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Old 23rd June 2005, 17:11   #16
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Quote:
Originally posted by steeroid

The one with the Turbo does about 102 bhp, if I'm not mistaken.
well, 109, actually..

i have heard of naturally aspirated scorpios for exports- dunno if they are available here.......i think the only engine options that are available here are the Crd-e, and the DI- both having turbos and intercoolers; the power figures being 115 and 109 respectively.... and the F.E ranging between 9-12 kmpl for the TDI and 10-13 kmpl for the Crde..

Quote:
originally posted by man23ish

Yeah, 8-10 kmpl is on the highways.. But in a city like bangalore you'll be lucky to get even 5kmpl.. For Mumbai 6-8kmpl might sound good..
5kmpl..... is the traffic so conjusted there that you are always stuck in first gear...?? the worst F.E that i have heard of is 7 kmpl- in city, mumbai (with a/c, of course- and the dude ripped every chance he got, and in every gear).........safari is capable of giving 12-13 kmpl, on the highway...provided you try to maintain a max of 2000-2200 revs (which is a pain, because the turbo and it's whistle, that is addictive, only kicks in between 2500-2600 R.P.M; so it takes some self control to not put pedal to metal)....

i myself have got some interesting figures- 7-8 kmpl (worst) and 12-13.5 (...!!...best..!!)....

Quote:
originally posted by shravan 316

And also, from what i've read the pump 'dusse' system develops higher pressure than the CRDi system.
yup, upto 1700 bar+.... and it's also more efficient.... in comparison- the octavia l&k pumpe' dusse' gives a F.E of 22 kmpl, with respect to the DI octavia's 18 (avg, in both cases). furthermore, the elantra gives just about 15, with it's CRD-i.... the PD manages to pump out almost the same power, (110 bhp as compared to elantra's 112 bhp), and better it's rival in terms of fuel efficiency, and kick it's butt (oops-boot) in the performance stakes.....


but, in the end, all are different forms and mechanisms of the same principle; Direct Injection- and like mpower said, at the end of the day, it's the pressure of injection, distribution of fuel, and atomisation of the injected spray while keeping it as cool as possible, that matters....
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Old 23rd June 2005, 18:26   #17
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Hmm so the figures are as follows.

Car N/A DI CRDI %Improvement

Scorpio
BHP 86 115 34%
Mileage 8-10 10-13 20-30%

Octy
BHP ?? 110 ??
Mileage 18 22 22.22%

Elantra
BHP ?? ?? ??
Mileage ?? ?? ??

Accent
BHP ?? ?? ??
Mileage ?? ?? ??

Safari
BHP ?? ?? ??
Mileage ?? ?? ??

Please help me fill the above table..

Manish.
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Old 1st May 2007, 17:21   #18
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Could anybody do a comparison between the two diesel engines ,The Direct injection common rail and the indirect injection one [please],for instance would maintainance costs reduce with crdi,Do crdi engines need to be started daily/which of the two engines has a better chance of starting when left unused for long periods,Does FE increase with crdi,which of the two is the better long term bet,Also do crdi engines also require idling before starting and stopping.

Last edited by rahul_intlad : 1st May 2007 at 17:28.
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Old 1st May 2007, 21:27   #19
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Just a wee bit curious. Correct me if I am wrong.

Isn't the PD of Skoda consists of a fuel injector and pump built into one compact unit to withstand high injection pressure as different to common rail where pump unit is seperated from injectors by a rail? And there is no rail for PD system?
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Old 24th March 2010, 01:06   #20
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Default Diesel Engines

Hi all

I would really appreciate if could somebody in detail explain the difference in between Direct injection engine and CRDi Engines.

Thanks

Amit
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Old 24th March 2010, 01:14   #21
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Hi Amit,
You just hijacked my idea that I was about to post- just kidding.
I am too perplexed with different types of diesel engines available in India and wondered which is better.We have engines terms like :
CRDI
VTVT
VGT
Multijet
DDiS
Mhawk etc
I am sure some are almost same and different companies just call different names to them but some of above are better refined and have better performance rating.
I am sure experts here would shed more light so that we can make better decisions while purchasing them.
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Old 24th March 2010, 02:31   #22
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Both are essentially a method of directly injecting Diesel into the combustion chamber (cylinder).
Direct Injection: Fuel pump > injectors > chamber
CRDi - Fuel pump > Common rail > injectors > chamber

On a side note, in IDI engines, the fuel is injected into a pre-combustion chamber that is attached to the cylinder.
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Old 24th March 2010, 02:49   #23
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The most basic difference between normal Direct injection and Common Rail Direct Injection is that in DI, the fuel injector pump provides fuel directly to the diesel injectors for each cylinder while in a Common Rail system, the fuel injector pump sends fuel to a single holding pipe, which acts as a pressure accumulator, from which the injectors are fed fuel at high pressures.

The major advantage of this system is that instead of a complicated diesel injection pump which had to provide fuel independently to all the injectors at proper time, quantity and pressure, now you have a much simpler pump which has to provide fuel only to a single accumulator where a certain amount of pressure needs to be maintained. This meant that much higher pressures could be reached which helped proper atomisation and mixing of the fuel air mixture. Earlier the best fuel injector pumps could help achieving injection pressure of around 800bar, while in common rail systems values close to 2000bar or more can be easily reached.

Also CRDi engines provide for much more easily controllable parameters for electronic control of the engine, unlike normal direct injection engines. They also mean that it becomes a lot more easier to have multiple injections per cycle which is much tougher to achieve in older direct injection methods. Some modern common rail diesel engines have upto 5 fuel injections per cycle.

Another method of diesel injection are unit injectors. In this method, the injector pump and the injector are in the form of a single unit (hence the name). Thus you had one pump and injector combo for each cylinder. This method had the advantage of not requiring any high pressure fuel lines. It also helped in achieving pressures and control ability similar to common rail systems. But the reliability and simplicity of common rail systems is generally found to be higher. VW's Pump Dusse engines used unit injectors. Nowadays almost everybody is shifting to common rail systems.
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Old 24th March 2010, 06:36   #24
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Quote:
Originally Posted by julupani View Post
This method had the advantage of not requiring any high pressure fuel lines. It also helped in achieving pressures and control ability similar to common rail systems. But the reliability and simplicity of common rail systems is generally found to be higher. VW's Pump Dusse engines used unit injectors. Nowadays almost everybody is shifting to common rail systems.
PD system also uses higher pressures similar to CRDi.
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Old 24th March 2010, 08:11   #25
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Quote:
Originally Posted by julupani View Post
The most basic difference between normal Direct injection and Common Rail Direct Injection is that in DI, the fuel injector pump provides fuel directly to the diesel injectors for each cylinder while in a Common Rail system, the fuel injector pump sends fuel to a single holding pipe, which acts as a pressure accumulator, from which the injectors are fed fuel at high pressures.

The major advantage of this system is that instead of a complicated diesel injection pump which had to provide fuel independently to all the injectors at proper time, quantity and pressure, now you have a much simpler pump which has to provide fuel only to a single accumulator where a certain amount of pressure needs to be maintained. This meant that much higher pressures could be reached which helped proper atomisation and mixing of the fuel air mixture. Earlier the best fuel injector pumps could help achieving injection pressure of around 800bar, while in common rail
systems values close to 2000bar or more can be easily reached.

Also CRDi engines provide for much more easily controllable parameters for electronic control of the engine, unlike normal direct injection engines. They also mean that it becomes a lot more easier to have multiple injections per cycle which is much tougher to achieve in older direct injection methods. Some modern common rail diesel engines have upto 5 fuel injections per cycle.

Another method of diesel injection are unit injectors. In this method, the injector pump and the injector are in the form of a single unit (hence the name). Thus you had one pump and injector combo for each cylinder. This method had the advantage of not requiring any high pressure fuel lines. It also helped in achieving pressures and control ability similar to common rail systems. But the reliability and simplicity of common rail systems is generally found to be higher. VW's Pump Dusse engines used unit injectors. Nowadays almost everybody is shifting to common rail systems.
Thanks buddy for the explanation

So the main functioning part is the fuel Pump. Are the fuel pump both in TDI or DI and CRDi engines electrically controlled?

Also if you could elaborate about the 5 fuel injections per cycle.

Does that mean cars of Ford like Figo or Fiesta have individual pressure pipes for each fuel injector?

Thanks

Last edited by amitpunjani : 24th March 2010 at 08:16. Reason: Add some more Questions
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Old 24th March 2010, 17:10   #26
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@header

I think I said the exact same thing.

@amitpunjani

Injector pumps in almost all modern engines are electronically controlled, does not matter what kind of engine it is.

In modern normal DI engines, there is one high pressure pipe from the pump to each of the injectors. In Common rail engines, the high pressure pipes runs from the accumulator to the injectors and another single pipe from the injection pump to the accumulator.

Modern diesel engines do not inject all the fuel in one single spray. Instead you can have multiple no. of sprays of different volumes at different crank positions. Smaller injections are generally made before and after the main injection. This helps in improving overall combustion. So, you can have 2 small pre-injection sprays, then one main spray when most of the fuel of one cycle is injected and then another 2 smaller sprays which then help in burning up unburnt fuel and some of the harmful wastes as well. This would be really difficult to achieve in normal injection pumps, as you would have to provide different volumes of fuel to the injectors 20 times (5 for each cylinder) for a 4 cylinder engine per cycle. Now as the injectors have a continuous supply of high pressure fuel, all one needs to is as the injectors to spray fuel whenever we want and in whatever quantity we want without having to do anything with the pump at all. All the pump needs to do is to maintain a certain amount of pressure in the accumulator.
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Old 24th March 2010, 17:17   #27
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@Anandg

CRDi, Multijet, Mhawk, and DDiS engines are basically common rail engines. They are just names used by different companies.

VTVT stands for Variable Timing Valvetrain. It is the abbreviation used to denote the variable valve timing technology used by Hyundai. This is generally used with petrol engines and not diesel engines.

VGT stands for Variable Geometry Turbocharger, is a kind of turbocharger which has higher efficiency over a wider range of rpms. Many manufacturers now use these kinds of turbos, instead of fixed geometry turbos. These are also called by a different names. For example, Tata calls then VVTs or variable vane Turbochargers.
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Old 24th March 2010, 17:26   #28
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Here are simple definitions:

CRDi - Amount of fuel present in a common pipe or rail is under an ample amount of pressure which causes the fuel to be atomised or broken into small particles. Fuel can now mix with air more efficiently. With proper direct injection, fuel usage will be highly efficient, with much less wastage of fuel escaping during exaust stroke.

Direct Injection - The fuel delivery is directly into the cylinder by spraying at high pressures, where the air is highly pre-compressed. The pressure maintained is not at common point but at different injectors.
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