air pumps and cat\'s

[catboy]

Could someone explain the function and operation of the air pump system on a \'89 turbo II?...    I have a cat-less exhaust system, and I know its been mentioned elsewhere that removal can result in idling issues, but I dont fully understand what the function of this unit is (prob just me being thick)...       ...it appears to come on for a few seconds each time I start the car (about 5-sec delay from engine start, and runs for about 3-5 secs then stops)
Thanks in advance
b

[bnaellis]

HI Catboy,
I am not entirely sure, expect someone with more knowledge to answer this when they get time. But to my understanding the airpump on an rx7 works on low rpm, I think below 3k rpm
and sends a lot of air into the catalyst to help reduce the hydro carbons etc that are emitted from the exhaust system. Thats about as much as I know on airpumps sorry.

regds

Brian Ellis

[Jus]

HMMM, that bloody air pump! I removed mine however; before you do you must know its function.

If your getting rid of your cat...the cat needs the air pump to work and reduce emissions. With a midpipe fitted there is no need for the air pump but... Carry on reading...

The air pump supplies secondary air injection at idle and low rpms under 3k. That’s why it runs like shit when you just unplug it without an ECU to tune out the extra fuel at idle.

Plugs will foul with a rich condition and will be noticed by the "miss" in the idle. With the air injection being gone will change the Air Fuel ratio at idle (If you ever come to sell the car, people will think your engine is goofed).

You can adjust the idle screw but raising the idle only tries to mask the problem. I suggest leaving it plugged in until you get an ECU like the Power FC (err FC equivalent) where you can pull out fuel at the 1000k rpm level. This way your not just trying to compensate for a problem you have created.

If you remove the air pump you will also need a pulley kit. A word of advice, I’ve had 3 air pumps fail (so I did what it took to remove), the symptoms start with a rattle (sounds like induction intake) if you hear this, change quick! If your air pump locks up, you will have no water-cooling as the pulley belt doesn’t turn. If it does it turn the belt will hit up and snap! (1 or 2 miles later) If not spotted, your engine will be fried…

Hope this helps...


Jus

[Grizzly]

I think to make it Simple, you have the Cat that filters the Exhaust gasses, the Rotary is prone to not to burn Eficantly (Lots of Hydro carbons in the Exhaust gasses off load) that if exesive will block your cat and cause loss of power or ever Engine damage.

The aim of the air pump is to lean out the off load (0-3000 rpm) mixture (lowering the Hydrocarbons) that will block up your cat.

So basicly if you remove your cat the air pump still has a Job to do (helps low load mixture as the engine was designed that way) but it can be removed causing the the Idle to become richer and genraly rougher.

Most people though remove the air pump as a reliablility mod, what happens is the pump bearings seize and causes the water pump belt to over heat and snap (then there is nothing driving the water pump). So the basic idea is if its not there is wont brake.


Chris

[Jus]

Thanks Chris, I kept it simple and you have confused the hell out of me now I thought you wrote the same thing as me but used different words to get the same result :p

No worries

Jus

[Grizzly]

Jus.

Could someone explain the function and operation of the air pump system on a \'89 turbo II?...

Not many people have EMS\'s on T2\'s and the Symptoms arnt as bad.

I was only explaning how they work.

Chris

[Jus]

[Grizzly]

On the T2 if memory serves correctly there is too V belts that both drive the Water pump, one if for the PS,AC, Alt & water pump.  The other drives the Air and water pumps.

So on the Second gen i\'d say its a safer bet to leave the Pump on or get a Dubble Alt Pulley.

I have had a near death experiance becouse removing the Air pump had taken one of the Drive belts off the Water pump, this made the remaining belt slip like mad. I tightened it up a few times but one day (duno if it was to tight or just worn out) it snaped causing the same water pump not turning problem.

Urm i was half way between work and home (not a nice feeling)

Chris