Out of curiousity why does everyone use 2.5" on the crossover pipe
01-30-2013, 10:36 AM
#41
Here is some data from real world applications that perform at the top level of competition.
From my import days I learned how important velocity was....
- 632 BB with twin 94s, 3.5" crossover
8300rpm, 35# of boost will make 3500hp
1100fps in the crossover
- 525BB with Twin 88s, 3.5" crossover
8500rpms, 42# of boost
1050fps in the crossover
(my turd which has gone 164 @ 3300 to the 1/8 mile)
438" small block with 106, 2.5" crossover
8500rpms, 40# of boost
900 FPS in the crossover
Lets say a 346 would make 450 at the tires NA, you would need 14-15# to double the rwhp assuming its built correctly
346", 15psi, 7500rpms
2" crossover yeilds 550 fps
2 1/8" crossover yeilds 480 fps
2.25" crossover yeilds 430 fps
2.5" crossover yields 350 fps
From my import days I learned how important velocity was....
- 632 BB with twin 94s, 3.5" crossover
8300rpm, 35# of boost will make 3500hp
1100fps in the crossover
- 525BB with Twin 88s, 3.5" crossover
8500rpms, 42# of boost
1050fps in the crossover
(my turd which has gone 164 @ 3300 to the 1/8 mile)
438" small block with 106, 2.5" crossover
8500rpms, 40# of boost
900 FPS in the crossover
Lets say a 346 would make 450 at the tires NA, you would need 14-15# to double the rwhp assuming its built correctly
346", 15psi, 7500rpms
2" crossover yeilds 550 fps
2 1/8" crossover yeilds 480 fps
2.25" crossover yeilds 430 fps
2.5" crossover yields 350 fps
01-30-2013, 10:40 AM
#42
So have you calculated the velocity and/or have you been able to put some type of device in the pipe(s) to measure the velocity or flow rate?
From what I recall during my engineering classes when I was getting ME degree, you need to know the pipe size and velocity to get the flow rate OR the pipe size and flow rate to determine velocity. You have to have two of the variables to calculate the unknown.
From what I recall during my engineering classes when I was getting ME degree, you need to know the pipe size and velocity to get the flow rate OR the pipe size and flow rate to determine velocity. You have to have two of the variables to calculate the unknown.
01-30-2013, 10:53 AM
#43
We will see how weak it is when it goes 175-180mph to the 1/8 mile.....
I think you might be able to go up on the turbine A/R.
Big pipes require more time and engine to develop the same drive pressure, once its up to pressure its going to take the same drive pressure to maintain boost and where the wastegate comes into play.
My motor makes about 1300hp through a single 2.5" OD pipe. Remember, pre turbo its about velocity.
I think you might be able to go up on the turbine A/R.
Big pipes require more time and engine to develop the same drive pressure, once its up to pressure its going to take the same drive pressure to maintain boost and where the wastegate comes into play.
My motor makes about 1300hp through a single 2.5" OD pipe. Remember, pre turbo its about velocity.
http://www.yellowbullet.com/forum/sh...d.php?t=308464
and have read all the pages on your build from day one! Ive talked to you many times on here and the bullet about my combo. I would love to have the drivetrain in my e46 bmw lol. But serious tho would 2" be to small for a 370/lsa heads, holley HR,and pt91.5 1k to 1.2k hp range? or 2-1/8 2-1/4 better?
01-30-2013, 11:34 AM
#44
Phil im joking dude...im read every page on the **** it turbocharging on yb
http://www.yellowbullet.com/forum/sh...d.php?t=308464
and have read all the pages on your build from day one! Ive talked to you many times on here and the bullet about my combo. I would love to have the drivetrain in my e46 bmw lol. But serious tho would 2" be to small for a 370/lsa heads, holley HR,and pt91.5 1k to 1.2k hp range? or 2-1/8 2-1/4 better?
http://www.yellowbullet.com/forum/sh...d.php?t=308464
and have read all the pages on your build from day one! Ive talked to you many times on here and the bullet about my combo. I would love to have the drivetrain in my e46 bmw lol. But serious tho would 2" be to small for a 370/lsa heads, holley HR,and pt91.5 1k to 1.2k hp range? or 2-1/8 2-1/4 better?
The calculator says 2" to a 2.5" combined merge section. I know it sounds small but remember 2.5" can easily handle 2000-2500hp.
01-30-2013, 11:42 AM
#45
So have you calculated the velocity and/or have you been able to put some type of device in the pipe(s) to measure the velocity or flow rate?
From what I recall during my engineering classes when I was getting ME degree, you need to know the pipe size and velocity to get the flow rate OR the pipe size and flow rate to determine velocity. You have to have two of the variables to calculate the unknown.
From what I recall during my engineering classes when I was getting ME degree, you need to know the pipe size and velocity to get the flow rate OR the pipe size and flow rate to determine velocity. You have to have two of the variables to calculate the unknown.
And yes, you can run a 3" crossover on a 346 or 370" and get good results.
01-30-2013, 11:50 AM
#46
Thanks for this!
I am about to order the piping for my crossover and would have bought 2.5" for my 76mm 1.0A/R cheap turbo, now I will buy 2.0".
Any suggestions on transitions from 2.5" to 2" with truck manifolds?
I am about to order the piping for my crossover and would have bought 2.5" for my 76mm 1.0A/R cheap turbo, now I will buy 2.0".
Any suggestions on transitions from 2.5" to 2" with truck manifolds?
01-30-2013, 04:11 PM
#55
Launching!
I ran a 2" crossover with a 390ci engine and S400-75mm T4 turbo. Response was good, did seem to drop-off a little early, which I expect was due to the small turbine wheel (never measured backpressure).
01-30-2013, 05:52 PM
#57
Launching!
Thanks Phil, I was about to post up a thread asking for advice on a new turbo. I don't suppose anyone knows the physical size of the Precision x275-88mm compared to an S400? The S400 was tight, but did fit, I don't think I'd be able to find much more room.
