Sports Cat - Advice

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Davz
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Sports Cat - Advice

Post by Davz » Mon Nov 13, 2017 8:55 pm

I want to improve the sound from the straight 6 plus improve the mpg.

11 yrs ago I had an rx8 which ate cats for breakfast, after mazda refused to replace the cat for the third time, instead wanting £1500 out of my pocket, I replaced the cat with a Blueflame 200 cell race cat. The sound at lower revs was slightly deeper but when it hit 4.5 to 9.5k it sounded like a v12 on steroids, performance and mpg was also improved, when I had it remapped to oem japanese tune (250bhp) it was putting out a smidge over 260bhp.

So I am thinking a midpipe 200 cell stainless cat with a port for the lambda sensor to prevent a CEL would be the way to go, expecting around 10bhp more and being more free revving? I don't want to knock out the insides of the cat, which would be the easy route, incase it is too loud.

Now for the questions:-
Has anyone done this? If so did you fit two seperate cats or one similar to what is already fitted? I have attached a pic of a jetex performance cat which looks like it will do the job except that there is no lambda port.

Is it really loud or just a bit deeper and burbly?

Did you get a CEL?

If no one has done this, what is the size of the tubing? 2"? 2.25"? 2.5"?

Has anyone just removed the mid cats completely? If so what is that like in terms of sound, mpg and performance.

Any advice/info much appreciated.
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Last edited by Davz on Wed Nov 15, 2017 12:19 am, edited 1 time in total.
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mjennings23
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Sports Cat - Advice

Post by mjennings23 » Tue Nov 14, 2017 10:57 am

I believe the straight 6s have four cats total, two primaries on the manifolds, and two secondaries (one set to each pipe, of course)

Which ones are you looking to replace? A few on here have removed or gutted the secondaries, nothing is needed here as they're downstream of the lambda sensors. The primaries are part of the exhaust manifolds, which is where the sensors also attach, so if you're wanting to get rid of them you'll need new manifolds making up.

MACK
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Sports Cat - Advice

Post by MACK » Tue Nov 14, 2017 12:56 pm

If it's the rear secondary cats your talking about some have removed them altogether without issue. Well other than the extra din.
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Davz
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Sports Cat - Advice

Post by Davz » Tue Nov 14, 2017 10:06 pm

Thanks Mack and Mjennings for the replies, much appreciated.

It is the secondaries I want to replace, standard will be 400 cell ceramic type and will be pretty restrictive.

The image of a cat I posted looks very similar to the standard except it is all stainless and at 200 cell much less restrictive. Hadn't realised there is no lambda on the secondaries, this makes this much easier, opens up the use of a 100 cell cat.

If the secondaries are removed completely how loud is it? bearable? totally unbearable and you look like a complete tool? I can get this done in stainless very cheaply and was something I hadn't previously considered.
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