oil injector vacum pipe?

[rustyrex]

ive been trying to find out why there is a vacum pipe on the oil injectors but cant find threads about these specific pipes.
so can any body tell me what they do?why are they there?
it seems strange that somthing that sucks is conected to something that squirts....:spanki thought the omp would pressurise the oil making it squirt out of the injector?so why have a vacum pipe?how does it all work?
cheers guys....:Thumbs-up

[andrewrx7]

They aren\'t vacuum pipes. They are lines that draw filtered air from the primary turbo intake. These lines go to the top of the oil injector in which is a one way valve. The valve only allows air to go to the engine, not away.
Why is it there? Simply really. Yes the OMP pumps oil, but into the nozzle chamber of the injector. Without the air line, it would be a closed system. Simple analogy - think about a straw full of liquid. Put your finger over the end and try to suck the fluid out. It won\'t come out since there is no way to feed air into the straw as the fluid is displaced. Now take your finger off the end of the straw - and hey presto, the fluid comes out. Same for the oil injector. As the rotor sweeps past the nozzle, it draws a strong vacuum and sucks the oil from the nozzle into the engine. The air line allows for some displacement that allows the oil to be drawn into the engine in a more efficient manner. The OMP keeps the oil replaced in the injector nozzle.

[rustyrex]

fantastic!!!:yes,thanks andrewrx7 i now understand how it all works.:god:god:god

[bumpstart]

the correct term is PURGE air
-most TB\'s will be provided with a purge air port,, taken adjacent to the throttle blade,, or just in front of it
-- so as to give only a weak signal at idle,, and not a strong one

whats also prudent to mention,,,
is the oil injectors can continue to leak down after shutdown if the purge system is set up blocked,,

 or with a vac trapped above them by a one way valve

( i mention it ,, cause its common to see such bodge,, years down the track )

[rustyrex]

Are you talking FD bumpstart :xconfused? on my fd the purge stuff is seperate to the oil injectors. theres a small vac pipe that goes from the oil injector nipples straight to the primary turbo inlet via a metal tee piece in the rats nest.
what i wanted to know is why does the oil injector have this pipe and why does it go to the primary turbo inlet?
i think andrewrx7 hit the nail on the head (thanks again) but would like to see as much info on this as possible so we all know exactly whats going on.
cheers

[bumpstart]

yes i was referring to the FC system,,
 though the FD is identical in principle
[ aside that FD EOMP has only two nozzles and a different purge air source
,, they still need that same  vacuum braking purge airflow ]

the oil injectors still use,, what is termed purge air
-- taken from in front of the butterflies,, or from turbo amounts to the same thing
ie
anything that is filtered air,, taken from the air-filter side of the throttle plate and used for purposes other than air fuel ratio
is usually termed as purge air
( on FC onwards there is also purge air to the injector bases )


the end result is the same,, though the FC works with pressure differential
( ie the purge air is boosted at some times )
and the FD works as just filtered, unboosted purge air

-- without it,, flow is erratic,, and in some conditions none existent,,
 and without the purge break the pressure left in the oil injection system
 will allow the oil injectors to bleed down into the motor on shutdown


( i recall 12a turbo\'s have the system without the purge,, and i think it contributes to smoky starts )

for further anecdotal reading,, ken himself mentions modification to the oil injection system necessary to make the HP for s8 FD
( they did more,, with less )

[rustyrex]

:chatok so the fd oil injector only needs fresh filterd air,what is your opinion on running the pipe to a small air filter rather than running to the primary turbo inlet?
:Thumbs-updo you have link to ken?