Exhaust theories

[phunky.buddha]

 

[Celerity]

The important things to remember are that straight pipes are WAY easier to work with. Turbos can be worked with too.. but I lack the talent and I haven't met anyone who could do it right. And if you take headers far off the block before their first bend, then you're looking at a torquier setup. How, I have no idea. Maybe it can fit 4 or so compressions in the header pipe before that first turn. But ultimately, your engine wants straight pipes out from the head. Your ears, however, disagree.

 

[99sidude]

Mechanical Engineering with a heavy focus on thermodynamics and fluid dynamics.

I'm in the same boat! Just got done with fluids, its cool stuff... Next semester is heat transfer

 

[Kanned]

Ok, so I won't ever fully understand this and I'm now comfortable with that. I'll just install cherry bombs and such until I'm happy with my exhaust =P.

 

[Celerity]

It's easy. Pulses are created by any reciprocation (Valves, actually) or pulsing (Rotaries do it too). Not with Turbines.

That pulsing DOES have energy. It moves a turbo, for instance (Well, it's a big part of what turns a turbo) and it's also a big reason for heat build up.

Those pulses travel not only out the pipe, but if they start short, hit a bend or exhaust canister, they go BACK. When you get those pulses travelling back into the reciprocation (The valve) it either helps or hampers the valve. Resonance and gas flow is well known in automanufacturers, and they build things like resonators and calculate pipe length for you. "Custom" or otherwise changed exhaust components change that equation, and throw the whole thing off.

"cold air" intakes do the same thing. Throws off the resonance of the air coming in, and onto the intake valve.

 

[Kanned]

All of that I understand, but I still wouldn't/don't know what kind of exhaust should go onto a motor. I just know more hp needs more flow and less hp doesn't need as much. I have no idea how to make even a rough estimate of resonator(s), cat, and other things that can be installed. The piping I can make a decent stab at, though. All of your info is helping me, don't get me wrong.

 

[Celerity]

Well, look at it this way.

If your 1.6 liter SOHC Honda comes with 1" pipe, it's got "Enough" to flow properly. That formula IS changed with mods such as headers, intake, fuel mods, even a drop-in filter (Although not so much, but cone filters, YES) But there is no one-size-fits-all formula for how to change it.

 

[phunky.buddha]

The important things to remember are that straight pipes are WAY easier to work with. Turbos can be worked with too.. but I lack the talent and I haven't met anyone who could do it right. And if you take headers far off the block before their first bend, then you're looking at a torquier setup. How, I have no idea. Maybe it can fit 4 or so compressions in the header pipe before that first turn. But ultimately, your engine wants straight pipes out from the head. Your ears, however, disagree.

I'm in the same boat! Just got done with fluids, its cool stuff... Next semester is heat transfer

Yay! :w00t: More enginerds!

Ok, so I won't ever fully understand this and I'm now comfortable with that. I'll just install cherry bombs and such until I'm happy with my exhaust =P.

It's easy. Pulses are created by any reciprocation (Valves, actually) or pulsing (Rotaries do it too). Not with Turbines.

That pulsing DOES have energy. It moves a turbo, for instance (Well, it's a big part of what turns a turbo) and it's also a big reason for heat build up.

Those pulses travel not only out the pipe, but if they start short, hit a bend or exhaust canister, they go BACK. When you get those pulses travelling back into the reciprocation (The valve) it either helps or hampers the valve. Resonance and gas flow is well known in automanufacturers, and they build things like resonators and calculate pipe length for you. "Custom" or otherwise changed exhaust components change that equation, and throw the whole thing off.

"cold air" intakes do the same thing. Throws off the resonance of the air coming in, and onto the intake valve.

That's how Bisi makes so much power from 9-11k in his D15. He's got some crazy resonance chamber design and good pulse reinforcement.

All of that I understand, but I still wouldn't/don't know what kind of exhaust should go onto a motor. I just know more hp needs more flow and less hp doesn't need as much. I have no idea how to make even a rough estimate of resonator(s), cat, and other things that can be installed. The piping I can make a decent stab at, though. All of your info is helping me, don't get me wrong.

You can take a few simple equations without knowing too much and calculate your guestimate exhaust flow based on engine rpm and exhaust temp.

Well, look at it this way.

If your 1.6 liter SOHC Honda comes with 1" pipe, it's got "Enough" to flow properly. That formula IS changed with mods such as headers, intake, fuel mods, even a drop-in filter (Although not so much, but cone filters, YES) But there is no one-size-fits-all formula for how to change it.

It's really best guess, even for most of us with engineering degrees... unless we really want to spend the time to get it right.

 

[nootrac22]

 

[NissanNiNjA2nd]

OMG.... teach me or tell me where to read to learn more on this subject.

 

[phunky.buddha]

linky

 

[Dustin_m]

OMG.... teach me or tell me where to read to learn more on this subject.

Free Online MIT Course Materials | Mechanical Engineering | MIT OpenCourseWare

MIT offers a lot of their course material for free online.

 

[phunky.buddha]

Oh cool.