Question about diesel engines

TheChamp

TheChamp

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Why is it that most of the time the diesel engine is always smaller in capacity than the petrol models on the manufacturers line-up? e.g NP200 1.6 petrol, 1.5 diesel,Since the diesel produces less power why doesn't it becomes a bigger displacement or equal?

Second question: what is it about diesel and diesel engines that results in higher torque figures? does a diesel engine without a turbo produce high torque as well?
 
Q1: you would need a much larger Diesel engine (normally aspirated) to get the same output as a petrol engine. You would then need to worry about the additional weight of the bigger engine. The choice is torque over power, and therefore an engine with just enough power and more torque.

Q2: higher torque is a result of the higher compression in Diesel engines. The ignition in each cylinder creates a much larger force resulting in higher torque. A turbo increases both power and torque, but importantly allows for more torque at lower revs. The turbo pushes more air in the cylinder at lower speeds, and therefore ups the torque at low revs.
 
Diesel engine are more efficient than petrol. You used to get the same size as petrol ( I had a 2l diesel D4D corolla exclusive ) , got like 5.6l/100km, torque 330nm ( absolutely ate hills ) , power I think was round about 95kw or 105kw.

Engine

Engine Size 2.0 l
Charger Turbocharger
Torque Max Total 300 Nm
Engine Position / Location Front
Power Peak Revs 3600 r/min
Cylinder Layout Inline
Power Max 93 Kw
Torque Peak Revs 1800-2400 r/min
Transmission type Manual
Engine Capacity 1998 cc
Torque Max 300 Nm
Cylinders 4
Power Maximum Total 93 Kw
Click to expand...

Modern equivalent - 1.4d

Facts & Figures
Price: R307 500 (March 2017)
Engine: 1.4-litre 4-cylinder turbodiesel
Transmission: 6-speed manual
Power: 66 kW
Torque: 205 Nm
Fuel Consumption: 4.5 L/100 km (claimed)
Top speed: 180 kph
0-100 kph: 12.5 sec

Less power but still high torque for its size which gives it good fuel economy even with the "lower" power.

Compare a petrol, left is diesel, right petrol

Economy
Fuel consumption average (l/100km) 4.5 7.0
CO2 emissions average (g/km) 119 165
Performance
Power maximum (kW) 66 103
Power maximum total (kW) 66 103
Power peak revs (r/min) 3800 6400
Power to weight ratio (kW/ton) 51.6 81.1
Torque maximum (Nm) 205 173
Torque peak revs (r/min) 1800-2800 4000
Torque maximum total (Nm) 205 173
Torque to weight ratio (Nm/ton) 160.2 136.2
Acceleration 0-100 kmh (s) 12.5 9.8
Maximum top speed (km/h) 180 200
Engine Details
Engine position/ location front front
Engine capacity 1364 1798
Engine size 1.4 1.8
enginedetailshort 1.4TD 1.8
Engine + detail 1.4 turbo diesel 1.8
Cylinder layout inline inline
Cylinders 4 4
Cylinder layout + quantity i4 i4
Cam sohc dohc
Valves per cylinder 2 4
Valves quantity 8 16
Variable camvalve timing std
Turbocharger std
Warranties and Maintainance
Warranty time (years) 3 3
Warranty distance (km) (km) 100000 100000
Service plan std std
Service plan time (years) 5 5
Service plan time (distance) 90000 90000
Service interval (distance) 15000 15000
Information
Price date 2017-07-01 2017-07-01
Brand Toyota Toyota
Range Corolla Corolla
Model 1.4D-4D Prestige 1.8 Prestige
Range model Corolla 1.4D-4D Prestige Corolla 1.8 Prestige
Brand range model Toyota Corolla 1.4D-4D Prestige Toyota Corolla 1.8 Prestige
Status c c
 
Because power doesn’t really matter as isn’t even measurable.

It’s a calculation of torque.

So you build engines of similar torque specs and in doing so the diesel is smaller for the same which makes it more efficient.
 
Dont want to hijack this but i wanted to ask ed quick one?
2010 BMW which my friend has and his mechanic says his car smokes black when he pulls off hard...because it is a diesel?

I would think that is a bull**** reason, am i right ?
 
ichocolate said:
Dont want to hijack this but i wanted to ask ed quick one?
2010 BMW which my friend has and his mechanic says his car smokes black when he pulls off hard...because it is a diesel?

I would think that is a bull**** reason, am i right ?
Click to expand...
No. Most diesels smoke when you accelerate hard. It's normal. Some more than others though.
 
ichocolate said:
Dont want to hijack this but i wanted to ask ed quick one?
2010 BMW which my friend has and his mechanic says his car smokes black when he pulls off hard...because it is a diesel?

I would think that is a bull**** reason, am i right ?
Click to expand...
It's pretty normal to see black smoke on hard acceleration, it's an oil burner after all. Even more so if the DFP and CAT is removed.
 
It makes black smoke when running too rich.

Which is pretty normal if you are accelerating hard, it is essentially burning oil after all.

If it was making black smoke by default under all conditions it would be a concern.

If you are seeing blue smoke though, odds are something is buggered.
 
@op : apologies for hijacking your thread
I also have a question about Diesel engines

I have an 4 year old X3 2.0d. Under motorplan

Have always used 10ppm. Sometimes 50ppm when along the coast and cannot get 10ppm.

I am wondering what would happen if I had to use 500ppm
 
midnightcaller said:
@op : apologies for hijacking your thread
I also have a question about Diesel engines

I have an 4 year old X3 2.0d. Under motorplan

Have always used 10ppm. Sometimes 50ppm when along the coast and cannot get 10ppm.

I am wondering what would happen if I had to use 500ppm
Click to expand...

500ppm is too "dirty" for turbo charged diesel engines, might cause the injectors to clog up and fail after I while.

Rather just fill up with 10ppm or 50ppm.

I hope one day, we get 10ppm in CPT :(
 
midnightcaller said:
@op : apologies for hijacking your thread
I also have a question about Diesel engines

I have an 4 year old X3 2.0d. Under motorplan

Have always used 10ppm. Sometimes 50ppm when along the coast and cannot get 10ppm.

I am wondering what would happen if I had to use 500ppm
Click to expand...

The more questions, the better, interesting one you have. The mystery that around diesel engines is just too much for me, I only learnt a couple of years ago that diesels don't use spark plugs :o
 
midnightcaller said:
@op : apologies for hijacking your thread
I also have a question about Diesel engines

I have an 4 year old X3 2.0d. Under motorplan

Have always used 10ppm. Sometimes 50ppm when along the coast and cannot get 10ppm.

I am wondering what would happen if I had to use 500ppm
Click to expand...
More sulphur , which is apparently bad for the engine (and environment) . That's why diesel cars are a poor choice especially when planning to keep a car for long term (imo).
 
The_Traveller said:
More sulphur , which is apparently bad for the engine (and environment) . That's why diesel cars are a poor choice especially when planning to keep a car for long term (imo).
Click to expand...

Higher sulphur in the the higher ppm fuels causes the engine oil to break down faster afaik. Although the sulphur in the fuel does lubricate some components (fuel pump, etc). Using higher ppm you would ideally want to change the oil more often. Vehicles with DPF typically also don't like 500ppm.
 
Reason 1 Very high compression

The first reason is a much higher compression ratio. This is the ratio of the maximum and minimum volume in the cylinder of an engine. It’s made larger in a diesel engine due to a longer stroke, meaning the piston is moving up and down a larger internal volume of cylinder. Diesel engines never rev as high as petrol engines due to the fact that the piston has to travel further for its full rotation, while a petrol engine uses its shorter stroke to move the piston in quicker bursts, meaning the engine speed can be faster.
diesels have compressions of 20 over 1 and higher. Petrol cars have low compression ratio 12 or lower.

Reason 2
Diesel is much denser than petrol and can store up to 15 per cent more energy per given volume. This means that each time diesel is combusted, more energy is transferred through to pressure on the piston, increasing the amount of torque acting through the crankshaft.

Reason 3 Diesels can run very high turbo boost. this due to forged pistons, closed deck block that is normally cast iron.

Piston stroke. shorter means higher revolution more kw less torque. Diesel can ref high so the longer stroke makes more torque.
strong heavy pistons.

take a small hammer and try knock down a door. The hammer moves fast but have not enough weight to do to much damage.
Use a huge hammer it moves slower but has a lot of weight to break down a door.
 
qscwbt said:
Reason 1 Very high compression

The first reason is a much higher compression ratio. This is the ratio of the maximum and minimum volume in the cylinder of an engine. It’s made larger in a diesel engine due to a longer stroke, meaning the piston is moving up and down a larger internal volume of cylinder. Diesel engines never rev as high as petrol engines due to the fact that the piston has to travel further for its full rotation, while a petrol engine uses its shorter stroke to move the piston in quicker bursts, meaning the engine speed can be faster.
diesels have compressions of 20 over 1 and higher. Petrol cars have low compression ratio 12 or lower.

Reason 2
Diesel is much denser than petrol and can store up to 15 per cent more energy per given volume. This means that each time diesel is combusted, more energy is transferred through to pressure on the piston, increasing the amount of torque acting through the crankshaft.

Reason 3 Diesels can run very high turbo boost. this due to forged pistons, closed deck block that is normally cast iron.

Piston stroke. shorter means higher revolution more kw less torque. Diesel can ref high so the longer stroke makes more torque.
strong heavy pistons.

take a small hammer and try knock down a door. The hammer moves fast but have not enough weight to do to much damage.
Use a huge hammer it moves slower but has a lot of weight to break down a door.
Click to expand...

Very detailed, thanks.
 
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