I just bought my 86' FC n/t and I was told by the owner when he did the exhaust he put new stock cats on it and stock pipes and mufflers because he heard that if u go with an aftermarket exhaust u will mess up the compression and begin breakign stuff...

is this true?
If so what to do use stock exhaust?
if not true what exhaust do u recomend?
since it is a n/t if I do change the exhaust should I leave the cats?

Dave

 

lol.. first off...that guy is a moron! (whew, got that out of my system)

second.... an aftermarket exhaust will do nothing to hurt your car... its just as safe and reliable as the factory ones....
most people here tend to go with racing beats exhaust systems.. they are relatively affordable, and are very good quality.. apex'i has a nice one also...or you can just have a custom one made... which tends to be less expensive in the end

the cats are up to you.... if your state has smog, then they need to stay for emissions (at least when you go to get it smogged) if not, they you dont have to keep the cats.... all they will do is quite your car down, and block precious hp.... but be forewarned... uncorked rotaries are very loud!

 

no emissions I usually remove cats just curious if I would harm anything if I removed them

I will prolly go to a custom made exhaust with dual titanium tip mufflers

Dave

 

I read this

"The 2nd gen NA's have aux intake ports that close for low end torque and open for high end power.
They are operated by exhaust back pressure on the S4's like yours."

if that is true should I leave my cats on then? or is that not true on my car?

Dave

 

Dave, I'd leave the exhaust just like it is, unless you plan to boost it. You won't hurt anything internal by opening up the exhaust system, but you don't stand to gain anything without too much sacrifice. You'll make more low-end torque with the current set-up, too.

 

yeah but it is just to quiet lol.. I would at least like to cut the stock mufflers off and add some nice titanium mufflers

Dave

 

I don't want to end up sounding like your father, so I'm just gonna STFU right now (lol!)

 

dude....go with something tasteful..
A little louder but not redneck sounding ok?

 

since we're on the same subject....when upgrading your exhaust...do you have to upgrade the 02 sensor also? sorry for "thread jacking" and thanks in advance!

 

i recomend the apexi N-1, or gt. pricey, but worth it.

my cat back is very quiet. maybe a tab louder than stock. but a very big difference in the tone, very deep.

 

now thats what I want not nessecarily loud but better deeper sounding

Dave

 

I've run several different systems, my personal favorite being the Apexi N1. I haven't used a Racing Beat cat-back at this point though. If you by the Racing Beat pre-silencer for your car it will have the split air pipe hookup (just like the main cat) which is what it takes to keep your 6 ports.

 

since you're running an S4, keep in mind when dealing with the cats that your main cat has a split air pipe that opens up the 5th and 6th ports on your motor, and unless you go plan on wiring up those ports they will not work when the main cat is removed, rx7.com offers a bonez high flow cat with a hole specifically for the split air pipe, let us know how it goes

 

im confused lol intake ports 5 and 6 yada yada lol I dont understand what u are refering to but ok..

I plan to JUST swap mufflers

Dave

 

On NA 2nd gens, there are auxillary ports that open at high-rpm's for better power, just like in the thing you quoted above. They are operated off of exhaust backpressure (or velocity). The only aftermarket exhaust that I know of that keeps the aux ports working is the Racing Beat presilencer. To use this, you either need to get a racing beat downpipe or header. If you use the downpipe, it connects up to the stock exhaust manifold, but everything else up to the y-pipe is replaced. After that, you can get whatever cat-back you want. If you get basically any single-exit exhaust, like the Apex N1, it will be pretty damn loud. From what you described, I would get the full RB exhaust. It has a nice deep sound an isn't crazy loud at WOT.
If you just want to swap mufflers, you might be okay with a single exhuast, but I've never hear one with the stock mufflers still on. Most of your gains will be from getting rid of the stock cats, though.

 

this car has dual exhaust (dual mufflers) I am just gonna buy aftermarket mufflers and chop the stock ones off and mount these in its place.. I want to keep my dual muffler setup

thx for all the info and advise

 

dude, get the Racing Beat mufflers, they BOLT TO THE STOCK EXHAUST, and sound amazing, very deep sound. seriously, consider it.

 

ill look into it!

 

225.00 PER MUFFLER!!!!! that alot

Dave

 

isnt it only in the s4's that the auxillary ports are operated off of exhaust backpressure? im not positive but correct me if im wrong, im just asking cuz i have a s5 na and im thinkin about swapping the exhaust, but dont want to have to worry about the aux. ports kicking in.

 

i paid $260 shipped for a PAIR. see if you can find some used, used doesn't hurt them at all and saves you mad dough

 

The s5 NAs dont need the split air pipe.

The s4s do...

My s4 NA has the bonez superflo which replaces everything from the manifold back to the Y-pipe, and has a high flo catalytic converter which flows much better than the stock setup, and works with the split air pipe. There is also a straight pipe made by racing beat that can be used with the split air pipe.

Replacing just the mufflers will not gain you much if any performance...

Heres a clip of my exhaust with the superflo and racing beat cat-back.

RB Sound Clip

Sounds very nice imo, ive had lots of positive comments on it from people.