SC owners: Pros/Cons of removing Air Pump

[J-RAD]

I'm wondering how many of you have removed or thought of removing your air pump system. My understanding is that it's part of the emissions control system for N/A cars, so I imagine this would be considered a sin in Cali...but how about the rest of you? Is there any advantage/disadvantage to removing it? Does it really impact the emissions that much? Does it potentially just divert a little power given that it's belt driven? or can it be considered dead weight? Just looking for some thoughts on the issue.

[Pillow]

Get rid of that turd!

Mine just passed GA emmisions today with out it. I am waaaaay lower than required levels of everything w/o any stinking air pump.

[Jdub]

I removed my pump without problems, which is to say I pass emissions just fine. The belt to the air pump was not hooked up when I purchased the car. The guy who PPI'd my car said not to worry everyone does that.

If you don't have a visual inspection in your state, my suggestion is that you search the archives and find out what nuts are needed to cap the air pump "intake" holes. Remove the pump, the tubing, etc. and put it all in a box, wrapping the unit in plastic or at the least wrapping the air filter so it stays reasonably clean.

If you have a visual inspection, or more to the point, must put the unit back on annually, then just remove the air pump, cap the hole into which the air feeds, and put the unit away, again protecting the air filter or better yet getting a fresh one for the unit.

Remember to snip three pieces of fuel hose or equiv. to cover the now-exposed threaded studs that run horizon. from the case. You don't want to bugger up the threads and have a hard time threading the nuts back on when you put the unit back on.

John

[Sean Hamilton]

But is there any evidence of a performance gain after its removal?
If not, then why remove it?

[bonedaddy]

I have a '75S with an air pump. I can't speak for the SC, but the effect should be similar. I set up my CO at around 2-2.5% with a Gunson Gastester with the pump disconnected and the hose plugged as per instructions on the fan housing. After re-connecting the pump, the CO dropped about another 1%, so it does have some effect on emissions. As noted by others, you can probably pass most tests easily without it.

[Pillow]

>But is there any evidence of a performance gain after its removal?
If not, then why remove it?<

Less weight and clutter in the engine bay.... Unless you like heavy cars that you bust your knuckles on

[Jdub]

Sean:

I'm with Pillow: the air pumpt just got in the way of plug changes and valve jobs. That's the only reason. I have a test pipe in as well, but I do not feel any difference in how the car performs as a result.

I felt more of a performance boost rebuilding my distributor! Now THAT is a job I'd recommend!

John

[Jadams1]

I have removed the entire system but keeping it just in case. I live in RI and just got inspected with it on. I'll let you know what happens in two years when it's time for a reinspection. I removed mine for astetic reasons and improved access to the left side of the engine bay. Do a search on the BBS for more info.

John

[JMPRO]

I have heard that the air pump also helps to cool the exhaust before it gets to the cat and prevents premature aging to the cat, headers and muffler. The pump at most uses 1 hp to operate . If you want big hp gains take off the fan belt.
Jerry

[Jadams1]

My car is a 80 Euro SC which doesn't have a CAT, just a pre-muffler.

[J-RAD]

Thanks, guys. Actually mine was already removed when I posted this topic. It's sitting in a box in my garage...just in case. Fortunately, I don't have to worry about emissions inspections at the moment (we don't have them in MN). However, I was curious how much the air pump even helped emissions. It seems kind of pointless to me but what do I know. JMPRO, based on my understanding (and I've been wrong before), I don't think it was a function of the air pump is to cool anything at all. Rather, it mixes "fresh" air in with the exhaust to dilute it somewhat. Thus, a "lower" emmission.

[Jim Sims]

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=66358

The above message is a warning not to do anything irreversible; who knows what the future may hold. If you take it off, do so in a careful manner and save the parts for yourself or another future owner. In addition, I've heard if one takes the air pump off one should also remove the air line and plug the ports in the heads. Apparently there is a check valve integral to the air line which can become clogged/jammed with exhaust debris if not continually flushed with air from the air pump. The thermal reactors off my '76 are carefully stored away and when I remove the air injection system, heater boxes and muffler to install SSI's and new muffler I'll do the same with those parts. Cheers, Jim

[Pillow]

>It seems kind of pointless to me but what do I know. JMPRO, based on my understanding (and I've been wrong before), I don't think it was a function of the air pump is to cool anything at all. Rather, it mixes "fresh" air in with the exhaust to dilute it somewhat.<

JMPRO is correct from my understanding that it is to cool the exhaust. At least from what I have been reading in the FI book by Charles Probst.

The older CATs are much more sensitive then todays 3-way CATs. Apparently to gain the most effecient cleanzing of the exhaust it needed to be a certain temperature to process the nitrogen ("No").

Also I think it was mentioned that in early CATs there was a problem of a rich exhaust mixture detonating in the hot CAT which would essentially blow itself to peices internally.

I skimmed this part in the book because I could care less about CATs, so take this analysis with a grain of salt.

[rlane]

I just removed the air pump injectors. You will need 6 plugs that our great host wayne sells as part number "PEL-BRC-02..Caliper Plug 914-4, All inner cap" 6 sets you back $30. Be CAREFUL removing the "injectors...a day or so of repeated exposure to penetrating oil REALLY helped!

[Bones]

Does anyone have a photograph of the holes to plug after the air pump is removed . Mine was removed a few years back and I have a suspicion that the holes were never plugged . If it is the case that they're not plugged I haven't suffered any side effects from not plugging them . But I can't tell till I see a photo of the holes . I noticed yeserday when a friend and I backdated the heating a threaded hole at the base of the inlet pipes near the injectors , are these the ones .

[Jadams1]

[jmohn]

Remember, air-pumps weren't used only by Porsche, American cars (and others) used them too. Whether their function was mostly dilution (which I think is somewhat true) or cooling the cat. (which seems unlikely, cat.'s must be hot to function) or the addition of oxygen as an aid in catylization (seems likely) is relatively unimportant. Keeping in mind how few of these air-pump equipped cars are still on the road, the slightly increased emissions they may produce if the pump is removed is a non-issue. As I recall, on American cars (this was a pre-Porsche period for me), after a few years, without maintenance (yes, they needed maintenance, filters, testing for efficiency, etc.), most air-pumps weren't doing much anyway. Most used cars, during that period, had the air-pump hanging there with no belt running it, usually because the bearings failed and no one wanted to fix or replace them. Also, as I recall, they were designed only to be effective at idle (emission testing, at that time, was performed at idle) the reasoning was, in high traffic situations, cars idled a lot and, in the pre-EFI days, generally ran rich at idle causing, realitively, more pollutants than when at speed. I don't think there's a great increase in HP if you remove the air-pump (maybe 3-4 HP) but it certainly cleans up that side of the engine and makes maintenance easier. Unless you need it for the visual portion of your local emissions test, it's just in the way and, probably, is virtually useless anyway.

Jerry M
'78 SC

[Bones]

Originally posted by Jadams1

Thanks...they are not where I thought they would be!

[tops911]

I thought the 1968 911s had air pumps, and they did not have cats. Anyway I think there were some early 911s whos air pump ran off the cam, which is why they cant be easly converted to the pressure fed tensioners. For what it's worth

[1980SC]

My understanding is that if you don't have the cat in place, the air pump doesn't really do anything. It is there to aid the 2 way cat. I don't think it is there for a dilution effect, but mostly to make the 2 way cat work more effectively.

The air pump can't be for the cat. The euro '78-'83 SC's came with the air pumps and NO catalytic converter.

Rob
1980sc euro