2 or 2.25 pipes for street build
2 or 2.25 pipes for street build Guys
I have an S475 turbo that im bolting to a 6L engine. Ive been reading about pipe diameters and based upon some of the more technical data, it seems like for a street build up to around 1000 hp, a 2 or 2.25" charge pipe to a 2.5/2.75 merge will keep velocities up and be a better setup as opposed to a 2.5" charge pipe
I cant think of a reason NOT to do a 2" setup for the street.
Help me understand why a 2.25" or a 2.5" is better.
thanks
I have an S475 turbo that im bolting to a 6L engine. Ive been reading about pipe diameters and based upon some of the more technical data, it seems like for a street build up to around 1000 hp, a 2 or 2.25" charge pipe to a 2.5/2.75 merge will keep velocities up and be a better setup as opposed to a 2.5" charge pipe
I cant think of a reason NOT to do a 2" setup for the street.
Help me understand why a 2.25" or a 2.5" is better.
thanks
TECH Regular
Joined: Jun 2010
Posts: 448
Likes: 0
I think you will be okay. Maybe if you were planning on turning silly rpm you might have a problem. Run a nice big down pipe youll be okay. I run a 2.25 on a 402. I will know definitive results in a couple weeks.
Thanks man... what size turbo are you running?
I know the s475 is a bit bigger than some of the T4s, but even though its bigger, i would still think it would benefit from getting higher pressure.
Correct my thinking if im wrong, but X hp requires Y air. The turbo only has Y air to work with, so it may as well get it at a higher pressure. and "let the gases expand in the turbo."
I can see a small downpipe being a problem, as that would not let the turbo exhale. But ill run a big downpipe (4-5").
But on the charge side, is there a thing as too much pressure? (the kind of excess that a 2" pipe would generate over a 2.5" pipe) Again, its the same quantity of air, just at a higher inlet pressure.
I cant see how the turbo would complain about too much pressure.
Maybe i need to think of this as
"at what pressure will small pipe (2") be vs at what pressure will the 2.5" pipe be to deliver the air required to make X hp"
Will that extra pressure be a problem on anything in the system? turbo/wg?
help me clairify this!
thanks
I know the s475 is a bit bigger than some of the T4s, but even though its bigger, i would still think it would benefit from getting higher pressure.
Correct my thinking if im wrong, but X hp requires Y air. The turbo only has Y air to work with, so it may as well get it at a higher pressure. and "let the gases expand in the turbo."
I can see a small downpipe being a problem, as that would not let the turbo exhale. But ill run a big downpipe (4-5").
But on the charge side, is there a thing as too much pressure? (the kind of excess that a 2" pipe would generate over a 2.5" pipe) Again, its the same quantity of air, just at a higher inlet pressure.
I cant see how the turbo would complain about too much pressure.
Maybe i need to think of this as
"at what pressure will small pipe (2") be vs at what pressure will the 2.5" pipe be to deliver the air required to make X hp"
Will that extra pressure be a problem on anything in the system? turbo/wg?
help me clairify this!
thanks
Im running 2.25 into the twin scrolls of my borg S475. They flared out very nicley into the divided flange as well. Secondly, i think you are on the right track, i actually toyed with the idea of 2" myself for about a half second, lol. I was actually considering 2.125 or 2.25, ultimatley, after talking with Phil we decided on 2.25.
Dont over think the charge side, remember, it also has to breathe through that side when not in boost. the S475 has a 3" discharge, im going to use a 3" discharge.
Dont over think the charge side, remember, it also has to breathe through that side when not in boost. the S475 has a 3" discharge, im going to use a 3" discharge.
thanks man...
just to clarify, your using 2.25" from engine to turbo and then 3" from turbo to IC/throttle body?
just curious... why didnt you go with 2" or 2.125"? velocity and pressure would have been greater.
why did you bump to 2.25? room to grow?
just to clarify, your using 2.25" from engine to turbo and then 3" from turbo to IC/throttle body?
just curious... why didnt you go with 2" or 2.125"? velocity and pressure would have been greater.
why did you bump to 2.25? room to grow?
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Staging Lane
Joined: Oct 2007
Posts: 89
Likes: 1
2 1/4 piping to a single turbo from your headers or manifolds is enough to supply up to 1900 hp.. if you are doing a big single over 2000 hp then a 2 1/2 Y pipe is enough big piping will loose spooling ability in the low end and top end!! long as your turbo turbine and EX housing is matched to your engine size you will have no problem with to much EX pressure.
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that looks good, that is similar to the setup i want, i am going to build log manifolds 1.5" primaries to 2" logs and crossover. i am only going to be shooting for 800whp max
Staging Lane
Joined: Jun 2011
Posts: 76
Likes: 1
From: Australia
thanks dude! yer the pipe is the thick walled stuff, same as racepartsolutions sells (butt joints) reall good stuff to work with, great to weld on, bit of a pain to cut, will hold heat in the pipes real well!specially when ceramic coated and heat wrapped.
One thing to consider...we went from the factory 1.75" up pipe to a 2.25" pipe on a 2.5 liter subaru motor (I know different engine) and actually picked up spool time by around 300 rpm. Consequently when we did smaller 1.5" primary and 2" collector on a t4 turbo it actually hurt spool up compared to larger 1.75" primary, 2.5" collector. Turbo systems can be odd beasts some times.
Sarg
Was all your experimenting on the same motor? What were your hp numbers? roughly...
i dont doubt that if a pipe cant support the hp, then it will suffer. but on a 4/inline 6 motor, one pipe has to carry the whole load. on a V6/V8, now each pipe only has half the duty to get the same hp.
thanks man!
Was all your experimenting on the same motor? What were your hp numbers? roughly...
i dont doubt that if a pipe cant support the hp, then it will suffer. but on a 4/inline 6 motor, one pipe has to carry the whole load. on a V6/V8, now each pipe only has half the duty to get the same hp.
thanks man!
Several different motors, several different hp levels, same results each time. These were primarily Subaru H 4 motors (2 cylinders on each side) from 2.0 liter to 2.5 liter and from 250 awhp to 400 awhp.
Think of it as half a V8
. When we switched to a 2" crossover leading to a 2.5" merge followed by a 1.5 foot pipe going into the turbo we almost always got better results. Now you are trying to do roughly double (or more) the displacement for a v8 and still using the same crossover. I am not saying it won't work, just sharing my experience.
Maybe do 2 inch or 2.25 to a 2 3/8 or 2.5 step before the turbo.
Think of it as half a V8
. When we switched to a 2" crossover leading to a 2.5" merge followed by a 1.5 foot pipe going into the turbo we almost always got better results. Now you are trying to do roughly double (or more) the displacement for a v8 and still using the same crossover. I am not saying it won't work, just sharing my experience. Maybe do 2 inch or 2.25 to a 2 3/8 or 2.5 step before the turbo.
