The Random Technology Hi Flow cat replaces the two existing cats on the RS with one. It is a direct bolt up that isn't all that tough to install. I purchased my system from Cobb Tuning (www.cobbtuning.com). They don't list them on the web page but if you give them a call they'll help you out. Specific info can be found at the Random Tec web site www.randomtechnology.com

The unit is stainless steel. The welds look nice and stainless good quality. It's also considerably lighter than the OEM set-up too. I didn't weigh it but, it has to be less than half the weight as the OEM one. There are bungs welded on the proper places for the O2 sensors.

There was a minor snafu during my shipment. The bolts for the rear flange never made it. The box was pretty banged up and wrapped in some clear tape so it's possible they fell out of the box. I called Cobb Tuning and they will be sending me out new bolts today. I'll be putting them in after I receive them and updating this page. I went and picked up some SS nuts and bolts at the local hardware store as shown below.

What you'll need:

Eye protection
Penetration oil
Ramps or something to put the car up on.
14mm socket (6 point preferred) 3/8 drive - remove flange bolts
14mm open end - remove flange bolts
12mm socket - remove OEM bolt from rear flange
15 mm socket - Center hanger bolt
6" extension- to get to that one front bugger of a nut by the header
Breaker bar - The front flange bolts are very tight use a 6 point socket to avoid buggering up these bolts.
7/8" (22mm) open end - remove O2 sensors
Never seize - For the O2 sensor threads (don't get any on the probe end)


The install is pretty straight forward. Get the car securely in the air. Spray the heck out of all the bolts you plan on removing with penetration oil. I removed the rear flange bolts first. The bolt is 14 mm and the nut is 12mm. Loosen the center hanger bolt (15mm) but don't remove it. The front bolts by the header flange are in there pretty tight. The rear one is easy to get at. The nut and bolt are 14mm. I had to use a breaker bar to get it loose. The front bolt is another story. You have to snake a 14mm socket on the end of a 6" extension back there to get at the nut. It's a tricky spot but with a little cursing (always seems to help me) you can get it. After you remove all the bolts unplug the front and rear O2 sensor from the harness. Find the clip an push it in and pull the plug apart. Now take the center hanger bolt off and drop the system.

Remove the O2 sensors, I used a 7/8" open end, I think it's really 22mm but it fit fine. Put them in the respective place on the Random Tec Cat. Take them off one at a time and don't mix them up. Make sure you put the front one in the front. Be sure that the washer is on the O2 probe too. I put a very small amount of never seize on the threads too. Make sure you don't get any on the probe end. There is a metal gasket on the front flange that you must reuse. the one by the header. Mine stuck to the cat side of the flange but came off easy enough.

Slide under the car with the new system and raise it up an hold it in place with the center hanger bolt. Put the front flange bolts in first, don't forget the gasket. Then the bolts on the rear flange. I put the new bolt together this way. I put a washer on that was large enough to keep the OEM spring in place, then the spring. I put that through the flange on the mid-pipe, through floating flange on the cat. On the part of the bolt that stuck out I put a flat washer then a lock washer. Next the nut. I tightened everything down as evenly as possible. Next tighten the center hanger bolt. I started the car up while it was still on the ramps and checked for leaks. At the rear I had a leak around the connection. I tightened it up more and went for a test drive.

The car defiantly pulls quicker to red line now. I'll do a G-Tec reading later, the Butt Dyno says it works though. It's also noticeably louder. I have a Strömung for reference. It's not as noticeably louder when just cruising but at WOT look out. Some have reported getting a CE (check engine) light after installing the new cat. From what I gather this is more likely to happen to 2000 on Imprezas. Mine is a 99 and so far no problems there. If you do get a CE, it will not effect the performance, it's just saying the cat is not at peak efficiency I believe.

Even after tightening the rear flange I still have a slight leak that I can hear. I'm waiting for the new bolts from Cobb and will put them in ASAP. I'll report back later.

Peaty

full view from front of car

Front Flange by Header from Drivers side

Front Flange from passenger side

Rear Section:

Rear Flange and bolts

These are the bolts I ended up using. I'll replace them after I recieve the new ones from Cobb Tuning

Random Technology that is :)

I've been communicating via e-mail with Dave at Random Technology about the cat. He had this to say about the CE light

Begin Quote:
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The alleged problem with low converter efficiency that triggers a Check Engine light isn't real. The OBD II system uses exhaust gas oxygen content to gauge converter efficiency. That's like using fuel pressure to monitor fuel flow. The assumption is that a given pressure in a line of a given diameter will flow a specific volume. However, if there's a restriction in the line, volume will be severely limited, in spite of system pressure.
With the OBD II system, the assumption is that oxygen content behind the converter will be substantially more consistent than content in front of the converter. And that's true when you have a restrictive converter that causes exhaust gases to back up in front of it. But when you increase flow capacity, the residual oxygen content behind the converter is not as consistent, so the PCM erroneously thinks converter efficiency has deteriorated. In spite of the fact that the system "thinks" converter efficiency is below the acceptable threshold, the converter is doing its job and the vehicle will pass an emissions test.

As for a fix, we're experimenting with different chemistry. There is no official specification for an OBD II-compliant converter.) As for existing vehicles with Check Engine light problems, the easiest fix is a "spoof" which incorporates two resistors in the rear oxygen sensor wiring. I have a wiring diagram if anyone would like to experiment and if we can find connectors, we'll make up plug-in units.

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End Quote.

To help Dave out with with a CE fix please contact him here:

dave@randomtechnology.com

As an aside I like to say that Dave at RT has been very helpful and quick to reply to my constant pestering of e-mails. As far as vendors go Random Technology has been very good.

Peaty

The proper bolts arrived from Cobb Tuning yesterday :) They were nice enough to send them second day so they would get here in time for me to work on the car this weekend. The new bolts are shorter than the ones I used. These you don't use w/ the spring like I did. So I removed the old bolts, made sure that the flanges and pipes were aligned straight when I put the new bolts in. And there is no more leak I'm happy to say.

New bolts, no leak.

Just a watch out, I was changing my oil this weekend and noticed the heat shield on the Cat was not attached on one side. I took it to a local shop and had it tac welded back on. Something to keep an eye on I guess. Not a big deal, it wouldn't prevent me from getting the upgrade :)

While I was under the car this weekend changing out the front Oxygen Sensor, I noticed that the connections in front and back of the cat were leaking a little. I took the cat out and put some high temp (700°F) silicone around the gasket flange in front and the flange connection in the back. The type of silicone I used was called Mega Copper 888, I'm sure there are other similar types. Just a heads up to check every once in a while. If I were smart I would have put it silicone there when I installed it the first time.

Peaty 11/16/02