[Technocrat]

For those who want to the Financial aspects between Diesel & petrol car please refer to This Thread

[srishiva]

Originally Posted by pachchu

few myth vs fact questions I had in mind - not covered until now - it would help if somebody could answer these as well

is it a myth or fact that diesel engines emit more pollutants than petrol engine? let's consider the latest CRDI engines for this discussion sake.

what is the reason for cheaper diesel in India? Is Govt subsidizing it for farmers (to run tubewells) or is this a trend worldwide in capitalist countries also?

CRDI engines emit less CO2 compared to petrols. Other pollutants are more in diesels.

The lesser price is basically due to government since it does not want transport sector to take the burden which ultimately increases the prices of everything.

[ImmortalZ]

Originally Posted by pachchu

few myth vs fact questions I had in mind - not covered until now - it would help if somebody could answer these as well

is it a myth or fact that diesel engines emit more pollutants than petrol engine? let's consider the latest CRDI engines for this discussion sake.

Diesels emit drastically less CO2 than their petrol counterparts. This makes them much more economical to tax in countries where CO2 emissions determine the tax band your car falls in. c.f. UK. However, they do emit more particulate matter (soot) and if bad quality diesel is used, SOx/NOx emissions occur. These are downright poisonous.

Serious efforts are taken to minimize emissions from diesel cars. A lot of the high tech in CRDi is all for reduced emissions and NVH.

Originally Posted by pachchu

what is the reason for cheaper diesel in India? Is Govt subsidizing it for farmers (to run tubewells) or is this a trend worldwide in capitalist countries also?

Diesel is cheaper in India because the Government subsidizes the fuel. So, for every liter you buy, a (large) part of the price is paid by the Central Government. This is to help the transport industry which indirectly keeps mass transport (buses) cost and commodity prices low.

I sometimes feel odd about this. A part of the tax the petrolheads pay for every liter of their chosen fuel goes to pay for the dieselheads.

[anupmathur]

This thread is about 'modern' diesel engines, which are all ECU controlled.
I'm surprised to see some people talking about amazing low-end torque.
The modern ones are closer in behaviour to petrol engines and require frequent downshifting.
It is the non-ECU controlled diesels (like in the Tavera, Sumo, Qualis etc.) that gave that legendary low end torque.

[ImmortalZ]

New age or not, all diesels have a huge advantage in torque to petrols because of the massive compression ratios involved.

Edit : Better explanation. Diesels have high compression ratios to compress air and force self ignition of the fuel. To achieve this, they have a higher stroke than your average petrol engine. A higher stroke means that the crankshaft is turned with more force (aka, torque). It also means that the engine can't rev as high as a low stroke petrol motor.

This difference is what gives diesels their massive torque.

You may be confusing turbo lag with lack of torque. You trade turbo lag for much better economy AND power from a similar displacement.

[bj96]

Originally Posted by Technocrat

engine doesnt warm up to the ideal working temperature which has its impact on the longer run.

There are two important facts hidden behind this generic theory:

1) Engine components are made of different metals and alloys. E.g. piston is a different alloy than the engine block etc. These metals have varying coefficients of thermal expansion. Till the engine reaches its operating temp the tolerances/gaps between different moving parts do not reach optimum level causing friction and wear of components etc.

2) Lubricants (multigrades) are designed to unleash their full potential when they are heated to a certain degree. Till then the molecular inertia and viscosty retards the free movement of components. E.g. 20w50 oil will be too thick at 6AM in Pune winter.


Petrol engines heat up faster and reaches a steady operating temperature in about 1-2kms low rev run (e.g. my WagonR) while diesel (e.g. my Safari 2.2) takes a longer 5-7kms of low rev run. This is because diesel engines are thermodynamically more efficient and looses less energy as heat. In that way a petrol is more suited for short errands . IIRC, petrol IC engines works at about 20% thermal efficiency while, diesels run at about 30-35% efficiency. Rest all are wasted.

Most of us probably can't afford to give up on short runs completely. E.g. my office commute is about 8kms one way city traffic. However, I make it a point not to rev the engine (rpm <=2k on Wgnr, <=2.2k on Safari- normally I avoid the beast, unless there is an office party) till its reaches the operating temps.

Also, stop and go wears out clutch and brakes faster- irrespective of petrol/diesel.

Tip: It is better to shift to 1st gear in bumper to bumper than riding half clutch on 2nd or 3rd gear while trailing a puttering auto in peak city traffic.

-BJ

[gemithomas]

Its quite simple. The Premium you pay for the diesel (compared to a simmilar variant petrol) would be around 1L. During normal service something like a diesel filter would be around 1-1.5K compared to around 200 for a petrol filter. So if you dont do a minimum running of around 30Km every day you would take more than 3 years to start profiting from the extra money you have spent. Thats the only simple reason for insisting on minimum running for buying a diesel.

[dadu]

Many of the queries are already answered here

[aZa]

Originally Posted by teknophobia

4) You will need to give the car it's head and run it at high speeds (100+) for at least 30-40 km at least once a month otherwise the EGR valve and the air intake will get choked.

Please explain this point !

[teknophobia]

It's pretty simple if you know how EGR works, what happens is that the exhaust gas containing soot is recirculated. If the velocity of the intake air is low and EGR is in use, the soot deposits on the intake and valve so you have to run the car once in a while at high revs for extended periods to clear off all the deposits (including soot in the exhaust). Its there in the owner's manual somewhere.

[sanagg1]

Originally Posted by aZa

Please explain this point !

I think EGR is dependent on RPM so the 100 KM speed is not neccessary at lower speed also you can afford the same RPM if in lower gear.

[teknophobia]

Originally Posted by sanagg1

I think EGR is dependent on RPM so the 100 KM speed is not neccessary at lower speed also you can afford the same RPM if in lower gear.

Actually, its not just the EGR that is affected, a lot of other moving components get a thorough workout as well, I have just mentioned what is stated in the manual. And finally, it's fun

[CBlazer]

Originally Posted by frankmehta

I'm no longer looking at the economical aspect of this. The crdi engine has won a lot of hearts and I am one of the victims.

Glad to know I'm not the only one thinking on these lines. I was wondering if it was worth considering the i20 CRDI instead of the 1.2 petrol. This was purely for the fun to drive factor.

Is it a myth that the clutch on a diesel feels heavier compared to a petrol?

[dushmish]

Loved the Dzire diesel's feel when the turbo kicked in. Petrol seemed so boring. Now that I have bought a diesel, thought, might as well drive it. Its so cheap compared to petrol. So have driven for 17250 km in 9 months. My commute to office is less than 4 km every day. :-) My average driving on petrol Zen over 5 years was 14,000 km per year. This included my commute to previous office - 45 km per (working) day. So you know what I mean when I say - I am driving my diesel.

[sanagg1]

Originally Posted by dushmish

Loved the Dzire diesel's feel when the turbo kicked in. Petrol seemed so boring. Now that I have bought a diesel, thought, might as well drive it. Its so cheap compared to petrol. So you know what I mean when I say - I am driving my diesel.

Man You are loving it
the "diesel" due to tubokick plus the low end torque
diesel is king (not for economy only)
have a tons of happy and safe driving
cheers