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Message
I understand that the vacuum port
causes a change in fuel
pressure as the manifold pressure changes, but I
don't understand why we want
the pressure to change. This seems like it
would make it more difficult
to tune the EC-2. What am I missing here?
As I understand
it...
I'm guessing that it
makes it a little easier to program, because it takes away a variable.
Think about it this way, when you open the injector, fuel sprays out. It
sprays at a rate that's not just related to the fuel pressure, but to the
difference between the fuel pressure, and the intake pressure. In an
extreme case, if you had 10 psi of boost with a turbo, and only had 10 psi of
fuel pressure, opening the injector wouldn't spray any fuel at all.
Now think of the real
situations. At idle, where there's the least need for fuel, you have the
most vacuum. This gives you the greatest fuel flow rate (appears to have a
larger injector), when you need it the least. Just the opposite happens at
full throttle. The pressure referenced regulators keep the fuel pressure
differential the same across the board, so your injector flow remains
constant.
Also, what is the preferred fuel pressure for a n/a injected
rotary? (I
recall Ed Anderson stating he runs 45psi... Is this correct
Ed). Mark S.
I'm not sure there is a
"preferred" pressure. Higher pressure will allow more fuel flow, and
perhaps a better spray pattern, but promotes leaks if you get carried
away. The only real standard is the one that's used when testing injector
flow rates, and that's 3 bar, or 43.5 psi. For lack of any
better setting, I adjusted mine for standard 43.5 psi.
Cheers,
Rusty (gotta
go finish my brake repair now)
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