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Hellow ! i found this sportex performance back box but i dont know if it is good to use it because i know that a 1,7 or 2" is correct for this motor. Did anyone have this? http://cgi.ebay.co.uk/Sportex-Mazda-MX3 ... 1|294%3A50" onclick="window.open(this.href);return false;

I believe that the exhaust is 2" or 2 1/4" from the motor to the cat, then it gets bumped down a size or 2 from there. You'd probably have to replace your cat and from there back plus get it bumped up alot to fit. In my opinion, it's not worth it unless you have some serious turbo plans in the works.

Get 2.25 custom catback. use a cherrybomb as your res. and get a 2inch muffler and your set.

I think 2.25" is too big for that motor. 2" will give you better mid range power on a 1.6L engine. A huge 3" muffler is going to be really loud and droning, but if that's what you're into...you might like it.

I agree with wytbishop.
You have to understand there's no such thing as a "bad exhaust". What does exist is a "bad exhaust for your application".
For example, everybody knows factory exhausts are restrictive. Do you think engineers make them that way to save pennies on pipe?
No, they're made restrictive to keep good torque and HP figures lower in the RPM range, where most people will use the car, and to keep a smooth response and good idle. From then on, the less restrictive you make your exhaust, the more power you release, and the higher into the RPM range that power will be, up to a point. Past that point, your figures will flatline, and then start to decay. As usual, everything in mechanics is a compromise of opposites. In this case, the opposites are backpressure and exhaust gas velocity. But EGV will vary with RPM, so an exhaust that has perfect EGV at 2000 RPM will be restrictive at 5000 RPM, and if it has good EGV at 5000 will not scavenge properly (too low EGV) at 2000. So it's not a "bigger/better" deal. You have to find the right size for your application.

I have a 2" exhaust on my B6 DOHC. I wouldn't dare go bigger.

ehhh i actually noticed a power gain with 2.25 did you guys notice a difference?

There would be more power at higher RPM for sure. The thing is do you want to have good grunt at 3000RPM or are you willing to wait till 5000 before you really feel it? I'm not really familiar with the torque/power curves of a B6, so I'm quoting RPM values for reference only. You won't get much scavenging below 4000 with a 2.25" exhaust. 2.5" would be horrendous I'm guessing.

I have 2.25" on my 2.5L and I have great torque at 3000. A smaller engine exiting about 1/3 less exhaust gas would need smaller yet to achieve any mid range power in my opinion. I'm sure someone has dyno'd and would be able to make a definitive answer.

courtesy of corksport:



As you can see, stock setup, you have the torque available to where you need it the most.

unless you can justify moving your peak torque from the 3.5k-4K range to a ridiculous higher range you don't often use.

thats a graph for the power gains of the new header not what kind of power you get from a new catback setup..?

Yes, but if you're smart *ahem* you can translate bone-stock gains and interpolate approximately how a larger exhaust setup affects your powerband.

were you not listening? you're not really "gaining" any power by going larger, you're shifting your powerband around, that's all.

It's been said several times already. Come on, it's not hard to read, I promise.

Did anybody notice the 3" he's referring to is the tip of the backbox? Not the actual piping.. Single 3" round tailpipe design is referred to the endtip of the backbox.. Doubt that would make much difference on the performance..

SstennizZ wrote:Did anybody notice the 3" he's referring to is the tip of the backbox? Not the actual piping.. Single 3" round tailpipe design is referred to the endtip of the backbox.. Doubt that would make much difference on the performance..

You're right. In the link he posted there's no actual mention to the pipe diameter.

While that's true, a full exhaust at 3" is not what he's talking about, the argument is still valid. Just sticking a huge open muffler like that on the end will have the same effect albeit to a lesser degree.

I purchased my 94' GS from a punk with a bad rice problem and he had installed a Ractive muffler with stock 1-7/8" inlet and 3-1/2" outlet and asside from being obnoxiously loud, it made the engine feel very restricted up to about 5k rpm where it literally felt like 3 of the cylinders had just woken up. I immediately went back to a stock muffler (because I hated the sound and I really like low end torque) and it went right back to being a stock engine. The stock muffler is very restrictive but it's designed as part of a system which works to provide a particular torque curve. Even changing part of the system will change the torque curve.

That's been my experience at any rate.

I hear a

coming up..