planing on t4 turbo need input

[95'RS-T]

ok so im going to pick up a Air Research t4 turbo with a 60/AR cold side and 152/AR exhaust side and was wondering if this would fit in place of my old t3/t4 eBay turbo and also what you guys think about it. thanks

 

[JusMX141]

152 a/r T4 turbine housing? Are you planning on spinning the engine to 15,000 rpms?

 

[95'RS-T]

no i have not clue if that's even right that's just what the dude wrote that's selling the turbo i was thinking maybe like .63AR or something but i do wanna run low boost like 8psi

 

[JusMX141]

Rule #1 in turbocharging.....pick a turbo based on airflow potential at your boost level- NOT it's size.

If you put something on your stockish engine with a T4 flange and a 152 a/r turbine housing, it will never hit boost no matter what level you plan on running because of the enormous volumetric efficiency required to fill a turbine housing that huge let alone spin the turbine enough to generate boost. That turbo is designed to be run on a diesel engine with 7 liters of displacement and a 18.0:1 + compression ratio.

At 8psi a T25 will "feel" faster than your eBay T3 because it will spool quicker, and the boost level is more in it's compressor efficiency range. Just as you wouldn't pick a huge turbo and run low boost, you shouldn't pick a small turbo and run huge boost.

The biggest mistake made when purchasing a turbocharger is "it's bigger, so it must be better!" Totally untrue. Even when talking about two equally-spec'd turbos, one having a larger compressor wheel than the other- if you're not set up to take advantage of the added airflow, about the only thing you're going to gain is lag. This is the reason a 16G is the most popular upgrade turbo for a DSM....most of the cars on the road can't take advantage of any additional airflow over what a 16G can provide.

To further prove this, two seasons ago my buddy went from a TD05H 20G (TD05H turbine, 20G compressor) to a Frank Level 5 20G (TD06H turbine, Garrett 60-trim compressor) on his '95 TSi AWD. At 20psi, the airflow between the two turbos was nearly identical....but the Frank 5 spooled 400 rpms later. At 25psi, it's a completely different story. The TD05H 20G is now out of juice, and the Frank 5 is just beginning to shine.

 

[95'RS-T]

right i understand so this maybe be a really really stupid question but do you think that i could use my ebay turbine and compresser housing with the internals of this t4 turbo?

 

[JusMX141]

Not without extensive machine work....probably enough to take the turbo out of the "good deal" category.

 

[95'RS-T]

ok thanks guys