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5" dump pipe into 2x3" pipes question. #880597 12/15/10 07:33 AM 12/15/10 07:33 AM
Joined: Dec 2005 Posts: 96 Australia G gg408 OP member
gg408 OP member G Joined: Dec 2005 Posts: 96 Australia	Due to lack of room in my 67 Valiant I was wondering if going from 5" dump pipe to twin 3" pipes will cause a lot of back preasure/restriction. S480 BW on 410ci W2 headed SB Mopar. Cheers gg408

Re: 5" dump pipe into 2x3" pipes question. [Re: gg408] #880598 12/15/10 01:47 PM 12/15/10 01:47 PM
Joined: Jan 2003 Posts: 28,071 Irving, TX feets Senior Management
feets Senior Management Joined: Jan 2003 Posts: 28,071 Irving, TX	A three inch pipe has an area of 28 square inches. Two of them have 56 square inches. A five inch pipe has an area of 78 inches. Maybe you could use three 3" pipes? We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon

Re: 5" dump pipe into 2x3" pipes question. [Re: feets] #880599 12/15/10 02:13 PM 12/15/10 02:13 PM
Joined: Dec 2005 Posts: 121 mid-mich turboplymouth member
turboplymouth member Joined: Dec 2005 Posts: 121 mid-mich	Quote: A three inch pipe has an area of 28 square inches. Two of them have 56 square inches. A five inch pipe has an area of 78 inches. Maybe you could use three 3" pipes? Actually it's radius sq. x Pi, but you probably know that So more like 19 sq. inches for a 5" pipe and 14 for two 3" pipes. So its like a 4 1/4" pipe or so. I did my dp like this for the same reason as you. '72 Scamp, 3500#, 440, S400, blowthrough, meth. inj. 9.78 @ 139 so far at 12 psi, 11.00 @ 131 on real street tires.

Re: 5" dump pipe into 2x3" pipes question. [Re: feets] #880600 12/15/10 02:16 PM 12/15/10 02:16 PM
Joined: Jan 2005 Posts: 3,635 Oakland, MI D dizuster master
dizuster master D Joined: Jan 2005 Posts: 3,635 Oakland, MI	Ummm... pi r^2 3" pipe 1.5 x 1.5 = 2.25 x 3.14 = 7.06 x 2 pipes = 14.13 sq in 5" pipe 2.5 x 2.5 = 6.25 x 3.14 = 19.63 sq in. So there is some reduction, but not that much.. 3.5" pipe is basically a wash, 3" is a little small, but really do you need a 5" pipe for an 80mm turbo? Probably not...

Re: 5" dump pipe into 2x3" pipes question. [Re: dizuster] #880601 12/15/10 02:25 PM 12/15/10 02:25 PM
Joined: Dec 2005 Posts: 121 mid-mich turboplymouth member
turboplymouth member Joined: Dec 2005 Posts: 121 mid-mich	Seems I remember seeing some tests showing that those turbos reduced down to 4" did'nt hurt power. I know there are guys making big power that way. '72 Scamp, 3500#, 440, S400, blowthrough, meth. inj. 9.78 @ 139 so far at 12 psi, 11.00 @ 131 on real street tires.

Re: 5" dump pipe into 2x3" pipes question. [Re: dizuster] #880602 12/15/10 02:38 PM 12/15/10 02:38 PM
Joined: Feb 2003 Posts: 4,953 Houston, Texas TheOtherDodge master
TheOtherDodge master Joined: Feb 2003 Posts: 4,953 Houston, Texas	"but really do you need a 5" pipe for an 80mm turbo?" My thoughts exactly!

Re: 5" dump pipe into 2x3" pipes question. [Re: TheOtherDodge] #880603 12/15/10 03:10 PM 12/15/10 03:10 PM
Joined: May 2008 Posts: 1,238 North Cackilacky S sdaurity pro stock
sdaurity pro stock S Joined: May 2008 Posts: 1,238 North Cackilacky	I saw no gain going from 4" to 5" on my large frame 101. I put the 4" back on because it fit so much better. but I'm not pushing it to the absolute limits. No need for 5" on an s480 anyways. One day I will have something cool here.

Re: 5" dump pipe into 2x3" pipes question. [Re: turboplymouth] #880604 12/15/10 03:32 PM 12/15/10 03:32 PM
Joined: Jan 2003 Posts: 28,071 Irving, TX feets Senior Management
feets Senior Management Joined: Jan 2003 Posts: 28,071 Irving, TX	Quote: Quote: A three inch pipe has an area of 28 square inches. Two of them have 56 square inches. A five inch pipe has an area of 78 inches. Maybe you could use three 3" pipes? Actually it's radius sq. x Pi, but you probably know that I thought it was A=pir2 but checked online to be sure. This is what I found: Quote: The radius of a circle is 3 inches. What is the area? Solution: = 3.14 � (3 in) � (3 in) = 3.14 � (9 in2) = 28.26 in2 Now, if you're an idiot like me, you see 3" radius and go with it. Nevermind the fact that you're working with a 3 diameter*. So, if he dumps the 10" pipe into two 6" pipes he'll need a third pipe. We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon

Re: 5" dump pipe into 2x3" pipes question. [Re: feets] #880605 12/15/10 06:02 PM 12/15/10 06:02 PM
Joined: Dec 2005 Posts: 121 mid-mich turboplymouth member
turboplymouth member Joined: Dec 2005 Posts: 121 mid-mich	'72 Scamp, 3500#, 440, S400, blowthrough, meth. inj. 9.78 @ 139 so far at 12 psi, 11.00 @ 131 on real street tires.

Re: 5" dump pipe into 2x3" pipes question. [Re: turboplymouth] #880606 12/16/10 06:58 AM 12/16/10 06:58 AM
Joined: Dec 2005 Posts: 96 Australia G gg408 OP member
gg408 OP member G Joined: Dec 2005 Posts: 96 Australia	Ok so if I go for a 4 " pipe how close to the turbo outlet should the reducer be and do I need to have a long reducing cone and if so what would the min length be? This is what I have now and am trying to get the 3" pipes to run up next to the eng so they dont hang to low under the k-member. Thanks Cheers gg408 6360485-Copyof101_0098.JPG (50 downloads) Last edited by gg408; 12/16/10 07:12 AM.

Re: 5" dump pipe into 2x3" pipes question. [Re: gg408] #880607 12/16/10 07:36 AM 12/16/10 07:36 AM
Joined: Dec 2005 Posts: 96 Australia G gg408 OP member
gg408 OP member G Joined: Dec 2005 Posts: 96 Australia	Another 1 6360490-101_0097.JPG (54 downloads)

Re: 5" dump pipe into 2x3" pipes question. [Re: gg408] #880608 12/16/10 07:38 AM 12/16/10 07:38 AM
Joined: Dec 2005 Posts: 96 Australia G gg408 OP member
gg408 OP member G Joined: Dec 2005 Posts: 96 Australia	And another 1 6360491-Copyof101_0095.JPG (56 downloads)

Re: 5" dump pipe into 2x3" pipes question. [Re: gg408] #880609 12/16/10 05:09 PM 12/16/10 05:09 PM
Joined: Jan 2003 Posts: 28,071 Irving, TX feets Senior Management
feets Senior Management Joined: Jan 2003 Posts: 28,071 Irving, TX	It would be best to have the reduction after the initial turn. The air will begin losing rotation as soon as it leaves the turbine but that first turn is still very turbulent. We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon

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