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Old 14th September 2010, 18:28   #16
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Originally Posted by rajivanoj View Post
Though Crdi is sensitive to poor fuel and mishandling of electronics which controls it, It depends on manufacturer.
Completely agreed & it does indeed depend on the manufacturer. Example : Tata. Their common-rail diesels are rubbish and suffer from poor (very poor) reliability. I've lost count of the number of complaints that keep rolling in on premature failure of the Indigo common-rail diesel engine. Sure glad they moved over to the 1.3 MJD "national engine".
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Old 16th September 2010, 16:51   #17
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From the mechanical component view there is not much difference in the DI and CRDI engines. Both operate at high compression zone, so that the engine block and head have to be mechanically robust.

In a CRDI engine the burn (the explosion of fuel) is more controlled, hence gives less shock to the structure which should ensure less fatigue thus longer life (and less noise as a bonus).

Thus all things being equal the CRDI should be more reliable. BUT things are not equal. In order to increase efficiency of the vehicle on the whole, all component weights are pared down. Now as the CRDI engine does not require as much protection as a DI engine, the manufacturers reduce the weight of the engine making it less solid than the DI. Any manufacturing defect in the block/piston/crank etc, or any injection problem which can induce higher shock would be detrimental to now slimmer components. Add to that tinkering by local mechanics who have little knowledge of the ECU and you can ruin a perfectly fine engine.

In conclusion, with good manufacturing practice, supplemented by maintenance by knowledgeable personnel, the CRDI will always be more reliable than a similarly design DI. Thus high mileage Toyotas and Mitsubishi diesels.
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Old 16th September 2010, 17:25   #18
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Safari 3.0 DICOR (2005 model): 2.8 lakhs kms without an overhaul, but once it broke timing belt at 2.3L. (my friends car who runs it as a Taxi for politicians.) That's a DICOR and I am pretty impressed.
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Old 16th September 2010, 17:37   #19
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Originally Posted by mercedised View Post
Safari 3.0 DICOR (2005 model): 2.8 lakhs kms without an overhaul, but once it broke timing belt at 2.3L. (my friends car who runs it as a Taxi for politicians.) That's a DICOR and I am pretty impressed.
The 3.0 Dicor is based on the tried and tested DI engine seen under the hood of the popular LCV- the Tata 407 and also seen in Tata Spacio. This Dicor version seen in Safari is known be reliable. Can be due to moderate state of tune(Just 115hp from 3000cc), fairly simple mechanicals(AFAIK it was a pushrod) and low engine speed (a 3000rpm redline).
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Old 16th September 2010, 21:09   #20
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rajivanoj:Crdi is sensitive to poor fuel and mishandling of electronics which controls it.
Thats the crucial point. Its the high sensitivity of the CRDi based diesel engine in comparison to earlier DI/IDI that may be the only weakeness in its armour and may affect CRDi based diesel engines reliability.
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Old 17th September 2010, 12:17   #21
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My understading about CRDIs is that their main purpose is to produce an extremely fine dispersion of diesel particulates in the jet which goes into the combustion chamber.

How that is achieved? By using extremely fine nozzle. Finer than regular DI/TDIs.
Don't you think you will have more chances of problems with this ultra fine nozzle?
Especially in India, where they may as well mix tar with diesel!

Fine mist is also because of extremely high pressure created in the "common rail" by the pump (known as bosch pump by mechanics). Higher pressure output from a pump means higher chances of failure. Besides being extremely expensive.
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Old 17th September 2010, 15:00   #22
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Originally Posted by alpha1 View Post
My understading about CRDIs is that their main purpose is to produce an extremely fine dispersion of diesel particulates in the jet which goes into the combustion chamber.

How that is achieved? By using extremely fine nozzle. Finer than regular DI/TDIs.
Don't you think you will have more chances of problems with this ultra fine nozzle?
Especially in India, where they may as well mix tar with diesel!

Fine mist is also because of extremely high pressure created in the "common rail" by the pump (known as bosch pump by mechanics). Higher pressure output from a pump means higher chances of failure. Besides being extremely expensive.
There is slightly more to this. In CRDI the timing and quantum of fuel injection is controlled by the computer, hence depending on the load, speed and environment the computer delivers fuel for optimum operation. This ensures that most of the fuel is burnt, hence higher efficiency.

Higher pressure if catered to both at design and during manufacturing does not necessarily mean higher chances of failure. Many off road vehicles use pressure higher than in CRDI engines in their hydraulic lines. As long as the whole chain can withstand the pressure there is nothing to worry. It is only when you skimp on quality that problems start.

Regarding ultra fine nozzles, the modern nozzles are moving from metal to ceramic tips. This ensures longer life and ability to work at higher temparature. Higher the temparature, less chances of tar or carbon depositing on the injector as they are vaporised easily. Thus longer interval between cleaning.

As the engine operation is computer controlled, you can have a number of profiles. One for economy, one for spirited driving, one for minimum noise and so on. This is of tremendous advantage to vehicle manufacturers, as they have one basic engine (BMW 2L diesel comes to mind), and various profiles - tunings. One basic engine produces a range of power from 100kW to nearly 200kW with matching torque. Each tune has various user selectable modes - sports, economy etc.
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Old 17th September 2010, 18:56   #23
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Is the CRDi version of an engine having better FE than its DI counterpart? (obviously, power will be more)
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Old 18th September 2010, 17:13   #24
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Originally Posted by ramzsys View Post
Is the CRDi version of an engine having better FE than its DI counterpart? (obviously, power will be more)
Old school DI's are phenomenally fuel efficient. I guess the only UV we can use for comparison is the Bolero : The DI is more efficient at urban speeds, but the common-rail gives better numbers on the highway. I don't think FE can make or break a decision between the two; either is respectable.
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Old 19th October 2010, 10:30   #25
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May be OT - still seems apt to the discussion here.

Engines from Mazda with beautifully implemented ideas.

Mazda Fuel-Economy Engines - Mazda Diesel and Gas Green Engines - Popular Mechanics

Less is more approach for both petrol/diesel engines !!!
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Old 31st December 2011, 18:08   #26
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Default Understanding Reliability of modern Diesel Engines - CRDi,CDi,DiCOR,DDIS,TDI et al

Hi everyone!
As the Indian car market gets filled with new iterations of the 1.3 Multijet Diesel sourced from FIAT and various other innovative small capacity diesel units, these engines are percolating into mainstream cars with new found levels of NVH. I'd like to stop and take a moment to understand the reliability and long term usage feedback from fellow BHPians based on their individual experiences over a period of 3 to 5 years.
Yesteryear Diesel engines in passenger cars were IDI (InDirect Inecjtion) or DI (Direct Injection) scaled down units of rugged trucks and off roading vehicles having drawbacks of NVH creeping through the life of the vehicle, reaching unbearable levels. However, the modern counterparts (referring to the Common Rail fuel Injection technology) are thoroughly refined atleast at the initial stages of life.
From my understanding there are only a few models that would come into the radar in this class such as the DDiS in the Swift / Swift Dezire or CRDI in the Accent / Getz etc.
However, I would like to understand the problems faced, if any with respect to Fuel Sedimentors, Fuel Hoses, Common Rail, Sensors, Injectors etc over the period of usage and also the increasing levels of NVH? I think it would be a good value add to a lot of prospective buyers contemplating to go ahead with a Petrol or Diesel car...
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Old 1st January 2012, 14:35   #27
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Default Re: Understanding Reliability of modern Diesel Engines - CRDi,CDi,DiCOR,DDIS,TDI et a

The Di & IDI engines were simplicity in design, with minimal number of parts augmenting the basic engine. That is why they were so reliable and long lasting.

The CRDI technology has added a whole host of auxiliaries to the basic design
. High pressure pump
. High pressure fuel line
. Precision injectors
. Computer control unit

The more parts, the more points of failure. Further higher pressures and finer injector nozzles necessitates better fuel quality, the system can now tolerate lot less particles in the fuel, which are now an added source of failure.

So as long as the fuel quality is excellent and the fuel filters work efficiently, CRDI engines will last long. As the older engines required no electricity to function they could be run without any battery/alternator. Not so with CRDI which requires electricity to function. Hence on a long term basis I would rate CRDI engines less reliable compared to the older technology. Unless you are a commercial transporter who want to get at least 5Lkm from the engine, the advantages of CRDI technology; at least for normal users; far outweighs its shortcomings - better FE, less noise and vibration, better acceleration and of course more power.
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Old 1st January 2012, 14:54   #28
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Default Re: Understanding Reliability of modern Diesel Engines - CRDi,CDi,DiCOR,DDIS,TDI et a

Great thread, I was wondering the same, especially since I just had a fuel pump failure in my 27 month old, 29000 km old i20 CRDi.

Another query...

Engine Capacities(Ltr) vs. Power(Bhp) and their relation to reliability.

If a CRDi engine is tuned for lesser BHP / Litre, does that raise the reliability of the engine?


For e.g. the Innova. CRDi engine 2.5 ltrs / 102 ps but good reputation for reliability/longevity.
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Old 1st January 2012, 15:17   #29
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Default Re: Understanding Reliability of modern Diesel Engines - CRDi,CDi,DiCOR,DDIS,TDI et a

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Originally Posted by AbhiJ View Post
For e.g. the Innova. CRDi engine 2.5 ltrs / 102 ps but good reputation for reliability/longevity.
+1, have seen so many Innovas which have lapped up 1.5-2.0 lakh kms and still going strong.

While most manufacturers detune the engine to meet the fuel quality of our country, i dont think its absolutely necessary that reducing the power output would increase the longetivity though it should help as the stress on the internals would be less.

We have a Scorpio, the only diesel car and its a 2006 with the 2.6 engine which has been subjected to all kind of fuels and conditions and its still going strong as the others on this forum, even the 2.2 Mhwak unit with increased output is as reliable as it could be. Despite being 400 cc less it is much refined and much better.

The internals of the engine in present day dont give up until they are in extreme conditions like low oil or overheating and some products are 3rd party where a manufacturer of the car has no control - for eg in your case, BOSCH provided injectors and pump failed, could be a case of QC fault or just bad luck with fuel quality. Its just that these modern engine are too sensitive to bad fuel.
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Old 1st January 2012, 15:18   #30
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Default Re: Understanding Reliability of modern Diesel Engines - CRDi,CDi,DiCOR,DDIS,TDI et a

In the CRDi technology, there is one more mix that determines the reliability of engine to some extend. It is the size of turbo which also dictates the reliability of engine. For e.g, Toyota's D-4D, Ranault's K-9 (1.5 Dci) and Ford's TDCi (I am not sure about this one) are CRDi engines but with much smaller turbo. Because of the turbo size, these engines are very reliable.
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