Garrett T25's In R32 Gt-R

[Samuel Leonard]

i have two rebuilt (nov 2004) Garrett T25 CHRA's with steel turbine wheels and 360 degree thrust bearings.

I am a first year apprentice mechanic and just wondering what these things mean.

few qestions specifically.

T25's is this the turbo size? or can a t25 turbo come in different sizes?

also, CHRA. what exactly does this mean? just water cooled and oil fed?

what does a thrust bearing do? is it just the turbo's main bearing?

the reason i'm asking all this is i'm thinking of removing the boost restrictor in the vacuum line to the pcm valve

and wanting to know if these turbo's (rebuilt that long ago) will hold up.

thanks in advance, Sam.

[BrynDETT]

maybe im a complete idiot, but didnt gtr's only come with t28's?

and im pretty sure all t25's were steel wheel? they were used on silvias, only skylines got the ceramic curse...

Edited January 8, 2011 by BrynDETT

[R31Nismoid]

T25 is the frame/cartridge.

However T25's, given they are bush bearing, could come with any wheel combo as far as I am aware.

These days ball bearing CHRA's come set with the wheels etc.

Either way the turbos are journal/bush bearing, so basically similar to a stock R32 GTR turbo, but a smaller frame.

So who knows if they will/wont. Without full specs, it's anyone's guess.

Don't expect them to perform well however, i'd be doubtful of them giving remotely similar results of the GT28 series in both power output and response.

[GTScotT]

CHRA means something like cartridge housing rotating assembly. It hasnt got anything to do with being oil or water cooled.

T25 is a 'loose' term for the type of turbo in question.. They are infact a GT25 of some form, the exact part number for a R32 GTR evades me..

As for having them rebuilt with steel turbines and a 360 degree thrust bearing, this should make them good for 20psi (as a rough figure). How much boost they actually make power too is anyones guess as they have been rebuilt and we do not know the exact specs. The same goes for how long they will last.. They could potentially have been rebuilt shit and die on you prematurely.

[Samuel Leonard]

CHRA means something like cartridge housing rotating assembly. It hasnt got anything to do with being oil or water cooled.

T25 is a 'loose' term for the type of turbo in question.. They are infact a GT25 of some form, the exact part number for a R32 GTR evades me..

As for having them rebuilt with steel turbines and a 360 degree thrust bearing, this should make them good for 20psi (as a rough figure). How much boost they actually make power too is anyones guess as they have been rebuilt and we do not know the exact specs. The same goes for how long they will last.. They could potentially have been rebuilt shit and die on you prematurely.

they were rebuilt by Advanced Turbo Performance. i shouldn't say rebuilt because it just says in the labour on the receipt "Strip, clean and quote. Build CHRA's. Blast, paint and assemble."

built on the 25th of nov 04. how long do turbo's last? am i stupid to remove the R32 GTR's factory boost restriction? will these exhaust wheels hold up compared to the standard t28's which i have heard will stuff the exhaust wheel and bearings down the exhaust?

and what's the reason for changing to t25's from t28's? i would've thought t28's are better?

Edited January 9, 2011 by Samuel Leonard

[StealthX]

T28s are bigger and would make more power, but with the trade off or more lag, but in a GTR sense, the difference in lag is negligible.

I wouldn't be putting t25s on a GTR, you'll be downgrading, and will end up with less power.

Turbos "lasting" is generally up to a few things, boost, oil supply and general treatment. If you keep them at stock or close boost levels, keep the oil supply clean and uniform, and dont rape the car when cold and give it a good cool down, the turbos will last almost indefinitely. But if you dont do any of those things, expect a shorter life. It's a bit hit and miss to run the stock turbos at above 12-14psi, but if you take out the restricter, and use the stock boost control, they should be fine. It's a common misconception that the GTR turbos can run more than 14psi safely, because some people think along the lines of: "two turbos = 7psi each for 14psi total", this is wrong, both turbos are spinning the same amount to build up 14psi, as a single would.

If the turbos are rebuilt using steel wheels as you say, then you could put them on, and set boost to say, 15-20psi , some nice flowing exhaust(s) and make more than stock power, but anything more than 450hp is probably pushing the boundaries of the efficiency range of the turbos.

[Samuel Leonard]

T28s are bigger and would make more power, but with the trade off or more lag, but in a GTR sense, the difference in lag is negligible.

I wouldn't be putting t25s on a GTR, you'll be downgrading, and will end up with less power.

Turbos "lasting" is generally up to a few things, boost, oil supply and general treatment. If you keep them at stock or close boost levels, keep the oil supply clean and uniform, and dont rape the car when cold and give it a good cool down, the turbos will last almost indefinitely. But if you dont do any of those things, expect a shorter life. It's a bit hit and miss to run the stock turbos at above 12-14psi, but if you take out the restricter, and use the stock boost control, they should be fine. It's a common misconception that the GTR turbos can run more than 14psi safely, because some people think along the lines of: "two turbos = 7psi each for 14psi total", this is wrong, both turbos are spinning the same amount to build up 14psi, as a single would.

If the turbos are rebuilt using steel wheels as you say, then you could put them on, and set boost to say, 15-20psi , some nice flowing exhaust(s) and make more than stock power, but anything more than 450hp is probably pushing the boundaries of the efficiency range of the turbos.

i'm not considering t25's the previous owner had this done. would it be cheaper than t28's? the receipt reads $2600 total for everything.

[Samuel Leonard]

could they be the standard t28's rebuilt with steel t25 wheels? i'd love to understand more about turbo's. i'm trying so hard!

[R32 TT]

i'm not considering t25's the previous owner had this done. would it be cheaper than t28's? the receipt reads $2600 total for everything.

Hi Sam, mate to learn a little more about all this stuff try this page:

http://www.turbobygarrett.com/turbobygarrett/tech_center/gt_basics.html

And indeed the rest of that site has some good info on it that might help you out.

Notice also on that page that at some stage (about 4-5 years ago from memory) Garrett changed the way they classified some turbos from T28 to T25.

For example the turbo's that I run are often called -5's (or dash 5's) by people on here.. it is short hand for their part number which is 707160-5. The actual turbo 'family' has been referred to both as GT-2860R AND GT-2560R. Mine have GT-2560R written on them.

I am not a full bottle on this - so can't be sure this applies to your turbos and I don't want to give you wrong info - but something to keep in mind while doing your research. Isn't it great when manufacturers changes things along the way??

Hope the link above sheds some light on things for you.