T-4 Mid Frame Ponderings
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From: Baton Rouge La.
T-4 Mid Frame Ponderings So I see most people say "go the T6 route and don"t waste your time on a T-4 set up". But..... I see a few 88mm mid frame set ups making some killer power on 6.0's. I understand a mid frame T-4 won't make the power a T-6 will on a large cubic motor, but what is "large"? I am at the point of a decision and really want to "buck the system" and make my little 370 cu in. run with a t-4 mid frame. I do want to turn the motor at least 6500. I feel it can be done with a 4" inter cooler and a 4" down pipe with a pt88 or equivalent. So in your experienced opinions..... whats the general recipe? Do I need to just bite the bullet and go T-6? I can get some good deals on the t-4 stuff right now. 
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From: Baton Rouge La.
Thank you all for the input!! I agree that the 76/78 will it the to the power level, but at what expense? Excessive Back pressure at 5500 rpm? That's where an LS type motor shines. Exactly why I want to turn at least 6500 on 370 cu in. I do understand an 88 will have some lag but with a 4000 converter on the t-brake? Lag shouldn't be an issue. A big 96mm t-6 type turbo would concern me on lag with my cubic inch. Not with an 88 t-4 with say a .96 or .102 ar. If thats a concern, I'm sure our sponsors could roust up a good little camshaft that would spool it 
Last edited by SILVERBIRD97; Jun 4, 2013 at 09:06 AM. Reason: wording
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From: Colorado Springs, Co/ Central, Ca
Times in sig are with a Gt76/94/T4 (same exh side as pt88)
Truck has a S480 now with ported T4 housing and been a bit quicker
Power will not cary as well past 6500 as a T6 but they get the job done and spool quick.
Truck has a S480 now with ported T4 housing and been a bit quicker
Power will not cary as well past 6500 as a T6 but they get the job done and spool quick. Thread Starter
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From: Baton Rouge La.
LOL well If I can get the right price for my 102/102 and tfs 225 cnc'd heads I may muster up enough to go t6, though the PT88 t4 will be hard to pass up. Id like to try the t/4 mid frame on a t6 setup with an adapter so if the T4 doesn't do how I want, its a turbo swap and down pipe away. Also whats you guys opinion on intercoolers? Air to water or air to air preference? I would like to have a very efficient intercooler setup so IATs wont be an issue.
I would highly recommend a BW S475, BW S476 or a BWS480 with 92mm turbine wheel, 1.0 AR housing and T4 flange for an awesome combination of lighting quick spool without back pressure being astronomical. With the correct cam that uses the proper valve events in relation to overlap you can have a combination that spools like a much smaller turbo.
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From: Baton Rouge La.
Martin,
Thanks for the insight. Your opinion is greatly valued. I will contact you for the cam selection when I quit procrastinating and start this build!! As she sits now It runs,drives and goes high nines so Its hard for me to down the thing.
Thanks for the insight. Your opinion is greatly valued. I will contact you for the cam selection when I quit procrastinating and start this build!! As she sits now It runs,drives and goes high nines so Its hard for me to down the thing.
Not a problem. Just let me know when you'd like to do something.
Remember high backpressure isn't as bad as long as your valve overlap isn't extreme... If you want to run a giant cam (which you don't need for your desired power level), then you need the big turbine. Even then it still won't spool like a smaller cam/smaller turbo setup will. I honestly have yet to see someone really challenge BW's 'small' 83mm wheel...
Thanks for your thoughts Martin, my thinking was like the op, on a larger engine a 1.08 to 1.15 would help the pt88 to not fight itself up top. It is however the physical size that attracts me to it, so if that would grow, could turn people away to a full T6 unit.
A mid-frame T4 set-up would certainly meet and exceed your goals! Given the opportunity, we would build it identical to our T6 kit, just use a T4 flange and a full 4" down pipe. I would run a T4 Borg Warner or the PT88 as many have already mentioned. Let us know if we can be of any help or assistance of your build! 
Jon
Jon
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