Header primary and collector size for T4 GT91
Header primary and collector size for T4 GT91 I am wanting to buy the Stainless Works down and forward facing headers to attempt to keep everything in the factory location with keeping the A/C. This is going to be a street car mostly which is why I chose to stay with the T4 flange. It is a forged 370 with the T4 GT91. I am kind of new to the turbo world so please don't criticize me to much, I just want to go fast. I would like to stick with a 2.5" crossover as I know people are making big power with them but don't know if I want to step down to 1 5/8 primaries. Josh at Kentucky Turbo is building amazing setups with the 1 3/4 tubes with 3" collector but I'm wondering if a 3" crossover is going to be too much for my setup. My hats off to him, he's really producing great work. I don't really like the idea of stepping the 3" collectors down to 2.5. What do you guys think? Glad to join you guys on LS1Tech and I'll get the build thread going soon once I get a few more pieces to the puzzle.
According to some things I been reading..... A lot posted by phil with that sick lsx mustang...
It sounds like 1 5/8" primarys and a 2.25" crossover is ideal for that set up... on top of that there is
Speculation (basicly what it is.. All of it.. Or educated guess) that having your merge come together into one pipe at least 6" before the turbo flange will also help. Flow and turbulence backed up by very persuasive and logical math ( what's behind the sizing and various insight on turbo piping design).
NotNearly as much discussion on the cold side. I have my opinions there tho....
Edit: With your goals it really doesn't matter. For the most part... anything you do will get u there
It sounds like 1 5/8" primarys and a 2.25" crossover is ideal for that set up... on top of that there is
Speculation (basicly what it is.. All of it.. Or educated guess) that having your merge come together into one pipe at least 6" before the turbo flange will also help. Flow and turbulence backed up by very persuasive and logical math ( what's behind the sizing and various insight on turbo piping design).
NotNearly as much discussion on the cold side. I have my opinions there tho....
Edit: With your goals it really doesn't matter. For the most part... anything you do will get u there
Last edited by Dragframe; Mar 6, 2011 at 08:08 AM.
I am wanting to buy the Stainless Works down and forward facing headers to attempt to keep everything in the factory location with keeping the A/C. This is going to be a street car mostly which is why I chose to stay with the T4 flange. It is a forged 370 with the T4 GT91. I am kind of new to the turbo world so please don't criticize me to much, I just want to go fast. I would like to stick with a 2.5" crossover as I know people are making big power with them but don't know if I want to step down to 1 5/8 primaries. Josh at Kentucky Turbo is building amazing setups with the 1 3/4 tubes with 3" collector but I'm wondering if a 3" crossover is going to be too much for my setup. My hats off to him, he's really producing great work. I don't really like the idea of stepping the 3" collectors down to 2.5. What do you guys think? Glad to join you guys on LS1Tech and I'll get the build thread going soon once I get a few more pieces to the puzzle.
When I did the headers and sent thme to Stainless Works to be reproduced we had a long discussion about collector size. I didnt like the abrupt stansison on the 1 3/4" Primary and 2.5" Collector. I made the decision to do the 3" Collector. If you look at the way I design my header setup you will see there is less than 12-16" of tube before the Turbo Flange.
In the application where the turbo is farther from the headers I tend to use 2.5" Charge pipes unless it is a max effort application where I will lean towards larger higher flowing pipe.
At the end of the day with a solid 370ci engine and the GT91 you could easily knock down 1000+rwhp reguardless of the primary and charge pipe sizes. I have done it with both 1 3/4" / 3" and 1 5/8 / 2.5" applications.
I have talked to Phil about the diffreneces in 1 3/4" and 1 5/8" Primaries and the differneces in the charge pipes from 2.25-3". There are benifit to smaller primaries and charge pipes is some applications.
When I did the headers and sent thme to Stainless Works to be reproduced we had a long discussion about collector size. I didnt like the abrupt stansison on the 1 3/4" Primary and 2.5" Collector. I made the decision to do the 3" Collector. If you look at the way I design my header setup you will see there is less than 12-16" of tube before the Turbo Flange.
In the application where the turbo is farther from the headers I tend to use 2.5" Charge pipes unless it is a max effort application where I will lean towards larger higher flowing pipe.
At the end of the day with a solid 370ci engine and the GT91 you could easily knock down 1000+rwhp reguardless of the primary and charge pipe sizes. I have done it with both 1 3/4" / 3" and 1 5/8 / 2.5" applications.
When I did the headers and sent thme to Stainless Works to be reproduced we had a long discussion about collector size. I didnt like the abrupt stansison on the 1 3/4" Primary and 2.5" Collector. I made the decision to do the 3" Collector. If you look at the way I design my header setup you will see there is less than 12-16" of tube before the Turbo Flange.
In the application where the turbo is farther from the headers I tend to use 2.5" Charge pipes unless it is a max effort application where I will lean towards larger higher flowing pipe.
At the end of the day with a solid 370ci engine and the GT91 you could easily knock down 1000+rwhp reguardless of the primary and charge pipe sizes. I have done it with both 1 3/4" / 3" and 1 5/8 / 2.5" applications.
I have read a lot of posts by Phil. I also like the idea of keeping the charge pipes real short and hanging the turbo. Since it will be a street car and not shooting for any records I going to stick with the 1 5/8 and 2.5 charge pipes. Do you have any of these is stock Josh? Either way, I've going to have to get them. I will be giving you a shout in the morning and getting them on their way. I appreciate the help.
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I dont keep them in stock. I have them drop shipped.
I can get the 1 3/4" headers done with 2.5" collectors. I will ask about getting them done in 1 5/8" with 2.5" Collectors. Give me a shout tomorrow.
I can get the 1 3/4" headers done with 2.5" collectors. I will ask about getting them done in 1 5/8" with 2.5" Collectors. Give me a shout tomorrow.
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