[anupmathur]

I think that article is an example of a very poor standard of reporting.
Only one pollutant has been highlighted.
What about the many other pollutants that comprise a typical exhaust gas?

I'd say this article is presenting a very incomplete/doctored view for reasons best known to them!

[kavesh55]

Originally Posted by GTO

I'd disagree with your statement. The hatchback segment is being dominated by a 1.2 liter petrol range, primarily due to tax benefits. Plus, technology has made it possible to extract a useable 80 - 90 BHP out of a puny 1.2 liter petrol.

Within the hatchbacks & entry level sedans, the 1.3 L Fiat diesel engine is pretty much the most popular.

1.5 - 1.6 liter petrols dominate the C segment, same as a decade back. And the D segment stays at <2.4 L petrols.

Even if you look at MUVs, common-rail technology has made more power from a smaller capacity possible. Mahindra & Tata have both shifted to the awesome 2.2 engine (from 2.6 & 3.0 respectively).

The only segment where I'd say engine capacities have gone up is the uber-luxury sedan. The E280 & 530, for example, with their stonking 6 cylinder engines.

Completely agree to you GTO, smaller engines are getting popular. Skoda is leading the pack with newer smaller engines, infact a car like superb has a corolla sized engine. I however dont know how reliable and good are these breed of engines. Small engines generating more power. For instance I personally feel a Maruti 1000 has better cruisablity compared to an alto. 1000cc generating approx. 45bhp versus 800cc 3 cylinder making 47bhp.

[Rehaan]

Originally Posted by teknophobia

You've clarified my point yourself, from being dominated by 800 cc engines, the hatchback market is now being dominated by 1.2/1.3 l engines.....

But teknophobia, your original answer of :

Originally Posted by teknophobia

One simple answer, the average sizes of the engines are getting bigger.

...doesn't quite answer srijit's question correctly in the technical sense he wants.

For example, take a look at the simple advancement from Carb to MPFI.

M800 carb to M800 MPFI - Both were the same 800cc engine size.
Esteem carb to Esteem MPFI - Both were the same 1.3L engine size

Now look at the changes that resulted :
- Much more power and torque produced
- Better FE
- Better emmisions (carbs couldnt really make it past the bharat/euro certifications)
- Less frequent mantainence required
- More adaptive to driving conditions (altitude, winter, etc)
- etc

So i think that should clarify, that within that engine size itself there were worlds of a difference in terms of old engine vs new engine.



Srijit,

If i had to do "New engine vs old engine in one word" : efficiency!

As easy point to highlight should be that carbs have a hard time mantaining an ideal air-fuel ratio. Things that could mess up the A/F ratio for a carb would be :
- Different ambient/intake air temperature than what the carb was tuned for.
- Different air pressure (altitude).

MPFI for example would have a bunch of sensors and actively correct the A/F ratio as you are driving depending on the conditions influencing it.

Also, heres a terribly old thread with a cool MS Paint illustration
http://www.team-bhp.com/forum/techni...ve-carb-s.html

cya
R

[teknophobia]

My answer had nothing whatsoever to do with Srijit's question, rather it was a reply to an issue raised that CO2/Km emissions were increasing across segments

btw.. though undoubtedly newer engines are more efficient, if what I can understand from the original question is correct, the poster wants to know the technical differences between how newer engines and older engines work, and to answer this question, we would have to go into a lot more detail than merely mentioning that carburettors have been replaced with fuel injection. You would have to enter into, inter alia, valvetrain design (including variable valve timing by whatever name called), electronics controlling the engine, material technology, turbocharging, emission control systems and that's only a small part of the changes brought about in the engine. We could also go on and on about changes to the body construction, drivetrains, tyre technology, steering, lighting and so many other things.

[anupmathur]

Originally Posted by teknophobia

btw.. though undoubtedly newer engines are more efficient, if what I can understand from the original question is correct, the poster wants to know the technical differences between how newer engines and older engines work, and to answer this question, we would have to go into a lot more detail than merely mentioning that carburettors have been replaced with fuel injection. You would have to enter into, inter alia, valvetrain design (including variable valve timing by whatever name called), electronics controlling the engine, material technology, turbocharging, emission control systems and that's only a small part of the changes brought about in the engine. We could also go on and on about changes to the body construction, drivetrains, tyre technology, steering, lighting and so many other things.

Do you really believe that is what Srijit wants?
My impression is quite different, based on this:

Originally Posted by srijit

I dont need much detail, just simple explanations should suffice

[teknophobia]

And that simple explanation would have to be substantially more than "new engines have MPFI, not carburettors"

[srijit]

I think Rehaan has hit the nail on the head. Thanks for that, R.
@anupmathur, yes, you are right. I just needed a simple explanation.
The situation was that an uncle of mine is an old school mechanic. He knows carbed bikes and cars well. But he has been out of the scene for a long time and was not able to witness MPFI revolution first hand, mechanic style.

So to put in simple terms, what would be the difference between a carb Maruti 800 and an MPFI one? I am not even thinking of trying to explain turbo's.

Thanks for all your help.

[Shan2nu]

The most important diff between carb and mpfi that i see is the new engine's ability to alter engine settings (in real time) to maintain the ideal "AFR".

This is one of the reasons why the new engine is more efficiant over varying conditions.

When i got headers for my car, most oldschool mechs told me that i would be reducing engine life by doing so.

This was prob true with carb engines where the extra airflow in the engine would make it run a lean mixture, causing heat / wear'n'tear. But the ECU on the mpfi is designed to varify readings from its various sensors and decide how much fuel needs to be supplied at what point of time, such that the engine runs at its optimum.

Even when my 02 sensor failed, the engine immediately started running slightly rich as a precautionary measure.

Shan2nu

[Rotorhead]

Take a look at the meaning of few terms such as common rails, ECU, VGT and MPFI to start off with and you will get a lot of understanding as to what all have changed from the earlier engines.

[csateesh]

Srijit

IC engines need fuel and air mixture to burn them and generate power.

For Gasoline engines (with Carbs) this is what needs to be done

Cars with Carbs had no way to control the air intake, amount of fuel and timing at which is injected (This will decide whether it is running rich or lean). Cams only controlled the lift of the intake and exhaust valves.

With FI Cars the ECU precisely knows the RPM, the TDC (Top Dead Centre), BDC (etc). It can inject pre-defined amount of Fuel into the Chamber which help controlling the ratio. And if the engine is cold the mixture is rich and when it is warm it is lean. This is controlled by the ECU.

Cars with Carbs for purpose of tuning (both mixture and idling) had to be at the optimum temperature. If done this way for a cold morning start it is a must to use choke to make the mixture rich.

And the timing was driven by a distributor which had a contact point that had to be replaced periodically. With the ECU driven there are no moving parts and hence longevity has improved

Diesel Engines

To improve NVH characteristics of a diesel engine it was important to accomplish the following

1. Inject diesel into the chamber at a very high pressure
2. Inject finely atomised diesel into the chamber multiple time in one power stroke to smoothen the combustion.

Indirect DI couldn't accomplish the above.

In the new generation CRDi the high pressure common rail is maintained at 1800 bar and the injection is controlled very well. To make the fuel extremely atomised the holes in the injector were made small in the first generation and second generation CRDi. But the 3 generation uses piezo electric crystals that will change shape when a electrical pulse is applied. This allows the ECU to inject very small amounts of Diesel into the chamber mutiple times. From what I know the new generation ones actually can have as many as 3 pilot injection + 1 Main injection + 2 Pilot injection. This makes the combustion extremely clean and less noisy due to progressive nature of the combustion.

The control that is possible with ECU's in CRDi is just mind boggling.

Hope this helps

Cheers

Sateesh

[srijit]

It does help. Every bit of it. Thanks all.

[teknophobia]

I guess I owe an apology for misunderstanding the question.

[anupmathur]

Originally Posted by teknophobia

I guess I owe an apology for misunderstanding the question.

Not at all, bless you!
Which of us has not been guilty of the same so many times?!

[shankar.balan]

I wonder if this is the right place to raise this question?
how long can I hang on to my Scorpio 2008 - which is BS3 compliant as of now?
Consider that I shall be living in a Metro/ "A" City for at least another 10 years. After say, another 7 years, will it become illegal for me to drive my BS3 vehicle on the roads?

[sgiitk]

CSE was founded by a late alumnus of my Institute whom we hold int he highest regard, But I have always looked at their reports with a good degree of scepticism.

Now I go a bit OT

1, They wanted the Supreme Court to ban Diesel vehicles altogether. This was around the time that Tata Indica was about the be launched in the market. Many people were suspicious of the timing of the campaign, and various motives were attached.

2. There was the infamous campaign about pesticides in colas & soft drinks. I heard that there was threat of litigation by the cola companies, who questioned the figures. Furthermore, if the GoI has no standards then why blame the companies. I am quite sure there was less pesticide in the bottled stuff, than in tap water supplied to us. I see no campaign on that.

I am sure there are more.

Activism is required, but balanced with reality.