FelixIsGod29X

iTrader: (50)

With all this talk about true duals, I have a RB true dual without the 5/6 port tube on it. The thing is in very good shape with minimal rust in between the 2 pipes and has never had an exhaust mounted to it, just mounted on the engine. I'll sell mine for 150+ shipping if anyone is interested just PM me.

My5ABaby

iTrader: (7)

Read my previous post.

coldfire

iTrader: (1)

ah i skipped that. good post.

JustJeremy

Not to hijak or anything .But I a question. I have been thinking about exhaust for a while and am trying to figure what to get.My fc is 99% stock engine wise. Would I be ok with a collected sytem that racing beat sells or should I just spring for the true dual?

tomoaac

Get The Racing Beat headers (2 pipes one from each rotor), then have a custom built from there, with Mid section compressing 2 seperate silencers fed from the header, Then have them converge together to form one pipe that runs to one back box and single exit.

JustJeremy

would that be the dual header or the other?

tomoaac

just edited above, the dual header, keeping both rotors seperate up until the converge point after the mid silencers.

KeloidJonesJr.

iTrader: (8)

Stock mufflers are heavy, so any aftermarket parts for it should be an improvement.

NZConvertible

The velocity is directly related to the pressure. Pressure increases to the square of velocity, so if you double the velocity, the pressure is quadrupled. The word "overcome" doesn't make any sense in this context.

Sorry, but everything you stated is completely wrong...

tomoaac

[QUOTE=NZConvertible;6955043]The velocity is directly related to the pressure. Pressure increases to the square of velocity, so if you double the velocity, the pressure is quadrupled. The word "overcome" doesn't make any sense in this context.
QUOTE]

I've been thinking about the problem, Not sure everything i said as been right so far.

It all comes done to The fricton factor of the piping taken from the Moody chart, and Minor losses within the exhaust system, Both of which have a velocity squared term within them.

Minor losses deal with changes in velocity and direction of the gases, ie bends and areas were the pipes narrow or open up.

Using the bernoulli's equation,That deal totaly with flow I think the outcome would be that if you increase velocity back pressure will increase squared
to keep minor losses down to min, Pipes need to be as stright as possible.

To get least back pressure need large diameter pipe to keep velocity low

NZConvertible

That's what I just said...

RX7Tuner.

MY RB mufflers are heavier than my stock ones. But I still think you are correct in saying they are an improvement.

RotaMan99

Hm, interesting.

To get the scavenging effect, you don't want the piping to big since you want just enough velocity.

Now there was a debate over on TeamFC3S about this and between that and reading up online about velocity, the bigger the pipe on a N/A, the worse it is since the exhaust pulse now has to push against stalled air instead of having the possitive pressure side of the exhaust pulse pulled into the negitive exhaust pulse before it. This correct?

sniperstevedave

For a S5 (S4?) NA rotary, the intake has a VDI (variable dynamic intake), also known as a resonant intake, where the intake ports are interconnected. The way it works is that the intake manifold is designed so that at a chosen RPM the high pressure wave from one intake port arrives at the other intake port just before it closes, pushing a little bit more air into the combustion chamber. This gives you better volumetric efficiency and thus more power, and is what Mazda is talking about when they say 'natural supercharging effect'.

The same principle applies to a collected exhaust, but in reverse. With an exhaust, at the proper RPM the low pressure wave from one port arrives at the other exhaust port just before it closes, sucking or 'scavenging' a little more exhaust gas out.

All the above is factual, below is what I conclude from it.

A true dual probably isn't such a great idea for rotaries since you won't get a scavenging effect, since the ports wouldn't be interconnected. I think true duals were probably developed for V6 and V8 applications, where the exhaust ports are on opposite sides of the engine and you have multiple ports on each side.

I don't know if aftermarket collected exhaust headers are designed for scavenging or not, if they are I would really like to get a look at their calculations, since I plan to design and build my own this year.