GT25R and GT28R info

[mgbond]

Found this site that had some good info.

I'm after the GT25R and it looks like there are two kinds:

Looks like I need the GT2560 as I'm sure I herd this from someone. An interesting note is there are two types of this turbo, one that comes with Inconel parts for higher temp applications. I wonder which one people used?

http://turbochargerspecs.blogspot.co.uk/2011/03/ga...

http://turbochargerspecs.blogspot.co.uk/2011/03/ga...


GT28RS

http://turbochargerspecs.blogspot.co.uk/search/lab...

Edited by mgbond on Monday 25th November 16:59

[mgbond]

I went on Garret's site and found this page that explains how to work out correct turbo for application.

http://www.turbobygarrett.com/turbobygarrett/turbo...

While assuming I want 225bhp from each turbo and assuming engine capacity is 1.25ltr per bank the a GT25R is no where near the right turbo.

Must be doing something wrong?

[Ant1984]

No idea if it is any help but when i had a GT4, the GT28rs i.e. Disco potato used to be touted to produce max of 340-350bhp with super fast spool. That was obviously in a 2ltr application though at approx 1.3bar.

[Mike Tuckwood]

Just read the compressor maps, they will give you the best indication of how each seperate Turbo is likely to perform.


Mike.

[mgbond]

Was I right by using 225 BHP and 1.25ltr engine. So basically combined I'll get 450bhp.

Based on this the point at 7200rpm is way outside the turbo map?

[mgbond]

Ant1984 said:

No idea if it is any help but when i had a GT4, the GT28rs i.e. Disco potato used to be touted to produce max of 340-350bhp with super fast spool. That was obviously in a 2ltr application though at approx 1.3bar.

The Spud is best used from 2.0ltr to 3.0ltr and the GT25R is 1.8-2.5. Only confusing bit is as we have one on each bank it's only 1.25 or 1.5 respectively so basically the wrong turbos. But that's what we all use with no issues?

Maybe in a TT application the formulars are different?

[mgbond]

I have found the GT25R60's the higher temp version for £675ea + Vat. Sounds good to me.

The only issue I see is that the compressor inlet and outlets are flanged when the std turbos you push pipe work on.
So some adaptors would be needed.

I would be interested to know if any has the GT25R's that they can see is they have an adaptor on them?

Maybe post a pic?

Cheers

[jdearden]

Mine have a adapter. Only issue is the cross member removable chassis rail won't fit back. Mine is wedged in place at the moment until I move the bracket

[jdearden]

Mine have a adapter. Only issue is the cross member removable chassis rail won't fit back. Mine is wedged in place at the moment until I move the bracket

[mgbond]

jdearden said:

Mine have a adapter. Only issue is the cross member removable chassis rail won't fit back. Mine is wedged in place at the moment until I move the bracket

Cheers James, is that an adaptor for air filter pipe work going in to turbo and an adaptor coming out to IC.

Can u pop up a pic at some point.

[paulspray]

Do all the said turbos have Alu rather than Ti compressor wheels ?

[Mike Tuckwood]

mgbond said:

Was I right by using 225 BHP and 1.25ltr engine. So basically combined I'll get 450bhp.

Based on this the point at 7200rpm is way outside the turbo map?

The compressor map will give an indication as to the amount of air it "may" flow in ideal circumstances. The earlier you hit peak HP, on whichever Turbo fitted, the sooner the power will tail off with rpm. If pushed to the limits of the Turbo, peak power trace on a dyno will very closely follow the indications from the compressor map.

Mine did exactly what would be expected of it based on the stock Turbo's compressor map. It tailed off from 6000 rpm (427bhp) to 6500rpm (380bhp). Competely stock 3R apart from slightly stronger actuators.

This directly tallied up with what could be expected based on the factory fitted Turbo compressor map, despite others suggesting the tail off was related to the so called "exhaust pipe bend restriction".


Mike.

[mgbond]

Mike Tuckwood said:

The compressor map will give an indication as to the amount of air it "may" flow in ideal circumstances. The earlier you hit peak HP, on whichever Turbo fitted, the sooner the power will tail off with rpm. If pushed to the limits of the Turbo, peak power trace on a dyno will very closely follow the indications from the compressor map.

Mine did exactly what would be expected of it based on the stock Turbo's compressor map. It tailed off from 6000 rpm (427bhp) to 6500rpm (380bhp). Competely stock 3R apart from slightly stronger actuators.

This directly tallied up with what could be expected based on the factory fitted Turbo compressor map, despite others suggesting the tail off was related to the so called "exhaust pipe bend restriction".


Mike.

Mike,

Not sure if that was answering my question? But the GT25R works on the 2.5 and 3 quite well. But according to the calculations it doesn't?

Have u fitted GT25Rs? The experts I spoke to today said if it works use it?

This is the GT25R60 map. By my calcs. Ratio is around 2.7 and flow is around 37 so as u can see it way out. At 3.5k rpm the flow is around 15 so still way out?




Maybe the GTX28R60 is a better choice?

Edited by mgbond on Tuesday 26th November 20:18

Edited by mgbond on Tuesday 26th November 20:34

[paulspray]

Mr Bond, so you need to run 1.7 bar boost ?

[Mike Tuckwood]

mgbond said:

Mike,

Not sure if that was answering my question? But the GT25R works on the 2.5 and 3 quite well. But according to the calculations it doesn't?

I'd suggest that the GT2554R in your first link at the top is the best suited for the performance suggested. (IMHO)
They should clear with ease 500BHP and should spool up quickly too. All of the other larger ones you've listed will have worse spool and you don't appear to want to be chasing crazy numbers?

The GT2860R's that you posted last, as a pair can move enough air to support + of 800BHP.

mgbond said:

Have u fitted GT25Rs? The experts I spoke to today said if it works use it?

No, I've gone for some hybridised GT28R's of my own spec for my own car.


Mike.

[mgbond]

paulspray said:

Mr Bond, so you need to run 1.7 bar boost ?

Not sure what you mean. According to the calcs I would need to run 1.4 bar to get 450 or 225 from each turbo being fed by 1.25 ltrs.

Again I know James on GT25R60s is getting just over 400 on 0.9bar (I think) and I 'm sure Steve on his 2.5 with GT28R60's gets 450 from 1.2 bar.

It's just concerns me that I know the GT25R's are the right ones to use but at the moments the maths doesn't convince me?

[paulspray]

But the y axis is boost, ie a ratio of 1:1 is zero boost, a ratio of 2.7 is 1.7 bar boost.

[paulspray]

Ie the ratio of the pressure at the inlet of the compressor and the pressure at the outlet the compressor the pressure at the inlet being very near to atmospheric 1013mb or approx 1bar

[mgbond]

paulspray said:

But the y axis is boost, ie a ratio of 1:1 is zero boost, a ratio of 2.7 is 1.7 bar boost.

Yeah I was just looking at this. Need to check what I did to get 2.7

In simple terms it psia 14.7+ boost (14.7) / (14.7 - 1 ( the -1 is losses, can't be arsed to look the reason up right now)

So 2.14. I'll check it out tomorrow. But even so the flow rate of 37 puts it outside. But I think I used to get max power at about 6200. Think I used 6750 in my calc. Oops so this might make it all fall in place.

Mike, I'm not chasing more than 450 in the 2.5 but one day I hope to drop a 3.0 in but still will only go to 500-550 due to 5 Spd.

Edited by mgbond on Tuesday 26th November 21:39

Edited by mgbond on Tuesday 26th November 21:42

[mgbond]

paulspray said:

But the y axis is boost, ie a ratio of 1:1 is zero boost, a ratio of 2.7 is 1.7 bar boost.

That's the simple way to look at it. Look at the second link I posted. There are a couple of formulas and to get 225bhp from a 1.25ltr at 7000 rpm and intake temps at 100F it all adds up to needing 1.77 bar?