when upgrading a t25 into a T28, for any decent power gains, you have to increase the flow of the hot side as well. Otherwise it will over spin and overheat, acting as a exhaust plug as you max it out trying to squeeze out the theoric power gains of that big compressor wheel.

most t25 turbine wheels are too small for any decent power but the largest T28 turbine wheel is similarly sized as a T3 stage1 and when using that wheel with at least .64 a/r, you can take full advantage of any larger compressor such as gt2860R 55 trim which is larger than t3 60 trim and good for up to 310 HP.

The problem with upgrading a T25 with both a larger turbine AND compressor side is the price: new t28 wheels and shafts and the workmanship to put them in can get costly.

 

i donno its supposed to be a bigger turbine wheel to, i think from the 60 trim T3 as well but i am getting 1k rpm more lag than b4 so i am pretty sure its a decent size bigger. The guy at Gpop said it should be increadibly similar to the Gt28 minus the little better spool you get with the BB turbo. Are you familiar with the Garrett big T28 it is not modified by the shop it is sent from garrett as a big T28 what kind of power gain would u expect between this turbo and the much smaller T25 Blaast?

 

Garrett don'T sell T25 and T28 anymore. they switched to the GT series. Even individual T25/T28 parts are for the most part discontinued at garrett. if you want a non BB turbo, you have to resort using the GT20 and GT22 series.
Ok I just checked and the nice turbine wheel to have on a T28 measures 1.85" X 2.12"
it compares to T3 stage 1 whcih is 1.93" X 2.56"
The wheel used on most recent gt25R and gt28R is 1.8" x 2.12" as well so it'S true that if you have that turbine wheel, you can make similar power than the GT's, even ithout the BB's, provided you use an equivalent sized compressor side, spool up difference due to the ballbearings is really not that bad and mostly not justificative of the twice higher price tag.

 

yeah thats why i was surprised with the small gain i saw over the T25 as my compressor and turbine are both much bigger. Its a 60 trim t3 compressor and turbine wheel from what i was told.

 

If you want t28-sized turbos, go look at MHI turbos. A big16g has a hotside like a small T3, but can do 350-400whp with the right motor.

The T28 is good for making more torque when it spools, but you're stll limited to the power the turbine can offer. Flow = power, both for intake AND exhaust.

 

I wouldn't take a big 16G past ~350 whp across 2WD drivetrain loss, 300 whp AWD. They flow more, but it overspins them and break shafts like no other make of turbo I have ever seen.

Nothing spools like a big 16G, though. Hitchhikkr had one on his 94 LS, ported turbine and O2 housing, the ****** would sling 10 psi at 1000 rpms. It was insane, and the car was HUGELY driveable.

 

God I wish I hadnt sold that car. It was the best daily ive ever had.

 

Rob, go to my Sweet Vid thread in GD. That is Mister Payne's youtube account, he has a couple videos of your LS.