Exhaust - twin outlet setup question

[ahew]

actually, that's a really good point Nacho. I've searched around the MR2 exhaust images and found one that may be similar to Kaz's setup:

This is a GReddy aftermarket setup. Just looking at the picture, I still don't understand how the gasses flow internally!

One that I think may work on the FTO is this setup:

Note I hate the mufflers but having a Y-Pipe after the mid-muffler/resonator section will be an easier setup. Not sure how the exhaust pipe is going to be setup through the middle of the car though.

Here's the picture of the XR6 Turbo Cat..
for those that are interested in what it looks like.

[kazbah]

Nacho, photo 3 (which isnt very good) shows a bent pipe and a straight pipe. The bent pipe is where the ehxaust enters the muffler and the straight pipe is the outlet on the left hand side of the car. Both the outlets expel exhaust.

[Nacho]

To my understanding a muffler works by reflecting/bouncing sound through little tunnels/chambers in the muffler through to the outlet. A resonator works by using sound absorbtion material. I might have it the other way around. But how does the other pipe work in terms of sound reduction? The gas flow shouldn't be affected too much. I mean an exhaust outlet is an exhaust outlet. But a muffler is just as important to making it legal sound wise.

[ahew]

I have a feeling there is probably a T type intersection of tubing in the muffler that splits it between both outlets

[Nacho]

I wonder where you could get a muffler like that? It would look really good having 4 exhaust pipes sticking out the back like some of the 350z and GTOs out there.

[smorison]

any decent muffler shop can build you what you want...

if you're going for a twin setup you wouldn't want more than 2" piping probably go even small 1.75" piping as 2 1.75" pipes have a much greater capacity than a 3" pipe ... but it all depends are you after looks / sound or performance ... depending on the answer you end up with two different setups....

someone mentioned it earlier the best way to do twin is to run seperate pipes from each bank... you can get a 2 into 2 CAT from V8's that'll work and should take care of the balance pipe problem... ummm but its a lot of weight to be adding to the car... but then i'm focused on track's not day to day driving so it may not matter to you

[FTOluv]

Ahew, that second pic of the exhaust is a very low hanging exhaust. I have a MR2 and that setup would have me scrapping the exhaust drum everytime i went over a bump. If u look carefully in that pic theres a lot of dents in it.
If i were u just go for the single drum. As Steve, most exhaust shops can make that for you.

[ahew]

hmmm i didn't know there were 2in 2out cats! that makes things a bit more complicated for me.

Do those RPW extractors have a 6>2>1 setup, if so then I'm thinking of getting them and instead of going from 2>1, get 2 separate exits, go into 1 cat(2in2out), exit 2outlets of the cat and then 2 catbacks down left and right side of the undercarriage.

is that what you mean smorison? coz if it is, that's a beefy system
it'd be a 6>2>1<2. If it didn't have to have a cat then it would be even better... but them's the Aussie regulations so don't want to break the law.

yeah 2x1.75" is probably max. works out to be the same as a single 2.5" system.

[smorison]

hmmm i didn't know there were 2in 2out cats! that makes things a bit more complicated for me.

Do those RPW extractors have a 6>2>1 setup, if so then I'm thinking of getting them and instead of going from 2>1, get 2 separate exits, go into 1 cat(2in2out), exit 2outlets of the cat and then 2 catbacks down left and right side of the undercarriage.

is that what you mean smorison? coz if it is, that's a beefy system
it'd be a 6>2>1<2. If it didn't have to have a cat then it would be even better... but them's the Aussie regulations so don't want to break the law.

yeah 2x1.75" is probably max. works out to be the same as a single 2.5" system.

pretty sure big v8's run the 2in 2 out cats.... they are out there but way overkill for our needs....

i wasn't recommending building that system but it is an option...

2 x 1.75 is actually has the flow rate of a 3" exhaust system... its not just a add the two together thing... if anyone can be bothered going back to highschool and getting out the circle stuff you should see that the area of two 1.75" circles is more than 1 2.5" circle and about the same of a 3" circle...

best thing to do is get a really strong idea of what you want and go to an exhaust shop (good one)...talk with them draw it on paper and they'll build it for you... UAS have a guy who builds exhausts by hand (everything) if you want a good setup they can have it built for you and guarantee its a one off... they're not cheap but imho i think they're worth it.

[ahew]

Nope.. it's 2.5" for sure... check this out:

High School Maths Lesson 101 -

Pi*r^2 = surface area of circle

1.75" is the diameter of one of the dual outlet pipes.

So.... 1.75/2 = 0.875" (radius of one pipe)

Pi*(0.875)^2 = 2.405sq.in.

Since there are 2 of these pipes, that means surface area is twice the surface area -> 2.405*2 = 4.81sq.in.

Now, if we are looking for the equivalenet radius then
Pi*r^2 = 4.81 ---> r^2 = 4.81/Pi ---> r = sqrt(4.81/Pi) ---> r = 1.24..... so d= 2*1.24 = 2.48" which is pretty much 2.5".

There you go... my High School maths isn't that bad after all


Anyway, thanks for the idea about the 2in 2out cat converter. At least I know there's another option out there although it is a little bit of overkill

[smorison]

i stand corrected....


lol now i'm going to go correct the person who told me that years ago....

[ahew]

hahaha yeah go tell them that they aren't a true geek like me.