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Old 17th October 2009, 10:16   #1
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Default MULTIJET & MPFI - Whats the difference ?

Moderators, I did search before posting this new thread. Couldn't find any so.

Hey Guys,

I visited one of the Fiat showroom yesterday to have a look at the PUNTO for my spouse.

On my drive back, was just wondering what could be the technology difference between the MULTIJET AND THE MPFI?

I would like to know the technical differences between the two, since the Sales guy at the showroom told that MULTIJET is superior than MPFI .

Guys, revert with your knowledge on these two technologies please.

Last edited by nandans2005 : 17th October 2009 at 10:18.
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Old 17th October 2009, 10:26   #2
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Isn't Multijet deisel technology?
i'm quite sure MPFI [Multi Point Fuel Injection] is for petrol engines.
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Old 17th October 2009, 10:32   #3
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Spruce,

Yeah, you are right, its for diesel.

whats CRDI in diesel then ?
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Old 17th October 2009, 10:35   #4
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The "multijet" is the name given to the common rail turbocharged diesel engines from Fiat. So its common rail + turbo - and FIAT likes to call that "multijet"

MPFI is a fuel injection method used in modern day petrol engines where fuel is injected into the intake port just upstream of the cylinder's intake valve.

The sales guy was trying to tell you that the diesel engine is better than the petrol engine (That's like comparing apples to oranges) .

Test drive both and then decide which one you like better.

Last edited by CrackedHead : 17th October 2009 at 10:39.
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Old 17th October 2009, 10:40   #5
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You can't compare Multijet with MPFI. Multijet is a diesel engine technology, whereas MPFI is a petrol engine tech.

@nandans, CRDi and Multijet are essentially based on same principal - that is common rail DI engines. However different manufacturers prefer to brand it differently. Hyundai uses "CRDi", Chevy "TCDi", Fiat "Multijet", Suzuki "DDiS" and so on..

Common rail - Wikipedia, the free encyclopedia
Fuel injection - Wikipedia, the free encyclopedia
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Old 17th October 2009, 10:51   #6
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Each OEM gives its CRDI engine different name. However based on same technology. Following are few companies in India.

1. Mahindra: CRDe
2. Hyundai: CRDi
3. Toyota: D4D
4. Fiat: Multijet
5. Suzuki: DDiS
6. Tata: Quadrajet, DICOR
7. Ford's: TDCi

and so on

Do not confuse with the names. All are Comman Rail Diesel Technology. Where as MPFI is pure petrol engine technology. Actually in MPFI also injector comes in place as of Commom Rail.

Better understand the engine difference between petrol and diesel and understand you needs based on engine. Then you can decide between Diesel and Petrol. These basic things are always required before buying a car for your mental satisfaction.

Last edited by anujmishra : 17th October 2009 at 10:52.
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Old 17th October 2009, 10:56   #7
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DCEite,

But CRDi is Commorn Rail Direct Injection and not Diesel Injection. This technology is for any type of fuel.

While MPFI - Multi point fuel Injection> This is a advanced replacement for the carb, which basically a device to mix the the air and fuel ratio and then feed it to the engine.

So whats MULTIJET, is it same as MPFI ?

i am really confused man , i really want to get clear understanding of this, i clearly know whats MPFI, but my only confusion is whether MULTIJET technology is same as MPFi irrespective of the fuel.

Lets forget the fuel used and discuss only two technolgies.
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Old 17th October 2009, 11:09   #8
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Anuj,

I do know a little on the different engines, since i did my mechanical engineering from UVCE.

But my confusion is about the fuel systems, man.I am writing based on what i have read, CRDI is common rail direct injection and it says, both kind of fuels can be used and MPFI is again for mixing air and fuel, i believe.

I do know a bit, but just want you guys to clear my doubts and be clear on these technologies.

help me out.
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Old 17th October 2009, 11:15   #9
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Quote:
Originally Posted by nandans2005 View Post
DCEite,

But CRDi is Commorn Rail Direct Injection and not Diesel Injection. This technology is for any type of fuel.
CRDi is technology is only for diesel engines. In CRDi engine , the fuel is injected at very high pressures( 1300-2000 bar). If petrol is subjected to that much high pressure, it will burn even before the power stroke( i think so).

fiat's diesel fuel injector have multiple nozzles,that's why they are calling it multijet diesel engine.
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Old 17th October 2009, 11:27   #10
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Quote:
Originally Posted by nandans2005 View Post
I would like to know the technical differences between the two, since the Sales guy at the showroom told that MULTIJET is superior than MPFI .

Guys, revert with your knowledge on these two technologies please.
As everyone said, one is for Diesel engines and other for petrol.

For a layman-
MPFI engines use multiple fuel injectors, instead of traditional single injector units. This is now the standard for any modern petrol engine

Similarly, FIAT Multijet means, its Diesel engines house multiple Injectors- up to seven in cases.

In both petrol (MPFI) and Diesel (MultiJet), the idea is to allow Engine management system to manipulate the injections based on driving condition, resulting in best fuel efficiency while maximizing power output.

Similarity ends here. How these are done in Petrol and Diesel engines vary vastly. CRDI for one, I'd say enabled use of multiple injectors in Diesel engines.

Last edited by WhiteKnight : 17th October 2009 at 11:29.
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Old 17th October 2009, 12:43   #11
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Quote:
Originally Posted by anb View Post
fiat's diesel fuel injector have multiple nozzles,that's why they are calling it multijet diesel engine.
Duh !!. Multiple nozzles? Where did you get that?

Please google before passing out such wrong info. Fiat was the pioneer for common rail diesel injection, and inital technlogy was unijet - one pilot + one main injection of fuel. Multijet involves 1 pilot + a series of main injections. I believe in our 1.3 MJD, it is 3. Thenewer MJD technology engines probably have 4 main injections, maybe one of our crdi gurus can confirm. Number of injections also change as per engine conditions and load,as quoted below.

"The sophisticated MultiJet technology of second generation JTDs differs from its UniJet predecessor in two essential areas; the injectors and the electronic control unit.Within a UniJet engine, a pilot injection raises temperature and pressure inside the cylinder to improve combustion at the time of the main stroke. However, by dividing the main injection into a number of smaller injections, a MultiJet engine affords a fuller, more gradual combustion whilst the amount of diesel burnt at each stroke remains the same; thus abetting smoother, quieter combustion, reduced emissions and increased performance.
To facilitate multi-injection, the injectors can both reduce the time lag between injections from 1500 to just 150 microseconds, and reduce the minimum quantity of fuel injected from 2 to less than 1 cu mm. In tandem, the new control unit modulates injection strategy continually to adjust to changes within three parameters; engine rpm, torque required at any given time by the driver, and coolant temperatures.
Thus, when coolant temperature is less than 60 degrees and torque requirement low, two small and one large injection are performed. As torque demand increases, the number of injections drops to two; one small and one large. Under conditions of high rpm and high torque demand, only one injection is required, whilst with coolant temperature at over 60 degrees, emissions are minimised with one small, one large, then one small injection in the sequence.
Hence, whilst performance is substantially enhanced, start-up times and exhaust smoke are reduced, noise levels and vibration are lowered to ensure a quieter drive and improved passenger comfort, and both fuel consumption and emissions are significantly reduced. All Fiat MultiJet turbodiesel units easily fulfil Euro 4 emissions requirements. "

Source - The MultiJet engine: a breakthrough in diesel technology

Last edited by kuttapan : 17th October 2009 at 12:46.
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Old 17th October 2009, 12:56   #12
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Quote:
Originally Posted by kuttapan View Post
Fiat was the pioneer for common rail diesel injection
Oh really i did not know that i always thought mercedes and bosch were pioneers of common rail diesel injection.
Well you learn something new everyday.
Thanks for that very informative post.
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Old 17th October 2009, 13:41   #13
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Quote:
Originally Posted by cooldude1988765 View Post
Oh really i did not know that i always thought mercedes and bosch were pioneers of common rail diesel injection.
Well you learn something new everyday.
Thanks for that very informative post.
FIAT sold the technology to BOSCH, when the company was severely cash strapped and needed to tide over.
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Old 17th October 2009, 13:47   #14
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Since we're on topic what's the difference between CRDI and PD(Pumpe Duse)? I remember someone saying that the PD is newer and better. How so?
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Old 17th October 2009, 15:29   #15
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Quote:
Originally Posted by McLaren Rulez View Post
Since we're on topic what's the difference between CRDI and PD(Pumpe Duse)? I remember someone saying that the PD is newer and better. How so?
There is a whole thread for the same -
http://www.team-bhp.com/forum/techni...nown-crdi.html (Pumpe-Duse diesel technology as against better known CRDi)
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