Converters with and without AIR tubes

[b4black]

My '82 and '83 TR's both use converters with AIR tubes and smog pumps. Since converters today are much more efficient than the '80's, is it possible to use a converter without the AIR tube and still pass emissions (dyno, not visual).

If so, I could get rid the pump, the diverter valves and all that tubing (and still be green ).

Thanks!

[gofstbuick]

If you have to pass a visual inspection, then removal of the plumbing leading up to the AIR port on the catalyst may cause a visual failure. One of the functions of the AIR system (during warm up) is to get the catalyst to light off, by adding oxygen to get the catalyst up to operating temps faster. Thus allowing closed loop operations sooner (bear in mind that closed loop is really a funtion of coolant temps and O2 switching).

[b4black]

Dyno, not visual.

I totally understand how a converter and the smog pump works. I just want to know it there are non-AIR converters that are replacements for the AIR converters. I figure converter technology has advance some in the last 20 years.

[b4black]

The SFI cars don't use a smog pump. How do they light off the catalyst???

[gofstbuick]

Originally posted by b4black
The SFI cars don't use a smog pump. How do they light off the catalyst???

I expect that the SFI cars uses the presets in the calpak to get the cat to light off, then the O2 takes over and makes the three-way-catalyst work more efficiently.

[b4black]

I just called Random Tech and asked someone who knows. They said converters for some time haven't needed smog pumps. They don't sell any with AIR tubes and they said their cats will have no problem lighting off.


If it lights off qucikly without extra oxygen and reduces (oxidizes actually) emissions without extra oxygen, the smog pump, valves and tubes becomes vestigial. They only reason to keep it would be to apease a referee (which I don't have to deal with).


Thankfully the IL EPA realizes that the objective is clean air and not enforcing ticky tack laws.

[Freddie's Buick]

Rich,

I have a differant version of the A.I.R. system on my '81 Buick and I believe it was only used on the 81's. Interesting to note is that it does not use a line that introduces O2 into the Cat, (the A.I.R. tube).

Nor is it like the A.I.R. system that was on the '79's and earlier that pumped O2 thru external steel lines that screwed onto the exhaust manifolds.

Instead, pressurized O2 flow is pumped internally via the intake into the exhaust ports on the heads. Thus, no line to the Cat, and no lines on the exhaust manifold. And it was California approved.

Why the later vehicles used the A.I.R. tube to the Cat I don't understand. But I assume that it probably might have something to do with changes to the 8963 head design.

(I don't think that the clean air requirements improved on the '82's. They were the same as the '81's).

I also have an '84 Buick with the A.I.R. tube and in my opinion the '81 is a better visual and practical system and design. It's also a whole lot easier to work on.

Also, after-market Cats come with the tube on the Cat capped. This is so the Cat can be used on either system. So I assume that the Cat plays no role in the mechanical catalyst. It's all in the plumbing.

[b4black]

Buick never used the tubes to the exhaust manifolds like a SBC. They always used the passages to the heads via the intake manifold. An an ECM car, these passages were only for the brief, open loop "light off" mentioned above. You can't pump here on an ECM car during closed loop, since this is up stream of the O2 sensor (it would get mighty confused).

The converters with the AIR tube have a reducing region and oxidative region. The air (oxygen) is introduced in the middle of the cat, at the start of the oxidative region.

My converters are monoliths. I think a '81 NA used a pellet bed. Pellet beds may not have had the two regions and maybe this would explain the lack of an AIR tube. So maybe yours only pumps to the intake at open loop and then diverts to the air cleaner cleaner the rest fo the time.

[Freddie's Buick]

So maybe yours only pumps to the intake at open loop and then diverts to the air cleaner the rest fo the time.

Yes and no.......no, air is only diverted to the air cleaner at WOT and at de-celleration. Yes.... during open loop air is constantly pumped into the ports.

Yes.....I think mine was a single bed pellet Cat design. The 4-Cat types were: Single bed and duel bed monoliths....single bed and duel bed pellet.

Also, two catalyst types were available: Oxidatation catalyst, (OC on the emissions label), or three way reduction, (ORC on the emissions label).

And yes...I have seen Buick engines with the A.I.R. tubes on the exhaust manifolds. But these were on the Buick V-8's.

[b4black]

Originally posted by Freddie's Buick

Yes and no.......no, air is only diverted to the air cleaner at WOT and at de-celleration. Yes.... during open loop air is constantly pumped into the ports.

Where does it pump during closed loop, when it's not diverting? I don't think it can be the ports, because they are upstream of the O2 sensor. Is there another place?

[Freddie's Buick]

Yes and no.......no, air is only diverted to the air cleaner at WOT and at de-celleration. Yes.... during open loop air is constantly pumped into the ports.

Oops correction!

Air is diverted out the 'exhuast muffler' on the air pump during WOT and de-celleration.

During open loop air is 'not' constantly pumped into the internal ports. I stand corrected, it is constantly pumped into the air cleaner. (Ever since I removed the entire system I'd forgotten how it worked).

[buick83-T]

Has anyone removed the smog pump or by-passed it on the 83 t-type and gained performance?

[Freddie's Buick]

It depends on if your state allows for this mod. The AIR pump works with/for the catalytic converter. Removing the pump renders the Cat inoperable.

My state no longer requires these emission checks. I removed the pump/cat. More flow, one less belt to run, a little more horse.

[b4black]

The drag created by the pump is pretty trivial, IMO. I bypassed it mainly because the tubing and valves really get in the way. Too much stuff bewteen the distributor and the carb, makes it very tough to do any work.

Turbo-Rich pointed out that without the pump in place, the bracket for it, the A/C and alternator becomes very flimsy. You'll need to get a shorty belt for the crank, water pump and alternator.



My emissions are due. I need to order that new cat.

[buick83-T]

Rich,
What size belt you get? Do you have part # for the shorter belt to by-pass the smog?

[b4black]

Carquest XL 7460
9.5/10mm / 1185mm

On the belt:
15460
11AV1170
2579


Fits around the crank, water pump and alternator

[b4black]

Got the non-air tube converter on and went for testing.

SUCCESS

HC = 0.161 on 0.407 std
CO = 0.749 on 3.804 std
NOx = N/A


I got a good deal on a unused, 2½" converter for a 84/85 TR. It's a Dynomax #15146. I had flanges made up and put them on using band clamps, so I can change them later when I change the DP or exhaust. So now I'm emissions compliant, but can still get rid of all that tubing, valves and pump.

[terryk]

Originally posted by gofstbuick
If you have to pass a visual inspection, then removal of the plumbing leading up to the AIR port on the catalyst may cause a visual failure. One of the functions of the AIR system (during warm up) is to get the catalyst to light off, by adding oxygen to get the catalyst up to operating temps faster. Thus allowing closed loop operations sooner (bear in mind that closed loop is really a funtion of coolant temps and O2 switching).

Sir, you are a wealth of information!

I am curious about one thing on air injection and manual trans. It appears that all manual trans applications use air injection whereas the automatics may or may not.

I understand what it does but why does a manual trans change that? On a 3.4L DOHC, the injection only runs on a cold start. I figure the cat would heat up the same as it would with an automatic. The service manual implies that the injection stops after the temps come up and it's not used after that. I notice the F/Y body use the injection on both auto and manual and that some ECM's have provisions for it but don't use it on the automatics (3800 V6 is a good example).

I'm not talking about the older carburated cars. I understand the need there. It's as if the air pump is a last ditch effort to keep the cat lit but why would it be different for a manual over an automatic?

[gofstbuick]

This is just speculation, but I suspect that since the auto trans shifts more consistently than a manual, so it would more consistently pass the FTP (Federal Test Procedure) emissions test.
Who knows how the manual transmission was shifted during the test? (rhetorical question)