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test pipes & air pumps on an 81

T

trent81

Guest
If I take my catalylic converter off and install a test pipe what do I do with the air tube from the air pump to the converter? Will the lack of back pressure from the cat harm the air pump? Don't want to remove the air pump, want to keep the stock appearence and make it easy to put the cat back on without to much trouble. Anyone know or have advice/experience with this?

Thanks
Trent81
 

Yoda

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1981 UL5
I removed the cat from my 1980, 1984, 1985 when I lived in Nebraska and just left the return tubing there. I didn't have any problems. I thought about making a hanger for them but just never got around to it :( I kept the original cats (as these were new cars at the time) and replaced the cats when I trade them.

BudD
:w
 
T

trent81

Guest
Bud,

Does the air-pump have any input to the ECM? Wonder what effect it would have on the computer if I just left the tube open from the air pump. I ordered a test pipe from Muffler Tech $45.00 to the door, includes all hardware for install. Just don't want to damage the air pump.

Trent
 

Tom Bryant

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1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
We had a test pipe on the '81 for several years. When we put a new converter on it I honestly couldn't tell much, if any, difference. A true dual system like Bud's would be a different story.

The air pump is just that, an air pump. It supplies oxygen to the exhaust manifolds to finish burning the unburned fuel that exits out of the exhaust port. It also supplies oxygen to the Cat so it will light off faster. The AIR pump isn't supposed to run with a back pressure as is evidenced by the use of check valves in the system to keep the exhaust back pressure away from the pump. So actually you will be doing it a favor by just letting the converter pipe blow. If you plug it off, it would have to force all it's output through the exhaust manifold tubes which it probably could. These things don't really put out much air. But then they don't need to for the job they do.

The computer worked just as well with the AIR pipe on or off as the cat tube is downstream from the o2 sensor and has no effect on it.
 
D

Dave L.

Guest
Ditto what Tom says.I have true duals on mine.I took the pipe off and the hose to the diverter valve off.I put a rubber plug with a clamp on at the diverter valve.I also removed the air pump belt.It has no effect on the computer,car runs extremely well.
 

Nut

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Trent,
I tossed the AIR Pump, original Cat, exhaust manifolds and the plumbing and added headers. The only thing it did was give me a 30 hp increase! The Pump will not affect the ECM.

Good luck.......... Nut
 

Tom Bryant

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Hey Nut,

Did you see this post from a454corvette with the '74 "SPEC" paint code car?

Tom
 

Nut

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I hadn't Tom. I've been on the Left coast for two weeks with Bud, BlackDoG and Bro Ken (and squeezing in a little work too). I just responded to it.

............ Nut
 

Tom Bryant

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1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
Nut,

Hanging out with that bunch it was a wonder you could function at all. :L :L

Tom
 

Yoda

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we were :cool we did a little :dance we :w at all the Corvettes & Ladies and we got out and :booty and had a little :J

Yoda
 

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