svs

iTrader: (1)

I知 replacing the exhaust on my 1987 NA. For now, I値l probably keep the stock mufflers (with the expectation of replacing latter). I知 looking for something that will give me more power without a lot of noise. I壇 also prefer the system to fit just like a stock exhaust so I can swap out parts. What do you recommend?

What kind of power gains can I get with just an exhaust upgrade?

infinidreams

well i have an 87 na with a borla cat back and a custom pipe from there to the manifold it was kinda pricey but i think in the end it was worth it it was maybe a 25-30 hp gain

<MaTT

NOPR

NO. WAY.

i'd say 10 MAYBE at the absolute MOST for an all stock n/a.

svs

iTrader: (1)

infinidreams, sweat. I'd love a 25+ hp gain.

I should add that my catalytic converter is shot, which is primarily what I need to replace right now. Whatever I do, it has to be emissions legal.

infinidreams

i live in sc and the only emision laws we have is it has to have a muffler so i have no cats so i really cant help u with that sorry

Marcus_F

Don't get sucked into believing this nonsense. There is no cat back under the sun that can give you a 25 HP gain over stock in an NA. A full exhaust? Maybe. Cat back? 100% BS



If you ran NOTHING from the cat back you wouldn't see anything near 25 HP. The ONLY way you could see 25HP is if your current mufflers were crushed shut.

N/Arx7

he doesnt have cats

staticguitar313

iTrader: (2)

exhaust help the n/a out quite a bit actually (when done right) changing form the stock 3 cat setup to the bonez high flow cat made a noticable difference, plus the K&N intake. the exhaust made the most difference though

cbrinega

I have the Bonez cat with presilencer from www.rx7.com. It works great, and it gave my NA a swift kick in the pants over the stock multiple cat system. It also allowed me to pass emissions in Ohio easily.

As for the rest of my exhaust, I hope to some day buy the Racing Beat cat back.

Oh, you may need to adjust how your 6 PI system works. See here or do more searching:
https://www.rx7club.com/2nd-gen-archive-72/how-air-pump-auxilary-port-activation-330310/

jgrts20

rb header and presilencer/straightpipe with dynamax CATback all the way!! love it, but loud!!

Jager

iTrader: (10)

He said he needed an emissions legal system. He couldn't pass it with a straight pipe.

If I were you (I don't know on how much you're willing to spend), but I would say go with the RB Header/Bonez cat combition from RX-7.com, you'll have the most noticable increase in power. For the cat-back portion go with Borla. For the money, its a good, reasonably quiet, smooth sounding, and emissions legal exhaust.

svs

iTrader: (1)

Everything except the mufflers is going to be replaced. The muffler shop recommended:

1) A custom fabricated header without the pre-cats,
2) A magnaflow cat (the $200+ cat magnaflow recommends for a 7),
3) A new custom y-pipe, and
4) New custom extension tubes.

This shop bends all the pipe themselves and has a great reputation. On the downside, they don稚 work with rotaries much.

Is the magnaflow going to have the correct back pressure? (They don稚 know anything about 5th and 6th ports. I'm a little shaky as well.) Is 2.5 inch pipe the correct size? Will the magnaflow hold up in a rotary?

This shop will make anything I specify, but I知 not sure I know enough to do it correctly. Since I have to have this done anyway (and very soon), I壇 like to get it right. What do you think?

Marcus_F

NA header design is a science. The specifications used are supposed to match the engine. Questions such as rev range, primary tubing ID, length of the primaries and the collector angle must all be answered.

A bad design can produce worse overall flow numbers throughout the rev range. A lot of guesswork can be eliminated by using a Racing Beat header. If you buy the new design, which appears to have been designed with the S4 in mind, the six ports will see plenty of pressure. This is regardless as to what follows the collector.

cbrinega

I've posted the sound of my exhaust system at WOT in the Audio/Visual section for your enjoyment:
https://www.rx7club.com/showthread.p...73#post4661573

idsigloo

just go with a rb header and pre-silencer. that will replace all your cats and bolt right up to your stock cat back. your looking at about $400 for both.

svs

iTrader: (1)

Thanks. Your setup sounds a lot better than my 17 year stock stuff.

BTW, My system looks welded together. Does that seem right for stock?

socalrotor

iTrader: (1)

no welds on stock stuff ....it's all flanges with bolts

cbrinega

Well, only my exhaust manifold is original. Everything else was replaced a few years ago. I wish that I knew about Racing Beat when I first got my car. I would have probably went with their cat back instead of having a local shop make an essentially stock replacement.

Your stock exhaust should not be welded together. You should have bolts and flanges here (working from the back forward):
behind each muffler
behind the y pipe
behind each cat

Thanks for the compliment. I like the sound of my setup quite a bit.