importboi22

collected exhaust!!!! ownz j00!! i've done alot of all motor HONDA tuning.... i used to always beleive in the jdm 4-1... but after spending about an hour or so doing the math with my friend and getting a tuned hytech header.... i will never EVER go back to the 4-1... ill just put it this way... switching from a 4-1 to a hytech tuned 4-2-1 overall output on the dyno below 4k rpms was 2fttq higher.... and around 5700rpms to 9k there was a 11ft tq gain may not sound like alot but when you only had 118ft tq before heheheheh 10% is quite an increase in tq.... ill just put it like that, from my experiences..... collected and tuned exhaust combionation will ALWAYS be better.... true duals crap is for lazy people... just like the JDM 4-1 header

mazdaspeed7

I am building myself a collected exhaust. Ive just had other projects taking my time and funds.

1987RX7guy

iTrader: (3)

Originally posted by mazdaspeed7
Its not worth my time to dig up numbers. ALL that matters is that there IS more friction with true duals, and singles WILL flow better for a given cross sectional area.
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Well without the numbers I can't just accept that there IS more friction in the duals than a single. AND does that apply to any and all pipe sizes or just a specific one? I also beleive that it IS worth it to the poster of this thread to see the PROOF. or atleast give us a way to get to this PROOF ourselves.
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Then why are you trying to argue when you just admitted you have no background in what youre arguing? Personal preference is JUST that. Its not facts, its YOUR opinion of YOUR exhaust.
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I have to start somewhere don't I? I am not going to say I am a physics proffesor but if we can see the formulas and numbers you used we can SEE for yourselves and therefore don't need to know about physiscs to see what you mean and if or if not that is correct.
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Why should I make you an exhaust? I know what works, and what doesnt. I have physics, and experience to back me up. If you cant realize that, then why should I even bother tryign to help you? If it wasnt for the other people reading this, I wouldnt even waste my time arguing with you. I could care less what you think. I just am sick of hearing this bullshit about your exhaust is best because mazdatrix says so.
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I didn't say you HAD to but I made that offer. I don't think it was half bad. given you use quality componensts it would cost around 800 dollars. that is a 500 dollar check to you from me for a good exhaust. How isn't that a good deal for both of us and the rest of the forum members?
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You want proof? The proof is in the theories. The numbers wont make the theories change.
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We still don't have theories to see.

mazdaspeed7

Are you internet challenged? Do some research, thats what search engines are for. I posted the theories in my second post, and referred to them in pretty much every post afterwards.

How can you say you have to see the numbers, even though you agree that there will be more friction with true duals because there is more surface area? The simple fact that there is more friction implies that the true dual will have lower flow numbers than collected. Whats the big deal with numbers anyways? Theyre just numbers.

Go read up on fluid dynamics and exhaust tuning, and then try to argue. You have no points, youre not making any logical arguments, youre just blindly defending your opinion by pretending its facts, and you know everything about exhausts.

1987RX7guy

iTrader: (3)

Lets see here. You know the theories. But all you said is more surface area- more friction. that is undesrstandable and true but what pipes are you talking about? what diamiter? WE all need to KNOW what you specifically used to come up with that conclusion. Not just accept the fact that it is true. It would have been very simple for you to post the FORUMULA(S) in your first post with YOUR numbers and data already plugged in to them. That way it is easy as 1 2 3. Plus if you are right which you say you are by posting the numbers and forumlas they are a result of you would END the argument right NOW.

1987RX7guy

iTrader: (3)

OH and I never said I knew it ALL. But I am asking you to show me and the rest what you mean specifically.

Your using to broad a statement and calling it a theory.

I could say if I have a rabit he needs X amount of space to live in. I could later add if I have 2 rabits they need Y amount of space to live in. But your still talking about X and Y here. You need to show numbers because without actual application data it is only a theory. You need to remember that a theory may have a different result when talking about different things. I would like to see your data and I would bet on it that everyone else would too.

ReZ311

iTrader: (4)

Man. just run a straight pipe!

ddub

my simple question has turned into an argument...

mazdaspeed7

Im trying to clear up the bullshit about exhausts here. Unlike 1987RX7guy, I have personal experience with both, and on top of that, I also have a knowledge of fluid dynamics to back up my opinions. What does it matter if the true duals flow 2% less or 20% less? it still flows LESS. That means that it will make LESS power. Why does it matter exactly how much? Do you have nothing better to say? Your arguments say nothing, except that your blinding defending something you dont understand.

To answer your question, the HKS mufflers are good. You would be wasting money to get a different cat back. Even straight pipes with no mufflers would only be worth a couple of hp over the HKS exhaust. And it would be A LOT louder. You have a very good setup for the street. I would just stick with it.

c-squared

No offence, but I find this very hypocritical.

You are making countless numbers of tests on an intake system you are trying to sell, and logging the change in temperature.

These temperature changes reflect power increases based upon properties of physics, and you stand by these proerties for your product.

You also agree that dyno graphs mean next to nothing since the changes between dyno runs mean huge changes in results.

So, in selling your product, you completely deny the need for dyno runs and assume physical testing is all that is required, and yet here you are completely backing dynameter runs from the same people selling the product?

Either you support the laws of physics, or you support the need for dyno proof. Don't stand on the top of the fence; pick a side.

Canadian Rotary Man

ok, being in physics I'm going to try and work this out.

Maybe we'll finally get some answers, my hypothesis is that true duals are better. But I will try to work it out to the best of my unbiased ability.

BigTone

-First, thank you for dropping "I won my race against max" argument, it sounded like a immature highschooler.

-Second, for the heck of it. Take a look at what all the sponsered cars, the japanese cars that everyone idolizes. What do they run? Collected exhaust.

-Third. Physics is not somthing that you can decide to follow one day, and pay no attention to it the next. Physics shows that a collected exhaust will preform better, if not substancialy better than true duels. Now granted, collected exhaust should be tuned, but the fact is, if you "like numbers" losing a 5lbs of torque below 3000rpm and then greatly execceding that output of true duels above that rpm range is well worth it. I think everyone who understands rotaries would agree that you dont buy a rotary car to puttz around at 3000rpm, you take that sucker up to redline and keep it there.

-Finally, I am a mechanical engineering student, so I will go and try to dig up some physic books for you.

Canadian Rotary Man

I found the following relationship:

Let the radius of each of the dual pipe be "r", and the radius of the single exhause pipe be "R", since pressure is directly related to the radius we only really need to worry about cross sectional area.

R = [(2)^0.5] * r

Example, you can get the same flow rating from two 2.5" duals as one 3.5355" single pipe. Note that the single pipe weighs much less than the duals.

However this does seem to break down when you aren't running straight pipes, once you introduce another velocity dependant force(a muffler or cat) favour seems to go to the duals, running double mufflers and cats in parallel. Which explains why mazda used the setup they did in 1986 for our mufflers(why not the cats, I have no clue).

Keep in mind that there are still lots of variables I didn't include, like the fact that exhaust pulsates and are at high temperature, which means the particles are quite violently bouncing around in the exhaust, slowing each other down, creating almost a "natural" backpressure pressure.

I'm in 3rd year applied physics at SFU. Hopefully this helps, i did whip it up quickly so there might be an error somewhere. But I'm looking into making an exhaust system, and this has helped a lot

mazdaspeed7

Youre ignoring the fact that with 2 pipes, there is more surface area than a single, so a 3.5" single will actually flow more than dual 2.5" pipes. But its a moot point, because in the real world, almost every other variable matters more. The main argument here is that true duals are NOT tuned. Their power increase is directly related to their increased flow over the stock system. A collected exhaust, on the other hand, is tuned. It uses the pulse from one rotor to create a low pressure area within the chamber of the other rotor shortly before the port closes. The idea is to trap the low pressure wave in the chamber by the closing of the intake so that there is less exhaust gas diluting the intake charge, and to a lesser extent, the low pressure within the chamber as the intake port opens sucks in the intake charge. That is where the power increases come from. But, keep in mind, it works best at a specific rpm, with diminishing gains on either side of the specific rpm. But even so, a tuned, collected exhaust will have more area under the curve than true duals. The number of collected exhaust compared to true dual in regulated forms of racing speaks highly of this. Mods are limited, and hp is at a premium.

Canadian Rotary Man

My calculations take into account the fact that there are two pipes in a dual system. That was the whole basis of them. Also, they only hold true at higher pressures, the lower the pressure the less of a factor surface area is.

I did ignore bernoulli's principles of fluid flow, as you mentioned. I didn't know that was how a collected exhaust worked. I assumed the exhaust was at constant flow.

1987RX7guy

iTrader: (3)

Dealing with the intake issue first. Temperature drop or changes was measured and so was ambient. I have two numbers to show and base myself off of. I can say on this day it was 88* and intake temps were 90*-93* from 0-100mph or whatever you please. Its information That doesn't really change HERE where I test the intake. Now if you look at a chasis dyno changing your tire pressure might change the power reading. Changing spark plugs changes the power reading. changing the oil in the car changes the power readings. Running the car 5 min. after starting it and then running the car after 3 hours of driving will change the power readings. You get the point right? Dynomometers while they are a good device and are probably very close to reading actuall HP can be manipulated. Just like Mazdatrix could have manipulated their dynosheet so could someone with a collected exhaust. The only way to test this out to show PROOF would be to do 6 runs on a dyno. Take 3 with duals and 3 with single. Have two oil changes done 8 spark plugs on hand, check the air PSI after each run, check that when you switch exhausts you start off with the same everything: coolant temps, new oil, new plugs, same PSI in the tires, etc. i.e. NO tampering. Then I would venture to say that the dyno would probably be accurate and a good reading of the change in power from dual to coolected or vice versa. Do I have the money to do this? no. If I did then I would do it. But taking a trip out of my city and having a second exhaust built for my car not to mention paying for dyno time and all the parts would not be easy on my wallett.

The reason that I don't see a need to dyno test my intake is because there is no intake that has dyno performance numbers out anywhere. If you ahve seen someone quote REAL hp numbers let us know. I would be interested to see who does that. Second to that I would need a dyno shop that can simulate atleast 60-80mph winds on the car. Otherwise the intake wouldn't get the EXACT same air flow over it as in real world driving. Then after that people would revert to the same arguement I just made above. Chasis dynomometers can be manipulated heavily.


Laws of physics are well duh true but I want to see proof not just the laws behind the oppinions. Mazdatrix showed me a dynograph and I e-mailed them for more info on the dyno run and so on. They satisfied me so I went ahead with their exhaust. I offered Mazdaspeed7 an equal amount of money to make me a better exhaust and I would buy it from him. Thats right I was going to give him 1300 dollars of my money if he could make me a better exhaust. Now given the cost of making a custom exhaust it would probably cost him around 6-800 dollars to make this TOPS. I think that 500 dollars is a good enough paycheck for maybe a day's worth of work don't you? He said he didn't have time well that might have been true but I offered up the green.


Santiago

1987RX7guy

iTrader: (3)

Japaneese FC's are all Turbo. I don't argue anything about TII's single all the way as big as you can make it.

No I didn't buy my FC to stay at 3k rpms all day but that does make up 80% of my driving. So I don't see any god comming from the loss of power with a tuned exhaust. Not to mention that this exhaust will have a free flow muffler which will make it damned loud. With only one muffler you loose 50% of your quieting power. I like my ears to NOT bleed thankyou.

EDIT: I only threw in the race for kicks. I love whoopin his but with my sport over and over. I can say that bolt on collected is not the way to go

Mr. Eccentric

This is a real marathon here. I've never seen rebuttals so lengthy and thought out.

In my opinion nobody here is an expert on this subject. You'd need to have a group of scientists (experts in different fields) and a dyno and experiment with a lot of different combinations of bends and lengths and dia. supplemented with existing proven theory to get a proper and final answer for this question.

My short opinion is that Mazdatrix dynograph is quite convincing on the surface. I think true duals are the sweetest set up currently.

mazdaspeed7

How many times do I need to tell you that collected does NOT mean single. You can still have a y pipe, and 2 mufflers, and STILL have more power, and STILL have a smoother exhaust tone, as the interference of the pulses(which happens to be what makes power anyways) cancels out some of the noise.

Im really getting sick of arguing with people who blindly follow their beliefs when they CANNOT back them up. Do your homework, so you actually halfway know what youre talking about.

Mr eccentric, how many times have I been through this. Dyno tests, just like statistics, is VERY easy to skew. And on top of that, its ONLY comparing it to a stock exhaust. Ill be the first to say that true duals make more power than stock. I have personally experienced this. BUT, true duals do NOT make the power of a tuned, collected system.

Why the hell do you keep bringing up the thing about having me build you an exhaust. I dont have time, nor do I care. My helpfulness here only goes as far as sharing knowledge. But thanks to threads like this(and every other exhaust thread), im very close to just avoiding this forum like the plague. Im sick of of people with very limited knowledge, and even less experience arguing blindly on and on. I have forgotten more about exhaust tuning that most people will ever know.

1987RX7guy

iTrader: (3)

Mazdaspeed7 is right guys. I am done. finished.

true duals suck *** just like he says. good bye to everyone. I am sorry to have taken up so much of your time. Forgive me.

Santiago

Templeswain

I just read this thread. And I'm glad that both Mazdaspeed and you had a competitive argument.

After switching out my exhaust from my s4fc to my s5fc I was considering replacing the 87 with a now bare underside to somekind of completely duel exhuast for each exhaust port.

I have absolutely no fluid dynamics background but I always thought that each port would breath better unimpeeded by the other port. But now that mazdaspeed seems to hate true duals I'm not so sure....

One point Mazdaspeed brought up was exhaust scavanging which I think is very important. Because if you need a little back bressure to scavange exhuast and keep it from contaminating the next combustion cycle, it would seem duals would be less accomodating for this factor.

One question I'd like to ask is: If you have more surface area for the duals that have to work against friction (granted more or less a quarter more pipe travel) for the exhaust to pass through, wouldn't it be reasonable to think that the pressure generated by each port would be cut in half for duals? Thus making the surface area a negligible factor?

I mean, if each pipe has less pressure, then shouldn't there be less friction anyway?

Oh well, I wouldn't get fluid dynamics if you tried to explain it to me anyway. Since Mazdaspeed has had a bad experience with them, then I'm going for the standard RB set up again.

But hey santiago. I bought my set up because of the dynograph on their site-but I thought that was for non-duals.

mazdaspeed7

Try next to nothing as far as scavenging. True duals physically could be tuned to a specific rpm, based on the reflection that occors when a pipe ends. The wave is inverted(a negative pressure wave) and sent back down the pipe towards the engine. With the proper length of pipe, it could be tuned so this negative pulse arrives back and enters the chamber, and is trapped there by the closing of the port. But, this cannot be done in a street exhaust. Mufflers add in resonance, which makes tuning less effective, and harder, and on top of that, the lengths would be way too short to be usable. Think of the headers on a nitro burning dragster. A pipe coming off each cylinder, but the pipe is very short, with no mufflers. So as far as street cars, or even any noise-restricted form of racing is concerned, true duals cannot be tuned. In those systems, power is achieved through flow alone.


I have no idea where you got that from. Coming off the engine, there is always one pipe per rotor. The collector is downstream of this. True duals would have more backpressure compared to a collected, given that the pipe cross-section is the same. The dual pipes have more friction opposing flow. The more the flow is opposed, the more backpressure there is in the system. Backpressure is never good. Velocity is. Backpressure always loses power. General lack of knowledge is how that fairy tale about backpressure making torque came about. Small pipes have a higher velocity for a given amount of airflow. But also have more restriction. The high velocity is what makes it have a strong low end, but as the rpm's climb, the pipe cant keep up with the flow requirements, and backpressure builds, and power falls off. Large pipes, on the other hand, have low velocity at lower rpm's, which reduces torque, but as the rpm's climb, the velocity goes up, but backpressure doesnt build much because the flow is still well within th elimits of the pipe.


It doesnt necessarily have more backpressure. All other things being equal, a collected exhaust will have less backpressure than a true dual. One more reason why it makes more power.

One more thing I need to make clear, that *some* people cant seem to understand. Collected does NOT mean a single exhaust. A collected exhaust can have a y pipe, and dual mufflers in the back, like the stock setup is. Collected ONLY means that somewhere in the system, the pipes converge into one. This also applies to x pipes and h pipes, which are basically true duals, that have the pipes merge together and then immediately split(x pipe), or have a crossover tube to allow for scavenging(h pipe).


Yes, I do not like mine. But I wont go so far as to say the design should be buried in the deepest recesses of hell. I dont want to make the choice for anyone. I want them to make the choice for themselves, knowing as much as they can about it. One of the biggest advantages of true duals is also one of its downsides. Its not tuned. BUT, its also not sensative to other variables. I was very happy with my true duals, until I got a ported motor(aside from the sound). With a mildly modded car, true duals would not be a bad choice opposed to a collected exhaust. The power gains of each will be very similar. But once porting comes into the equation, the whole setup needs to be optomized around the porting to get the most out of it.

Would you like to show me where santiago had a competetive argument? I managed to make every single one of his points go down in flames, because they were either based on opinions, flat out wrong, or inconclusive.

edit: had to fix the quotes

Templeswain

Thanks for explaining this to me. Obviously I don't really have a complete understanding how pressure waves are generated, cancel each other out and create feedback etc....But I think I have a better one now.



Would you like to show me where santiago had a competetive argument? I managed to make every single one of his points go down in flames, because they were either based on opinions, flat out wrong, or inconclusive.


All I meant by that was, even though santiago might have been categorically wrong about anything and everything, I believe that he was very well mannered given the circumstances-something else I need to learn sometimes. I've had my share of flame wars and i'm just getting too old for it these days. I'm done with them.

Santiago retained his class and his dignity by curtailing any possible malice regardless. Since no one is perfect, this is competitive, and I repect that.

Sometimes I find that people don't walk away with anything valuable when they're being crushed by the weight of facts data and or opinions I have. I find that shooting down someone's view in flames doesn't help the other person gain a better understanding of what it is that I may try to convey.

In the end, no one ever cares about these self proclaimed victories except me. And It blinds me to my own stupid assumptions about the world and makes it harder for me to relax.

Thanks again for responding to my questions about the exhaust, I appreciate it.

mazdaspeed7

I dont know if you kept up with it from the beginning, but I was only trying to helpful at first. And I never flamed him. Just made it very clear that he was wrong. I could care less what he thinks, but when someone is spreading misinformation to other people, i wont just sit back. There is so much bullshit floating around from just that.