MPFI & CRDI

None Same system different delivery.

multi point ie injector for each cylinder fed by pipe to each injector from a central pump

common rail supply to each injector comes from a common delivery tube,each injector is controled by the ECU,

No, I don' think they are the same.

Common rail injection is a form of direct injection (fuel injected directly into the combustion chamber).

Multi-point injection injects fuel into the intake port, just upstream of each cylinder's intake valve.

Or, am I mixing it up?

all the common rail refers to is the presurised manifold to which all the injectors are attached, the individual injectors on this system operate by signals from the ecu.

the other sort are fed individualy normaly from an injection pump.

either system can be indirect injection ie into the inlet manifold norm just before the inlet valve, or direct injection direct into the cylinders like diesels.

this is taken from second link

In common rail systems a high pressure pump stores a reservoir of fuel at high pressure — up to and above 2,000 bars (29,000 psi). The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high pressure fuel. This simplifies the purpose of the high pressure pump in that it only has to maintain a commanded pressure at a target (either mechanically or electronically controlled). The fuel injectors are typically ECU-controlled. When the fuel injectors are electrically activated a hydraulic valve (consisting of a nozzle and plunger) is mechanically or hydraulically opened and fuel is sprayed into the cylinders at the desired pressure. Since the fuel pressure energy is stored remotely and the injectors are electrically actuated the injection pressure at the start and end of injection is very near the pressure in the accumulator (rail), thus producing a square injection rate. If the accumulator, pump, and plumbing are sized properly, the injection pressure and rate will be the same for each of the multiple injection events.

• 1 Common rail - Wikipedia, the free encyclopedia Common rail direct fuel injection is a modern variant of direct fuel injection system for petrol and diesel engines. Common rail fuel injector ...
  History - Common rail today - Principles - See alsoen.wikipedia.org/wiki/Common_rail - Cached - Similar
• 2 The Common Rail Diesel Injection System Explained 7 Jun 2004 ... The modern high-pressure injection systems VP44 distributor-pump, Unit Injector and Common Rail have transformed the ponderous, ...
  www.swedespeed.com/news/publish/.../printer_272.html - Cached - Similar

Well, right there is another difference:

"In common rail systems a high pressure pump stores a reservoir of fuel at high pressure — up to and above 2,000 bars (29,000 psi)."

Multi-point injection delivers fuel at about 60 PSI.

I am seeing a number of differences. Was that not the OP question? True, they are both injection methods, but there are some differences between the systems.

I took it as meaning injection system or delvivery system the injector part of the systems are fundamentaly the same the difference is the way the fuel is stored prior to injection.

ie fuel stored at high presure in common rail

or fuel stored in pipes between the pump and injectors.

sorry my understanding of symantics is not as good as yours.

also i dont want to guide them by the hand i think it is wise to point them in the right direction and leave them to find out exactly what they if during their learning process they discover i was wrong then great they have learnt somthing new.

Right on, man!

(Thought you might like another new smiley!)