TakumiJr

True duals is very nice , but if you go custom true duals its goin to be loud. I hear the Mazdatrix isn't too loud, but 1987RX7GUY can clear everything up about that . I had both single and dual set-up b4 and i liked the duals better, sound nice and look nice cuz of our exhaust cut out on the bumper.

Slacker7

iTrader: (2)

Sorry I can't state those rules I just thought it could be an important factor. However if all of those engines are N/A I could see how a single collected exhaust could take advantage of exhaust velocity and acoustic scavenging.

Since those cars should be significanly lighter, the weight savings might overcome the power advantage.

Also I have to say that there is a law of diminishing returns as far as exhaust sizing is concerned.

Howi

iTrader: (2)

[QUOTE]hey, use your head hpw can one pipe flow better that two????????????

QUOTE]

i'm really trying to use my head, but i still have to conclude that what you said is the most ignorant arguement i have ever heard of.

howi

FC-chan

My Alum hood is about 20lbs, I'm told the steel is about 50.

Icemark

No, the painted alum Non turbo hood is about 29 lbs, and the painted alum turbo hood is about 30 lbs.

The painted steel turbo hood is around 52 lbs.

projekt

i thought all turbo hoods were aluminum

Evil Aviator

No, some are steel.

NZConvertible

Who cares about the weight of the stock system? It's heavier than any aftermarket sytem, including duals.

You're missing the whole point of my argument. The claim made in the first post was that "single exhaust systems provides far more power than a dual setup". This statement basically says that a single exhaust system made from drinking straws will flow better than a dual system made from 4" pipe. Does that sound logical to you? Of course not! It completely ignores all the other variables in exhaust system design, especially pipe size.

Race cars use single sytems almost exclusively for simplicity and weight reasons. On all of the examples you posted dual systems would be more difficult to install and have no advantage. Our road cars are completely different. They are designed to have a dual system, so it's no more difficult to install. The tiny weight difference can't even be noticed. They also have one more very important difference; they aren't allowed to be nearly as noisy as a racecar, and dual mufflers have a huge advantage over a single in that area.
I've never said "a dual outlet exhaust allows for better performance", because that would be just as much of a nonsensical statement as claiming single is better.

And show me all this evidence. Where's all the back-to-back testing with various configurations and pipe sizes? You can't pull off a stock dual system, slap on a big single and claim single is better. Similarly you can't compare for example the dual RB system (engineering to be quite quiet) to the CS single (loud as **** apparently) because the design philosiphy is totally different.

I give you this to consider. Which system do you think would provide the least restriction: a single 3" system, or a 3" system that splits into two 3" pipes with the same type of mufflers? Simple fluid dynamics says the dual system will be better, but "single flows better" mantra says it can't.

My position here is simple. Some people claim a dual system can't make as much power as a single. I say this statement is wrong. That's the only claim I'm making.

Evil Aviator

In most cases a dual system cannot make as much power as a single. For a given cross-sectional area, a dual will always have more surface area, which reduces performance. Of course, there are many variables involved, but a blanket statement isn't really out of place IMO. If you want to argue that a poorly designed single will not perform as well as a well-designed dual, then you may also argue that an RX-7 is faster than a broken Space Shuttle, and a turtle is faster than a dead rabbit.

Absolutely. This is a good point because I have known several people who have installed an excellent single exhaust system on their NA RX-7, only to have to resort to power-robbing inserts or other add-ons to keep the car within legal sound limits. The end result is that they would have been better off with a quiet dual or collected single with pre-silencers that had slightly less power than the original single design that was too loud.

Howi

iTrader: (2)

mmm... nz, i disagree w/ your above statement. before i express my opinion, i wanna make sure that i'm not misinterpreting what you were saying. k, are you saying that given the following 2 systems:
1) 3" single stright through w/ a muffler A
2) 3" single then splits into two 3" pipes w/ 2 muffler A
that 2) will flow better than 1)? if this is the case, i would have to say that i do not see how this can happen. please provide me your theory.

howi

projekt

I CAN PEE FURTHER THAN YOU CAN!

RX-7Havik

Team Blue : Dual Exhaust


Team Red: Single Exhaust


Hmmm.........which will prevail???

Blue or Red peops?

NZConvertible

I've explained this so many times I must sound like a stuck record. You are correct that twp pipes with the same combined cross-sectional area as one bigger pipe will cause more restriction, because of the increased surface area. That's why you don't simply use pipes with half the area when you split to two pipes. That would be pretty dumb.

Two 2.5" pipes cause less restriction that a single 3" pipe when both flow the same amount of gas. This is not based on a simple comparison of cross-sectional area, but the measured pressure drop though the pipe(s), which is a result of both increased cross-sectional area and surface area. Reduce the dual pipes to 2.25" and the result is the opposite; the 3" flows better.

And yes, I know there's some loss at the Y, but it's not nearly as much as people seem to think, particularly if it's well made (another of the variables I mentioned).
It is when most of the time the person making the claim has no frickin' clue what they're talking about. They're just regugitating the same line they've heard over and over, without having the knowledge to back it up. Personally I don't care what exhaust someone uses, as long as they don't post BS to justify their choice.

BTW, I noticed your FC has a dual exhaust.

Can you not see that the section of exhaust with double the flow area will have half the restriction? It's not a theory; it's simple, proven engineering. It's also incredibly bloody obvious...

Evil and I are mature enough to have an engineering-based discussion without either of us thinking it's a pissing contest. Come back when you have something useful to add.

Howi

iTrader: (2)

not so "bloody obvious" to me nz.
if you have a 3" single coming from the engine, this is the diametre that is going to limit the exhaust flow. having the same exhaust system spliting at the end is only going to give you diadvantages. yes, you will obviously have more x-sectional area, but it doesn't matter because it is at the end of the exhaust system.

if anything, by having such a setup, you have:
1) restriction at the y (as you have mentioned previously)
2) loss of exhaust momentum.

you lose momentum because the exhaust velocity will decrease after the y due to the increase in x-sectional area. since momentum=mass x velocity, if velocity goes down, so will momentum. the loss of momentum will decrease the exhaust system's ability to help suck out the exhaust the engine produces.

a y setup (single splits into double) is totally useless in terms of performance. it's there for appearance and sound.

not so bloody obvious to me.

howi

andrew lohaus

[QUOTE]Originally posted by Howi

Quote:

hey, use your head hpw can one pipe flow better that two????????????

QUOTE]

i'm really trying to use my head, but i still have to conclude that what you said is the most ignorant arguement i have ever heard of.

howi

look man, if you dont like my point of view i can care less. but it is far from "the most ignorant arguement ever"

this statement was assuming the same dimeter and lengths of the piping in which case 2 pipes will flow better than one. obviosly a 4" single exhaust will flow better than a dual pipe 1 1/2."

on another note.

people are such uptite nightpickers on this forum especialy some of you guys that post all the time. its like you just go hunting for ways to shoot peoples comments down and dont add anything to a thread yourself. its like you gota spell everyhting out to the "t" not for the sake of preventing confusion, but just to keep some of the uptight blowhards from quoting you and saying "hahaha you were wrong, I am the god of all rotary knowledge and you better admit it" this isnt directed at you howi, just a general stement. ive had some realy assinine posts put up by different people and i geuss i just need to blow off steam.

NZConvertible

You're wrong, and I'm quite sure I've explained this to you at least once before, maybe even twice. Restrictions in pipe systems are cumulative. That is, the contributions from each component in the system (straight sections, bends, mufflers, etc) are added up to get a total.

If you have 10 feet of 3" pipe with a one foot section of 2" pipe in the middle, this does not make the whole thing act like 10 feet of 2" pipe. If you replace one section of an exhaust system with a less restrictive part (i.e. a muffler change), the entire system will flow better.

By your theory, cat-back exhaust systems bolted to the factory front section would have zero effect, but we know they do. Do you have an explanation for that?
All things considered, I don't think you have the knowledge or experience of fluid dynamics and/or exhaust design to make that statement.

TakumiJr

Is there a option 3 for a team that agree with both?

Howi

iTrader: (2)

first of all, i'd like to appologize for my statement. I agree that I sounded over confident when stating my statement.

I'm not the fuilds mechanics god, so I should not have made such a firm statement.

But I do know some fluids. This is why I have the following opinions:

If you have a well-flowing exhaust pipe, and is connected to a restrictive muffler at its end, it is obvious that the system will flow better by removing that muffler.
Let me give you this example to help you visualize this y-pipe situation. Imagine that a stock muffler is bolted directly onto an engine's exhaust ports. This is obviously a terrible exhaust system and the engine will breath like ****. Now, do you think that by attaching two 3", 10 feet long dual muffler tips will help the situation? I'm sure that we'll all agree that it will not.

This is the same idea as having a Y (single to double) pipe. By having a single coming from the engine, the single pipe has already become the primary restricting factor (like the muffler in the previous example). Even if you split the system into two 5" pipes at the end (like the dual muffler tips in the previous example), it will not help.

Again, this is an invalid arguement, becuase this is like having a 3" single and down to .25" all of the sudden. Obviously, removing the cat (or the 0.25" restriction) will provide better flow.

I'm sure you already know that I'm not one of those "single all the way" guys (w/out knowing ****) you hate so much. Next time, please take the time and read my replies a little slower, instead jumping in and say that i'm wrong.

howi

VietFC

BLUE TEAM!!!!!

projekt

do you know what the term bottleneck means?

Howi

iTrader: (2)

i don't think nz, or any of us care.

howi

projekt

this coming from the person who used it in his argument?

Howi

iTrader: (2)

sorry, didn't know that you got serious about this topic all of the sudden.

my bad, thought it was some kindda joke.

howi

Evil Aviator

I think the problem here is that your record is stuck on pressure, while most people use velocity as a target when designing an exhaust system.

There isn't much loss if it is well-designed with a small-angle split. However, one of those horrible T-intersections is not so good. (sorry Chito)

Hehehe, I feel your pain.

Yes, my FC has a Y-exhaust modular assembly to keep noise down for street use at the expense of performance. What you may not have noticed are the slip joints and v-band clamps that allow for several quick-change exhaust configurations on that car.

Unless I am mistaken, doubling the cross-sectional area would half the velocity, not the pressure. It would result in 1/4 the pressure, right?

References:

Velocity = Volume Flow Rate / Area

and

P = 1/2pV^2

NZConvertible

Ugh, another damn exhaust thread to waste my time on...
Exactly, replacing one section of the exhaust with another less restrictive one will result in higher flow. It doesn't matter if it's a muffler swap, new cat-back, or a bigger cat.
Actually, I work with this sort of thing every day, so I can visualise what happens in a Y pretty easily.
That is a bizarre example. I can't see what it proves.
Go and read what I said again. The narrowest part of a system does not cause the rest of the system to act as if it was all the same size. You need to get that idea out of your head because it's just not what happens.
I wasn't talking about a cat, I was talking about the rest of the system. It's a perfectly valid argument. If you bolt a 3" cat-back to a the stock 2" pipe, there's an increase in flow. We all know that. But you're saying the 2" pipe is "the primary restricting factor" so reducing restriction after that "will not help". That makes no sense. Both the theory and practice says this is wrong.

We're not talking about the tuned section of the exhaust here (the headers). After the headers (NA) or turbo you want the least backpressure possible. I've seen plenty of people measure backpressure to determine exhaust improvements, but never velocity. It you want fast exhaust, just make the pipe smaller...
Yeah, I think you're right actually. That system just got even better.