what is the best exhaust system with horse power in mind? i understand there are sound restrictions but do you go mainstream with racing beat or something else? thanks

 

The off the shelf packages are not designed for racing.

Most race cars use a custom, Mazdaspeed/ISC, SDJ, Rotaryshack or RB (budget friendly) header. After that it's ISC (NLA) or custom with various mufflers, silencers, expansion chambers, etc.

Also depends on your definition of "racing".

Plug Mazdaspeed header for sale - https://www.rx7club.com/showthread.p...3#post10797733

 

Dont use corksport. That was the first exhaust we used. Its too thinwall to hold up in racing conditions. We melted the inside of the presilencer, and broke welds on both the header and the muffler...

IMO, start with a racing beat header, then have a guy who does race exhaust build a long primary or true dual exhaust downstream from that.

 

Something like this:



True dual NA setup and dyno proven 200 rwhp.

 

RB Header with custom exhaust.

3" straight back with 9x18" borla pro-xs.

Good tone and doesn't set off the dB meters at the track.

Whatever you choose, it MUST (<-- look at that word ) have stainless packing.
If you don't, you won't have a muffler for very long. The heat will blow out the glass or set it on fire.

Also, a good thing to note is that you will want to make sure that your tip is at least 1-2" past your bumper so things don't get all melty.

 

this is all very interesting, thanks for the information.

 

the corksport cat-back really seems designed for a car that still has a stock exhaust manifold and/or a cat. with an RB header and midpipe it is way too loud to make sound levels at the track. I have to run the silencer insert that necks it down to 1-inch at the exit, which kind of defeats the purpose.

(b/c of the cooling of the exhaust you dont need a full 3"+ exit, but the silencer definitely robs some power.)

the borla is a better solution. or the RB. their full race dual header system with a collector at the rear is a reasonable "off the shelf" exhaust.

 

Best performance option I have run across as mentioned above.
Racing beat or similar (budget allowing) equal length header (not that bullshit jc whitney unequal length crap)
Then run two 2" pipes back, under the rearend side by side, and collect them into a 3" collector.
THen add a ceramic packed borla, or Edlebrock, or mazda lava rock (heavy) muffler. with a 3" exit, and then add a 3" turndown from Jeggs or similar.

This will give you the best power if the length is proper. Check with the tech section of RB in the exhaust part. I believe its 118 to 120 something inches from the engine is where you collect them. You cant collect the RB road race header right after the flange, it messes up the tuning of the exhaust. run the two pipes all the way to 118.

On my N/A 91 its at 118, and it screams to life after 5500-6K. this is with all emissions removed and the funkadellic S5 intake open only, 6-ports removed and a Wolf 3D running it.

But on all the other N/A race cars that has been the best option.

For proof.. testing back to back with a racing beat long collected street port exhaust on a stock FB. THe hp difference between the RB and above system was 1hp less for RB, but 1FTlb more torque.. So its essentially a wash. Except for the heavvvvvvy weight of the RB system.

 

On my 2nd gen ITS car, we had the RB race header, to two long tubes that merged into a Dynomax Ultraflo muffler. For a little added assurance we put on an adjustable tip so we could change the direction the sound went (for sound control reasons). That thing was awesome! I just bought a 1st gen IT7 car (picking it up this weekend). It has a RB race exhaust and two full length tubes to a RB muffler. I'm going to swap out the muffler soon enough and go with another Ultraflo.