Out of curiousity why does everyone use 2.5" on the crossover pipe
#121
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
A 12-1300hp import if using a pipe manifold would be using 1.5" sch pipe.
I have been thinking about making sch10 1.5" pipe manifolds for my personal car. Just have not laid the whole turbo kit out in my head yet.
Fathouse
I have been thinking about making sch10 1.5" pipe manifolds for my personal car. Just have not laid the whole turbo kit out in my head yet.
Fathouse
#122
Teching In
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
This is what I came up with so far. I do not have huge goals. It will be a single TC78 with the goal of 600-650 HP. I have a Edelbrock Pro Flo XT, 80 lbs Siemans injectors, and plan on running E85. The sc10 2 inch I remeasured and is 2 1/8 ID. The waste gate is on the front and is a Precission 46mm. I should have the Tial 50 mm BOV on monday. Does this log manifold look like it will work or should I start over? The Chevy 2 has not much of an engine compartment. I see other guys have went to twins on their Chevy 2's but I dont want to go that far. Thanks for any input. I have truck, Corvette, CTS-V, old and new F-car exhaust manifolds and this is about the only thing that fits easily. It would have been nice to just use truck manifolds.....
Mike
Mike
#123
TECH Addict
iTrader: (6)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Hi Phil,
Oddly enough, I was going to finish my 2.5 cross over for my 5.3 single turbo. It is about 1/2 way done, but I'd rather get it right now than do it all over again to optomize it later. I am using an f-car manifold on the left and a log manifold on the right. The manifold has a piece of schedule 10 2 inch stainless which has an ID around 2.25. The log on the right is sc 10 2.5 inch which matches the T4 flange nicely when ovalled with a vice. That all being said, I grabbed my copy of Maximum Boost and was not able to find the math to determine the correct cross over size. There was a mention of mach numbers and flow in the intercooler section. I would like to understand the math behind this. I would greatly appreciate any help so that I can size this cross ove correctly.
Thanks
Mike
Oddly enough, I was going to finish my 2.5 cross over for my 5.3 single turbo. It is about 1/2 way done, but I'd rather get it right now than do it all over again to optomize it later. I am using an f-car manifold on the left and a log manifold on the right. The manifold has a piece of schedule 10 2 inch stainless which has an ID around 2.25. The log on the right is sc 10 2.5 inch which matches the T4 flange nicely when ovalled with a vice. That all being said, I grabbed my copy of Maximum Boost and was not able to find the math to determine the correct cross over size. There was a mention of mach numbers and flow in the intercooler section. I would like to understand the math behind this. I would greatly appreciate any help so that I can size this cross ove correctly.
Thanks
Mike
Thanks for the info though Phil. It made me question my build a bit, but for now I am just going to run what I have since it is 95% done and I just can't justify the expense to rework it for 200-250 rpm. But when I DO rework it I will go to a smaller size thick wall tubing like Geoff recommends.
#124
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
This is what I came up with so far. I do not have huge goals. It will be a single TC78 with the goal of 600-650 HP. I have a Edelbrock Pro Flo XT, 80 lbs Siemans injectors, and plan on running E85. The sc10 2 inch I remeasured and is 2 1/8 ID. The waste gate is on the front and is a Precission 46mm. I should have the Tial 50 mm BOV on monday. Does this log manifold look like it will work or should I start over? The Chevy 2 has not much of an engine compartment. I see other guys have went to twins on their Chevy 2's but I dont want to go that far. Thanks for any input. I have truck, Corvette, CTS-V, old and new F-car exhaust manifolds and this is about the only thing that fits easily. It would have been nice to just use truck manifolds.....
Mike
Mike
#125
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
I was chatting back and forth with Geoff the turbo engineer at Full Race the other day about this and he seems to think I would only be giving up 2-250 rpm of spool using the 2.5" tubing with its ID of 2.35", so for now I am just going to run it. His advise was a thicker wall tubing like Sch 10 stuff as well. I plan to eventually rework my kit so at that point I will probably neck it down if it is too bothersome and go to a thick sch 10 pipe. If you are half way there I don't know that I would worry about it overly much.
Thanks for the info though Phil. It made me question my build a bit, but for now I am just going to run what I have since it is 95% done and I just can't justify the expense to rework it for 200-250 rpm. But when I DO rework it I will go to a smaller size thick wall tubing like Geoff recommends.
Thanks for the info though Phil. It made me question my build a bit, but for now I am just going to run what I have since it is 95% done and I just can't justify the expense to rework it for 200-250 rpm. But when I DO rework it I will go to a smaller size thick wall tubing like Geoff recommends.
#126
TECH Addict
iTrader: (6)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Well, that is about what we are talking about here.... around .25" going from 2.25" tubing to 2.5" tubing. Mine is right at 2.35 ID. I am assuming 2.25" would be right at 2.10-2.15 ID for the same tubing, so around a .25" change. For now I am going to run it and see how it does. I plan to coat and wrap the manifolds when I am all done. Nothing is 100% perfect on them, but for my first time TIG welding my own manifolds I think they turned out pretty decent. All that is left is installing wastegates. I have seen worse from "professionals" out there, lol.
![Name: IMG_20130209_173634_zpsb3c1170c.jpg
Views: 3639
Size: 620.7 KB](https://ls1tech.com/forums/attachments/forced-induction/610068d1501327284-out-curiousity-why-does-everyone-use-2-5-crossover-pipe-img_20130209_173634_zpsb3c1170c.jpg)
#130
Teching In
iTrader: (3)
Join Date: Jun 2006
Location: ky
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
![](https://ls1tech.com/forums/images/ranks/ls1tech10year.png)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Ok guys I'm fine with criticism I have a stock lq9 with tu2 cam s475 1.32 ar I have already built a 3" hotside is this gonna make my car a complete turd or is it jus gonna take a lil longer to spool when I see these formulas it jus turns to scrambles but I'm fine with building another hotside if I have too thanks all you turbo gurus
#131
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
Ok guys I'm fine with criticism I have a stock lq9 with tu2 cam s475 1.32 ar I have already built a 3" hotside is this gonna make my car a complete turd or is it jus gonna take a lil longer to spool when I see these formulas it jus turns to scrambles but I'm fine with building another hotside if I have too thanks all you turbo gurus
#134
#135
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
With all this talk about crossovers I got a question. Looking at running a a/w intercooler in my s10 in the cab what size charge piping would you guys recommend? Is it horsepower dependent or similar to crossover being the smallest to keep the velocity up? I'm leaning towards 3.5 but I've already got some 3" charge piping I could use.
#136
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
With all this talk about crossovers I got a question. Looking at running a a/w intercooler in my s10 in the cab what size charge piping would you guys recommend? Is it horsepower dependent or similar to crossover being the smallest to keep the velocity up? I'm leaning towards 3.5 but I've already got some 3" charge piping I could use.
#138
#139
TECH Senior Member
iTrader: (59)
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
phil try some nice cast manifolds?
didnt read it all but are you considering temperature drop along the pipes and its effect on volume / velocity
similar note have you considered the surface area of the pipes / combining pipes sooner to reduce it and associated drag / tempterature drop.
didnt read it all but are you considering temperature drop along the pipes and its effect on volume / velocity
similar note have you considered the surface area of the pipes / combining pipes sooner to reduce it and associated drag / tempterature drop.
#140
![Default](https://ls1tech.com/forums/images/icons/icon1.gif)
phil try some nice cast manifolds?
didnt read it all but are you considering temperature drop along the pipes and its effect on volume / velocity
similar note have you considered the surface area of the pipes / combining pipes sooner to reduce it and associated drag / tempterature drop.
didnt read it all but are you considering temperature drop along the pipes and its effect on volume / velocity
similar note have you considered the surface area of the pipes / combining pipes sooner to reduce it and associated drag / tempterature drop.