how much is this exhaust system restricting me?
i am legendary
Joined: Sep 2003
Posts: 8,478
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From: Kirkland, WA
Well easiest way to know is if your catback on your current exhaust is available separate. See if you can buy the catback by itself that is supposed to bolt up to the stock cat, then it should fit with any downpipe/midpipe combo that mates up to the stock catback.
Example racing beat downpipe by itself will not mate up to the stock cat or stock catback locations, but the downpipe/midpipe combo from racing beat will mate up to the stock catback location. Just like the racing beat catback exhaust will mate up to the stock downpipe/cat location. Does that make sense?
Example racing beat downpipe by itself will not mate up to the stock cat or stock catback locations, but the downpipe/midpipe combo from racing beat will mate up to the stock catback location. Just like the racing beat catback exhaust will mate up to the stock downpipe/cat location. Does that make sense?
"I may be drunk"
Joined: Nov 2004
Posts: 71
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From: Pa
Just a mental note dual 2.5's do not flow what a single 5 would as taken from earlier post to this.
Single 3 will flow as much as dual 2.5 now on with the quote.
And I quote "duals are for fools" and quote.
save some weight get, some speed. 3' turbo back single.
Single 3 will flow as much as dual 2.5 now on with the quote.
And I quote "duals are for fools" and quote.
save some weight get, some speed. 3' turbo back single.
i am legendary
Joined: Sep 2003
Posts: 8,478
Likes: 1
From: Kirkland, WA
I never said dual 2.5's would flow like a single 5"
If you had actually read the post you would've seen later in that paragraph I said "(it doesn't work EXACTLY like that but you get the idea, a dual 2.5" has more volume than a single 3")"
And no, dual 2.5's do not flow the same as a single 3", they flow more. Why do you think the dual catback for the turbo exhaust from racing beat is 2.375" after a 3.15" downpipe?
If you had actually read the post you would've seen later in that paragraph I said "(it doesn't work EXACTLY like that but you get the idea, a dual 2.5" has more volume than a single 3")"
And no, dual 2.5's do not flow the same as a single 3", they flow more. Why do you think the dual catback for the turbo exhaust from racing beat is 2.375" after a 3.15" downpipe?
I'm a boost creep...
Joined: Jan 2002
Posts: 15,608
Likes: 8
From: Auckland, New Zealand
Originally Posted by dDuB
Measure around the outside of the pipe, the thickness of the wall is small enough it wont matter too much.
Originally Posted by 3turbos
Single 3 will flow as much as dual 2.5
Originally Posted by 3turbos
Just a mental note dual 2.5's do not flow what a single 5 would as taken from earlier post to this.
Single 3 will flow as much as dual 2.5 now on with the quote.
And I quote "duals are for fools" and quote.
save some weight get, some speed. 3' turbo back single.
Single 3 will flow as much as dual 2.5 now on with the quote.
And I quote "duals are for fools" and quote.
save some weight get, some speed. 3' turbo back single.
Originally Posted by 3turbos
Just a mental note dual 2.5's do not flow what a single 5 would as taken from earlier post to this.
Single 3 will flow as much as dual 2.5 now on with the quote.
And I quote "duals are for fools" and quote.
Single 3 will flow as much as dual 2.5 now on with the quote.
And I quote "duals are for fools" and quote.
The rest of it you just made up as none of it is supported by fact. I have a flowbench and a bunch of pipe BTW if you want me to prove that statement as wrong.
Here's a better quote: "If you aren't flow testing, you are flow guessing."
Quit guessing.
You've Been Punk'd
Joined: Jun 2002
Posts: 4,727
Likes: 1
From: Branson, Missouri
what kind of car is that?
Mine goes 3" then splits to two 2 1/2", and I'm getting 407 rwhp with my setup.
My problem is that the increasing diameter does little to quiet the exhaust. If you're looking for a really loud setup, use mine. If you like bass, use a big resonator, but this will really decrease your ground clearence. I'll want to dyno test a 3" to two 1.5" in the future, and compare volume vs. power.
Exactly...this is called "exhaust scavenging". There's a fine art to it. If you decease the tailpipe diameter, torque come on in the lower rev areas...to a certain point. Overall horsepower may suffer, but having the torque come on sooner will make up for it on street cars with way too much horsepower already.
Originally Posted by Green Spyder
Mine goes 3" then splits to two 2 1/2", and I'm getting 407 rwhp with my setup.
My problem is that the increasing diameter does little to quiet the exhaust. If you're looking for a really loud setup, use mine. If you like bass, use a big resonator, but this will really decrease your ground clearence. I'll want to dyno test a 3" to two 1.5" in the future, and compare volume vs. power.
HTML Code:
13 Beast -- As the exhaust gas exits the pipe, it also helps pull out whatever other exhaust gas is in the exhaust system.
i am legendary
Joined: Sep 2003
Posts: 8,478
Likes: 1
From: Kirkland, WA
Originally Posted by rotarygod
First off it would take four 2.5" pipes to equal the area of one 5" pipe.
The rest of it you just made up as none of it is supported by fact. I have a flowbench and a bunch of pipe BTW if you want me to prove that statement as wrong.
Here's a better quote: "If you aren't flow testing, you are flow guessing."
Quit guessing.
The rest of it you just made up as none of it is supported by fact. I have a flowbench and a bunch of pipe BTW if you want me to prove that statement as wrong.
Here's a better quote: "If you aren't flow testing, you are flow guessing."
Quit guessing.
Since you have all of this great testing equipment why dont you tell us exactly what sized dual pipes flow the same amount as a 3" single.
"I may be drunk"
Joined: Nov 2004
Posts: 71
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From: Pa
The circumference of a circle is the actual length around the circle which is equal to 360°. Pi (p) is the number needed to compute the circumference of the circle.
p is equal to 3.14.
Pi is greek and has been around for over 2000 years!
In circles the AREA is equal to 3.14 (p) times the radius (r) to the power of 2.
Thus the formula looks like:
A= pr2.
In circles the circumference is 3.14 (p) times the Diameter.
Thus the formula looks like:
2pr or pd.
2.5 diameter = circumference of 7.85= area of 4.908 x 2
3.0 diameter =circumference of 9.424= area of 7.06
lets get it right
p is equal to 3.14.
Pi is greek and has been around for over 2000 years!
In circles the AREA is equal to 3.14 (p) times the radius (r) to the power of 2.
Thus the formula looks like:
A= pr2.
In circles the circumference is 3.14 (p) times the Diameter.
Thus the formula looks like:
2pr or pd.
2.5 diameter = circumference of 7.85= area of 4.908 x 2
3.0 diameter =circumference of 9.424= area of 7.06
lets get it right
Last edited by 3turbos; Dec 16, 2004 at 03:21 PM.
i am legendary
Joined: Sep 2003
Posts: 8,478
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From: Kirkland, WA
Welcome to 7th grade math... What exactly are you trying to prove? Your previous post you were saying that 3" single flows the same as dual 2.5" which is wrong, and you JUST proved so again.
Originally Posted by dDuB
Since you have all of this great testing equipment why dont you tell us exactly what sized dual pipes flow the same amount as a 3" single.
I'm a boost creep...
Joined: Jan 2002
Posts: 15,608
Likes: 8
From: Auckland, New Zealand
I don't have a flow bench, but I do have flow calculation software that we use at work for sizing HVAC pipe and duct systems. According to that, using a 1m length of pipe and the industry standard 250Pa (1inH2O) test pressure you get the following results:
The actual numbers from a flow bench wouldn't be exactly the same, as I haven't allowed for entry and exit losses, but the percentage difference would be similar, and the 2.5" pipes would still flow a lot more.
- 3" pipe (76.2mm OD, 1.5mm wall, 73.2mm ID): 148 l/s (314 cfm)
- 2.5" pipe (63.5mm OD, 1.5mm wall, 60.5mm ID): 89 l/s (189 cfm)
The actual numbers from a flow bench wouldn't be exactly the same, as I haven't allowed for entry and exit losses, but the percentage difference would be similar, and the 2.5" pipes would still flow a lot more.
Last edited by NZConvertible; Dec 17, 2004 at 07:25 PM.
You've Been Punk'd
Joined: Jun 2002
Posts: 4,727
Likes: 1
From: Branson, Missouri
Originally Posted by 1987RX7guy
MG(A/B) dunno which model but I think its an MG.
It's a convertible 
Anyways, as for your setup I would suggest 89mm DP and MP then reduce from 89mm to your 60mm (curent Cat back) and you have one pretty good flowing exhaust system. at least equal to that of RB, if not better.
NZ is right (again) that 2.5" X 2 will outflow one 3" The math supports it.
Anyways, as for your setup I would suggest 89mm DP and MP then reduce from 89mm to your 60mm (curent Cat back) and you have one pretty good flowing exhaust system. at least equal to that of RB, if not better.
NZ is right (again) that 2.5" X 2 will outflow one 3" The math supports it.
i am legendary
Joined: Sep 2003
Posts: 8,478
Likes: 1
From: Kirkland, WA
It depends. Like I said, if your catback exhaust currently on there is in the stock catback location, then any downpipe that is meant to bolt up to the stock cat location will work. But it's hard to know if your catback is actually in the stock location or not.