| Author |
Message |
DGS (Dgs)
Member
Username: Dgs
Post Number: 427
Registered: 5-2003
| | Posted on Tuesday, October 21, 2003 - 3:05 pm: | |
Wha? A diesel injection pump, magnesium alloy pressure lines, injectors that don't open until 380 PSI (!) (compared to 50 on CIS), injectors bolted into the side of the engine ... and it's on the other side of the intake valves?
Isn't that a bit like wabbit hunting with a bazooka? ;)
I can't believe I never noticed that before, in 24 years of ownership. (So much for "unreliable" Alfas.)
DOH!
But then, I never had a Spica service manual until last fall. From the pattern description (0.8 diameter at four inch distance), this seems to be what racing EFI systems refer to as "laser beam injection", where the injectors fire through the intake valve. But most racing LBI systems manage on 50-70 psi fuel rails, not nearly 400psi! (Be vewwy vewwy qwiet. I'm hunting wabbits -- ka-BOOM!) |
PSk (Psk)
Intermediate Member
Username: Psk
Post Number: 1057
Registered: 11-2002
| | Posted on Monday, October 20, 2003 - 7:58 am: | |
Er,
quote:I find this "new" technology a bit amusing, considering that the Spica mechanical injection system on my 1979 Alfa spider is also a direct injection gasolene system (but with non-variable injection timing).
Your 1979 Alfa Spider injects into the inlet manifold/throttle body not into the combustion chamber, thus it is not a direct injection system.
Pete |
DGS (Dgs)
Member
Username: Dgs
Post Number: 417
Registered: 5-2003
| | Posted on Saturday, October 18, 2003 - 11:53 am: | |
Most EFI (and CIS) systems are "port injection" -- the fuel is injected into the intake manifold at each intake valve "port", and drawn into the engine on the intake stroke. Direct injection systems inject fuel into the cylinder directly, during the compression stroke.
Apparently GDI is being investigated as a way of running very lean, by injecting fuel late in the compression stroke, creating a "profile" mixture -- the fuel mix is combustable near the spark plug, and lean (approaching zero) further away. Changing the injection timing lets you run a "normal" fuel mix for more power.
I find this "new" technology a bit amusing, considering that the Spica mechanical injection system on my 1979 Alfa spider is also a direct injection gasolene system (but with non-variable injection timing). |
Kds (Kds)
Member
Username: Kds
Post Number: 314
Registered: 5-2003
| | Posted on Saturday, October 18, 2003 - 11:20 am: | |
Isn't this diesel technology for gas engines...more or less ?
I believe it speeds up delivery of the combustible. |
James Dunne (Audiguy)
Member
Username: Audiguy
Post Number: 349
Registered: 6-2003
| | Posted on Saturday, October 18, 2003 - 11:17 am: | |
Can anyone tell me how direct injection actually works? I have been reading the material from Audi on how it will improve performance, fuel economy, emissions and the whole works. I know sequential, mechanical and port injection but is there a real difference in the new direct injection system. And you would think that I would be the one to tell you how it works. |
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