I just bought an Rx7 a while back and i finally have a good paying job where i can spend money on my car and still have money left over. I havent done anything to my car yet so its completely stock but i was wondering if there is any way to add a decent amount of hp to the car without making it loud?(thinking about 300+) I had a car with intake and exhaust and ive gotten annoyed of driving a car with a loud exhaust. so i want to make this car faster but keep it quiet.

 

single turbo stock exhaust

 

High flow cat, downpipe, and racing beat muffler.

Add all the stock twins goodies you want.

 

if you keep the stock main cat, it'll really deaden the noise. The RB cat-back is pretty quiet, but with a high flow cat and downpipe, it's pretty noisey.

 

i have a downpipe/midpipe and the stock catback and its pretty damn quiet...

 

Only when you mash the throttle and the secondary throttle plates open up. Otherwise, it's not that much louder than a completely stock exhaust.

 

Stock twins with Borla MP with RB Dual. Keeps it at the right level in stop and go and allows you to still carry on a conversation with the ladies.

Keeping it quiet means you're restricting the exhaust which means your HP suffers. I'm close to 300rwhp at 12psi.

 

I run an old-styleRB dual tip cat-back with mid-pipe and downpipe on a ported motor with seq. twins. Very quiet except at full-throttle. No droning at cruise speed. Makes for a nice sleeper effect to unsuspecting prey.

Most people have to ask if I have a resonated mid-pipe.

I think the newer style RB mufflers are louder but not by much. Dual tip seems to be make less noise than than the single tip RB.

Jack

 

single turbo, downpipe, midpipe and stock cat back and it's pretty annoyingly loud.

 

Because FDs are the kind of car anyone expects to be slow, right?

And ya, my friends car (with the dp, hf cat and RB dual tip cat-back) is pretty loud. It's definately not "stock sounding" at idle or partial throttle. WOT it's just obnoxious.

 

Keep the stock exhaust and run a downpipe.

Or if you really want an exhaust, try to find an rsr catback. I think they dont make them anymore but its REALLY quiet when matched with a dp and the stock cat. I have a dp, stock cat and a PFS catback and its not terribly loud at idle, when im on the throttle its loud. I want the old style RB duals but those are hard to find.

 

With a little work, you could convert to plutonium and once you get it stabilizing around 1.21 gigawatts, expect an estimated 148 rwhp increase. This way, not only will you achieve more hp, but you will be just as quiet as you were before.

 

With my mods, around 300 rwhp. I still have the oem main cat. Very close to stock loudness.

 

I had a RX-7 store resonated MP with a HKS dp and a Greddy EVO exhaust running non-seq. It was very livable. I also had a friend that got a Pettit DP with the same MP and RB Twin exhaust. He added a small resonator to the dp and it was very quite.

 

Um..."obnoxious"? You obviously haven't heard an FD with a MP (hell, even with a hi-flow cat) and some of the louder CBs, like Apexi N1 duals...

No, a DP/hi-flow cat/RB dual tip doesn't "sound stock" at idle or partial throttle (I'd certainly hope not, as otherwise I'd be looking to get my money back from Racing Beat), but again, at idle or anywhere below 1/2 throttle off the secondaries, it's not even loud enough to gain the attention of law enforcement-- and it doesn't take much to do that. I've driven my FD past plenty of cops (in areas where they were/still are cracking down on modified cars) with their windows rolled down, and they didn't even give me a second glance. Which was fine by me.

 

I got sick of my exhaust sound when I had hiflow cat with n1 catback and downpipe. Once I traded out the hiflow cat for a RES midpipe I was much happier.

 

I've heard the Apexi N1 cat-backs...IDK how people drive like that. The RB is definately tame compaired to that, you're right. My main point was that it's not really quiet and it definately doesn't sound stock, which you seem to agree on.

If he wants to keep it close to stock sounding, his best bet is to keep the OEM main cat. Like Adamc said, he can make the power he wants keeping the OEM main cat, and it's quiet.

 

Keep the stock cb, can still make good power but with the stock cb the exhaust moise will be nice and mild. Also keeping the stock twins sequential will really cut the exhaust noise during normal driving, going non-sequential or single turbo ups the volume significantly expecially if you have a cb upgrade.

 

I've heard a lot of FD over the years and to me, you simply can't beat the sound and power combo of a downpipe, stock cat (or some high-flows) and a Racing Beat dual tip. This combo is pretty quiet at idle, but with a deeper, 'throatier' sound and just flat roars (not screams) at WOT.

 

ok this helps me alot. THANK YOU for all the people who replied. i think i have an idea of what im going to try out now

 

this is an informative thread!

So do most people feel keeping the OEM cat is the quietest route, or would running a DP and resonated midpipe with the stock cat back be quieter?

also, how would the HP #'s be affected

.....DP,OEM cat, RB cat back

.....DP,Resonated mid-pipe, OEM cat back

which one would make the most power, and which one would be the quietest?

 

Is the Apexi GT 4 inch too loud? Will it attract a lot of officers without the silencer?

PS. should I put the silencer in?

 

I think it doesn't even matter which makes most power or which one is the quietest. IMO it is about which setup gives you the best overall results when taking reliability, power, sound, longevity, etc into account. So looking for all these qualities in a certain exhaust setup...
I would have to go with Pettit or equivalent 3" DP, OEM cat, Choice of aftermarket CB. My favorite aftermarket CB is the Blitz Nur Spec. It gives a mild look, deep tone, and is just overall a nice piece. If you are wanting a CB that is close to stock but gain in performance then RB Duals. If you don't care about noise and want maximum performance gain then go with Apexi GT Spec. With this setup you do not necessarily need engine management.

If you went with the DP, Resonated MP, and OEM CB route it would probably be more quiet but I don't think you would get as much performance gain as you could with the other setup. Plus upgrading your MP without engine management is a big "no-no."

The ultimate noise to performance exhaust setup would be DP, Aftermarket High Flow Cat, RB Duals. But I must say...with my new single turbo the exhaust setup (3" A-Spec DP, Rx-7 Store Resonated MP, and Blitz Nur Spec) sounds and performs amazingly. It is exactly how a rotary should sound. This new setup is much more quiet then when I was in non-sequential, 3" DP, 3" MP, Blitz Nur Spec.

As far as other modifications without making it louder...CAI, Efini Y-Pipe, Aftermarket I/C, Spark Plug Wires, Larger Injectors, PFC or other fuel management, HKS Twin Power, etc. Basically anything other than modifying the exhaust too much. If you change your CAI piping to aluminum it makes it slightly louder though.

 

^ So running a MP with OEM cat back will still cause boost creep? but you also think it will be quiter?....


thats leads me to believe(just based soley on what you said) that the midpipe, with OEM cat-back will yield higher HP #'s, versus, OEM cat, and aftermarket cat-back.


boost creep is caused by too little resistance in the exhaust path, and you're suggesting that the OEM cat-back offers little enough resistance to still cause boost creep?

does everyone agree with this? do you also agree that OEM cat back will be quieter?

 

Don't laugh, there are a lot of idiots out there. People come up to me sometimes and say "Hey man, is your car fast?" I say "No, it's madd slow." They say "Oh, well it still looks nice!"

edit: Just realized that you wrote that quite some time ago