THSCC Forums

I've given up waiting for a used Borla and the price of new one is not in my budget so I'll be going to R&J next week for a custom catback.

I wasn't able to find more than one source for info on dyno tuned cutom exhaust. The spec miaita forum had a long thread on this see first post below. I may try as described or consider larger dia. by .25 in.
(of course mine would only be from cat back but otherwise copy of plan below)




Many have asked what system I use. Thought I would post it here now that we know the exhaust rule.

You can find it on most of the top cars, several hundred hours of dyno time testing various units that we could still call a muffler.

DynoMax straight through race muffler, # 24215

Mount it near the rear end, no bends in the pipe at all, turn down just after the rear most section of the lower bushings. The center of the muffler minus 3" from the front should be in line with the flange on the input shaft of the rear end. That means you will have to up size and down size two sections of pipe to meet the rules. NAPA has band type stainless steel compression clamps and the 2-1/2" to 2-1/4" offset pieces you will need.

With no bends, using the clamps and just two welds, it is a snap. Total cost about 90 bucks and 3 hours tops.

Bolt on 3-5 pounds of torque/HP (I'm being conservative) once you re-dyno the car setting the specs again.

BAM, kicked up a notch!!

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'91 Miata STS2 project
'96 328i Sport Pkg

So what kind of advice do you want? I assume that post came from Jim Daniels, and if so, it is gospel. Just do it, as they say.


--Donnie

I will likely copy Jim Daniels exhaust since its been tested. What I was wondering is if there may be additonal gains by using same formula but increasing the diameter by .25 inch since I'm not limited to the spec miata 2.25 dia exhaust? ( ie try 2.5 into 3.0 in expansion chamber(muffler) and out 2.5 in turn down)

The interesting thing is that JD isn't using this exhaust anymore, he switched to Asa's exhaust, which apparently gains another 1hp and is not as loud. I can't seem to find what Asa's exhaust is He has a web site but no mention of exhaust specs.

It's probably better to go with a known gain than to risk a loss of power by trying something different, especially since I won't be doing any dyno tuning of the exhaust

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'91 Miata STS2 project
'96 328i Sport Pkg

Hey Dan,
Why not just go with a Flowmaster? Cheap. Lots of options on size and orientation. R&J has all kinds in stock.

Plus, they have basically "0" obstructions. If you're keeping the CAT in the car, they have just the right amount sound control...

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Brad

The way you drive Dan, I wouldn't really worry about it too much.

I'll give my limited input. I got an FM dual exhaust off of Ebay. The previous owner removed it due to loudness. I should have gotten a clue then. Instead I bought it and had it installed, complete with left-side cutout. Can't go back now but will try to find a quieter dual exhaust to replace it with eventually.

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'99 Mk IV Jetta VR6 now claimed by the better half.

'90 Miata A-package, Floats like a butterfly and buzzes like a BEE with loudspeakers.

TWO WORDS: STEEL WOOL! That will fix a overly loud exhaust

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02 Focus SVT
STF 9

I've got a few questions about that.

1) How much to use?
2) Do I pull it apart or stuff a whole pad in?
3) How to get it in there? This thing's got roughly 90* bends for either tailpipe.
4) What's that gonna do to the power?
5) Rust factor? Will putting rust-prone steel wool into a stainless muffler cause it to rust out in a year or 2?

Thanks for the tip
Doug

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'99 Mk IV Jetta VR6 now claimed by the better half.

'90 Miata A-package, Floats like a butterfly and buzzes like a BEE with loudspeakers.