Jay Wellwood

Just curious you're impressions and results if you do.

refresh951

GT25 is a very small turbo, 240 max HP. I cannot recall any one using a GT25. Did you mean GT35?

alxdgr8

+1, I don't think a GT25 would be any upgrade over a 26/6.
I ran a GT28R (which I belive they have basically renamed the GT25R) on a 1.9L SOHC engine and that spooled very nicely. I think you'd definitely be getting choked with a 2.5L

Dave W.

ATP has a turbine housing with a T25 flange that will accept GT28 through GT35 turbos. The GT25 bolt pattern is very close to the stock K26 bolt pattern, just file the mounting holes a little bigger.
http://www.atpturbo.com/mm5/merchant...egory_Code=GTH

Adonay

I always wondered how a gt28 would spool on our engines . If i had 2 cars i would try it but i dont and doubt i could live happyli with it.

Paulyy

The GT2560R (largest) would be similar size to a k26 compressor or just smaller.
and the way the garretts spool, it'll just choke

Jay Wellwood

Thanks for the candid feedback guys.

Dougs951S

A big GT28/30 hybrid might be interesting. A GT2871 or a GT2876 would probably spool like stock or even better and would definitely support more power than a k26.

Thom

Except that Garrett found fit to associate the larger GT30 turbine to both the 71 and 76mm compressors in the forms of the GT3071R and GT3076R.
In some cases a larger turbine is needed to spin accordingly a compressor, in addition to giving more room regarding back pressure.

There will be cases where the turbine wheel will be small enough not to spin the compressor in its best working range - typical case being the GTX3076R, often considered as a mismatch. The GTX3576R that uses the same compressor works much better, in my experience, though results may vary from a car to another depending on the rest of the set up.

Dougs951S

Interesting info Thom, thanks for the response. I've always thought it strange too how many crazy configurations garrett will allow you to order. Things like a GT3088 or a GT2882 (the latter is not available from garrett but is from other vendors) I could never imagine would sort of application would require such mismatched turbos.

If I wasnt trying to make a lot of power and just wanted a really nice powerband, I'd probably try a 3071.

Thom

Yes, the GT3082R is another example of a big mismatch yet it seems to give good results on some EVOs... Go figure.

Garrett now seem to be recycling some of their classic journal bearing T4 turbos with new billet compressors - the new GTW range. The GTW3476 in particular should perform pretty well on a 3L engine.

Dave W.

IMHO the compressor/turbine size can be tailored to suit the boost pressure and overall airflow goals. On these cars we tend to run low boost while making good power with larger displacement. For our needs a larger turbine wheel works better. For a small displacement engine that can run high boost levels, such as a DSM or EVO, the small turbine/big compressor works better.
to a certain degree.
BTW I'm still enjoying the PTE 5558 on my 2.85L engine.

Thom

I agree. The head flow/engine capacity ratio on our 8V engines is pretty poor by todays' standards and a "large" turbine with a "medium/small" compressor should give the "best" results.

Some interesting notes here on turbine efficiency.
Basically it tells us that a GTX3071R will perform "more efficiently" (spool earlier) than a GT3076R while providing the same output.
Following the same logic we can deduce that a GTX3576R should perform "more efficiently" than a GT3582R while providing the same output.

Dougs951S

I'd agree with this, but how much later will the GTX3576 spool vs a GTX3076 and will it make significantly more power since its a "more efficient" combo?

Thom

Well, I can only share my experience on my 3l 8V, but the GTX3576R 0.82 flows more than the GTX3076R 1.06 by the time it comes into boost, and if it reaches my desired peak boost perhaps 300rpm later the engine makes more torque in any load situation than with the GTX3076R - with a short runner intake. I wouldn't bother with a GT35-sized turbo with the stock intake. This 76mm compressor felt just wrong with the GT30 turbine, though it did not become really obvious before trying out the GTX3576R.
The GTX3576R takes a very brief longer time to spin by the time the engine is at 0 bar of boost but once the turbine begins to be "cranked" it spools much harder than the GTX3076R. It reflects in my wg duty cycle table. The higher flow is also shown by the fact I had to chop down the ignition map by several degrees anywhere above 0 bar. The engine was knocking pretty bad with the settings of the smaller turbo.