MULTIJET & MPFI - Whats the difference ?

McLaren Rulez · 17th October 2009, 23:13

^Thanks for that! A wealth of info in there

ritedhawan · 18th October 2009, 08:02

The multijet is diesel technology, whilst MPFI is for petrol.The biggest difference is that : mulitjet is based on direct injection of fuel in the combustion chamber during the compression stroke.In MPFI, injectors are located in the upstream of intake manifold. In the intake stroke , as intake valve opens,injectors inject fuel and air + fuel mixture reaches in the combustion chamber, in the intake stroke thus in-direct injection.In comparison only air reaches in the combustion chamber of diesel multijet.

Someone here said, that just because there is a common rail, thus its enables them to identify it as diesel engine. Not, true i would say. I have seen an accumulator or rail in MPFi cars too.

Manas · 19th October 2009, 01:30

Quote:

Originally Posted by kuttapan

... 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...

Siemens is another major player in high pressure common rail Direct injection systems. The glow plugs offered by Siemens (used in Mercedes) has a pressure sensor right near their tip (as against body mounted knock-detection sensors on other engines)... This significantly improves knock detection and contributes to a quieter engine performance.

"Multijet" derives its name from the multiple-jets that the piezo injectors deliver as explained before. These injectors spray the diesel AGAINST a very high pressure developed during the compression stroke of the cycle.
MPFI Injectors, on the other hand, inject during the intake stroke of the cycle. Further, as gasoline is more easily atomised than diesel, High pressure injection is not required.

However, GDI (Gasoline Direct Injection) technology is the next step in Gasoline engines. I'm not sure if it is available in any production vehicle. AVL had developed a prototype Engine named "Spectros" with GDI.

kuttapan · 19th October 2009, 16:09

Quote:

Originally Posted by Manas

However, GDI (Gasoline Direct Injection) technology is the next step in Gasoline engines. I'm not sure if it is available in any production vehicle. AVL had developed a prototype Engine named "Spectros" with GDI.

The new Holden models feature SIDI. Spark Ignition direct injection, basically the same as what you said. They have increased power and fuel efficiency at the same time, while using a smaller mill. WOW, I should say. Waiting for the car to be featured at rentals, to get hold of one.

nandans2005 · 22nd October 2009, 08:34

Dear All (Especially Kutappan),

Thanks so much for the classes on the subject i had doubts.

Would you also let me know on E F I - Electronic fuel Injection please.

Ravveendrra · 22nd October 2009, 08:48

PD, CDI, Multijet etc. are all extensively discussed in the thread "Pumpe-Duse diesel technology as against better known CRDi" at: http://www.team-bhp.com/forum/techni...ighlight=Pumpe.

Cheers,

Note to mods: Perhaps this thread can be merged with the older one.

17th October 2009, 23:13	#16
McLaren Rulez Senior - BHPian Join Date: Dec 2007 Location: Mysore Posts: 3,465 Thanked: 5,536 Times	^Thanks for that! A wealth of info in there
	() Thanks

18th October 2009, 08:02	#17
ritedhawan BHPian Join Date: Aug 2009 Location: Noida Posts: 344 Thanked: 737 Times	The multijet is diesel technology, whilst MPFI is for petrol.The biggest difference is that : mulitjet is based on direct injection of fuel in the combustion chamber during the compression stroke.In MPFI, injectors are located in the upstream of intake manifold. In the intake stroke , as intake valve opens,injectors inject fuel and air + fuel mixture reaches in the combustion chamber, in the intake stroke thus in-direct injection.In comparison only air reaches in the combustion chamber of diesel multijet. Someone here said, that just because there is a common rail, thus its enables them to identify it as diesel engine. Not, true i would say. I have seen an accumulator or rail in MPFi cars too.
	() Thanks

22nd October 2009, 08:34	#20
nandans2005 BHPian Join Date: Oct 2009 Location: Bangalore. Posts: 640 Thanked: 43 Times	Dear All (Especially Kutappan), Thanks so much for the classes on the subject i had doubts. Would you also let me know on E F I - Electronic fuel Injection please.
	() Thanks

22nd October 2009, 08:48	#21
Ravveendrra Senior - BHPian Join Date: Jan 2008 Location: Hyderabad Posts: 1,390 Thanked: 447 Times View My Garage	PD, CDI, Multijet etc. are all extensively discussed in the thread "Pumpe-Duse diesel technology as against better known CRDi" at: http://www.team-bhp.com/forum/techni...ighlight=Pumpe. Cheers, Note to mods: Perhaps this thread can be merged with the older one.
	() Thanks