Why round exhaust pipe?

[chevy3100truck]

so why not simply answer "a glasspak flows less because it creates a low pressure area inside the muffler?" then you would say "because the pipe is no longer smooth, the exhaust slows down and creates a pressure difference, that difference allows the sound to collide with itself and cancels some of the noise out." and finally you'd close with "that noise cancellation creates restriction in the exhaust thereby slowing the exhaust down. The flowmaster uses a difference principle and causes LESS restriction because the exhaust flows through the muffler and the sound waves bounce inside the muffler. Again, those sound waves cancel some of the other sound waves out thus reducing the sound."

Or don't you know that basic principle? seriously, at least TC puts out an opinion to be discussed, right or wrong, it helps others understand the mechanics of engines. I'd even venture to guess that the attackers have heard that opinion before and had someone with more patience then they have (a grownup) explain why that principle is right, wrong, or incomplete. Others resort to personnal attacks, which seriously makes people question whether or not they have any idea about what they're talking about. Still others have no clue and have read another article which tells them that a flowmaster doesn't restrict flow - those people are known as Trolls. Don't be a troll.

Oh yes, to those who think they're the judge of what's on the net - if you're stupid enough to believe everything you read on the net, then you deserve the result you get.

I know how it works and could do the modeling on it if I had time. (guess what - I design equipment for liquid flows, same principals). Just not worth bothering to explain things to TC.

[TC]

No, I'll post in here all day without you being around. Each additional post you make, is one less person who wants you to be here.

Meanwhile, why don't you do at least one of the things you bragged about on here? You know, Easy EFI tuning with HPT or megasquirt? Weren't you going to open up a tuning business, or was that before you got afraid of using a computer for something other than pretending to know something on the internet?

Sure would like to see you get off your ass and do SOMETHING with a hot rod. ANYTHING at this point, would be good. Right now you just look completely foolish for everything you claimed you were going to do, but every single time wussed out. What's the point of lecturing us on Exhaust tuning when you're not ever going to do it?

See made you do it again.....

[TC]

BTW, the flowmaster will mess with the pulse wave as well (in case you can't figure that out)

The FlowMaster will make the Pulse think its at the end of the pipe.......Like the Muffler wasn't even there....... Though Tube diameter and muffler placement I'm sure has a lot to do with it.......

[dieselgeek]

I gave the info I seen on headers and I believe I gave a pretty good reason why
to primary lengths and why they should be equal... some may disagree and thats
fine... since all I'm doing is saying it... if I could have grabbed all my test data
before I retired I would have posted it.... but I cant(that data was not allowed
to go with me)....... have fun boys
EDIT
I got to get back out to the shop to finish putting my engine together...
I want to be on the dyno on Wednesday

No worries, everyone here except one fool knows that your real world testing trumps Barnes and Noble by a lot!! Hopefully you stick around a while and not get run off by the one lone buffoon we have here. ;-)

[MR P-BODY]

The FlowMaster will make the Pulse think its at the end of the pipe.......Like the Muffler wasn't even there....... Though Tube diameter and muffler placement I'm sure has a lot to do with it.......

If you think flowmaster flow good... continue reading... they were one of
the worst flowing that I tested... dynamax were far better and a few others

[Bob Holmes]

If you think flowmaster flow good... continue reading... they were one of
the worst flowing that I tested... dynamax were far better and a few others

And that's why when you call them and ask for flow information they tell you, "we don't measure their effectiveness that way." Actual statement made when I called them.

[MR P-BODY]

And that's why when you call them and ask for flow information they tell you, "we don't measure their effectiveness that way." Actual statement made when I called them.

Thats weird... you would think they would have all sorts of number to
baffle the people with

[TC]

Vizard actually addresses that issue to and explains why a better flowing(cfm) muffler isn't always the best...... Like I said it's about tuning the exhaust pulses.......

He even explains how those muffler shootouts aren't done correctly and skew the results, because they are not placing the mufflers for optimum pulse tuning......

What's funny is all the negative points made Vizard makes reference to in his books and explains why they are wrong.......

[MR P-BODY]

Vizard actually addresses that issue to and explains why a better flowing(cfm) muffler isn't always the best...... Like I said it's about tuning the exhaust pulses.......

He even explains how those muffler shootouts aren't done correctly and skew the results, because they are not placing the mufflers for optimum pulse tuning......

What's funny is all the negative points made Vizard makes reference to in his books and explains why they are wrong.......

If your testing on a car its pretty hard to move the muff all over the place.....
so if you stay in one area you look for the best that works... muff manufactures
know where the muff is located so build the best you can.... if you cant...
find something else to build... in the lab where I worked we didnt give a
company more than a couple of shots at it... then it was time to move to
the next one... your Visard book sounds great in theory but not so much
in real life

[Barry_R]

Lots to read. Some of it interesting. Some of it silly.

About the only things I can add is that - after extensively testing a huge variety of headers, collectors, lengths, diameters, and mufflers on essentially the same engine altered for each year's rules, I know less now than I thought I knew going into the effort several years ago.

Either I am getting stupider with time and practice - always possible - or I have discovered that the damn motor cannot read. You just take all the stuff you own and throw it at the darned thing. And run whatever performed the best even if it's ugly and don't fit the current fashion trends.

Last year everbody told me that the 3" Flowmasters would kill peak power at higher RPM because of the restriction, but taht I'd see good torque through the midrange. Installed the mufflers on a pretty well sorted tune and after a dozen tweaks we were within 3 or 4 horsepower at peak but brutally murdered the torque. So much for the theories.

I've had 1-3/4 primary pipes make the exact same power as 2-1/4, I've had $150 cheap pickup truck headers do better than $800 equal length race car parts, and have had different collectors make every change from none, to negative, to huge.

[TC]

your Visard book sounds great in theory but not so much
in real life

But that is the thing it's not his theories, it is his results from extensive dyno testing on race engines..... But then again it was on the motor that he was testing, so your results may vary.......... And his writings are good reading, I'll be jumping into Intakes and Carb's next........ as the book I just finished doesn't get into much depth and just kind of hits the highlights of each subject......

[MR P-BODY]

But that is the thing it's not his theories, it is his results from extensive dyno testing on race engines..... But then again it was on the motor that he was testing, so your results may vary.......... And his writings are good reading, I'll be jumping into Intakes and Carb's next........ as the book I just finished doesn't get into much depth and just kind of hits the highlights of each subject......

Thats why I said its great in theory but just the headers.... if you
cant put it on the car its trash.... same goes for the muffs and you
dont get much of a choice where you put them ... the lab I worked
in was fuel & exhaust and we were last in line for space.... so it was
pretty difficult to package a fuel tank and exhaust

[Bob Holmes]

Thanks for commenting Barry.

We've found the same thing. Last years super zooty, everything per the theory set of headers were crap. The headers that we thought wouldn't stand a chance, small primary long collector, put 54 hp and big number score on the next closest set. They should not have worked, and we just put them on to assure ourselves that we weren't leaving any stone unturned.

This year, with a lower compression ratio, and lower operating range, that great set from last year is the crappy set. The longer primary shorter collector larger tube headers put up better numbers across the board.

Theory is one thing, testing trumps it every time.

[Beagle]

Lots to read. Some of it interesting. Some of it silly.

About the only things I can add is that - after extensively testing a huge variety of headers, collectors, lengths, diameters, and mufflers on essentially the same engine altered for each year's rules, I know less now than I thought I knew going into the effort several years ago.

Either I am getting stupider with time and practice - always possible - or I have discovered that the damn motor cannot read. You just take all the stuff you own and throw it at the darned thing. And run whatever performed the best even if it's ugly and don't fit the current fashion trends.

Last year everbody told me that the 3" Flowmasters would kill peak power at higher RPM because of the restriction, but taht I'd see good torque through the midrange. Installed the mufflers on a pretty well sorted tune and after a dozen tweaks we were within 3 or 4 horsepower at peak but brutally murdered the torque. So much for the theories.

I've had 1-3/4 primary pipes make the exact same power as 2-1/4, I've had $150 cheap pickup truck headers do better than $800 equal length race car parts, and have had different collectors make every change from none, to negative, to huge.

Nice! Spewed tea ALL OVER the screen. I love that, may quote it for my tag line - vote for quote of the year!

[SuperBuickGuy]

Thanks for commenting Barry.

We've found the same thing. Last years super zooty, everything per the theory set of headers were crap. The headers that we thought wouldn't stand a chance, small primary long collector, put 54 hp and big number score on the next closest set. They should not have worked, and we just put them on to assure ourselves that we weren't leaving any stone unturned.

This year, with a lower compression ratio, and lower operating range, that great set from last year is the crappy set. The longer primary shorter collector larger tube headers put up better numbers across the board.

Theory is one thing, testing trumps it every time.

Hmmm.. it almost sounds like you're leaving it up to whatever higher diety you subscribe to.... while rules would be excellent, having a theory to test makes life so much simpler because you build on your knowledge. Honestly, if an engine builder told you "well, we don't know what hp that motor will make or where it will do it" would you spend any money on having them build it? Or better, "well, that motor will make somewhere between 200 and 2000 hp somewhere between 750 and 10,000 rpm".... I agree, testing is the culmination of theory, but without theory and scientific study you're back to caveman (sorry tony ). IIRC the fundamental purpose of engine masters was to eliminate variables and start a foundation of knowledge that the magazine buyers could use to develop their own motors.

To paraphrase DF's old tagline, you need more motor for the cam - you need to build the motor for those headers, it's not the headers fault your motor is unable to use its attributes ()

And Barry, I agree with what you're saying if this is what you're saying "I started with theories, but then realized the mountain was substantially higher then I first realized" thus even though you have a vast amount of knowledge, it only showed you that there's even more knowledge to be gain (FWIW, experts always say "I know less then when I started)