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Discussion Starter #1
So i've seen builds on here that use small tdo4 turbos to get quick spool....my question is does that also work with performance turbos? Like say if I put a precision 62mm on my 5.0L engine. I was looking to get an old technology T70 but for a few more hundred I could get one of those BB billet precision ones with new technology that support the same amount of HP that the old T70s do. I'm just wondering what the experts on here think. Thanks!
 

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it will feel like a stock turbo volvo or something, a good bit of midrange torque, but the small turbo becomes more of a restriction on the top end. you'd be better off with a medium sized turbo, or twin babies.
 

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too small of a turbo on too large of an engine causes a few issues.
back-pressure, compressor surge, turbos overheating, turbos running out of topend.

There is a formula out there to determine your turbo based on a few factors.
1. displacement of engine
2. airflow or cfm
3. powerband, topend power or lowend power
4. power goals

usually you take the top factors and compare the results to a turbos efficiency island plot.

The most simplest way with a 5.0 would easily be a twin turbo setup so you would need to plot out 2 smaller turbos.

Imo I go with a larger twin scroll single turbo and split the pulses between both exhaust manifolds. Twin scroll will spool faster and a larger single turbo will run more efficiently and cooler. There is more fabrication with that setup though.
 

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This is gonna sound ape shit crazy, but I seriously hear people complain about spool on the mustang forums when running a single 62mm turbo...

I wouldnt say a precision 62mm would be "too small", but it certainly would be on the small side.
 

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Discussion Starter #8 (Edited)
Then use a twin-scroll exhaust housing. Excellent spool and more flow capacity up top.
That's what i'm planning! Which side is the best for the front scroll? I can have one header exit right at the turbo, but the other will have to travel around 3-4 feet after the collector to get to the housing.

For the most part, you need to make sure that the hotside will not choke your engine. Putting a t3 turbine on a v8 is fail, unless there are 2 of them ;)
I honestly had no clue as to what housing those turbos used. But if it a T3 then yes that's small!

This is gonna sound ape shit crazy, but I seriously hear people complain about spool on the mustang forums when running a single 62mm turbo...
Yeah i've seen most of the street turbo kits for foxbodies use small 60mm turbos. But the kits have Shitty ass kit exhaust systems. That's where the late spool comes from i'm guessing. So much heat is lost trough them. Also 5.0/5.8 stock heads flow very poorly, well when you compare them to the Mod heads or any other 4 valve head for that matter.
 

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Discussion Starter #9 (Edited)
I think imma start saving up for this bad boy.



http://www.precisionturbo.net/Street-and-Race/ss/600-800HP/details/Street-and-Race-Turbocharger---PT6765/241

Precision 6765
• 67mm inducer compressor wheel
- T4 Divided .84

Cant decide on weather I should get the
- "S" compressor cover 4.0" inlet/2.5" outlet or
- "H" compressor cover 4.0" inlet/3" outlet

It seems small, but its rated for 755HP.

My scat rods are only rated to 700HP, and the late roller block I will be using is only safe to 600.
So i'll be happy in the 400-550 range.
 
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