Another thread about exhausts
 

The FC is more of a race car than a road car anyways and the more modular it is the better, ease of service is key.

The twin exhaust looks good and sounds good, aside from it never sitting square in the bumper cut outs...

So I'm thinking of going to a single exhaust so I can deal with it easier but with this engine setup I through a cat-back on (when I still used a RB pre-silencer) and put on my friends ebay 3" to fart can SSautochrome exhaust and it was WAAAAAAY to loud. I put videos up on my youtube,

www.youtube.com/fidelity101

(for reference)

but now I;m thinking of sticking with my 2.5" header back to a muffler with 3" outlet.
I'm thinking a borla possibly either oval or round. For rotarded sake (and roughly same price) the racing beat furai triangle muffler looks good.. http://www.racingbeat.com/RX7-1986-1...rts/16031.html but I would just to 2.5" all the way back which would be good for my application because I would get great velocity and torque for my midrange which is ideal for rallycross.


Anyone got suggestions or tips?

I'm thinking magnaflow or a glasspack will be too cheap and either rust or be WAY to loud.




engine is S5 NA w/ large pinapple racing streetport and turbo sleeves with 6pt sleeves removed on a mikuni 44mm side draft with a racing beat header.

i've been working at this too, i have no concrete info really, but i do have some experience.

1. i put two glasspacks under the car, the packing lasted 7 laps, and after another 14 or so, they are starting to sag...

2. you need ALL of the exhaust hangers, when you heat the thing to 2000 degrees, it can't support itself.

3. you could make a case for stainless steel being the best choice in the front.

4. i had to run a buttplug this weekend to meet sound, and it did a lot. pic is attached, the pipe is 3" the hole is 2". it cut the noise outside the car a bunch, didn't do much inside the car. peak power was down but not by a lot. it screwed up the throttle response though.. anyways at the 200hp level, i don't think you really need to run 3", at least in the rear. so perhaps collect into 3" find a muffler that flows enough, and you could run a 2.5" tailpipe, or maybe smaller?

5. in theory a larger bodied muffler is quieter. all the mufflers that are easy to get in the US are pretty small. all the rotary people outside the us run an 8"x20" can (on a 1st gen) which is impossible in the US...

Your exhaust is probably not holding you back very much. I made 170whp through a 1 7/8" pipe and a baffled muffler, so at least for the street port that I had, it wasn't too restrictive.

If you want it more modular, weld in some V-flange units so you can drop the middle section out and be done. Then put a Weber 48DCOE or 50DCO on the thing and sign up for Mazdaspeed, since it appears that the contingency program covers Regional rallycrosses now.

(Ya. F'ing. Rly.)

I planned on going stainless, my "pre-silencer" aka a 2.5" pipe about a foot long that is stainless, all I need is a 5' section to of pipe and decent muffler.

No its not holding me back its just heavy and I'm lazy, that and I can't stop dicking with this car or my setup.

I already am signed up with mazdaspeed, but it only used to cover national rallycross... hrmmmmm

maybe they have been getting a lot of our results lol.

the carb will come, after all my tax return is right around the corner...

have you ever dynoed the car with this setup? how much power do you think its making as is?

currently dynos at 132whp and 122wtq at 7000krpm

14.8 @80 mph in the 1/4

95% used parts/seals/springs

that is crazy low power. I wonder is it due to lack of compression or the too small of a carb.

HOLY SHIT I JUST SAW!

:nod:

both, I'm running at about 90-95psi last time I checked on both rotors.

the mikuni 44 is too small for an s5 streetport, the fuel bowl especially.

it was a mustang dyno and my car was the guinea pig to work out the kinks too...

You can take it for what it is worth, but my S5 Mazda reman with 6 port actuators and sleeves removed, running an S4 intake and stock S4 ECU made 178 rwhp on a Mustang dyno. I was running a Racing beat Road Race header to 2 2" pipes running the length of the chassis, then collecting through a Brezinski venturied collector to a 3" pipe. This went through 2 90 degree bends then into a Borla 3" inlet and outlet Road Race Muffler to a megaphone that grew to 5" at the outlet.

Seemed to work very well and wasn't ungodly noisy. Way too loud for the street, but way quieter than unmuffled piston engined cars on track. It has lasted almost 7 years now with no issues. I am going to dyno it as soon as the weather gets better with the 4 port 1/2 bridge and ITB setup thats on the car now.

Eric

what im planing on doing here in a short little while is a street port s4 na with a weber 45 dcoe. your low power number kinda scare me that I will choke that motor down so much to where it wont be worth doing it.

I have 38mm chokes, the carb is basically meant for a 12a, unless I were to run twin side draft mikuni 44phhs.

I'm in limbo currently, the chassis is built the engine is just what it is, I haven't decided how to complete the next engine but I got half of the parts laying around so its going to be SC or PP.

it was about 200 dollars or so for the setup, just want to drive it, and its cheap.

Also bear in mind that it was not a Dynojet... my engine put down something like 135 or 138whp on the same day, and fuel pulsewidths and 1/4mi trap speeds both indicate about 180 at the crank. So the readout is a lot more lossy than your typical Dynojet readings.

I forget what kind of dyno it was, but it was an electric brake style unit.



Kevin - WOR is considering a 96db sound limit, measured at the starting line. I don't think my VW would pass that.

yeah that is quiet! passing will depend on how they do it... at laguna the limit is 92db, i think drivers right, so you point the exhaust to the left..... however stock cars don't always pass 92db!