I have 86 N/A rx-7 - stock exhaust
I asked a friend who runs a muffler shop about cutting the cats off and just putting in new pipe he said he did that once and the guy came back the next day with 250 dollars to put a cat back on because it was so loud.
Few questions here
1. How loud is it?
2. Is there a silencer that they cut off thinking it was a cat, which made it sound horrible?
3. exactly what comes stock? 2 cats? 2 cats and silencer?
4.I dont have the cash for a nice exhaust system (yet)
so would this be the best/cheapest way to gain some HP and meaner sound?

Would like alot of opinions on this please before I spend the money - cause its alot more expensive to go back.
I dont want to gut the cats because I heard it sounds like a nasty chainsaw.

Also I have a possible related question... when I really get on it it smells like a nasty egg fart is this the cats? or an oxygen sensor or what?

thanks in advance

 

A downpipe, performance cat, and catback isn't too loud. You can run a performance presilencer if you want to quiet it down a bit.

A downpipe, straightpipe, and catback is even louder and requires more muffling. You'd definitly want to run a presilencer and pick a performance catback that's not too loud.

 

1. Pretty loud
2. No, the stock exhaust has no presilencer
3. 2 pre-cats, 1 main cat, 2 mufflers
4. dont buy an aftermarket expensive exhaust system, shop around the exhaust shops and you'll find they can make one up for you according to you're budget (single exhaust cheaper, can also use stock main cat)

oh yes, dont gut the cats... i have a gutted main cat.. it sounds like a low powered motorbike coming down the street

 

I have a header, and presilencer, as well as a N1 catback (4in tip, very big) in the mail. I am told that because I have no cats it will be VERY loud. I do have a presilencer coming, and that will help out the sound a lot. www.racingbeat.com Hands down the best RX-7 specific exhaust manufacturer on the PLANET!!!!!!! Lots of performance, not too much noise.

 

You really need to ask this more of the NA guys than anyone with a T2. The T2 has a built in muffler (called a Turbo and exhaust manifold) at the engine that changes the exhaust note quite a bit.

IMO the HKS system with a high flow replacement main cat and a exhaust shop's custom pre-cat replacement pipe is a good choice for a NA, but it can be considered on the borderline too loud. If you live in a neighborhood that noise is a concern you may want a pre-silencer in the custom pre-cat replacement pipe.

The HKS cat back is supposed to be the quietest for the NA, But I haven't heard the new RB system that they came out with this year.

 

If your running the stock mufflers then just put a straight pipe in place of the convertors. Mine really sounded nice that way and was never to loud. If you are running some aftermarket straight thru muffler you will really need a presilencer. The straight pipe w/stock mufflers is the least expensive way to go and there is a noticable gain in engine power.

 

Like Icemark said- You need to talk to N/A guys. The guys with turbos can do different things (no 6-ports) and the turbo will quiet the engine some.

As far as my experience has gone (I have a N/A). I gutted the first 2 precats (they were starting to clogg). The car felt SLOWER afterward. Yup I was pissed. I don't think the 6 ports were opening anymore. The car was louder too (I still had the main cat) but not alot.

I have a BONEZ super flow system on it now (presilencer and main cat). It is louder than just having the 2 pre cats gutted and drones a bit below 2k (I advanced the timing and it helped the droning some). Anyway....

My bro has an '87 N/A where someone has modded it to have a straight pipe (no cats) to the y pipe with fairly standard mufflers. The thing is loud. Not defanning but definately annoying if driving far. Car has less low end torque and the 6-ports don't actuate. Basically my car with a presilencer and cat (and working 6-ports) will clean his clock.

The rotten egg smell I believe is from bad cats.

Good luck....I'm still contemplating which mufflers to put on. It is hard to decide on exhaust components.

 

Anything that adds backpressure acts as a muffler, that's one of the reasons factory exhausts are so restrictive, it's the cheapest way to quieten a car. If noise is a concern replace the cat with a straight-through muffler, but don't expect to pick up power and be as quiet as before.

 

I've got an '80 12A race car and it's pretty loud without the cat, I wouldn't really recommend it for a street car.. and it sounds like a chainsaw

 

what about the RB Cat Replacement w/ presilencer and everything else stock?

well its 50/50 so far on the sound of NO cats and straight pipe w/ factory Y and stock mufflers. how loud is loud? hehe wish I could hear one *sigh*

thanks everyone for your input.

 

Not too much noise? You've never heard that setup have you. It hurts my ears just standing next to it at 3000 RPM's

 

I have the bonez superflo (presilencer to hi-flo cat) and the RP 50mm catback. It's great for street cruising, but once you get above 3K on the tac, it's LOUD, but if you like a nice "HMMMMMMMM" going down the freeway, it's a good setup for not a lot of $$.

Before I bought my current exhaust setup I gutted all 3 cats, and with stock mufflers it was LOUD. Can you say Chainsaw On Steriods? It sounds like ****, trust me.

Also, my 5th and 6th ports would not open because they would not get enough backpressure from the main cat to open, so I ended up losing power on the top end until I replaced it.

- JB

 

spend the money and get the bonez pipe with silencer. This is what I have with stock mufflers and it is awesome. I noticed a big gain in power right away. Plus it keep the 6 port working as well. I have heard 7's without presilencers and it is too much for a daily driver unless you are a punk kid that likes noise over performance.

 

If you have good mufflers, not rice mufflers, even gutted cats is not that loud. Get HKS or RB