2.5 or 3 inch charge pipes
04-04-2005, 04:53 PM
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2.5 or 3 inch charge pipes
I have a garette g35-40r turbo, fully built motor, masive intercooler with 2.5in and out pipes.... the motor put down 479WHP last year....
I am redoing my charge pipes and want to know whats the best combo???
It use to have all 2.5 inch exhaust for the intake charge pipe going to the throttle body was 3inch.....
should I leave it like that or do 2.5 all arround.... keep in mind I have a bbk 70MM throttle body and a edlebrock manifold!!!
thanks
Tyler
my street map is 16 PSI!! if you need to know that?
I am redoing my charge pipes and want to know whats the best combo???
It use to have all 2.5 inch exhaust for the intake charge pipe going to the throttle body was 3inch.....
should I leave it like that or do 2.5 all arround.... keep in mind I have a bbk 70MM throttle body and a edlebrock manifold!!!
thanks
Tyler
my street map is 16 PSI!! if you need to know that?
04-05-2005, 03:54 AM
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Re: (ATgrills.com)
I did some quick number crunching and with the aid of THIS site I figured out the airspeed of your intake air. It would help if I knew the actual CFM of your setup, but I just used 700 CFM.
The area of a 2.5" pipe is 4.90625 square inches
The area of a 3.0" pipe is 7.065 square inches
That online site uses length x width.
The equivalent L x W for a 2.5" pipe is 2.453125 x 2
The equivalent L x W for a 3.0" pipe is 3.5325 x 2
Now input 700 cfm and 2.453125 for the length and 2 for the width. Select speed as MPH. The speed for your intake air with a 2.5" pipe is 233 MPH or 0.31 MACH
speed calculator
Now input 700 cfm and 3.5325 for length and 2 for width. Speed will still be in MPH and for a 3" pipe the speed comes out to 162 MPH or 0.22 MACH.
If you stick with the same overall setup and just go from a 2.5" to a 3" pipie you see that there is a 40 MPH decrease in velocity. That's assuming that you are flowing 700cfm, but you get the general idea. That lost velocity translates into increased lag. Because when you shift it takes longer for the 3" pipe to pressurize because the air inside is only moving 162 MPH, vs 233 MPH for a 2.5" pipe.
The area of a 2.5" pipe is 4.90625 square inches
The area of a 3.0" pipe is 7.065 square inches
That online site uses length x width.
The equivalent L x W for a 2.5" pipe is 2.453125 x 2
The equivalent L x W for a 3.0" pipe is 3.5325 x 2
Now input 700 cfm and 2.453125 for the length and 2 for the width. Select speed as MPH. The speed for your intake air with a 2.5" pipe is 233 MPH or 0.31 MACH
speed calculator
Now input 700 cfm and 3.5325 for length and 2 for width. Speed will still be in MPH and for a 3" pipe the speed comes out to 162 MPH or 0.22 MACH.
If you stick with the same overall setup and just go from a 2.5" to a 3" pipie you see that there is a 40 MPH decrease in velocity. That's assuming that you are flowing 700cfm, but you get the general idea. That lost velocity translates into increased lag. Because when you shift it takes longer for the 3" pipe to pressurize because the air inside is only moving 162 MPH, vs 233 MPH for a 2.5" pipe.
04-05-2005, 04:02 AM
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Re: (BlueShadow)
I used my measurements for a 2.5" pipie in that calculator and I kept increasing the cfm to increase the speed. According to Corky Bell pg 61 of Maximum Boost the velocity of the intake air should not get higher then 0.4 MACH or 304 MPH. At that speed, drag increases and you start experiencing flow loss.
With a 2.5" pipe to get the intake velocity up to 0.4 MACH or 300 MPH you would have to be pushing 900 CFM. All this stuff is basic math, so unless I botched up with the area of a circle and the online site then my numbers should be accurate.
With a 2.5" pipe to get the intake velocity up to 0.4 MACH or 300 MPH you would have to be pushing 900 CFM. All this stuff is basic math, so unless I botched up with the area of a circle and the online site then my numbers should be accurate.
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04-05-2005, 04:05 AM
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Re: (ATgrills.com)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ATgrills.com »</TD></TR><TR><TD CLASS="quote">thats for much.. you just make my day!!
Ill be making my 2.5 inch charge pipes today
Tyler</TD></TR></TABLE>
no problem, but you might wanna check with some of the experts on here first. See if what I posted was accurate. I'm no turbo expert, but all that stuff I just went over was basic math. The only thing I'm worried about is where I took the area of a circle and found it's equivalent in the area of a square. I'm confident that I did that correct, but it never hurts to get a second opinion.
EDIT: since we were talking about 2.5" vs 3" I still think it's a good idea to stick with 2.5. I guess you would have wanted some proof of why that would have been better though. hehehe
Ill be making my 2.5 inch charge pipes today
Tyler</TD></TR></TABLE>
no problem, but you might wanna check with some of the experts on here first. See if what I posted was accurate. I'm no turbo expert, but all that stuff I just went over was basic math. The only thing I'm worried about is where I took the area of a circle and found it's equivalent in the area of a square. I'm confident that I did that correct, but it never hurts to get a second opinion.
EDIT: since we were talking about 2.5" vs 3" I still think it's a good idea to stick with 2.5. I guess you would have wanted some proof of why that would have been better though. hehehe
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