Sizing primary for twins

C

Chowderhead72

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Jan 24, 2008
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Is there a ratio? In other words if one was to use a 75lb secondary (gtx3582r in my case) what would the benefits and detriments when deciding between a 4202, 4508, or even a 4708?

I would assume there is a sweet spot somewhere. If I were to go gtx 4202 for crazy fast spool how bad would the top end dp be? Would the 4508 kill my spool up time? 4708 just too much of a good thing?

Please help.
 
Primary will flow roughly 80% what it would flow as a single.

Garrett also provides flow for the exhaust side. No clue how to math that out though.

Maybe someone could provide that info, I would like to know how to do that.
 
What turbine housing on the GT35? Seems like even with a larger primary whether it be the 87 or 92mm turbine wheel, the secondary may come up short without bypassing it a good deal.
 
Smokem said:
What turbine housing on the GT35? Seems like even with a larger primary whether it be the 87 or 92mm turbine wheel, the secondary may come up short without bypassing it a good deal.
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1.06 t4. Going as loose as possible.
 
I think you are taking a step backward using a small turbine with a larger AR housing, taking away that much shaft power is counterproductive. You may be able to wastegate the secondary enough to reach your goals, but getting a turbine better suited for that power level seems more sensible.
 
Smokem said:
I think you are taking a step backward using a small turbine with a larger AR housing, taking away that much shaft power is counterproductive. You may be able to wastegate the secondary enough to reach your goals, but getting a turbine better suited for that power level seems more sensible.
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Recommendation?

Truth be told I would prefer a t4 gtx3782r with a mid range ar (.85-.91) but not available it would seem anytime soon.
 
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I am a fan of Garrett, but in that frame size the Borg Warner stuff is really tough to beat.
 
Ok, while we are on the subject Smokem, how about an S465 and 106mm for 1,000rwhp on a 12 valve. EGT control and response are an issue, just not max power. The 65mm will be bypassed for max power at higher rpm, and a good amount of drive pressure will be diverted to the big turbo. Looking for 80-100psi.

Goal is a 2,000rpm-4,000rpm powerband.
 
Smokem said:
I am a fan of Garrett, but in that frame size the Borg Warner stuff is really tough to beat.
Click to expand...


Agreed.... It seems the Garrett stuff in the gt3? Series has few options that will flow the volumes and pressures needed for diesels. Hopefully the gtx35 is an exception; we will see shortly. I will have a gtx3582r in t4 1.06 on a htt t4 stainless manifold but planning for future twins. The original plan was gt4508 over gtx3582r but it would seem the the 45 may be a bit much.
 
I have heard compound chargers are most efficient if their is a 30% difference in the two?
 
JQmile said:
Ok, while we are on the subject Smokem, how about an S465 and 106mm for 1,000rwhp on a 12 valve. EGT control and response are an issue, just not max power. The 65mm will be bypassed for max power at higher rpm, and a good amount of drive pressure will be diverted to the big turbo. Looking for 80-100psi.

Goal is a 2,000rpm-4,000rpm powerband.
Click to expand...

Lol that signature is great. Sorry, I don't have much other information for you in regards to that set choice other than I would think it is a bit large for your projected power goals. If response is of concern I would not think that set should even be in the discussion on a 12v but again that is nothing more than speculation on my part.
 
JQmile said:
Ok, while we are on the subject Smokem, how about an S465 and 106mm for 1,000rwhp on a 12 valve. EGT control and response are an issue, just not max power. The 65mm will be bypassed for max power at higher rpm, and a good amount of drive pressure will be diverted to the big turbo. Looking for 80-100psi.

Goal is a 2,000rpm-4,000rpm powerband.
Click to expand...

GT55 106mm or Thumper 106mm?
 
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