Paddok

On Rx7store.com it has exhaust systems and then high flow catalitic converters.

Could someone explain the difference between them to me ?

Are the both required ?

Sorry, still learning about cars =/

FDeez

Exhaust is used gasoline in vapor form. After the engine combusts the gas, it turns into exhaust. It flows through the exhaust system and vents into the atmosphere. The RX-7 (stock)exhaust system is equipped with a pre-catalytic converter and a main catalytic converter, and a muffler. Catalytic converters (cat for short) are to process the gas and make them less harmful to the environment. However, they create a lot of back pressure which causes a traffic jam in the exhaust system making the car lose power. The freer flowing the exhausts, the better your car will be in terms of performance. Almost everyone replaces the pre-cat with a downpipe. A pipe w/o a pre-cat. With out this pre-cat, the car will still pass emissions. The RX-7 uses 2 cats (the pre and the main for cleaner exhaust air). The main cat is required for in order to still pass emissions. The muffler (aka tailpipe) also restricts some air passage, so an aftermarket one will help flow as well. The main cat creates most of the "traffic jam" in the exhaust. A hi-flo one will help solve some of this.

I hope this has helped you clear some of this up. It's not a complete explanation but other people may have more to say.

Tad

great! it's learnin time!
i'm also pretty clueless as to whats actually goin on
down there, ESPECIALLY in these rotary setups.

anyone mind telling me what goes on before the air hits
the downpipe?
maybe a diagram??

i'm just wondering how the order of things go,
like, i'm guessing it goes intake... then some sorta pipe,
then maybe the engine, then another pipe? then the turbos?
then precat, then maincat, then muffler???

by the way, what are you getting when you buy something
like the apexi N1 dual setup,
is it just the muffler?

oh and are there headers in there somewhere, like piston driven cars??
thnx

Paddok

So If I were to buy a whole new set up , would I have to buy the cat and the muffler ?

Ack im tierd.

Ill assume the answer is yes =/

SleepR1

The FD exhaust system is the piping and muffler aft of the main catalytic converter. You're only freeing the back pressure from the catalysts out to the tail pipe.

The high flow catalytical converter is freer flowing than the factory cat, and allows the exhaust gasses to exit at faster rate from the turbos outward to the tailpipe.

I'm not familiar with the Rx7 Store's hi flo cat. I bought my hi flo cat from Rotary Performance (www.rx7.com located in Garland Tx). Their's is a hi flo catalytic converter replacement. RP's system replaces the factory precat and main cat with a downpipe and high flow cat (which is basically a midpipe with a hi-flow cat cartridge inline with the midpipe). The RP system is a full 3 inches in outer diameter and will mate with just about any aftermarket 3-inch OD piped catalyst-back exhaust system.

You really must be careful with the hi-flow cats. They let so much more exhaust out that if you have an aftermarket intake system (anything from a K&N filter/Racing Beat intake duct to an M2 airbox), and a catalyst back aftermarket exhaust, your turbos will easily exceed the factory computer's fuel maps. Your turbos will spool up faster and make more boost quickly, thus overwhelming the factory ECU. This will lead to a lean fuel-to-air mixture, and you risk blowing up your motor. This is, in fact, how many modded FD motors blow up!

I don't plan to upgrade my ECU until I get a midpipe, M2 Large IC, and M2 airbox; so I tuned the boost with a wastegate orifice pill that's slightly larger in size compared with the stock pill. This limits the boost to a safe 10 psi spike. In fact my boost pattern is a perfect 10-8-10. Without the modified wastegate pill, my boost spiked to 15 psi. Very risky!

Also, with a hi flo cat, your exhaust notes will be much louder than with the stock cats in place. If you have an exhaust system that's loud like the Apex N2 dual, along with a hi flo cat, you'll need to wear ear plugs while driving. The sound pressure level will be at race car levels! I have the Greddy Sport Catback. This catback makes a deep bellowing tone. With the stock cats, the noise level was moderate. With the hi flo cat, I wear EAR ear plugs while driving.

There's much to consider.

Good luck!

cruser

I have the N1-dual along with a Bonez hi-flow cat and a downpipe and I don't think it is too loud at all. It has a nice mellow burble at idle and is relatively quiet until about 4500 rpm when the second turbo kicks in, then it is just sweet, especially if you can find a tunnel to go through.