off road pipe to replace catalytic

[PJ Reynolds]

Has anyone replaced their catalytic converter with an "off road pipe"? I want to, and found one at: http://proficientperformance.com/Mer...&Store_Code=PP

I have no clue if the above web address will link through or not. Anyway setting my ineptitude for clever computer manuevers aside. Will using this off road pipe in any way affect the oxygen sensor? I expect that replacing the cat with this pipe will only increase horsepower, and make my 91 RS kick ass just a little more than she does now. As always I look forward to any feed back

[Benm109]

Putting in an "off-road" pipe will not affect the oxygen sensor. The only thing is that you can get an exhaust shop to weld in a pipe for less. $80 is too much for just a straight pipe. Have you gotten rid of your smog pump (or AIR injection)? If you have, then that's another reason not to get that pipe. If you don't have AIR, then you won't need that piece on the side, either.

Basically, just get a straight pipe welded in at an exhaust shop and leave the AIR line that went to the cat off (it is OK to do this, the previous owner of my car did it). And, assuming you don't have emissions in your state (since your taking the cat off), get rid of your smog pump/AIR stuff, too (I can give you a step by step if you need it, it's not hard).

[PJ Reynolds]

That sounds better

Thanks for the feedback BenM109, You have actually given me good info in the past. Yes, I would like to know "step by step" procedure to remove my smog stuff. I live in Florida, we don't even have inpections here anymore. If I could remove the emmision stuff I would be in a much better position. I'm not sure if I can just roll into any old muffler shop & have them weld a pipe in for me. Now that you mention it though I will go back to the shop that did my Flowmaster and ask him to do just what you suggested. Then I will follow your step by step instructions to remove the air pump. Actually, I'll do that as soon as you share those steps with me. So, if you would, and if you don't mind, let er rip Ben, I am all ears.

[Benm109]

OK, here I go. Doing this mod will also give you a lot more room under the hood. Before I start though, you should know that you will have to buy a couple of things, a new belt ($10-$20) and pipe plugs ($2-$3).

Disconnect the negative battery cable. Locate the smog pump (the pulley directly under the AC compressor). Loosen the 3 bolts on the pulley. Remove the belt. Now unbolt the pulley from the pump. Look behind the pump and unbolt the hard line (2 bolts). Remove the black box located behind the AC compressor by popping off the cover and disconnecting the 2 wire connectors (put them somewhere safe). Look at the AIR pipes that go into the exhaust manifold. Disconnect the large hose that connects them on both sides and slide it out. Unbolt the pump (2 bolts) using torx bits and "shimmy" the pump out of the engine compartment. Reinstall the 2 bolts for the pump where they were (trust me on that one). Somewhere during this you are going to have to remove the hard line that goes to the cat, but I don't know when since I didn't have to (don't forget to cap off that connection off the cat, or you'll have an exhaust leak).

Now remove the AIR lines from the exhaust manifold. Sometimes you can just unbolt them. Or sometimes (like me) you have to cut them off (sawsall, hacksaw, tubing cutter, etc.) and then unbolt them. Plug the holes with 1/4 pipe plugs (hardware store, plumbing dept.) and teflon tape. The last thing you have to do is reroute a new belt (part number 968K6 , it's longer so it will work right) and put the negative battery cable back on and you're done.

I'll post a picture in a minute of how to reroute the belt. Also, I know this may seem like a lot to do, but it's easy and can be done in about 1 hour. It will give you so much more room under the hood.

[Benm109]

Here's a picture of how to route the new belt (part number 968K6). It's not the best picture. If you can't figure it out just let me know and I will try to find another, better picture.



Oh, now that I think about it, you can still use your old belt if you buy a delete pulley from the dealer (GM part number 10186167). The only thing is that is expensive (listed as $38 but since it's a "special order" item it's more like $60 to $70). I would recommend just rerouting the belt, it's cheaper .

That's all you have to do. If you need a better explanation of anything, just let me know. And, once you get rid of the AIR stuff, and you want to get rid of more, just let me know. I have removed a ton of stuff from my engine bay (AC, AIR, heater valve, cruise control, stock intake) and it look 10 times better. I need to take some pics of mine, soon.

[PJ Reynolds]

Thanks Ben

Thanks alot Ben, I really appreciate this information. I will approach this adjustment hopefully this weekend, and I will let you know how it went. I will be cureous to see how much of a kick up in ponies this provides too.

[DeWynter]

It probably wont be much in the pony area, as the air pump has very little resistance. Bes ides it only actually pumps air when you start the car and for a few minutes after, then the valve switches and it just blows air out under the car.

[Benm109]

DeWynter is right, it won't give you any more HP, but I promise you'll be glad with all that extra space. Taking the cat off might give you a little, but not this mod.

[PJ Reynolds]

No emission restrictions here!

I'm not as concerned over making more room in the engine bay, as I am in making more GO POWER. I am determined to get the cat off the car though. One of the guys I work with advises me to keep anything I take off in the cat dept. because here in Florida they are likely to change the rules back to inspections on a whim. That was the primary reason I was looking into the "off road pipe" in the first place. I was thinking it might be easier to change things back, if and when they ever did change the rules backwards. Either way though, that cat is coming off. I had an 88 RS that I had the 305tbi rebuilt & I hallowed out the cat, it did make a noticable difference, but that was then, and this now, and we no longer have some employee for the State looking around under the car, so, it's coming off as soon as I get a chance. I am looking forward to hearing my baby scream without that restriction thwarting the decibles of my exhaust note. Plus with less resistance to the air flow, I know she will get up & go a little bit better, and every little bit helps.

[Benm109]

I understand. I just wanted to make sure you knew that taking the AIR off won't give you any noticable HP, but taking the cat off will give you some more HP and your car will definetely sound better!