3" exhaust outcome on N/A

[Dephective]

Originally Posted by jamesm

My point remains though. A 2.5" overpipe isn't going to flow as much air as a 3" overpipe just because you bolt a 3" front pipe to it, and all of the exhaust still has to go through it, it's still the limiting factor so to speak.

Yes, 2.5" pipe will not hold as much gas as a 3" section at any given time. But, the amount of flow doesn't necessarily always favor the 3". The exhaust gas velocity is really what you should considered, as the gas has to move faster to make way for more gases to take its place since the amount it can hold in a given space is less than larger diameter piping, therefore more gases can move through the system at a given time. Diameter, and changes that occur throughout the piping (diameter, bends, obstructions, etc) all change the velocity of the gas, for better or worse. These things work together like a sliding scale.

I don't profess to be an expert, but generally how things work.


P.S. The faster the exhaust gases move, the more of a vacuum effect it has on MORE gases coming out of the engine. This allows for more air/fuel mixture to complete it's burn and move out if the system rather than some exhaust being left in the combustion chamber along with the mixture, giving a less efficient burn, and resulting most notably torque loss. It quite literally pulls more of the gases out.

[campy]

Originally Posted by Dimman

Nice to see how far general knowledge of NA tuning has advanced on the internet...

How to maximize power on an NA engine: put a turbo on it

[Dephective]

Originally Posted by campy

How to maximize power on an NA engine: put a turbo on it

Soon. I'm enjoying the lack of all the hassle of having FI for a while.

[Anthony]

Originally Posted by FR-S Matt

That's technically not true.

Originally Posted by jamesm

that's not true.

Originally Posted by Dephective

Incorrect.

False.

[Dephective]

Originally Posted by Anthony

False.

Certainly helpful...

[Anthony]

I try.

[Turkish]

So, from what I have read thus far from both pages of this thread is that everyone agrees that they disagree.

[JimmyMac]

Originally Posted by Turkish

So, from what I have read thus far from both pages of this thread is that everyone agrees that they disagree.

To some point...

[FR-S Matt]

There, end of discussion. Yes, that's a 3" flange going to the cat.

[jamesm]

Originally Posted by Dephective

Yes, 2.5" pipe will not hold as much gas as a 3" section at any given time. But, the amount of flow doesn't necessarily always favor the 3". The exhaust gas velocity is really what you should considered, as the gas has to move faster to make way for more gases to take its place since the amount it can hold in a given space is less than larger diameter piping, therefore more gases can move through the system at a given time. Diameter, and changes that occur throughout the piping (diameter, bends, obstructions, etc) all change the velocity of the gas, for better or worse. These things work together like a sliding scale.

I don't profess to be an expert, but generally how things work.


P.S. The faster the exhaust gases move, the more of a vacuum effect it has on MORE gases coming out of the engine. This allows for more air/fuel mixture to complete it's burn and move out if the system rather than some exhaust being left in the combustion chamber along with the mixture, giving a less efficient burn, and resulting most notably torque loss. It quite literally pulls more of the gases out.

I think the difference here is I'm talking about an ideal fluid in a tube, you're talking about an exhaust with all of its extra considerations. You're presuming less than ideal flow, like in a real exhaust. I'm just saying that the absolute maximum amount of fluid a system of tubes can move, all else equal, is limited by the size of the smallest diameter tube.

Yes, in an exhaust header where 'tuned flow' not 'max flow' is the goal, stepping diameters can be helpful. If you wanted max flow, though, you'd run a header with an infinite primary diameter, or to say none at all.

A2.5" overpipe flows what a 2.5" overpipe flows at max, regardless of what it's bolted to, and if that's less than ideal (which on a turbo car it is) then that's still the overall limiting factor of how much exhaust can get out of that engine for a given pressure.

[Dephective]

Originally Posted by FR-S Matt

There, end of discussion. Yes, that's a 3" flange going to the cat.

Who's 3" is that? And do you have any dyno info on that? I'd really like to accept that 3" is okay for n/a in our case, so I don't have to end up swapping out after I go FI.

[FR-S Matt]

Originally Posted by Dephective

Who's 3" is that? And do you have any dyno info on that? I'd really like to accept that 3" is okay for n/a in our case, so I don't have to end up swapping out after I go FI.

Nameless. The only dyno info came from one of their prototype header tests with a full 3" exhaust.