How does the air injection system work (evo 4)?

[Melons]

Hey guys. I'm curious as to how the system works. I have removed the intake pipe that runs from the intake inlet (just before the throttle body) to the air injection valve, and blew into the pipe to fill the valve with air. When I did this, air seemed to be leaking and I suspect it was leaking into the pipes that go to the exhaust manifold. This doesn't seem right. I would have thought that the air should build up pressure and release when the solinoid activates? Is this correct?

Cheers

 

[Steve220]

It's call the secondary air system, it works under boost on idle the valve is pulled shut and a solenoid keeps it shut then when the engine is under boost then opens it when required. Hope that helps.

 

[Simon@NTS]

er no. SAS is actually switched off, unless you activate it so it does nothing.......However, SAS is ECU controlled, injecting air predetermined by the ecu, in combination timing retard and fuel overun injection..........to add pops and bangs run up to -10* of timing where real antilag runs -35+*

 

[Steve220]

Is that 'er no' to me? As i got that from Mitsi's press release.

 

[sponners]

It is activated in the standard ecu in a very mild form and is supposed to help with keeping the turbo temps down by injecting air on the overrun. These parameters are raely met and hence why a lot of sas valves have seized on older models.

People take advantage of the system by using it for the famous 'pops and bangs' by injecting tha max amount of air possible and in conjuction with retarded ignition timing as Si has said.

The sas valve is held shut via a spring and is activated by a vacuum tank located under the inlet manifold which opens the valve on lift off diverting some of the boost pressure directly into the exhaust manifold.

Hope that helps.

 

[Simon@NTS]

wish i wrote it like that.....+1

 

[Melons]

Thanks for the info.

So if I was to simulate boost by filling the valve with air by wrapping my lips around the inlet and blowing into it, and it doesn't hold pressure, then this is not good? Leaky valve, so replace with new one?

Was just curious to test the unit as I haven't heard any pops out of it when driven very hard.

 

[sponners]

yeah mate, take it off and have a look as it might just be seized slightly open (wd40 is your friend) if this doesn't work then get another one fitted.
some of them also crack/corrode so check for that as well.