorkel) are capable of going through water streams etc. without failing like normal gasoline engines.
Hope this helps.

[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..

[sivic]

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]

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]

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]

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]

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!):
http://www.jegs.com/photos/151superbtwin.jpg
Plus you have other standard diesel performance upgrades like exhausts, proane injection, chips, and even nitrous.

[muli]

Im in love with the new Audi A6 3.0DT, these things are absolutely beautiful. Looked up on the net and i found a few already modified in europe.