Science behind Exhaust ideal exhaust size

[Chr1s]

Bit of a strange defense mechanism going on lol..no offense but the reaction you are looking for is not to be found on this forum, you better off bringing this up on physicsforums or engtips.

Also, an undergraduate Thesis is far from an "expert" publication

Out of curiosity, what uni do you go to?

[MassiEk4]

Bit of a strange defense mechanism going on lol..no offense but the reaction you are looking for is not to be found on this forum, you better off bringing this up on physicsforums or engtips.

Also, an undergraduate Thesis is far from an "expert" publication

Out of curiosity, what uni do you go to?

"an undergraduate Thesis is far from an expert publication" That is exactly why I am on here. LOL
I am going to RMIT.

I am not sure about physics forums, I recon there would be a problem with people on that forum not seeing how the idea would apply to a car.
I thought that since there are people who are experienced with cars they could also have a better understanding than me regarding this stuff; so I can learn more off them or improve/correct this I idea I have.

[DreadAngel]

Instead of going so technical bro and coming on all big shot [Just saying what most others would feel when they read your thread man, no hate] check out what others have said and the discussions that ensued.

I'm no engineering student [Switched from Civil to Finance after 2yrs], don't need to go screw ya head over it man...

Science behind Exhaust design? Flow v Backpressure for the absolute basics... For example [Disclaimer: Not 100% so yeah...]

For Small NA: For most application, you want to retain a certain amount of backpressure to ensure that you have low-mid range torque otherwise you will lose whatever torque the engine can muster and if it really is too big ie too free flowing, then you'll lost power too!

eg - Majority of the hypo JDM 1.6L - 2.0L NAs run 60.5mm centre pipe while the ends are smaller than 100mm.

Too big? Saw the result in practice and on the dyno... Kid had a nice custom system, 60.5mm with a 90mm tip, produced some ~120PS @ the wheels like the rest of us, switched to a HKS Muffler made for a Supra, definitely too big and the result? Loss of 15PS+, loss 20Nm+ and the curve had much less area than the rest of us. That's how sensitive small NA engines are...

Turbo: Bigger usually is better [within reason obviously], much less emphasis on retention of backpressure [unlike NA, force induction has mechanical aid so lack of torque low down not much of an issue]

As others have talked about, pulse, scavenger effect, etc is more to do with the path and shape etc...

Anyway, no need to go all physics 101 man =)

[Chr1s]

Well, I don't want to burst your bubble, alot of the guys on here are very educated but not exactly educated on literature or on an academic basis such as ourselves, this is not to say that we know more than them and they know nothing. At times it's quite the contrary... at your level of studies I wouldn't come on here and fight with other guys, you will find yourself digging a hole because they don't like someone coming here and derivating the maths behind their engines, it's a shame but it's a fact of life (for forums lol), don't know why.

I have some real advice for you, stop wasting your time on here (not that it's a bad place, but it's bad for what you are trying to do), go down to the workshop at uni, introduce yourself to the FSAE guys there and get on the powertrain team. You will find yourself in a puddle of mud quick smart and you can have a ball designing the exhaust for their IC car and not use any of your money!!

PS - don't switch to civil, stick with mechanical.

Edit: http://www.fsae.rmit.edu.au/ - see you guys in Melbourne in 30 days!

[MassiEk4]

Well, I don't want to burst your bubble, alot of the guys on here are very educated but not exactly educated on literature or on an academic basis such as ourselves, this is not to say that we know more than them and they know nothing. At times it's quite the contrary... at your level of studies I wouldn't come on here and fight with other guys, you will find yourself digging a hole because they don't like someone coming here and derivating the maths behind their engines, it's a shame but it's a fact of life (for forums lol), don't know why.

I have some real advice for you, stop wasting your time on here (not that it's a bad place, but it's bad for what you are trying to do), go down to the workshop at uni, introduce yourself to the FSAE guys there and get on the powertrain team. You will find yourself in a puddle of mud quick smart and you can have a ball designing the exhaust for their IC car and not use any of your money!!

PS - don't switch to civil, stick with mechanical.

Edit: http://www.fsae.rmit.edu.au/ - see you guys in Melbourne in 30 days!

Thanks man, it is really frustrating when you try to explain something or your ideas and people taking offense and calling you a douche for expressing you ideas.

In no way am I trying to show that I know so much, in fact I know nothing and thought I could learn more off someone on here.

I had been wanting to do mechanical engineering ever since I knew it existed, but looking at the news and hearing from family friends about the lack of Jobs for mech engineers and even chemical engineers, I am a little worried, so I would rather do Civil and have a solid Job that can financially support my passion for cars and such. Who knows I might go back and pick up mech engineering once I work for a few years.

[Chr1s]

No way! Don't listen to people who "can't find jobs" - finding work is entirely up to yourself and you can't base your direction/career because someone else can't get a job. I have friends who struggle getting work and some have 3 or 4 offers coming at them.

Not to bash the FSAE drum again, but do FSAE and your chances of finding work will increase dramatically, go ask the guys who have done FSAE before. Our team leader last year was offered every single job he had an interview for - hard to find work apparently?

Every career right now is doing it hard.. stick to what you love mate.

[MassiEk4]

No way! Don't listen to people who "can't find jobs" - finding work is entirely up to yourself and you can't base your direction/career because someone else can't get a job. I have friends who struggle getting work and some have 3 or 4 offers coming at them.

Not to bash the FSAE drum again, but do FSAE and your chances of finding work will increase dramatically, go ask the guys who have done FSAE before. Our team leader last year was offered every single job he had an interview for - hard to find work apparently?

Every career right now is doing it hard.. stick to what you love mate.

I pm'd you more about this.

[rpm boy]

id love for your text books to find there way to my house lol
your always going to get the mechanic v engineer animosity so take it with a grain of salt, your heads in the right place but theres alot of by products created from different varients in exhaust design, if you a really looking to get into the exhaust design start from the newest design of car exhaust and start reverse engineering and reading up on how different problems are resolved, someone mentioned transonic speeds as an example, now there are car campanies spending millions of dollars and using teams of engineers looking into things like that and really without the proper tooling or equipment at your desposal its going to be hard.
theres always going to be new ideas getting thrown into the market and it will never be a 100% efficient exhaust throughout the exhaust but if you pick a point at which you want to start ie high rpm, torque etc you wil find how differet setups work and what there draw backs and keep trying to push the envalope untill your resonably happy.
so keep studying and keep playing around, i quote my old electronics teachers " you know the formulas, now prove it to yourself "