I am looking for a lightweight single exit exhaust for my 2nd gen RX7. The point here is to lose weight. I would prefer exiting on the drivers side at the rear OR passenger side before the rear tire. Any ideas? It also needs to be quiter than 90 dB.
2nd) I am looking for some lightweight 15" wheels. They NEED to be 5 x 4.5 and 8" wide with a 4.75 to 5" backspace.
Any ideas are appreciated!
Rob R.
For wheels, I got a chance to handle some aero race steelies - for the price they're not bad. I think it was their 56 series which is a 15x8. That particular model only comes in 15x8 with a 5x4.5" bolt pattern. I'm unsure if they do custom backspacing though (just checked their website and they only list up to 4" backspacing).
For exhaust, I am assuming you already have ditched the stock exhaust manifold for a header. If not, do so and don't buy the cheap headers from Pacesetter etc. They will burn out QUICK and you do NOT want that happening in your engine compartment! I'd just have someone bend up a 2.5" pipe to the rear, minimize the bends as much as possible. That's easily done on a 2nd gen. Muffler: for 90db you might have to trade off. The Racing Beat presilencer will be a big help, it is sorta pricey though. If it's mounted in the middle of the car you might be able to get by with a straight through muffler at the rear. If you do the presilencer and straight muffler and it's still too noisy, the DynoMax will get you where you need to be with a loss of some top end, it's noticeable but not the end of the world.
Having said this, a buddy is running a rotary in a Spitfire (NASA Outlaw Vintage), it has a custom header, a RB presilencer and a RB straight through muffler at the rear. I have no db numbers but the damn thing's pretty quiet yet very quick. On the NASA dyno (yeah I know all about the controversy) it made 139 at the rear wheels. Considering Mazda rated the S4 13B at 146 flywheel, it doesn't seem to have killed his car.
Wheels: there's a ton of choices out there. The RX7Club guys LOVE the Crown Vic BBS lookalikes, I don't know the specs but it's a bolt on, fits without clearance issues at all. Mustang wheels will fit too but to me it looks like the offset is weird. Just my .02.
You'll most likely need two mufflers to hit that DB target. Racing Beat and Mazdatrix are among the best manufacturers if you aren't rolling your own.
This guy is very knowledgeable about NA rotary power: http://www.rx7club.com/naturally-aspirated-performance-forum-220/best-exhaust-n-fc-775745/page2/#post9290548
The crown vic wheels are 16 x 7. Boo.
I have a few sets of wheels for the car now. I am looking for that "perfect fitment" wheel that also happens to be light.
Right now I run the 15" BBS gold jeep wheels. They look awesome! But they are not 8 inches wide and they are not perfect offset and they are not that light.
The current exhaust on the car is a racing beat header to a Borla stainless Steel catback (dual). it is under the noise limit as is. I just want something considerably lighter.
The problem is that neither RB or mazdatrix (which doesn't make exhaust anymore that I can tell) make a lightweight version.
hmmm.
I thought some of the Crown Vics were 15"? Checked car-part.com, yes there are 15" BBS lookalikes but they are 15 x 6.5 inch. My bad. If you don't mind a special order and maybe a bit of weight, Bassett will make 15x8's in any reasonable backspace for not a lot of money. I've been using their 13 inch wheels, they have been fine. You might have to request a bead hump though.
Check out burns stainless (grm sponsor). Probably a good alternative to the racing beat/mazdatrix. Stick a turndown on whatever you go with.
What does the land of the rising sun carry? Uras, Trust/Greddy, HKS, Apexi, Revolution, RE-A, R-Magic? None of it will be cheap - but some might be light.
If you have the money, just go to a local exhaust shop and have them custom fab something out of aluminized steel. I had a straight pipe on one of my cars made of the stuff, and it held up fine on the street. The entire system from headers back only weighed 10-15lbs. Thats decent weight savings, considering the stock exhaust on my car weighed almost 100lbs. This pipe was stupid loud tho.
But yeah, if its just going to be for the track, you can build it with no cats, a muffler, and maybe a few resonators to keep it below 90db. They can weld in new O2 sensor locations and everything. Only thing is you will probably end up spending upwards of $800-1200 bucks for a custom setup.
The stock Y pipe and muffler are really heavy if they are factory units. The two pre-cats in front of the main cat are not light either. You can drop a fair bit of weight just replacing the stock units.
Get a Racing Beat muffler for the side you want and have somebody mandrel bend a 2.5" or 3" pipe with a resonator/presilencer to whatever side you want it to exit from and call it a day.
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