How does BMW direct injection work?
Discussion
I'm not looking for the answer "not very well", for, although this may be true, I'm trying to find out what modes it operates in and under what conditions. I recall with the Mitsubishi GDI (years ago) that the engine only ran in lean burn under certain load conditions, and was wondering if the BMW is similar.
Our 330i piece of crap has occasionally stuttered around 1500rpm since new, but now it is bad enough under load to shut a cylinder down until the engine is restarted. I'm wondering if during the mode switch around 1500rpm, something is not behaving as it should.
Our 330i piece of crap has occasionally stuttered around 1500rpm since new, but now it is bad enough under load to shut a cylinder down until the engine is restarted. I'm wondering if during the mode switch around 1500rpm, something is not behaving as it should.
Petrol direct injection works in almost the same way as modern common rail direct injection really
A low pressure pump in the tank feeds fuel at fairly normal pressure (about 4 bar) up to a mechanically driven high pressure fuel pump, which increases pressure to about 1500 bar
This then feeds fuel to the injectors (electrically switched) and injects fuel, as the name would suggest, directly into the cylinder (hence the requirement for such high pressures - as it has to inject against compression pressure)
The biggest advantage is better atomisation of the fuel, resulting in a cleaner burn, and consequently lower emissions.
The engine will be running as direct injection all the time - I'm not quite sure what you mean about the Mitsubushi GDI engine only running it part time, as that would suggest that it ran a conventional injection system the rest of the time and would then need 4 conventional injectors to feed the inlet manifold - obviously meaning more cost.
If you have problem that is shutting down a cylinder, then it sounds like a problem that warrants further investigation before it creates a bigger problem
A low pressure pump in the tank feeds fuel at fairly normal pressure (about 4 bar) up to a mechanically driven high pressure fuel pump, which increases pressure to about 1500 bar
This then feeds fuel to the injectors (electrically switched) and injects fuel, as the name would suggest, directly into the cylinder (hence the requirement for such high pressures - as it has to inject against compression pressure)
The biggest advantage is better atomisation of the fuel, resulting in a cleaner burn, and consequently lower emissions.
The engine will be running as direct injection all the time - I'm not quite sure what you mean about the Mitsubushi GDI engine only running it part time, as that would suggest that it ran a conventional injection system the rest of the time and would then need 4 conventional injectors to feed the inlet manifold - obviously meaning more cost.
If you have problem that is shutting down a cylinder, then it sounds like a problem that warrants further investigation before it creates a bigger problem
Superhoop said:
The engine will be running as direct injection all the time - I'm not quite sure what you mean about the Mitsubushi GDI engine only running it part time
Sorry, didn't make it clear. Apparently there are three modes.http://en.wikipedia.org/wiki/Gasoline_direct_injec...
The engine management system continually chooses among three combustion modes: ultra lean burn, stoichiometric, and full power output. Each mode is characterized by the air-fuel ratio. The stoichiometric air-fuel ratio for petrol (gasoline) is 14.7:1 by weight, but ultra lean mode can involve ratios as high as 65:1 (or even higher in some engines, for very limited periods). These mixtures are much leaner than in a conventional engine and reduce fuel consumption considerably.
"BMWs" GDI system is of course actually "BOSCHs" (MED ems system)
it runs with a rail pressure of circ 120bar (not the 1500+ for Compression ignition DI) becuase it does not inject fuel during the compression stroke, but during the intake stroke.
If the EMS detects a partial misfire on a cylinder then i will turn off all fuelling to that cylinder to prevent any catalyst damage occuring (from the unburnt fuel exotherming in the cat substrate). Hence your car running on 5 till your restart. (diag codes will have been stored to tell you what level of misfire and on which cyclinder this occured)
see:
http://tbr.gr/122hp/SSP_405_1.4l_90kW_TSI_Engine_w...
page 17 onwards for MED system description etc
it runs with a rail pressure of circ 120bar (not the 1500+ for Compression ignition DI) becuase it does not inject fuel during the compression stroke, but during the intake stroke.
If the EMS detects a partial misfire on a cylinder then i will turn off all fuelling to that cylinder to prevent any catalyst damage occuring (from the unburnt fuel exotherming in the cat substrate). Hence your car running on 5 till your restart. (diag codes will have been stored to tell you what level of misfire and on which cyclinder this occured)
see:
http://tbr.gr/122hp/SSP_405_1.4l_90kW_TSI_Engine_w...
page 17 onwards for MED system description etc
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