I've searched and read all through this thread which had a lot to say about Performance and Horsepower... I just want a true dual for pure BadAssity. Is it a stupid idea? I've done a little bit of math, I think the optimum NA size of exhaust is 2.5 right? Anyways, I'm pretty much no good at math but I've come up with a diameter (for the dual) of .88 which I'll probably round up to .9.

So am I totally off my rocker with this idea?? Set me straight people... I have no idea what I'm talking about anymore!!


I'M ON A RAMPAGE!!

 

Road Race from racing beat:
enjoy

 

A Rotary is not a 2 stroke. A 2 stroke exhaust is designed to send a pressure wave back to the valve so that the intake charge doesn't get drawn out the exhaust.

Area = pi * radius squared (A=pi*r^2); I have no idea where you came up with 0.88 or 0.9. The optimum diameter would be 2" tubing for duals.

Area of 2.5" 16ga tubing = 4.43 sq in
Area of 3" 16ga tubing = 6.49 sq in
Area of dual 2" 16ga tubing = 5.52 sq in

A properly collected header will produce more power then a true dual setup. A true dual exhaust is only effective on a stock port engine. Once you start porting the engine the dual setup loses efficiency.
Read the book Scientific Design of Exhaust and Intake Systems if you really want to know why.

 

My motor is completely stock and I don't plan on doing any porting (at least not on this motor). Would I still lose power with a true dual?

Me neither, cause that's the equation I used... As I said, NO GOOD at math! lol...

 

sorry to steal your thread but , i got a qeustion, i got a pacesetter header with a obx-r turbo exhaust single exit by the driver side,the header is a diameter of 2.5in., and then i got a reducer of 2.25in., because the turbo exhaust comes up shorter dont know why,but anyways the exhuast is 3in., is that good exhuast setup?

 

here is what I have found while losing myself using the very great, mysterious, arousing SEARCH feature:

https://www.rx7club.com/showpost.php...2&postcount=19
Regarding the Racing Beat Road-Race exhaust setup.






HMMMMMMMMMMMMM, the search is so sexy. I wanna make love to it every time I have a question. It truly IS instant gratification. Just don't talk dirty to it. It doesn't like it. damn, it's all over my computer now.

 

Thanks! I never found that thread for some reason... I searched my *** off too...

 

i just want to know what people think? thats all , beause i felt a difference when i did that exhaust system

 

I didn't really get your train of thought. I was lost.

 

i would like to know if the sizing of the piping would be a good set up? because im deciding of changing it.

 

that's where i'm lost. So you have the pacesetter headers. I got that. Then you have a turbo exhaust (2.5") and a reducer to 2.25". Then you ask about 3" exhausts.

To avoid further headaches: Stick with 2.25" or MAX 2.5". 3" will be overkill on the NA.

 

oh, sorry i mean't that i have the 2.5 headers,2.25 reducer and then to a 3in.exhaust, and then im asking if that sizing of the piping would be good?

 

For a turbo (Which I believe is what you said you had), The standard rule of thumb is that bigger is generally better... But you don't want an exhaust SO large that the gas cools too much because then it becomes more dense, and thus harder to get out...

3 inches should be fine. You may want to see if you can get a 3.5 in case you ever plan on upgrading your turbo...

 

Its A N/a

 

I've got the Racing Beat true-duals on my daily-driver. LOVE IT. It's basically the nicest exhaust you can get for a street-driven N/A... Extremely high-quality.

GREAT power-increase and fantastic sound. If you can afford it, I would recommend it... I got mine for a great deal, so I lucked out.

 

So far, this FC has been the greatest deal ever for me... Let's hope I can get this exhaust for a deal too! I think I'm gonna get mine custom done... What Mufflers should I get????? Lol...

Mario, whatever it is that you have, you're restricting the exhaust by having so many size changes. *SOMEONE CORRECT ME IF I'M WRONG!!* But I believe the optimum size diameter for NA is 2.5 inches. Try to get yourself a full setup with that size pipe on it and you'll be good to go. As it is now, you're probably losing a little bit of power.

 

so why the 2.25 reducer this i dont get?

 

bunch of guys get borla. DO a search under "muffler" and you'll find the info and maybe even soundclips.

 

i was thinking for the backpressure its a s4

 

I am running RB true dual and it's a great exhaust. I think one of the benfits is knowing the characteristics of each housing. because each housing has it's own pipe, you can feel for exhaust pressure, buring oil or coolant, and backfiring (timing/fuel).

Brian

 

hey rx7tuner, on your sig is that your current ride or old one? cause i would like to know your numbers (hp) to the wheels on that setup.

 

Yes, the Mazdatrix "true dual" exhaust was advertised as a performance enhancement only for stock ported engines. I still doubt it performed better than a properly designed long collected exhaust, but it was probably close enough for government work.

FYI to those reading this thread, "true dual" in technical terms is called an "uncollected" exhaust.

You can maybe use the following information as a design basis. As per my crusty old 2000 Racing Beat Technical Manual for racing exhaust systems collected into a 10-18" long megaphone with a 4" dia exit...

Stock port, street port, or bridge port with a small carb:
- Inside diameter 1.7-1.8".
- Short primary system collected at 22-25".
- Long primary system collected at 120-125"

Bridge port with a large carb:
- Inside diameter 1.7-1.8".
- Short primary system collected at 15-18".
- Long primary system collected at 113-118"

Peripheral port:
- Inside diameter 1.9-2.0".
- Short primary system collected at 10-18".
- Long primary system collected at 89-94"

For those who don't know the difference between short and long primary design:

Short Primary (header collects near the firewall):


Long Primary (dual exhaust pipes collect near the rear of the car):


Your header is slightly too large, and your reducer is probably not so good. Collectors should be the same cross-sectional area or larger than the smallest pipe that they collect. However, I would not bother replacing anything if it is just a street car because the performance difference is would not be significant. Sometimes people on this forum get too stressed about the small stuff.

As for an exhaust system with an increasing exhaust pipe diameter... yes, this is recommended by Rick Engman of Downing Atlanta. The theory is to start with the proper header diameter (about 1.75" ID), and then gradually increase the diameter of the next exhaust components by maybe 1/4-1/2" ID so the entire exhaust system forms a type of megaphone. He recommends this setup with an exhaust collected at about 27".

 

It is my current ride. But I don't know the HP at the rear wheels because I never took it to a dyno. I thought about it last summer but dynos are mostly relative and it would just put an unscientific number on how much power it has. I could go around telling people it dyno'd at 190hp but it might really be 180 or even 195. I think I'd rather just keep it a mystery. I can tell you, it doesn't make enough power to keep me from wanting a turbo...

Brian

 

Are there any other mufflers that are compatible with the RB exhaust? I'm not a big fan of the muffler styling.

 

I imagine that any muffler would be compatible. I've got Mercedes AMG mufflers on mine. The exhaust shop down the road welded them on for me.