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Discussion Starter · #1 ·
Currently have a 52mm. Porting out my 782 head on a 2.5 , installing a ported and hogged out neck 2-piece and TU cast ex manifold / 3" ex. Large IC / 2.5" pipes. Will going to a 58mm TB with my hybrid 2 stage turbo help with air flow over the 52mm?
 

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if you have a sheet metal intake that is straight through, and had 3in piping the whole IC system from turbo to TB, then yes it would
 

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Discussion Starter · #5 ·
if you have a sheet metal intake that is straight through, and had 3in piping the whole IC system from turbo to TB, then yes it would
OK, Let me ask this another way. Say my IC piping, intake neck and TB are all 2.5 inches ID. Then I install a 2" ID pipe swedge in the middle of my IC pipe between IC and TB, would it be restrictive?
 

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OK, Let me ask this another way. Say my IC piping, intake neck and TB are all 2.5 inches ID. Then I install a 2" ID pipe swedge in the middle of my IC pipe between IC and TB, would it be restrictive?
With the TD the intake dictates the TB. A one piece ported or not stays stock 46. The 2 piece after porting stays 52 mm. Any larger and you need a plenum of a new neck, a new neck on the upper half of a 2 piece is kind of dumb. So that leaves making a plenum to use the 58, use it by not having a restrictive neck, using it to fill a good plenum and using it to match a high RPM range with the shorter higher volume intake runners. Then the 58 is a 54mm TB untill ported. So everything to use a 58 TB is a big PITA. Your set up can use a plenum, so when your ready for one your ready for a 58. With a turbo you have to create enough flow velocity through a TB that the high velocity is creating back pressure. It just takes a ton of CFM to back up a 52 mm TB. I am build 3 plenums, 2 will run 52s.

Next bit of info, you can get as much CFM through a 52 as the 58 if you shave the throttle shafts and knife the TB blade. The 58mm TB is really a 54mm TB before porting. The 58mm TB should be considered for engines over 400 WHP or 7,500 + RPM engines.:)
 

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Discussion Starter · #7 ·
With the TD the intake dictates the TB. A one piece ported or not stays stock 46. The 2 piece after porting stays 52 mm. Any larger and you need a plenum of a new neck, a new neck on the upper half of a 2 piece is kind of dumb. So that leaves making a plenum to use the 58, use it by not having a restrictive neck, using it to fill a good plenum and using it to match a high RPM range with the shorter higher volume intake runners. Then the 58 is a 54mm TB untill ported. So everything to use a 58 TB is a big PITA. Your set up can use a plenum, so when your ready for one your ready for a 58. With a turbo you have to create enough flow velocity through a TB that the high velocity is creating back pressure. It just takes a ton of CFM to back up a 52 mm TB. I am build 3 plenums, 2 will run 52s.

Next bit of info, you can get as much CFM through a 52 as the 58 if you shave the throttle shafts and knife the TB blade. The 58mm TB is really a 54mm TB before porting. The 58mm TB should be considered for engines over 400 WHP or 7,500 + RPM engines.:)
Interesting, I thought you might want minimum back pressure at the TB. You said the neck on the 2-piece ported is 52mm. Mine ported is over 58mm as far down as I can measure. It could be a smaller diameter at the throat, it's hard to measure at that point. I'll stay with the 52 for now and see what the dyno says. Don't think I'll see 400, but it's heading in that direction.
 

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i agree with the Pope, I run my 58 on a TIII 16V motor with a large Turbo and im running 23+ lbs of boost with alki injection and i rev my car to 7K or so. on an 8V i honestly dont think it makes any difference trying to go with a 58 over the 52. plus a 58 only has one vacuum port so you would have to set up you vacuum system to run on one, not a problem really. a straight through plenum design benefits the most from a larger TB, a 2 piece with that elbow bend and all really does affect the flow. my TIII is a straight through that was 52 from the factory and then ported and opened to accept the 58mm by Lonewolf performance
 

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to get the RPM out of both engines you need a plenum with the CID of the engine. Stock both intakes have about half the volume needed in the plenum. Neither intake needs more than one step bigger in TB with the stock plenums. I don't think you can find anyone with a 2 piece and a 58 making power and a T3 with a 65 making more power
 
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