planorx7

Hi, I have a 90 vert and I really want to trick it up. If I understand most of the threads I have read, the first thing I should do is get a complete new exhaust system. Here lies the ignorance....what are all the components that make up an exhaust? Are cats the catalytic converter, precats the thing just before the cat, y-pipe..is it where the pipe splits into dual pipes, I am guessing the downpipe is the tube coming from the exhaust manifold. Headers......hah, I know this one...its the thing I did on my minibike when I ran into a 3 foot brick wall!!! Can anyone give me an idiots rendition of every single component I should get to create a performance exhaust. Cost is a consideration so budget performance parts would be nice. I have a local muffler shop that can build just about anything but I need to tell them what it is I need. Oh yea, I have searched many, many threads and most are still over my head. So....masters.....grasshopper awaits your instruction. Just for grins, what should I aim for after the exhaust...keep in mind, I don't know my posterior from a hole in the wall when it comes to rotaries. Thanks

Icemark

What are you going to use the car for?

Do you need to pass emissions in your locality?

Do you mind smelling fumes stuck at a traffic light?


These are all things we need to know before recommending parts for you.

But your interpretation is basically correct.

Starting from the motor and working your way back:

Exhaust manifold, on a NA like your 'vert this can be replaced with a header, although headers are very loud on rotaries.

Then comes the pre-cat(s). On a series 5 car like yours you only have one, but series 4 cars have two. This can be replaced with a downpipe if you don't have visual smog inspections. The pre-cat does the job of the Main catalytic converter (or cat) when the car is cold.

The comes the main Cat. This can be replaced with a straight pipe or test pipe, but note that it is against federal and some state laws. Removing the cat and replaceing it with a straight pipe, you will smell fumes when the top is down and you are waiting at a light or other idle situations, which many people find offensive. There are also high performace replacement versions of both the Cat and pre-cat made by Bonez. Some people also will use a pre-silencer inplace of the main cat to help reduce the noise level.

Then comes the cat-back which includes the Y-pipe which splits the exhaust to both mufflers. Again there are high performance versions of both, but do not use a Glass-pack mufflers or mufflers not designed to work with the extreamly high exhaust temps that come with a NA rotary motor. Some people like the single output muffler rather than the factory style dual output, but generally it is way too loud for a 'vert.

rx_7_driver

um i got a question
i also got a 90 vert n/a and i have 2 pre-cats
y is this??
i know the owner befor got rear ended and hand to get a new back end would the s4 exhaust fit on an s5? that is the only reasion i could think of that it would have two pre-cats

Icemark

Probably busted in the accident or cats got clogged and he found a junk yard one from an 88 'vert so he could pass emissions.

planorx7

Thanks a million for the spoon feeding and "exhausts for idiots" explanation. We do have emissions testing but I can get around that.....don't ask! This car is not my daily driver, it is something I can play with and really get the feeling of a performance car...so daily comforts are not really a concern. I prefer not to smell fumes but if performance gained is significant, then bring on the gas mask? A little noise is ok but I really don't want anything obnoxiously loud. I don't plan on taking it to the strip but ya never know....It's those obnoxious little Juvenile ****** in their momma's vette that I am really gunning for. Plus those little Honda's with all the glowing lights....they really annoy me. I really want to show them a nice peek at my posteriror as I roar into the sunset.

Keep in mind, I am on a budget. This may be a long term project. So, oh masters of the Rotary, your student awaits.

Icemark

A few things to think about:

Its maybe 2 to 3 HP replacing a free flowing cat with the pre-silencer. On average about 20 HP for clearing up the exhaust. Another 5-6 HP using a K&N or Apexi cone filter and cool air box.

What I generally recommend for 'verts is the bonez downpipe high flow cat combination, and then the racing beat cat back. This seems to give the best combination of emissions legality, noise, and exhaust fumes. The only other street (again if you don't care about fumes) choice is using the racingbeat 'vert down pipe and pre-silencer, with the racing beat cat back. Although the cork sport single cat back may be an option for the RB cat back. They claim (by phone) that it is not much louder than stock with a presilencer or factory cat and its cost is almost half of the racing beat cat back.

But for topline HP is the only concern, go for the header, and true duals all the way back, but it will be very noisy. I think Mazdatrix or racing beat (I forget who) says the header with true duals all the way back and no cats is worth about 25-30 HP on a NA FC.

rico05

RB has the true duals, but Mazdatrix also sells the unit. I have a header, and I would reccomend it if you don't care about noise pollution. Man it is LOUD. I say do what Mark said. Get the Bonez unit.
http://www.rx7.com/cgi-local/2catalog.cgi?cat=4&part=1
I run a Racing Beat (RB) header, presilencer, and N1 single cat back. It is nice, but like I said, not quite in ANY respect.

PlayinW/Wankel

Does any one have proof of the horsepower increase over stock with a true dual set-up? Also which is better for low-end torque, a true dual, or single outlet. Thanks

RETed

Uh, actually, I WISH!

I've had my tales of blunders.&nbsp I mean I've rebuilt my engine 3 times over the past 20k miles.&nbsp Some of it was stupid, and some of it was just out in left field.&nbsp I've destroyed a LOT of housing to get a decent grasp of porting motors (especially side housings!).&nbsp I've been guilty of one spacer slipping in the front housing, which eventually destroyed the whole motor.&nbsp I *TRY* to learn as much as I can from my mistakes and don't duplicate any pervious errors!




-Ted

planorx7

True duals? What are true duals? When I had a v8 true duals were 2 straight pipes all the way from the block. On a rotary, where does the single pipe from the manifold/header split into 2? I am assuming just past the cat? Still ignorant but getting there! Thanks

Icemark

Some headers have an output for each rotor that does not collect.

In that type, you can run a dual pipe system all the way to the rear, an independent exhaust pipe for each rotor.

They are typically very loud, but the torque increase is sizable. Emissions typically skyrocket as well, as there is little exhaust gas retained in the combustion cycle.