Air pump - everything you wanted to know...

[Prof]

Ok,
 
Lots has been said about the air pump, what it does, can it be taken out - what will happen if I do, ya da ya da ya da.
 
I have been researching this for some time, and have come up with the following useful bits of Info.
 
1)  The air pump is part of a secondary air supply system that provides unmetered air for 2 systems on the car:
 
a) Split air system which feeds fresh air to the cat - main converter - it runs from the ACV - air control valve unit on the side of the manifold - it sits under the BAC and looks a little like a carburretor - and along a metal pipe to the main cat.
 
b) Anti Afterburn system - also known as the Port air system - where fresh air is introduced into the exhaust ports (actually into the inlet ports) during deceleration to aid burning of any unburnt fuel.
 
2) The air pump works in conjuction with the ACV which contains 2 valves.  When it is not supplying air to one of the systems above, the air pump vents to atmosphere through a damper and silencer.  You will find this piping along the drivers side of the car, under the air box and the silencer is under the front drivers headlight - small white thingy.
 
3) If you have fitted a decat system to the car, there will be no need for the split air system, and so this port can be left venting to air.
 
4) Ok, if the car is decelerating, the throttle plates are closed, the revs are reducing, and the air pump will not be pushing much air around.  It is at this point that the port air valve will open and allow air into the chambers to aid burning of any unburnt fuel.  However, there will not be much unburnt fuel because fuel cut off will also be in operation.  With the throttles closed, there is quite a vacuum created, and with the port air valve open, air will be sucked into the engine with or without the assistance of the air pump.  There is a check valve built into the ACV unit to prevent exhaust gas coming out.
 
All of which means the following:
 
1)  If you have changed the exhaust system for a decatted one, you no longer require the split air system - the piping can be removed all the way to the ACV unit.
 
2) If you remove the air pump, air will still be drawn in by vacuum to the port air system used when the car decelerates to prevent after burn
 
3) Without the air pump fitted, the air relief hose and silencer are no longer required and can be removed from the car
 
4) If your not bothered by a bit of flame at the back, you can remove the ACV entirely, and use a block off plate.  You will get error codes for the 2 solenoids for Split air and Port air, unless you use a load resistor to fool the ecu into thinking they are still on the car.
 
5) If you retain the ACV, you should fit a breather hose onto the pipe that used to go to the air pump, as air will be drawn in through this on deceleration.  The other 2 vent holes can either be left open, blocked off or breathers fitted, as there should be no movement of air in either of those with no air pump.
 
6) Removing the air pump will mean the pulley for the water pump is no longer getting good drive.  You either need to use a dual alternator pulley, or follow the link here to use a 3l220 belt just for the water pump
 
The following thread will help with removing the Air Pump
 
Cheers,
 
Prof :cheers

[grinder]

oohhh i like it matey - so i can go home and wield a spanner in anger then ?

you need some diagrams with big red circles saying "leave this","remove this","block this" etc..

stu

[prisspringle]

but what happens at MOT time does it all have to go back on?

chris

[grinder]

nah - the blue EGI didnt have an air pump and it was no probs - cause they are pre 1992 - its not tooo bad

[prisspringle]

good good helps clear some space and one less thing to build for the exhaust

chris

[lanciachris]

This is of interest to me

When I took my egi into rx motors for the rusty exhaust to be replaced they fitted a system with no thermal reactor and also removed the air pump and blanked off the fitting where it was.

After a while ive started to get a bit concerned - huge kerblams when coasting downhill and the like. I\'m sure that this is in part due to a less than perfect ignition system, but is there anything in the air pump removal that could be related? unblocked pipes? car wont idle at the moment, just stalls if you let off the loud pedal

[Prof]

Good point there.
 
In actual fact, the Airpump or something covering for it, is required on the EGI to operate the 2 additional ports - the VDI system has 6 - not the 4 we have on turbo models.
 
There is a good article here about that.

[Prof]

ok - little update on this thread.
 
After having the emissions stuff removed, Air pump and ACV, the CO levels did rise.  This is because the unmetered air that is allowed to pass at idle no longer does so.  Levels on my car went to 7% which would be an MOT failure.
 
However, the good news is...
 
 
 
... the MAF sensor has an adjustment screw to allow some air to bypass it, the adjust screw is normally blocked off, but can be tweeked to allow a much smoother idle and lower CO levels (mine are now between 3.5 and 4%), so with a bit of work this would be an MOT pass.

[grinder]

ooohhhhhhh i need to do this - will make the engine bay a lot cleaner

just need to work out what i can remove and what im supposed to leave in place

if and when i do it - i will take pics ( you all know i like taking pics of what im doing !! )

[Brett]

My egi was fully derestricted with no airpump and its AVC removed and plated over etc.  We found we had to find a way of introducing unmetered air into the LIM at idle to pass on the emissions - cue a bit of engineering using an old gas valve, the block off plate we made and a copper/rubber hose combination running to the airpump feed off of the K&N induction kit.  Worked lovely :yes

 The TII was left running the airpump- this meant that I was getting air into the ports, CO2 and hydrocarbons were always fine.

[grinder]

well my plan at the mo regarding this is

1 - my exhaust has the air pipe attached ( bolt on )
2 - so gonna remove the air pipe
3 - bolt a blanking plate on the exhaust
4 - if it pass\'s then remove air pump and such like
5 - if it fails - then refit air pipe and have a re-think

Stu

[Prof]

You will pass easy without that air pipe (split air) as that\'s just to feed the cats\'.  If you\'ve decatted this pipe will do little or nothing save maybe diluting the exhaust mixture with some fresh air.
 
With the air pump still on and that pipe removed, running full decat exhaust my CO was 0.44% - pass with flying colours
 
You can do that mod safely stu - no worries !:Thumbs-up

[grinder]

cool - so its just when i come to remove the ACV ( ? ) that i will get the probs ??

[lanciachris]

Wish I had a camera to take pics of what my car has and doesnt have as it is still stuck with these stalling problems (other projects jumped in the way). Where the air pump was on the side of the engine now has a blanking plate in the way. I think ill go looking for this other component to see whats missing there

[sparkgap]

Thanks to Prof for an informative article.
 
My car is fully decatted so I was considering the need for the air pump.
When I disconnect the air pump plug, my idle becomes lumpy and unpleasant, almost like random misfiring.
Is there a way of correcting this?
I have an Apexi.
Any help appreciated.
 
Martin