Surprised myself by coming this far in rotary knowledge and I still don't really know what the air pump is for.



Where does the air get pumped to, and why? Will removing it have any noticeable effect?



J

they air pump is used to put fresh air into the exhaust ports between idle-2500/3000rpms (it varies), it um makes it pass smog. if you take it off the only thing that happens is that it will idle a little rich, because the airpump air throws off the o2 sensor, but the ecu is expecting the signal



mike

okay so how does the air get to the exhaust ports then? Because the hose is definitely connected to a thingy (technical term) on the intake manifold . . .



J

it goes in the the acv (thingee) and thru some ports in the block to the exhaust ports



mike

hm, ok, thanks



J

It pumps air https://www.nopistons.com/forums/pub...IR#>/smile.png.



Actually, on the 79-80 cars, I believe it pumps air first into the ACV (air control valve) where its then metered out into the thermal reactor which acts as a form of catalytic converter.



On the 81-85 cars, it pumps air first into the ACV, and then is metered out into the catalytic converters. Without the fresh air supply, the cats would fall apart and clog the exhaust. Removing it without removing the cats will significantly decrease the lifespan of your cats.



~T.J.

ding ding ding.We have a wiener. https://www.nopistons.com/forums/pub...#>/biggrin.png i read that on a wankel site before.Thats one of the things that makes a SA unique.Amongst others. https://www.nopistons.com/forums/pub...IR#>/smile.png

The air is pumped into the exhaust either right at the header or at the catalytic converter under most operating conditions. The air helps complete the combustion of hydrocarbons coming from incomplete burning of fuel in the engine. The rotary is a pretty dirty engine and puts out a lot of hydrocarbons.



If you disconnect your air pump the catalytic converters will not function well at all and will run a lot cooler. There is a temperature sensor on the main catalytic converter that detects when it is overheating. If this occurs then the air control valve (ACV) directs the air pump air back to the air cleaner lowering the temperature of the catalytic converter.



I do not think that the life of the catalytic converter will be affected if the pump is disconnected but it also will not be doing much cleaning of the exhaust either.



Hope this helps.

it rarely meters it into the cats directly, thats an evil forum myth



mike

OK, so it won't provide any gain to remove?



I have a full dual exhaust and an intake kit. I just have a little filter on the pump, but was thinking of removing it altogether...

you could always use it to open your 6 ports



mike

you could always use it to open your 6 ports



mike [/quote]

Its very useful to open the 5th and 6th port .. Actually works great for that. I just make a small hole in the hose coming from the air pump and add a dual sided barb to connect the Aux port actuators to it. Hooked all the hoses back up (its actually good for your cats to have that fresh air pumping through.)

Re: What Does The Air Pump Actually Do?
 

I know this is a really old thread but just had to add this... because so many people over there (I'm in Japan) seem to wreck their engines and say rotaries are unreliable because they don't really know what everything is there for....

The air pump is not just there for emissions. The air pump (on an FD at least) pumps metered air into the exhaust manifold in order to thin out the hydrocarbons (unburned gas/carbon) and accelerate the exhaust going out from its thermal expansion (not combustion mind you, thats why its metered so it doesnt explode in the ex. manifold and blow it apart), mainly at low RPM ranges when the combustion efficiency is low and you've got more unburned gas and carbon. Its just how rotaries work, they don't burn efficiently at low RPM. If you remove or stop the air pump without removing the cat or while having a small diameter restrictive exhaust system, it will:

1. Eventually clog the catalyzer and/or cause it to heat up and cause detonation inside it which will crack the honeycomb of the cat(which is more likely and so it wont clog in this case lol) and make it totally useless
2. If you use the engine alot in traffic; ie low rpm ranges, no airpump /restrictive exhaust will cause more carbon buildup in your engine because you are not thinning it out and ejecting it out of the ex. manifold as much. The rotors will rake the carbon back into the engine if you don't rev high to push it all out - you always need to rev high in order to keep your engine from fouling the plugs with the excess carbon/causing carbon build up on the rotors/seals. Thats why removing the air pump is best left to track only cars or if you live somewhere with no traffic.
3. Lose a bit of low end torque for some power gain+ for not having to turn the air pump on the belt.

If you get rid of the air pump or stop it you pretty much need to take out the cat or it will eventually heat up and crack, which happens more than clogging I believe. Even if you have a big diameter free exhaust/no cat you will also need to drive the car differently; drive it at high rpm alot to prevent the plugs from fouling up; good for race cars, Not practical if you use your car in any traffic, because it will foul the plugs easier and lose a bit of low torque.

If you only drive on highways and the track, by all means pull it out, but just be aware of the above. And people who have plug fouling issues/unstable low rpm/idle with their FDs often removed their air pump, or if they have a working air pump have a clogged up ACV that meters the air in this system, or the check valve going into the cat. Which can lead again to a blown engine from the excess carbon.
I've never fouled plugs on my SA or the FD (light tunedw/full exhuast/sport cat/intake/power fc) in the 26 years I've owned it.

You have to realize Mazda engineers put years of thought into balancing the engine for everyday use.... if you mod it to be a track car you have to treat it like a race car ...break it down and inspect it after every run etc. Removing stuff will make the engine operate differently, and also require the user drive the car differently... or they will eventually have fouled plugs, detonation from the carbon = lose compression and blow the engine.

Re: What Does The Air Pump Actually Do?
 

Old but still useful. Spot on about balancing....

Other issues without the air pump (that can be found in books and many threads):

• the water pump pulley & belt have too little contact. Over-tightening the belt to compensate destroys the bearings.
• Per Chiltons the air pump cools the exhaust flow at the injector (and then obviously heats it in the header / pipe as the fresh O2 reacts with hot, unburned fuel). An aside, this can result in glowing red headers meaning a tune-up is needed to make the exhaust a bit less rich.)
• With newer cars, the O2 sensor & computer are thrown off, and the car doesn't understand how it should react. On carbs, it is a similar but an analog balancing act
• Reactors and cats definitely need oxygen to work and airflow so as not to overheat. The air pump provides both. Rotaries run richer than pistons, meaning cat's get a heavy-duty work-out even when optimally tuned
• Even if the reactor / cats are all deleted, there is still value in keeping the air pump