Why do diesels accelerate so slowly even with high torque?

[Watwheels]

I thought torque is the turning force that pushes the car off the line? So with so much torque how come they're still slower?

 

1.Diesel engines, because they have much higher compression ratios (20:1 for a typical diesel vs. 8:1 for a typical gasoline engine), tend to be heavier than an equivalent gasoline engine.

2.Diesel engines also tend to be more expensive.

3.Diesel engines, because of the weight and compression ratio, tend to have lower maximum RPM ranges than gasoline engines (see Question 381 for details). This makes diesel engines high torque rather than high horsepower, and that tends to make diesel cars slow in terms of acceleration.

4.Diesel engines must be fuel injected, and in the past fuel injection was expensive and less reliable.

5.Diesel engines tend to produce more smoke and "smell funny."

6.Diesel engines are harder to start in cold weather, and if they contain glow plugs, diesel engines can require you to wait before starting the engine so the glow plugs can heat up.

7.Diesel engines are much noisier and tend to vibrate.

8.Diesel fuel is less readily available than gasoline.

 

http://auto.howstuffworks.com/question399.htm

Very U.S. and very out dated.

[Cerano]

I agree with this observation. I've seen a Mercs cab accelerate from stationary very very quickly. Dun play play.

 

ok la.

their 0-100 slow >7s not that power despite their super high torque

[Cerano]

You dont get what i mean.. nevermind.

 

think will just try one last attemp.

 

Assuming Rev at various rpm

rpm Torque Bhp Top Speed

1000 200 50 30km/hr

1200 200 55 35km/hr

2000 200 60 50km/hr

2500 200 80 80km.hr

3000 200 120 150km/hr.

 

something like that??

 

i geddit i geddit

 

but as mentioned, the all involving figure should be the 0-100 figure.

if u got 1000tqs but cant accelerate <5s for fark also no use

[Cerano]

E 220 CDI 2,148 cc (2.148 L; 131.1 cu in) I4 169 PS (124 kW; 167 hp) 400 N

Edited May 27, 2010 by Cerano

[Joseph22]

i geddit i geddit

 

but as mentioned, the all involving figure should be the 0-100 figure.

if u got 1000tqs but cant accelerate <5s for fark also no use

 

Yeah... you are right but if you are using it for heavy duty industries purpose then it might be of some use??

[Cerano]

Yeah... you are right but if you are using it for heavy duty industries purpose then it might be of some use??

 

yup heavy vehicles i can understand. but to lump diesel with any sort of performance for passenger vehicles doesnt really make sense

[Watwheels]

but diesels cannot rev much. their redline very low leh

LOL... diesel engines are not design to rev. Their characteristic are such that they deliver max torque at low revs. One of the characteristics is the diesel itself. It's less volatile dan petrol and less ready to combust, hence the high temperature and high compression ratio for the diesel to self ignite. eg. the air/fuel mixture of petrol is compressed to 1/10th of its original volume in the combustion chamber while diesel is compressed higher to 1/20th its original volume.

 

Diesel has more hydrocarbon molecules dan petrol that's also why it gives better mileage as it has more to burn. You dun rev a diesel engine, once you reach the max torque you quickly shift up gear. Thus gear ratios also plays a part. Those found in commercial vehicles the gear ratios are stacked closer and shorter for pulling power so that it does not feel out of breath when carrying heavy load.

[Cerano]

LOL... diesel engines are not design to rev. Their characteristic are such that they deliver max torque at low revs. One of the characteristics is the diesel itself. It's less volatile dan petrol and less ready to combust, hence the high temperature and high compression ratio for the diesel to self ignite. eg. the air/fuel mixture of petrol is compressed to 1/10th of its original volume in the combustion chamber while diesel is compressed higher to 1/20th its original volume.

 

Diesel has more hydrocarbon molecules dan petrol that's also why it gives better mileage as it has more to burn. You dun rev a diesel engine, once you reach the max torque you quickly shift up gear. Thus gear ratios also plays a part. Those found in commercial vehicles the gear ratios are stacked closer and shorter for pulling power so that it does not feel out of breath when carrying heavy load.

 

yup true but... some people like reviewers tend to associate turbo diesels and their great torque with high performance or even people who compare taxis.

 

there's torque but it still accelerates slowly

[Joseph22]

yup heavy vehicles i can understand. but to lump diesel with any sort of performance for passenger vehicles doesnt really make sense

 

but the Diesel engine now is very good wor and fast wor.... just look at some of they are coming out with. Easily less than 8 sec for Acc of 0~100km/hr

[Cerano]

but the Diesel engine now is very good wor and fast wor.... just look at some of they are coming out with. Easily less than 8 sec for Acc of 0~100km/hr

 

i think for displacement for displacement wise no FI diesel can out accelerate a FI petrol

[Joseph22]

i think for displacement for displacement wise no FI diesel can out accelerate a FI petrol

 

but it will out last the petrol one..

think for this we have to see the whole package.

[Happily1986]

I have seen some people say that only BHP matters for pick up. But actually both torque and BHP play a role in pickup. Before we start asking ourselves why generally diesel vehicles have poor acceleration, we need to be certain that we have a valid basis for comparison. Are the vehicles equivalent in unladen weight and gear ratios?

 

If you put in a 400BHP engine in a car weighing about 1000kg or so and put the same engine and mate it to the drivetrain in a bus weighing roughly 3~4 tonnes, the results will be very different. This is the reason why I think it is best to not quote absolute BHP and/or Torque figures but instead weight to BHP ratio and weight to torque ratio.

 

Torque refers to the twisting force that the engine exerts at the wheels in order to incite a turning momentum. Because the shafting motion produced by the engine is originally vertical wise and converted to a rotational motion by the crankshaft and flywheel (and transmitted by the transmission), the BHP and WHP quoted are different.

 

Anyway, Torque is important for the initial phase of pickup. What is acceleration?

 

Acceleration is how fast your speed increases i.e. the rate of change of velocity. What change are we going to discuss if the vehicle can

[Knighthunter]

Isuzu D-Max 3.0L ITEQ turbo diesel can out run honda civic 1.8 easily in Thailand. My top speed with this car is 175 kmh once it hit 180 kmh speed limter cut in.

[Cerano]

I have seen some people say that only BHP matters for pick up. But actually both torque and BHP play a role in pickup. Before we start asking ourselves why generally diesel vehicles have poor acceleration, we need to be certain that we have a valid basis for comparison. Are the vehicles equivalent in unladen weight and gear ratios?

 

If you put in a 400BHP engine in a car weighing about 1000kg or so and put the same engine and mate it to the drivetrain in a bus weighing roughly 3~4 tonnes, the results will be very different. This is the reason why I think it is best to not quote absolute BHP and/or Torque figures but instead weight to BHP ratio and weight to torque ratio.

 

Torque refers to the twisting force that the engine exerts at the wheels in order to incite a turning momentum. Because the shafting motion produced by the engine is originally vertical wise and converted to a rotational motion by the crankshaft and flywheel (and transmitted by the transmission), the BHP and WHP quoted are different.

 

Anyway, Torque is important for the initial phase of pickup. What is acceleration?

 

Acceleration is how fast your speed increases i.e. the rate of change of velocity. What change are we going to discuss if the vehicle can

[Cerano]

Isuzu D-Max 3.0L ITEQ turbo diesel can out run honda civic 1.8 easily in Thailand. My top speed with this car is 175 kmh once it hit 180 kmh speed limter cut in.

 

exactly mah. turbo diesel and somemore 3.0L bro

[Kelpie]

exactly mah. turbo diesel and somemore 3.0L bro

 

Any 3.0L can outrun a 1.8L car easily and you don't need a turbo . There is no replacement for displacement.

 

Regards,

[Cerano]

Any 3.0L can outrun a 1.8L car easily and you don't need a turbo . There is no replacement for displacement.

 

Regards,

 

i wonder if that 3.0L turbo diesel can outgun a 2.0T

[Kelpie]

7.Diesel engines are much noisier and tend to vibrate.

 

Yap, even new Benz cab also noisy from the outside. I wonder is it because of the design of what, generally diesel cars are noiser, if not, it is just a matter of time, IMHO.

 

Regards,