The Technical Truth? :Petrol vs Diesel

[tsk1979]

Originally Posted by jat

(somebody with specialising in this branch, please help). Governors are required where seperate precise speed control is required and where speed is affected by many external factors (e.g. generators, petroleum pipeline pumps etc). In fact, fitting a gorvernor on a car engine can make it sluggish (it doesn't matter if it is a petrol or diesel)

About ECUs, the cost of ECU is same whether for petrol or diesel. It mostly depends on what type of processor is being used, what functions it controls(just engine management or other stuff also eg in BMW)
OEM cost of ECU for sub 10L cars is around Rs. 2000-8000 for the manufacturer. This cost includes software too.

[hrman]

I think the premium for diesel cars is more to do with the perceived Fuel Savings between petrol and diesel over a long term. To that extent the premium is justified.
I wanted to post this question to T-BHPians.
1. Lets say the cost of one liter of petrol and diesel is the same. Would you still pay the premium on diesel engine cars? Or would you opt for the petrol vesion?

2. The price of Petrol and diesel per litre is the same, and the cost of the car is also the same. Then what would be the choice?

For all those who would still choose diesel, the driveability and pleasure of driving takes over. Enthusiasts would enjoy the low end torque of the diesel engines, the low murmur , and the turbo which jack-rabbits you from 0-100. This is where the Skoda Rider Diesel, the Swift VDi, Verna diesel and the Getz D would score over their petrol siblings.. Your views please..

[Sankar]

To answer your Q no 1 I'd say I'll go for the Petrol car.

To answer your Q no 2 I'd say I'll go for the Diesel car provided it's a modern CRDi/Pump Deuse diesel.

[Thad E Ginathom]

Diesel is more expensive in UK. It carries more tax. Given the lower consumption, cost of fuel overall is still lower. Diesels tend to be bought only by very high-mileage drivers

[groom]

Originally Posted by jat

I would like to clarify few points here:

1. The query raised was for cars available in India and I don't thing Gasoline direct injection cars are commonly available in India. If the Gasoline DI cars are made available, the cost difference won't be much. But still the fuel injection system manufactering cost for diesels would be higher.

2. 200 bar injection pressures for diesels was long time back in 20s and 30s. Therefore, the gasoline engine makers do not have to carry out heavy research on building new technology for fuel equipments. They carry research on modifying the system. On the contrary, diesel engine maker are still struggling for finding not only the cheaper materials to withstand such pressures, but also the processes to reliably make such equipments. Hence gasoline fuel system cost will be less.

3. The fuel injection control (timing) is more delicate in diesels as there is no spark plugs. But the these system, although a bit complex doese not add so much to the manufactering costs.

4. The thermal efficiency of diesel engines are much higher than gasoline engines. (highest eff achieved has been around 55% for commercial engines)

5. (OT) HP water jet (about 4000 bar) is being used to cut steel and other materials in manufactering processes (special cases) although it is not common due to high cost involved.

6. Regarding governor, please elaborate.
The cars already have ECU for precise fuel management system and I don't think the cost of software can make so much difference in petrol and diesel cars cost (somebody with specialising in this branch, please help). Governors are required where seperate precise speed control is required and where speed is affected by many external factors (e.g. generators, petroleum pipeline pumps etc). In fact, fitting a gorvernor on a car engine can make it sluggish (it doesn't matter if it is a petrol or diesel)

for your point no 2:
--Inline fuel injection pumps - max 550bar Pump pressure and max 650bar injection pressure
--Radial Distributor pumps - max 700bar pump pressure, max 900bar injector pressure (Electronic Distributor & Part electronic pumps will not have any change in pressures)
-- Common rail 1200bar to 2400bar (depending on which generation and application) (Multi Cylinder pumps)
-- Unit Injector System (Skoda and VW) - 1200 to 1800bar again depending on generation
lastly ---
--- Single cylinder pumps with common rail system ( 1200bar and upwards) Typical low cost solution ...

GDI systems involve HELL of development work than Diesel and Gasoline system..

Point No 3:the so called timing - is delicate in both gasoline and Diesel.. but the system in Diesel is more sophisticated and need to be extremely robust and at the same time sensitive...example - Multi Jet Common Rail.. (involves two pre injection and two post injection with Main injection completely shape able

And last pojnt.. for point 5: Irrespective of Electronic Diesel or Mechanical Diesel Fuel injection, the Governor is a must, in traditional system the governor controls the Idle, Part loads and Full throttle limits... and in advanced systems the same is done using ECU..
Governor is a MUST for diesel engines ...

[subbarao]

Hi,

Below news is about to price hike in diesel & diesel private vehicle price to go up with already higher price.

19 Dec, 2007,
Source Centre may discourage diesel-run private vehicles- Automobiles-Auto-News By Industry-News-The Economic Times




NEW DELHI: The Centre is contemplating measures to discourage diesel-run private vehicles. The steps under consideration include a higher tax on diesel cars, a ban on its use in specified cities or a gradual removal of the price difference between petrol and diesel. The proposal may give a major boost to Delhi chief minister Shiela Dik****’s recent drive against private diesel vehicles.

“We are working in this direction. Most mega cities are choking due to vehicular pollution. Discouraging diesel vehicles, higher tax on personal transport, stricter emission norms, including implementation of Euro-IV standards in all cities, and a price parity between petrol and diesel are some of the measures we intend to take in the due course,” said an official in the urban development ministry.

Concerns have been voiced over increasing air pollution in cities in the 11th Plan document and it has suggested measures to check vehicular emissions. “States not conforming to the directives would be penalised by stopping funds under the Jawaharlal Nehru National Urban Renewal Mission (JNNURM),” a Yojana Bhawan official said.

The broad strategy to reduce vehicular pollution includes uniform fuel quality and emission standards across the country, removal of fuel price distortions, high charges for parking and a higher tax on personal transport, he said. The proposal will become a national policy on Wednesday after the National Development Council (NDC) gives its nod to the 11th Plan.

“The government has received representations from NGOs in this regard and we are examining them,” said an official in the urban development ministry. The Centre for Science & Environment (CSE) has asked the government to remove the price incentive for diesel cars. “A flawed fuel tax policy that keeps diesel taxes nearly 40% lower than petrol is inciting dieselisation. Equalise fuel taxes and prices,” CSE demanded. It cited examples of several countries, where steps are taken to discourage diesel vehicles. In Brazil, for instance, cars are not allowed to run on diesel because of lower taxes on the fuel. In Denmark, diesel cars are taxed heavily to offset the lower price of the fuel.

CSE advised the government to levy higher taxes on diesel and cars to prevent the use of cheap and poor-quality diesel, and persuade people to consider cleaner alternatives.

[BUSA]

1. Lets say the cost of one liter of petrol and diesel is the same. Would you still pay the premium on diesel engine cars? Or would you opt for the petrol vesion? Its not the cost of fuel its the fact the diesel cars have better driveability.

2. The price of Petrol and diesel per litre is the same, and the cost of the car is also the same. Then what would be the choice? Diesel, diesel, diesel....... and so on and so forth.

[hrman]

Originally Posted by BUSA

1. Lets say the cost of one liter of petrol and diesel is the same. Would you still pay the premium on diesel engine cars? Or would you opt for the petrol vesion? Its not the cost of fuel its the fact the diesel cars have better driveability.

2. The price of Petrol and diesel per litre is the same, and the cost of the car is also the same. Then what would be the choice? Diesel, diesel, diesel....... and so on and so forth.

Hmm interesting.. I do miss my diesel Indica's low end torque, no need to touch the accelerator when shifting from neutral to 1st gear, and easy manageability on upward slopes, lower cost when I tell the fuel pump attendant, "fill 'er up"!
Im still coming to terms with this in my Petrol-City, still not mastered..

[reignofchaos]

Originally Posted by BUSA

1. Lets say the cost of one liter of petrol and diesel is the same. Would you still pay the premium on diesel engine cars? Or would you opt for the petrol vesion? Its not the cost of fuel its the fact the diesel cars have better driveability.

2. The price of Petrol and diesel per litre is the same, and the cost of the car is also the same. Then what would be the choice? Diesel, diesel, diesel....... and so on and so forth.

I'm curious on what basis do you choose diesel if the fuel costs are the same. I would not even look at diesels then.

First of all its the racket that diesels make compared to the refinement of a petrol. The NVH of diesels though having improved of late is still no way close to petrols.

Secondly the way modern CRDi engines deliver power is kinda ridiculous. The power band is really narrow, typically between 2000 and 4000 rpm. At any engine speeds below that, the car refuses to move. Its as if the engine says... hey I'm sleeping, don't pester me . Agreed there's a huge torque wave when in the power band but inside city driving is painful. Its the same with verna, optra, VW Passat, Swift D and every other diesel i've driven. The only notable exception is the octy.

[jat]

groom:

I think you have got me wrong. I am not denying the complexity and development costs eplaination as mentioned by you. There are developments on artificial intelligence of engines but they are not commercially available yet.

What I tried best to explain the query raised by magma. I belief that he has asked about the C-class cars commonly available in India. And to compare, we have to have some common base line. For example we can not compare the development cost of iDSI engine of NHC with first generation Indigo diesel (Indigo diesel was just copied from Indica with small refinements and development cost was negligible while iDSI engine was developed from scratch with entirely different marketing theory) Again if we compare between diesels, the cost of development of Fiesta DuraTorq is more expensive than the initial Accent CRDi. I have tried to explain with a common people market in India and not with tried to explain advancement in technoligy.

Busa:
I will go for diesel if they keep on producing engines as Hyundai guys have set the trend.
Though, depending on the market demand, the petrol guys will change the design of their engine to match the diesels any day. You can see the performance of NHC. Low power, but the peak torque is occuring at lower rpm compared to their older engines and hence offers good drivability and fuel economy.

[ananthkamath]

To summarize: The future is going to be diesel. Or at least it should be.

[dvswift]

Originally Posted by tsk1979

About ECUs, the cost of ECU is same whether for petrol or diesel. It mostly depends on what type of processor is being used, what functions it controls(just engine management or other stuff also eg in BMW)
OEM cost of ECU for sub 10L cars is around Rs. 2000-8000 for the manufacturer. This cost includes software too.

I agree. Normally, the ECU cost is negligible as compared to the overall system cost - for instance, in a CRD system, the cost of the HP pump, injectors and rail account for almost 80-85% of the cost. The software in a low-cost market like India, is almost free of cost. Almost no OEM in india, pay development charges at actuals. They pay a fixed development charge worked out along with the quote package.

[kpzen]

Originally Posted by BUSA

1. Lets say the cost of one liter of petrol and diesel is the same. Would you still pay the premium on diesel engine cars? Or would you opt for the petrol vesion? Its not the cost of fuel its the fact the diesel cars have better driveability.

2. The price of Petrol and diesel per litre is the same, and the cost of the car is also the same. Then what would be the choice? Diesel, diesel, diesel....... and so on and so forth.

In that case i would always opt for a super smooth petrol engine.
BUSA Please think beyond TORQUE also...

[rippergeo]

Originally Posted by reignofchaos

First of all its the racket that diesels make compared to the refinement of a petrol. The NVH of diesels though having improved of late is still no way close to petrols.

Secondly the way modern CRDi engines deliver power is kinda ridiculous. The power band is really narrow, typically between 2000 and 4000 rpm. At any engine speeds below that, the car refuses to move. Its as if the engine says... hey I'm sleeping, don't pester me . Agreed there's a huge torque wave when in the power band but inside city driving is painful. Its the same with verna, optra, VW Passat, Swift D and every other diesel i've driven. The only notable exception is the octy.

I've been driving the DDiS and the verna CRDi and I find that they are better in the city compared to the swift petrol, the zen petrol, the 800 petrol(all of which I've driven and are all known to be exceptionally good city cars)

for example, in the swift ddis, in the city, most of my driving is between 1000rpm(idle) and 2000rpm(turbo still hasnt spooled up) and the car is responsive, I've no problems shutting the doors on any overenthusiastic petrol bike/car/auto who's tring to squeeze into the gap in front.

AND

if I'm feeling like a hooligan, I can exploit the huge torque between 2000 and 4000 and squeeze into someone else's rightful space.

especially the swift DDiS is so much fun in the city that I'm actually itching to drive into cochin city just for the heck of it.
ask any other diesel driver on the forum, they'll never want to drive petrol after getting a taste of common rail torque.

I admit that the NVH is better in a petrol, but have you tried the new verna?it clatters embarrassingly outside the car, but in the passenger compartment with the windows rolled up, its difficult to say if the engine's actually on.

I think the problem you are facing with diesels is that, you're trying to drive it like a petrol, trying to rev it to the red. there is no need to do that. just let the car do the work, you just have to help it along. thats why i like the new gen diesels. they work on their own.

[reignofchaos]

Well the basic flaw in your reasoning is that you are comparing petrols with lame engines to the verna and swift-D. Try driving something that actually has some power.