I'm having a hard time choosing a cat back for my car. I did alot research already, but I still couldn't find a good answer on this, I heard all the audio clips, but they all sound about the same....I want a single exhaust for weight deduction purpose, but I don't want anything too loud, that would make my car jumps out. I know both corksport and N1 are very loud, but the GT is suppose to be a bit better, anyone has the Apexi GT Spec here? how loud is it? daily drivable?

 

The weight difference between a single-muffler exhaust and a dual-muffler exhaust is less than 1% of the car's total weight. You'll never notice (or even measure) a difference in performance from it. The only reasons to put a single-muffler exhaust on an FC street car are because you prefer the look and/or you prefer the cost.

 

And as we wait for someone to actually answer his question.

 

I ordered the gt spec, still waiting for it to arrive. It's all SS and very nicely made. Go for it.

 

Turbo or n/a? There are folks here that run the exhaust so search for it and you'll find numerous exhaust threads mentioning that system. It has bigger piping dia. than the N1 and it is a loud system. The N1 single exit will be quieter than the GT, but not much. If you insist on having single exit then your options for a quiet exhaust (outside of custom) are very small, if any. Keeping your pre-cats and main cat?

 

GT Spec is louder than the N1. But if you really want it decently quiet, then just get the GT Spec or N1 and stick an ATS in it. It's really not that bad that way. Not as good as an open exhaust but it's worth it for the trade off considering it's better than those regular silencers.

 

I Thought Spec is suppose to be not as loud...humm...I think I ll go with the RB ones then.

on another note, on the RB presilencer, there s a lil tube to support the 6 port system. But my question is do I have to use it? I want to keep the air pump on there for the moment, will the air pump still work? I'm still new to rotaries, so I don't really understand why you have to remove the air pump, once u take off your cat. because, I''m thinking about just get a down pipe to from the exhaust manifo, to the cat back, and not worry about the air pump and all that stuffs at the moment, It will save me some money too.

 

the GT is not that loud. i have it. i love it. get it.
its totally worth it.

 

It's not that loud with a cat, but without one they get crazy loud. The GT spec is louder than the N1... It's 1 step closer to a straight pipe from the N1.

 

Get a borla as a presilencer.

 

I'm going to run my gt spec to stock cat at the moment, but in like two weeks, I'm going to be buying a racing beat header and presilencer from my friend. I'll get some audio clips when I get the exhaust finished.

 

sweet, I ll wait for the audio clip before I make my decision then.

I have been driving mid 80s to early 90s Japaneses car for my entire life up till now, and they all had single exit exhaust, so the double on the 7 makes me feel weird some how....XD

still, some one answer my question, if I just replace the cat with ( http://rx7.com/store/rx7/FC25racepipe.html ) , will the air pump still function right? I still don't quite understand the whole 6 port, air pump remove after taking off cat thing.....

 

I'm not to sure about the whole 6 port thing either, I've only owned 1 other n/a, and I never did anything to it. Didn't have to worry about it in my t2. I'm probably just going to remove the 5th/6th ports.

 

Yes, the silencer insert really does make a huge difference. It kills a good bit of the low end droning sound. You still get a good exhaust note but it doesn't drone at cruising speed, which is my biggest complaint about the N1, and I assume GT would be the same.

 

the GT has a really nice low-end rumble. i assume thats what you mean by the "drone"

 

Mine comes in Tuesday, I really can't wait haha.

 

I'm talking about driving on the highway. There is a constant sound that gets really annoying after a while. It makes it difficult to talk with anyone in the car and all but impossible to talk on a cell phone (not that you should when driving anyway...) I love the low rumble too, but it sucks when driving long distances.
I am actually planning on getting some videos of this tomorrow. If I do I'll post them up here.

 

Do you have to pass smog or no? If no, then it doesnt matter if you remove the cat or the air pump, as they are emissions devices. Now, if you did replace the cat with a straight pipe, the air pump will still pump air. However, it wont pump it through the cat, which is what it would do normally. So, if you remove cat, might as well remove air pump, since it would be dead weight at that point.

I dont understand the 6 port thing all that well, but I believe that it has something to do with airflow into the motor above 3500rpm, or some such. DO NOT QUOTE ME though, I am not sure.

 

I am assuming that you have an s4 (86-88) can since the presilencer has the tube on it. If this is the case then the air pump is useless once you remove the cat. As the above guy said, the air pumps sole purpose in life on an s4 car is to pump air into the cat. Once the cat is gone the air pump is completely useless. Until you get a dual belt pulley for the water pump it would be a good idea to leave the air pump hooked up, though. Otherwise you can get belt slippage on the water pump at high RPM.
As for the aux ports (6PI system, whatever), they operate on exhaust backpressure, to put it simply. At approx 4k they open up wen stock.

 

not to thread jack, but if you bought a full RB system headers back, assuming you remove the cats for their presilencers and test pipes, would you need to modify the 6PI system to work?

 

Just wanted to post that I put my gt spec on today. Still stock cat, clogged precats, and stock "header". Picking up a racing beat header and presilencer from my friend tomorrow for $200, not sure if I'll get a chance to put it on or not. Also, one of the studs on the cat is stripped so I have a lovely exhaust leak. Need to fix that. Once I get the full exhaust on, I'll get a video for everyone. I also didn't feel that much of a difference with the gt spec on. Also, didn't sound that much different. My stock exhaust was completely dead and full of holes and rust.

 

Once you get rid of the clogged precats, I'm sure you will notice a big difference.

 

Yea. Hopefully tomorrow, depending on the weather. Don't know what I'm doing about the stripped stud on the cat. I need to find a replacement.

 

i have a Racing Beat downpipe + presilencer (which keeps the aux ports working) + Y + mufflers and i HIGHLY recommend it

 

Thea header and presilencer will replace all of the cats, so you wont have to worry about the stripped stud. If its the nut thats stripped, then vice grips are your friend.