Alright, ive got it all planned out!

~All done with 3 Inch piping!

~2 Inch Header to 3 Inch Collector
~Resonator Muffler
~Flowmaster Delta Flow 40 Series Muffler
~All to a Dual DTM Tip

Its about $350

 

Not good. For a normally aspirated application, your pipe should not exceed 2.25 inches to the back. Too big, and you lose exhaust velocity and the scavenging effect from the headers.

3" is only for Turbo applications that need as as little restrictions as possible

 

Actually you want no more than 2" on a rotary... there's an article about it on mazdatrix.

 

But ill be supercharging it next Spring

 

I was considering getting the rb road race header, and having a "true dual" exhaust. from the header, running 2in all the way from each of the pipes , with 2, maybe 2.25in straight through race mufflers. who knows, just an idea

 

Still, too big. Only Turbo's need 3"

 

The Flowmaster is NOT a very good flowing muffler. Look into something from Dynomax or Magnaflow if you want the ultimate budget exhaust. Both flow much better than blowmasters, not to mention they sound better.

As for size...it all depends on your power levels. A supercharged motor making 300+ horsepower would definetely benefit from a 3" exhaust.

 

I have a supercharged V8 engine with well over 300 rwhp.
When doing a supercharged engine, one of the LAST things you do is get a bigger exhaust. You move the torque curve way too high in the powerband. You must do all the mods before the supercharger (to the intake, pullies,etc) to make all the difference. Even my 5.4L supercharged V8 uses 2.5" exhaust tubing. The only reason fo me to upgrade is if i was going to bild a full race engine running over 20 PSI. And even then, I would need a more efficient S/C.

Not all forced induction is the same, It really is apples and oranges. What applies to turbo's does not necesarily apply to superchargers, and vice versa.

 

Your Harley truck would gain some serious horsepower with larger exhaust tubing. Trust me. And, offhand, I don't believe it breathes through a single 2.5" pipe. That is plain RETARDED, and I will never buy another Ford if that is true.

I'm a Mustang guy, don't make me go dig up dyno sheet after dyno sheet of supercharged V8's gaining massive power from upgraded exhaust, please! I'm tired!

Even stock 225 hp 5.0's came factory with dual 2.25" pipes, and the 03 Cobra guys are showing huge gains when swapping on larger, more efficient exhausts on their rides.

Yes, power adders are different, but horsepower is horsepower. Any 300 hp motor requires (or at least will benefit) from a larger exhaust piping than a 150 hp motor! The motor is flowing a certain amount of air in order to make that power (turbo's are not all that much more efficient than superchargers) and it must release that air somehow....

 

Peak horsepower gains are not the same as average horsepower gains. I'll admit I know very little about supercharged V8s, but if you put 2" header pipes dumping to 3" back on a supercharged ROTARY, you're going to feel like an idiot when it makes shitty, unusable horsepower. This would hold especially true on a 12A.

 

Maybe those 4.6's are different from the 5.4's. I spend as much time on Harley, Lightning, FTW, and F-150 forums as I do here.(Too much really...)

The most common exhaust mod we do is an X-pipe. It is 2.5 x 2 BTW, I see in my previous post where it may appeared as I meant a single pipe.

Every single exhaust upgrade on these trucks that I have seen, have increased peak horsepower and torque, yet moved the powerband so high up that it felt like "turd" compared to before. They would lose the gratifying feeling of instant acceleration.

That's not me talking, that's the other L and HD owners. That's even after re-burning the chips to deal with the new mods too. Maybe we got the the properly sized exhausts, and the Mustangs got too-restrictive ones - I dunno.

Again, in a full out drag race, who cares - just like the guys here who insist that wiring their 6 ports open is better than having a working set on their 6-port 13B's.
There, the power curve won't feel any different, because you're at full throttle anyway.

For the sake of arguement - I will agree with you.

While I am speaking from my relatively limited experience with supercharged V8's, and my extensive knowledge about rotaries. (at least I believe so)

A Turbo II rotary producing 300rwhp can easily get by with a 2.5 single exhaust. Only when producing bigger numbers does it need more. Ask the 2nd Gen guys, and they'll agree. They only need more when getting a larger more efficient turbo, a port job, and are putting down some real numbers, with more CFM.

A Supercharged 12A Rotary won't even get anywhere near 300rwhp, no matter what Atkins claims.

I am not saying Larger exhaust won't help - definatley better than stock, but for his purposes - a 2.5" would be the maximum diameter to even consider. If it was mine, I would run 2.25 all the way back, and collect at the axle. A supercharged exhaust is very similar to an N/A exhaust, only a little more stout.

 

one of my friends has an FC he took a RB Header, had it cut and had the piping made, its 2.5" and its true duel. he has it to where there is a muffler for each rotor. there not connected in any way. just 2 seperate pipes all the way back with RB mufflers. its realy nice.

 

i want to do cam girl....

lol

-greg

 

Directfreak is right on this one!!
you only need big exhaust on a bridge or p-port, or turbo!
if you are looking for peak power ,then bigger is better , but a broad powerband will get you better et's, smaller exhaust, for stock port or streetport!

 

Is that only for a 12a? For my 13b (decompressed) 4 port I was told that 2 and 1/4 was the optimal set up by the local rotary tuners.

 

Hey wait, doesn't the madtrix 86-92 exaust system use a 2 1/2" presilencer? I now the pipe on the downside of the "Y" is 2"; but I believe that from the header to the "Y" is 2 1/2".

I am looking on thieir webpage for details.