Carsound & Borla Exhaust Overhaul
[an error occurred while processing this directive] Short Cuts

By: Jeff Yokomura- 1/2001

Graphic courtesy   of Carsound
"There are three basic types of catalytic converts; Two-way, Three-way and Three way + Air. The first catalytic converts were Two-way."

Hi-performance Catalytic Converter and Muffler

Imagine this, you're driving down the road listening to the hum of your tires and the wind through your hair. Next thing you know you're hearing a rattling sound coming from under your truck. Sound something like a old bean can rattling under there. This how this all started. With a simple rattle.

At first we suspected the catalytic converter (Cat) had gone bad. This is common for one to start to rattle once the ceramic material comes loose. So instead of going through the trouble of checking we ordered a new Carsound Catalytic Converter from Truck Performance Center. The cat had to fill a few requirements though. It had to be hi-flow. Since we were going to replace it we might as well get some performance gain, right? The second requirement was that it had to be stainless steel. All the auto manufacturers have switched to stainless steel exhaust for the main reason that it hold up well to the elements. How many old cars have you seen driving down the road with holes in the exhaust? The last requirement is that it had to be bolt-on. We wanted to be able to install this ourselves without any special tools.

There are three basic types of catalytic converts; Two-way, Three-way and Three way + Air. The first catalytic converts were Two-way. They were used between 1975 and 1980. These convert hydrocarbons and carbon monoxide into water and carbon dioxide by oxidation. Three-way converter has two jobs. It reduces nitrous oxides into nitrogen and oxygen. And, like the two-way converter, it oxidizes unburned harmful hydrocarbons and carbon monoxide into water and carbon dioxide. The Three-way + Air has the addition of secondary air between the two internal catalyst substrate which improves the oxidation capabilities of the converter. The secondary air is pumped into the middle of the converter between the two separate catalyst coated ceramic substrates. The front ceramic performs the reduction and the back ceramic performs the oxidation. Confused yet?

Graphic courtesy  of Borla
BORLA PERFORMANCE INDUSTRIES is the leader in the design and manufacture of stainless steel performance exhaust.

Before going out and buying a new catalytic converter make sure to check your extended warranty. The catalytic converter is covered under the Federal Government and is required by law on vehicles made since 1975. There are only two ways you can replace a catalytic converter legally. One is if it gets damaged. This could be for several reasons. An accident, or more common to trucks damage from driving off the beaten path. The Ceramic substrate is fragile and can crack if shaken or beat on too hard or too many times. Poorly tuned engines can also damage the cat. Oils, lead or carbon can damage the cat from performing at full efficiency. The other way the cat can be replaced legally is if the extended warranty expires. In that cases the cat is supposed to be replaced anyway.

After removing the cat we did a visual check on the old cat. It looked to be in one piece but since we already had the old cat out and any warranty the Jeep had was well expired there was no point in keeping it. There was another problem with the old Borla cat-back and stock cat combination. The input on the muffler was too short and a extension was needed to bridge the gap between the cat and muffler. This became a problem again because the new cat was designed to the original cat's length. We had a 6" extension piece made at a local exhaust shop but not this piece was stuck on the old cat. We ended up bringing the muffler closer which was a temporary fix. After everything was reattached we started up the Jeep and heard that annoying rattle again!

Graphic courtesy   of Carsound
Car Sound Exhaust System, Inc. is a world leader in the manufacturing of automotive catalytic converters.

So, this meant we had to get the muffler replaced too. At least this wouldn't cost us any money. Borla is known for their quality craftsman ship and their Million Mile Warranty. This pretty much means for the life of the car. So we called them up and after telling our story, they had a new muffler sent to us at no cost. We just had to wait a few days for it to arrive. Being Christmas season it could of taken weeks but it only took seven days. UPS and FedEx practically know us by name.

The new muffler was packaged in the typical Borla fashion. The muffler was in a plastic bag and then placed in expanding foam. This packs the muffler into the box tightly and can make a mess when removing it. The two mufflers had the same parts number but they were very different. Not different enough that it wouldn't fit but they have redesigned it slightly. First off the output on the old Borla was offset. The new Borla was straight pipe. Looking though the input pipe we could barely see light in the old Borla while the new Borla was bright as day, so to speak. The other big difference was that the input on the new Borla was about two inches longer. This means we won't need the extra extension piece. Borla's Cat-Backs use exhaust clamps so there is no need to have access to a welder. This means you can install the Cat-Back without any special tools. It also means we were able to adjust the pieces to account for changes made to the Jeep. It is best to put the pieces together but not to clamp them until you are able to check everything for clearances. There are a few places where the exhaust pipe might come in contact with the cross-member or gas tank and could cause rattling. Once it's in place we used the stainless steel exhaust clamps to pinch the pipes together. The connection should be tight and not leak but doesn't have to hold pressure. Small leaks are acceptable.


Photo by Jeff Yokomura Photo by Jeff Yokomura Photo by Jeff Yokomura Photo by Jeff Yokomura
Before installing the compressor, make sure you have enough room on the passenger side wheel well. There is a big difference between the stock cat and the Carsound hi-flow cat The two cats have similar monolithic honeycomb design. The two Borla's have the same parts number but are very different.

One problem area we ran into with the installation was that we had a transfer case lowering kit installed. This lowered the skid plate, and catalytic converter down a inch or so. Because there is a slight drop the mufflers hanger wasn't long enough to use. This hasn't been a problem and we'll reuse the mounts once we move the transfer case back up. Otherwise, the install is straight forward. If the we hadn't installed the Borla previously, we would have had to cut the tail pipe off the muffler to remove it. There might be enough room to snake the pipe past the rear axle also.

Photo by Jeff Yokomura Photo by Jeff Yokomura Photo by Jeff Yokomura Photo by Jeff Yokomura
Earlier Borlas mufflers had a slight offset to them. The new Borla muffler is a straight through design with less obstructions The new muffler bolted to the new cat using muffler clamps so there is no need to weld. The Borla Cat-Back uses all the original hangers making it easy to install.

So with everything in place we topped it all off with a nice Borla exhaust tip. This is the only thing anyone will see and recognize as a Borla. So with the new Borla Muffler and Carsound Catalytic Converter we were set. A turn of the key and the engine came alive. A nice low rumble came from the exhaust tip. The exhaust note is louder then the factory muffler but not obnoxious as some other mufflers out there. With the Hi-Flow cat the exhaust note dropped a little lower because of the increased exhaust flow. Our main concern was to get rid of the rattle. With the new muffler in place we had accomplished that. With the 2.5L there was a nice increase in torque. Actual results will very depending on the engine and modifications.


Photo by Jeff Yokomura
This is the only thing that will show off your Borla exhaust.

If you have simple hand tools and are replacing both the cat and muffler then you should be able to replace both in about 30 minutes. All that is needed is a hack saw and a ratchet set. If only the cat or muffler is being replaced then a torch might be needed and it will take longer to do. So is it worth it? Well with a 2.5L there isn't that much out there for us to take advantage of. So we try to pick up power anywhere we can. Would we do it again if we had to. Yes. They are all quality parts and Borla's warranty speaks for itself. For those looking for a muffler that's not too loud and increases performance, here it is. For those who want a quality cat and increased exhaust flow, here it is.



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