I am looking into buying a high-flow cat, but I'm concerned mostly about performance, sound, and ground clearance.
I've read many threads on here talking about high-flow cats vs midpipes and high-flow cats with certain catbacks, but I haven't seen anyone compare all the different high-flow cats currently on the market feature for feature.

Note: I'll be using this high-flow cat with the stock catback.

 

well, i tried to get each company to give me specs for rated temps and flows... but never heard anything from any of them

 

^i wouldn't imagine you would

 

What about performance? I know of the RP high flow cat and the SR Motorsports High Flow cat. Which one is better?

 

The concensus is RP.

However if you consider how long they will last, you'll have to wait 50,000 miles.

 

Where's the best place to buy an RP from?

 

www.rx7.com ,perhaps.

 

RP Performance for most hp (cat. is tiny). If you want less noise then SR Motorsports hi-flow cat (& tell them to add the additional resonator).

 

The RP is $395 (+$30 Bolt & Gasket kit).
The SR Motorsports is $449 (+$89 Bolt & Gasket kit). (optional +$59 for resonator)

That's an incredible price difference!

How much difference in sound are we talking here? Sound clips anyone (remember ... with the stock catback!)?

 

For me when I had the Racing Beat Cat back on I thought the sound was just about perfect. After I added the Sr Motorsport w/hi-flow cat I thought it was a bit loud. After I put the turbo on the sound got much quieter. There is a clip of someone with RB exhaust & RP Performance pipe on as well. Didn;t sound too bad. it really depends on how much noise you want. Some people want it close to stock (RB Exhaust), some people want it louder (Greddy, Borla, etc.). SR Motorsports is always expensive/overpriced. if I had to do it over again I probably would get the RP unit.

 

Thanks Fanman -- I think I'll definitely go after the RP model then. Did you notice a big difference when you installed your high flow cat? How much of a difference in terms of power did it make compared to when you got your flywheel?

 

I had stock exhaust and ordered the Greddy SP2 and RP high-flow cat and installed all at once. Let me tell you, the difference is night and day! My friend has just the Greddy SP2 exhaust and his exhaust sounds non-existant in comparison to mine with the RP. The RP or any pipe makes a big difference in loudness. I love the way my exhaust sounds and wouldn't change it at all, but like they said, it all depends on your perspective. The SP2 is already one of the loudest cat-back systems, so with the RP, it definatly screams starting around 3.5k all the way to 9k. The addition of HP can be felt in the higher rpm range, I love it.

 

I noticed a little bit of difference, but more so the sound. It's tough for anybody to notice 5-10 hp. Effect would probably be similar to when you got your intake & air duct put in. With the flywheel, I noticed that it revved faster. If $ is a concern right now I would do the hi-flow cat first. Installation takes all of about 1/2-1 hour at a muffler shop. The flywheel, unless you are pretty mechanically inclined (& can do this in your driveway) requires you to take down the tranny. That is a good 4-6 hours in labor for most skilled mechanics (about $400-$500). Also, if you plan to go forced induction in the future I would highly recommend that you replace the clutch & flywheel at the same time. That is another consideration.

 

Aside from the RP hf cat I'm still considering the flywheel and clutch as well. I'm not too worried about cost at this moment, but somehow I don't see myself buying all of those parts at once. :-( I am already ordering my RB sways though. :-D

Install-wise, I told myself that I wouldn't do anything to my car unless I could do it myself. This was after a horrible experience after getting a custom sub enclosure put in from Best Buy. The two fiberglass enclosures were mediocre, the lid for the bottom hole in the trunk didn't even fit the hole, there was glue all over the place, wires showing, carpet didn't even match, etc. -- the list goes on. It was a truly horrible job. I've never fiberglassed a thing in my life, but I bet I would've done a better job. (I am somewhat competent; I have a computer science and computer engineering background.) I went back and spoke to the manager. I told him to simply look at the job and tell me what he thought as an individual. Long story short, they redid everything. They also recarpeted not just the enclosures and lid, but my entire trunk; fixed the lid and added plexi, neons, and cooling fans. (The manager ended up doing everything himself.)

After going through that mess, I just said to myself: "if I can't do it, then it (insert mod here) doesn't deserve to be put in my car." The first job I did was my Valentine 1 Radar hardwire, and I wasn't sure about the whole ripping apart my sunroof bit, but atleast I knew how to splice wires, measure voltages, etc. That install was a blast and I decided to pursue other stuff like the intake, etc. Also, reading the service manuals, forums, and researching a bunch of other stuff definitely helps me understand how stuff works.

Going back to subject... As far as the flywheel goes, if I get one, it'll be the ACT ProLite Flywheel http://www.rx7.com/store/rx8/rx8driv..._flywheel.html. It seems to have the lowest MOI out of all the other flywheels. The site mentions that it includes approriate couterweight and hardware, but somehow I doubt it has all I need for a DYI, but maybe someone here knows. Also, I haven't seen a DYI posted for installing a flywheel and/or clutch.

I haven't decided on which clutch to go with. (I will be going down the FI trail but not anytime soon -- maybe 2 years out or whenever we can do over +350 rwhp safely and cost-effectively.) Did you do the install yourself? If so... Which clutch did you go with? Where did you order it from? Which parts did you have to order? Which tools did you use?

I've noticed that everyone here that installs a high-flow cat has some type of aftermarket catback. Since I am keeping the stock catback, will I be getting less power out of the RP hf cat? Could it cause any issues or is an aftermarket catback a must? Anyone notice any improvements on gas mileage?

-jc

 

Read everything on the web site on the RX8 you can:

http://www.racingbeat.com/FRmazda4.htm

From Racing Beat:
"Remove catalytic converter and resonator from the engine completely, and replacing with "cat" replacement tube – max benefit 8 HP – regardless of what muffler is used (or even no muffler)"

Thus I think you should keep the stock muffler and get the high flow cat..should be close to the same HP Gain...thus save your money on the Catback and get something else

 

I have the RP Supercat and stock exhaust and I am very happy with it. The noise difference is minimal. You'll notice the biggest difference in sound when the cat is cold, when the cat warms up (which is pretty quick in the 8) the noise level drops to near stock.

You should have no problems with the install its really easy. If you still need a sound clip, let me know.

T

 

actually if you have a sound clip i wouldn't mind getting a hold of it... i've been planning to do the RP supercat + stock exhaust

 

Give me a few days to record it and post it. Can someone tell me what is the best way to record and post? I was just going to record a mpeg on my digi cam and than post the vid, will that work?

 

Cool -- looking forward. What would be awesome is to get a hold of a stock Rx8 and film the two side by side. Under ideal situations, both of them should be cold.

 

http://www.secureperformanceorder.co.../powercat.html

http://www.secureperformanceorder.co...&CategoryID=58

 

ahh, so thats who makes RP's cat...

 

I should have the clip posted tonight.

 

I like my HF CAT from Random Technologies.
http://www.randomtechnology.com/

I originally purchased it through canzoomer
http://www.canzoomer.com

 

that's a ceramic catalyst cat, the link I posted above is for a metallic cat, it will not break or shatter, metallic cats also have thinner substrate walls hence allowing more flow for a given area

 

Ummm, sorry fella's. My wife took my digital camera on her trip so I can't record a sound clip until next week.