3" DP to Dual 2 1/4" catback

[dsm-onster]

I'll tell you up front that I don't know. But I can look it up or ask a professor or two. . .

My impression's on such a shape would be purely "bench physics".

I could be off a hundred miles. . . Since we're concerned w/ "surface resistance" primarily (and how much surface is the determinant here) then I'm assuming that you would make the oval round (mathematically) by using the same "perameter length" of the oval and derive the radius for a circle of that same number circumference. Plug in that radius. It might be close.

 

[AWDGreenMachine]

To tell the truth, my first thought was to add a resinator but, I was afraid of the potential loss in power by adding it. That's when I decided to go the route of dual 2 1/4". I also thought there could possibly be an increase in exhaust flow but, again, that wasn't my reason for doing it. Getting rid of the low rpm drone without power loss was my intention.
Just for the record...I did say in the original post that I feel an increase in acceleration/power.

 

[underradar92]

I always thought it added a little more TQ?

My understanding is this, turbo's want NO backpressure post turbo. B/P post turbo slows the turbine, absolutely. That canNOT create MORE power or torque anywhere in the powerband, period.

I also believe that any flow restriction after a (this is a key phrase, pay attention) "properly made tuned header", will hurt horsepower and PEAK torque.

Backpressure after the collector does not add torque, it adjusts it to a lower point in the rev band.

This may be semantics (spelling?) to a degree but I belive it to be accurate.

 

[dsm-onster]

To tell the truth, my first thought was to add a resinator but, I was afraid of the potential loss in power by adding it. That's when I decided to go the route of dual 2 1/4". I also thought there could possibly be an increase in exhaust flow but, again, that wasn't my reason for doing it. Getting rid of the low rpm drone without power loss was my intention.
Just for the record...I did say in the original post that I feel an increase in acceleration/power.

I'm glad it worked for you. It looks clean and is quite individual. Overall I like it! When/if you upgrade to significantly bigger turbo and decide to push it, just run a electronic cut out. They can be had for $200 or so. And would only open when you "say so".

 

[underradar92]

I'll tell you up front that I don't know. But I can look it up or ask a professor or two. . .

Since we're concerned w/ "surface resistance" primarily (and how much surface is the determinant here) then I'm assuming that you would make the oval round (mathematically) .

'Twould be interesting to know.

I hope it's nearly that simple.

 

[dsm-onster]

My "sources" say that Poiseuille's Law addresses surface area. In such a case of an oval pipe, Poiseuille's Law would cause the mass to flow equally in an ovular exhaust as in a circular exhaust with the same circumference as the "perameter length" of said oval exhaust.

However, since turbulance IS a characteristic of exhaust gas flow, then there likely are losses in velocity as the gases exit the turbine wheel at an angle (thus spiraling out into the o2 housing). And, it is likely that the spiraling continues after that. Changing the momentum vector of the exhaust gas particles to a more acute angle (at a rate dependent on the ovular shape) as it goes "around" the perameter of the oval exhaust pipe would lead to slowing the gases down. A perfectly circlular exhaust pipe would negate this as much as possible.

It is conluded by me that if you're tempted to use a particular "perameter length" oval exhaust pipe that it would be more advantageous to use pipe w/ the an equal circumference and would likely be simpler to fabricate, bend, mount, add to, modify, etc.

 

[JOEY A]

So weres the sound clip?

 

[AWDGreenMachine]

I'll try to get a clip using my phone, tomorrow.

 

[AWDGreenMachine]

This is off topic but, the four exhaust manifold to turbo bolts keep coming loose. I mean, if it wasn't for the heat shield, I wouldn't have any bolts. How can I keep them tight. They're torqued to spec also.

 

[dsm-onster]

Do you ahve the washers on them? In the right direction?

 

[AWDGreenMachine]

Tried to get you guys a clip but the site doesn't accept .wav files.

 

[AWDGreenMachine]

Do you ahve the washers on them? In the right direction?

Yeah, I have washers on them. How do you know if they're on the right direction?

 

[dsm-onster]

Mine came shaped like a oh say, . . . a contact lens. one side was concave; the other convex.. I put the concave end down, ad havn't had a problem YET.