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 (http://www.1300cc.com/howto/how2/belt.htm) to use a 3l220 belt just for the water pump
The following thread will help with removing the Air Pump (http://www.mazdarotaryclub.com/forums/showthread.php?t=14205&highlight=air+pump+removal)
Cheers,
Prof :cheers
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.. :D
stu
but what happens at MOT time does it all have to go back on?
chris
nah - the blue EGI didnt have an air pump and it was no probs - cause they are pre 1992 - its not tooo bad
good good helps clear some space and one less thing to build for the exhaust
chris
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
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 (http://forum.teamfc3s.org/showthread.php?t=50005) about that.
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.
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 !! )
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.
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
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 :D
You can do that mod safely stu - no worries !:Thumbs-up
cool - so its just when i come to remove the ACV ( ? ) that i will get the probs ??
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 :)
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
On the FC, the removal of the air pump means that some of the unmetered air that was coming in through the air pump is no longer there, and so the fuelling at idle is a little rich and the car could run poorly. The solution on the FC is to adjust a small bypass valve on the air meter, which allows a given quantity of unmetered air to pass. This is normally blanked off, as it\'s set at the factory, but you can remove the plastic cover bung, and get to the adjust screw.
I would guess that you need to do something similar on the FD - either adjust fuelling on the Apexi to cater for the loss of some air, or allow air bypass through/around the AFM.
On the FD the air pump is switched so it only works below 2500rpm (IIRC) the air pumps on the 2nd gens are running all the time, so the same techniques do not apply accross the board I\'m afraid.
Quote from: BrettOn the FD the air pump is switched so it only works below 2500rpm (IIRC) the air pumps on the 2nd gens are running all the time, so the same techniques do not apply accross the board I\'m afraid.
Running all the time yes, but the ACV switches where the air goes depending on Revs, so in that respect it is similar (air goes to one of 3 places, into the intake, into the cat or into the silencer pipe under the front headlight). At idle, some air is fed into the intake.
Quote from: ProfOn the FC, the removal of the air pump means that some of the unmetered air that was coming in through the air pump is no longer there, and so the fuelling at idle is a little rich and the car could run poorly. The solution on the FC is to adjust a small bypass valve on the air meter, which allows a given quantity of unmetered air to pass. This is normally blanked off, as it\'s set at the factory, but you can remove the plastic cover bung, and get to the adjust screw.
I would guess that you need to do something similar on the FD - either adjust fuelling on the Apexi to cater for the loss of some air, or allow air bypass through/around the AFM.
The FD doesn\'t have an AFM but your comments led me in the right direction.
I unscrewed the air bleed screw about 2 turns under the throttle body and it\'s idling sweet and even without the air pump now.
Thanks Prof.
Can you tell me exactly where this afm bypass valve is please? Unbolted the air box and lifted it up to look on the underside of the afm (pressuming im right in thinking this is the metal block before the intake pipe), and couldnt see anything.
Secondly, been reading up on after removal of the air pump the secondary ports ( or 5th & 6th ports ), are no longer activated because it was the air pump that activated them.
How are you meant to make them open now? electronically or using a cable system?
Has anyone done this???
Thanks,
Matt
So what benefit does removing the air pump actually have? Does it increase bhp?
It removes excess drain from the engine, all belts to power steering pumps, A/C etc are extra items for the engine to run.
When i got my car the air pump was gone already, but imagine it felt a bit more free once it was taken off.
what hadnt been done is the thermal reactor / heat exchange hadnt been taken off. this is a box in the exhaust after downpipe, it uses an air supply from air pump. the idea is it cools down exhaust gases before emmiting them into the atmosphere.
mine was blowing on a flange, so had the box cut out and a straight pipe welded in.
assuming yours is the same, and you havent got any cats anywhere, this can be removed and i found does free up the car a bit. this must have some gain i imagine 10 -15 BHP.
you will have to get a dual alternator pulley, and double up the alternator belts, to keep the required tension on the water pump pulley (at the bottom).
Im sure another member on here will tell you about blocking off the air pipes from air pump removal aswell. mine was already done so i cant be certain what needs blocking off.
I think for the hassle of removing it etc I might as well leave it on. I don\'t have air con either. Surely if they cause that much of strain on the engine Mazda wouldn\'t of installed one in the first place!:) But that\'s only my opinion.
its not so much strain, its just extra strain that isnt realy needed especially with a couple of exhaust mods. when my blanking plate and belt come through, that bad boy is going in the shed ;)
Quote from: pjd7325Surely if they cause that much of strain on the engine Mazda wouldn\'t of installed one in the first place
It helps burn off the horrendous pollution in the exhaust that the wankel produces.
Since I did away with my cat, the air pump just made the car backfire loudly everytime I lifted off the throttle, even in traffic. So I have disconnected the electrical plug to disable it. Idle is not as smooth without the pump but raising the idle speed to 1000 and opening up the bleed screw has helped. I daresay a bit more PFC map fiddling would sort it out at normal idle RPM.
Quote from: sparkgapIt helps burn off the horrendous pollution in the exhaust that the wankel produces.
Since I did away with my cat, the air pump just made the car backfire loudly everytime I lifted off the throttle, even in traffic. So I have disconnected the electrical plug to disable it. Idle is not as smooth without the pump but raising the idle speed to 1000 and opening up the bleed screw has helped. I daresay a bit more PFC map fiddling would sort it out at normal idle RPM.
:Laugh I bet that\'s all the un burnt fuel setting fire in the exhausts! Entertaining though I bet. I\'m going to leave mine on I think it\'s not doing any harm as I don\'t use my car for track days etc. Just my everyday car. Going off the subject.... someone came up to me while filling with petrol and asked what porsche I was driving! I sarcasitly pointed out what it said on the back!:Laugh
I dont use mine for track ,well not yet, i definately saw an improvement when i took the thermal reactor off.
haha, i havent been asked that but the porsche 924 does look similar.
Kind of a double edged sword with the air pump, just took the RX to the local garage and said "I think you\'ll have to look it up". He failed it even though WGT\'s recommended MOT station passed it less than 6000 miles ago. 6 on the CO instead of 4 minimum.
I\'ll take it back tomorrow and reconnect the air pump first and if that doesnt do it then i\'ll try the test setting on the PFC for the injectors to lean it out temporarily.
My TII exhaust is standard but for decat pipe welded in and stainless cans.
The exhaust shop welded the Air Pump feed into the decat pipe.
Sorry if this has been covered in the thread, but does the Air Pump pump into the \'cat\' at idle? If not can I fool it into doing so? I like the idea of diluting the exhaust fumes at idle!
I\'m not bothered about removing the pump just want an MOT pass at this stage.
Quote from: doddySorry if this has been covered in the thread, but does the Air Pump pump into the \'cat\' at idle? If not can I fool it into doing so? I like the idea of diluting the exhaust fumes at idle!
It does - one of the side effects of removing the air pump means you have to play fiddle and tune before MOT day to get through the CO/HC test - you can normally pass one of the tests but both is tricky.
I\'m figuring on cutting some fuel for idle using the eManage, it may run lumpy, but normal service is just a dip switch away :cool
A TII will pass the emissions with a DCAT exhaust - assuming it still has the air pump. :yes
I really must be hard of thinking at the moment, can someone just confirm/ disprove the following for an FD?
the airpump provides a pressurized air supply to the ACV, which then provides it to one of the following: to the cat, into the exhaust port, or re circulates it back into airbox (or induction system). above around 3.5k rpm the pump cuts out and does nothing, and if you want you can always unplug it. If you go for an after-market exhaust, then the supply from the ACV to the cat is removed, however if the pump is plugged in then at low rpm (i am thinking idle) the ACV directs the airpump air straight into the exhaust port. this would explain how cars that have been decatted but still have a functioning airpump and ACV sail through the MOT, as un-metered air is pumped straight into the exhaust. also you cant get away with removing the air pump and fitting a breather on the ACV, as there has to be a positive pressure so as to overcome the exhaust pressure.
Is this right? i ask as i am bout to remove my airpump and acv, mainly out of spite as i have lost a lot of knuckle skin on the pipes between the two. at the moment the car has an aftermarket exhaust and apexi pfc, and when i plugged the pump in for the MOT it sailed through. after they completed the test i unplugged the pump and asked them to do a sniff, and the emissions were sky high. I originally put this down to the fact that i had given the car a good spirited drive to the garage and asked them to do emissions straight away, and once the car had sat for a while the emissions had increased. No i am starting to think it was the port air, and as such i should leave the pump well alone. Anyone else got an opinion on this? I know i could go down the route of fiddling with the apexi settings, but just how in depth is this?
I know the yanks have taken off the mechanical air pump, on both FC\'s and FD\'s (FD one has electric clutch in it)and there is a mod to fit a Corvette Electric Smog pump feeding into the ACV. That was to get through emissions tests in California.
At idle, the volume of exhaust gas is not that great, so the air pumped into the exaust ports must be enough to dilute the emissions down below the limits. It must be possible to plumb in an air feed into the exhaust system at some point, using a check valve and electric air pump to get through those MOT\'s. It\'s either that or play with the ECU and cut some fuel and risk a lumpy idle - although you can fail on that as well.
oh well, i guess the pump will have to stay on then, was hoping the \'rag it and quickly sniff\' would help get it through!
Quote from: Profto get through those MOT\'s.
My next MOT is tomorrow at 16:10 (you may know that we have a centralised MOT system rather than MOT approved garages...). Since my air pump is still plumbed into the exhaust I\'ll get some benefit from it.
Is there anything I can do to ensure that it really is pumping well at idle?
Nothing you can do really - its fed from the airbox same as the intake. Just make sure its all upto temperature before you take it in :yes
see my TII now legal post :> :> :> :>
For me reconnecting the air pump electrical clutch may have been the way to pass the MOT at my local garage.
I was enjoying the better idle, although lifting off at 2000 rpm would always produce backfire even off-load.
I\'m starting to think that leaving the air pump connected may have been a mistake though.
I think that the exhaust gas temperature has been raised considerably with normal city driving.
My O2 sensor is now intermittent and I get more smoke upon startup, more concerning is the overboosting that I have been experiencing.
The A\'pexi is cutting the fuel at 4500rpm WOT and the boost is peaking at 1.1! It normally stops at 0.8.
I can only imagine that I may have damaged a wastegate and the O2 sensor.
Obviously the Air pump is diluting the gas but it also assists burning unused fuel in the exhaust, which will happen in the manifold and turbo before anywhere else.
I thought I could smell that odour that you only get from a new downpipe off any car shortly after but ignored it.
The pipe that fed the removed secondary cat was blocked intentionally, therefore the exhaust manifold is getting that extra air as well.
Starting to think I should have driven 500 miles to WGT and back for the MOT because it passed there last time without the pump!
I finally got round to solving the overboosting problem.
My fears that I had somehow overheated the turbo were unfounded, it was just a split silicone air line from the secondary control solenoid. Happy days.
Air pump remains disconnected now.