Pros/Cons of Air Pump Removal
 

So I think I've read just about every thread on the Air Pump delete. Mine is noisy and I want it out if its feasible. So I decided to sum up here what I believe the pros/cons are and would appreciate any confirmation or input.

Purpose:
Air Pump forces oxygen into cats at 3800 RPM and below to help the cat burn better at lower temperatures encountered at lower RPM's to allow for lower emissions.

Impact on Engine and HP:
The Air Pump has zero affect on fuel/air ratios, boost etc i.e. no impact on the engine what so ever other than a very marginal HP gain since the Air Pump will no longer draw any engine load.

Positives:
No Air Pump Noise. Cleans up engine bay. Almost negligible HP Gain.

Negatives:
Cats may potentially not last as long since carbon build up can occur with less burning occurring at lower RPM. This is subjective from what I can tell based on reading.

Failed Emissions test that can be overcome utilizing a high flow cat? Can this be confirmed?

Potential roughness of at idle which can be overcome with an idle adjustment.



Feel free to interject or confirm, but I think I have this figured .... famous last words :dunno:

Thanks,

Chad

Remove air pump = failed emissions. If you remove the air pump, you should remove the cat as well as its just gonna clog. High flow cats provide more flow, not better cleaning, they provide less cleaning in fact.

thewird

BioHistoryMechaniChemistry
 

If you don't have oxygen injected into the cat, the hydrocarbons will sit on the cat since there's no oxygen to react with it and pull it off the metal. So the cat becomes coated, covering the catalytic metals and reducing its effectiveness. No RX-7 would pass Cali smog without an air pump; CO and other unreacted HCs would be too high.

Here's the BioHistoryMechaniChemistry behind it:

We use oxygen and a spark to blow up dead dinosaurs and fish to form CO (carbon monoxide = bad, hurts the environment, stinks, unhealthy to life forms, black, likes to stick to rear bumpers), which leaves the engine and goes into the cat. When an O2 molecule is pumped into the cat, it splits and reacts with the 2 CO molecules to form 2 clear odorless CO2 molecules, which the same exhaust people make when we breathe. (Some oxygen radicals also bond to loosely-bound protons, and you get a little H2O as well.) But CO doesn't spontaneously convert to CO2. The reaction is *catalyzed* by the hot platinum, rhodium and palladium honeycomb in cat. CO2 is also what green plants absorb as a reagent for photosynthesis, which in turn produces more oxygen for us to use to blow up more dinosaurs. :)

As far as performance, the air pump itself is somehow more parasitic than it being "just a pump/pulley." When the air pump comes on, some people including myself notice a subtle drop in power. And it likes making clicking and moo sounds.

hahaha love the explanation m8.

Point taken guys. Tolerate the quirky air pump sounds or run the car with no regard to emissions. thanks.

Also, if you remove the airpump and cat, be prepared to take on an entirely new Odor!!! ;)

That can be mitigated with proper tuning and leaving the stock 550cc injectors alone.

thewird

*There is more space and less weight w/o the AP. I removed mine with all other emissions (I don't have testing in my state).

*From what I remember reading, effects of AP removal varied alot if you remain on the stock ECU. Some reported absolutely no effect on engine performance, while others reported hesitation on throttle tip-in, poor idle quality etc. Your results may vary.

*I saw/sensed absolutely NO performance gain. None.

*Hi-flow cats seem to be unaffected by the removal of the AP. I removed my AP nearly three years ago with a Bonez HFC that was already 6 or 7 yrs old. Still seems to be flowing just fine...and I'm still on the OMP along with a little pre-mix as well. Last winter I pulled it off and the surfaces inside still looked clean too. This is NOT necessarily so with stock cats. From what I understand, they will plug from no AP but I have no direct experience.

*I sensed NO change in the smell from my exhaust after removing the AP... and keeping my Hi-flow cat.

* You will be forced to buy either an under-drive pulley set or an idler pulley to take the place of the AP pulley. This is necessary to keep at least minimal belt contact with the water-pump pulley. Emphasis on minimal. IMO, the under-driven pulleys had too many downsides for a streeted car. I went with a GARFINKLE idler pulley for various reasons, but others like CHADWICK and PINEAPPLE RACING offer these idler pulleys too.

Thanks guys. I dropped the car off for pulley installation and aluminum AST last night as well as fluid changes. I has the car two weeks and am experiencing a chain reaction where I'm doing one thing that leads to another. I sense a light wallet in my near future! Anyway I'm dumping the air pump and will go for the ecu as well as downpipe, catback and high flow cats and see how it goes as soon as I can.

I had the fuse to my airpump blow once when I was on the stock ECU and I thought my car was broken. The ECU uses the O2 sensor to set idle and light load mixture, since the ECU knows the air pump injects air and that fouls the O2 sensor readings it "fudges" the numbers so it knows what the true O2 sensor output is.

With no airpump, the ECU fudges the numbers the wrong way, resulting in an incorrect mixture. This makes for rough idle, loss of idle vacuum, and rough and stumbling cruising/light load driving. Basically it will drive you bananas.

This also holds true for a chipped ECU.

With the PowerFC, there's no problems at all.

You could, in theory, unplug the O2 sensor and it will drive OK. But the stock ECU runs VERY rich on purpose with no O2 sensor so you'll be drinking gas bigtime. And, that's just a stupid hack way to do it.

IMHO, if you are going to remove the airpump, you need an airpump idler and a PowerFC to do it right. If your airpump is noisy, just buy a good used one for dirt cheap and put it on until you save up for the proper parts.

Dale

One thing to add that I read somewhere, was that removing the airpump (and setting it on the shelf for a period of time) results in air pump failure (for future use) because of it sitting still.... just not sure how valid this is.

Does the airpump go bad after sitting for awhile? after sitting for a short while? Is this true of "any" air pump?

I already have Chadwicks idler pulley. I'm looking to buy a Bonez high flow unit. have a petit ecu I need to install and also looking to get a nice afr unit.

I could care less about emissions (though I will need to hook everything back up every 2 years to pass) ... mostly I care about making things simpler and with the airpump out, it's easier to get to the turbos and troubleshoot boost issues.

as for smell and/or rough idle, I understand there are ways around this... my idle is already high at 1100 or sometimes even 1300. The only thing annoying about this is trying to get back into 1st gear when not at a complete stop. Otherwise, I prefer a slightly high idle. Also, I think we should be knowledgeable enough (almost even required) to adjust idle/mixture on our cars, not just for the sake of removing the airpump, but in general.

I think this is good advice Dale. I'll being doing this stuff within the next 30 to 60 days so I'll only put up with any idle/cat issues for a short duration.

My car generally idles better and smells a lot less with the air pump connected and working. I sometimes think of removing it but there really isn't any good reason to that I can think of. The smell gets annoying real quick.

The main reason I can think of removing the air pump/acv is due to fuel system upgrades.

I haven't seen an aftermarket secondary rail that will work with the acv in place, but then I probably haven't looked very hard either.

Thinking of removing air pump...
 

So I have an 89 GTUs. It has the air pump still in and running, only one cat. I already have a power FC installed and tuned in the car. I dont really care about emissions, im just over a year away from my car being a classic so I dont have to pass emisions. Would it be in my best interest to delete air pump and go straight pipe? Or go to a high flow cat. Im trying to squeeze what ever power I can out of her without doing any major motor mods or turbo because it was recently rebuilt and its just too soon to pull it again. I had planned on getting this:

1986 - 1991 Mazda RX-7 Power Pulley Kits. Import Performance Parts Store.
So is blocking off the air pump in my best interest? should I get the pulley kit, and piping then have my power FC re-tuned?

Thanks for the help guys.

If you have a Power FC in a 2nd gen non turbo, your airpump probably isn't even working right anyway. I can't say I've dug deep into this kind of question, but the solenoids in the ACV probably aren't even wired up. So there may be no effect from taking it out from an emissions perspective. However, the smog pump supplies air your variable intake runner and auxiliar port system. So you will have problems with those.

Your choice of exhaust is going to depend on how much you care about sound and smell. I can say from firsthand experience you will probably have a better overall daily driving experience if you go with the high flow cat.

So if its not running properly anyway shouldnt I just block it off? Is the air and smog pump the same thing? Im not super clued in on the air pump stuff. I found the block off plate I need online, and I found the pulley kit I want. But what could be done to accomplish this the correct way?

I'm looking to get rid of un-necessary things, the AC has a full delete. But I want my car running nice and fast. Im down to take steps to avoid problems.

short answer: if you had a turbo engine, you could just go ahead and get rid of it. Since you have a non turbo s5 engine, you will lose power if you just get rid of it because it's used to control the intake air system--assuming the Power FC is even controlling it at all. Imagine an NSX without working VTEC and variable intake runners.

More detailed answer: I'm assuming you are using a slightly modified version of the Banzai Racing power FC adapter for 2nd gen cars S5 cars. There are two functions of the air pump on an S5 non turbo: secondary air injection and operation of the variable intake system. I haven't looked at the exact wiring of it, but if the solenoids aren't hooked up right then the emission function may not be doing anything.

Basically, there are three main components to the secondary air injection system. There's the pump itself, which is driven by a belt. On the 3rd gen there's a clutch to actually disconnect the pump. Then there's the Air Control Valve. The air control valve actually directs the air using a series of valves and solenoids. In most cases, the air is going to the exhaust port to lean out the mixture at idle and low loads for improved emissions and better stability in combustion.

The third part of the secondary injection system is the split air pipe. This is the pipe that runs to your cat. Most people think the air pump just sends air to the cat, but that's only under certain highway cruising conditions.

Now, that's the emission function of the air pump. The horsepower-related function, found only on the 89-91 non turbo, has to do with increasing volumetric efficiency at high rpm. Remember how I made a reference to an NSX (or say a GS-R integra) with VTEC + variable intake runners? The S5 FC is the same thing, but instead of using oil pressure to drive it like on a Honda it uses air pressure from the air pump. The air pump blows open a separate set of intake air ports (auxiliary ports) which essentially changes your "lift" and "duration" for high rpm. Then at the highest rpm, the air pump helps rotate a valve that shortens the intake runners. This improves high end horsepower and torque.

If you get rid of the air pump, this air intake system won't function. However, I'm not even sure how you have it running right now with the Power FC. Maybe you already have these systems forced open (killing low end). The Power FC's sequential turbo controls can be used to operate at least one of those functions, but if you knew about that we wouldn't be having this discussion.

So, if your Power FC or airpump is still controlling your intake air system then you shouldn't get rid of the air pump. If those systems are already forced open and you don't have a problem with that, you can get rid of your airpump.

thread mark (y)

Is this only true on 6 port engines?

The part about the air pump controlling the additional intake ports and variable runner system? Yes, that applies only to an 89-91 non turbo Rx-7. Previous 6 port engines used exhaust backpressure. Rx-8's have those same type of systems but they are controlled by vacuum and electric motors.

Are s4 n/a's 6 port? I thought they were 4?

Can anyone else confirm that air pump removal usually results in poor idle quality?

The previous owner of my car removed the air pump, added 3 inch DP, removed the cat and has a full 3 inch exhaust.

The car is still on stock ecu.

If you want confirmation of bad effects, I think post #10 pretty well covered it....

^ thanks for calling that out, i read over the thread a few times but must have skimmed over that.

I guess thats where the stubbling is come from on the light throttle and trying to slowly take off in 2nd, i just thought thats how a rotary drove lolz