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Garrett GT25BB vs. Garrett GT28/71R 

15 replies to this topic

#1 DLRIUZ

  • Joined:20-August 05
  • Car:Widebody GT30/40 S15 previously ownedT78 powered 95 MKIV Supra, 97 S14A, 93 S13

Posted 20 January 2007 - 03:27 PM

i own a R32 GTST current mods are as followed:

RB20DET
powerfc
Z32 AFM
Hybrid FMIC
fuel pump
700cc sard injectors
sard FPR
Greddy cam gears
GT25BB
3.5 turbo back exhaust
hi flow cat
HD clutch
AVC-R running 16psi

i about to get a tune soon but i was contemplating swapping turbos for a GT28/71R to see if i'd get better response. Im aiming at about 220-230rwkw but without sacrificing too much response. Recently the car made 200RWKW on 15psi without the injectors, fpr, cams, hi flow cat. if any of you have used any of the two turbos listed can you please let me know the pros and cons and which is better for response.

if you dont have anything useful to say keep it to yourself.

Cheers

Brodie

#2 51CAZ

  • Joined:04-July 04
  • Location:Australia QLD
  • Car:180sx - FD3S S8

Posted 20 January 2007 - 03:53 PM

Hey man, I assume you mean the GT28bb? like from a jdm s15? Cos i've never heard of a t25 ball bearing turbo before...

From what I know the gt2871r is a step above the turbo I'm looking at the gt2860rs. The difference with the gt2860 and the standard gt28 is a faster spool time delivering more low end torque for a good responsive driving feel. With your engine and mods I reckon you would have only small gains compared to your current turbo (possibly 220ishrwkw), where as with the GT2871 i'd expect with cams and those size injectors you should pull about 240-250rwkw? With boost being evident at around 3700-4200rpm? Obvisouly with the right tune and ur PFC shuld be able to handle that easy enough.

I'd have a look into the larger exhaust housing on the GT2860RS the .86 housing as it is a little higher end pull than the smaller .64 but with little sacrifice for response. From what I know as well the GT2871r is the largest you would really want to go while minimising the lag you will get, even though the turbo is good for like over 450hp.

If anyone disagrees with me please post it constructivley.

#3 sinister

  • Joined:16-December 04
  • Location:Australia QLD
  • Car:180sx

Posted 20 January 2007 - 04:09 PM

The turbo on an S15 is not a GT28bb, it is a T28bb. There of course is GT25 turbos (all GT turbos are ball bearing), just check out the Garrett website. Also when you say standard GT28, I assume you mean T28. No model Silvia came with a GT turbo.

Now, I don't see why you'd want a GT25 for starters, it's not barely an upgrade from stock. I'd got the GT28RS or GT2871R or RS myself. With the mods you have I assume you are chasing some decent power, the 700cc injectors are a give away. If you are chasing the 250rwkw mark go the 2871R or RS. If you wish to sacrifice a little power but gain some response go the GT28RS.

#4 MidnightMods

  • Joined:19-December 03
  • Location:Australia VIC

Posted 20 January 2007 - 04:15 PM

Guys i belive he may mean this turbo

Garrett GT25BB 400hp ball bearing turbo

This unit has a T25 type base flange and GT25 type rear flange for the exhaust. Features a huge .70 comp cover with smooth machined bellmouth inlet and 4" inlet. This unit has a .64 exhaust housing in the 400hp form . The comp wheel actually flows 44 LBs/Min and itself is rated near 450hp. Usual ultra reliability and superb response from the Garrett ball bearing design. Sometimes called a GT25/40. Very similar to the HKS GT25/40 but with a different comp cover and different number of blades on the compressor. Great upgrade for SR20DETs and other 2 litre's.

How much power are you after?


The 2871r would be a better turbo.
As i have heard the GT25BB is a laggy turbo.

#5 51CAZ

  • Joined:04-July 04
  • Location:Australia QLD
  • Car:180sx - FD3S S8

Posted 20 January 2007 - 05:03 PM

Yea I meant T28 sorry, not GT28 as all the new Garrett turbo's are GT's now and yes BB.

But as far as a GT25...wow tuche...I learnt shit too ;)

#6 Spazo

  • Joined:27-September 06
  • Location:Australia NSW
  • Car:JDM S15

Posted 20 January 2007 - 05:38 PM

A friend of mine had a 25/40 fitted to his SR 180... I didn't actually drive it but apparently it was laggy and he couldn't really make use of it without forged internals. So... probably a little big, I'm going with the T2871R myself...

#7 ufoboy

  • Joined:05-July 06
  • Car:corona

Posted 20 January 2007 - 06:18 PM

i went to bels dyno day and put my car up fpr a run it has a gt2535 in it and has supporting mods the response of it was good and made 241.8kw there was another car that had similiar mods but had a gt 2871rs he made 243.8kw had a bit more power than me but my response showed on the graph was better than his

#8 salad

  • Joined:17-August 05
  • Location:Australia SA
  • Car:S8 FD RX-7

Posted 21 January 2007 - 12:26 AM

The GT25BB is the GT2540, or GT2876. 76mm compressor wheel driven by a GT25 turbine. Not the best combination...
The GT2871R has a 71mm compressor and is a much better match with the GT25 turine.

Can I ask why you went such big injectors?

#9 DLRIUZ

  • Joined:20-August 05
  • Car:Widebody GT30/40 S15 previously ownedT78 powered 95 MKIV Supra, 97 S14A, 93 S13

Posted 22 January 2007 - 02:23 PM

View Post51caz, on Jan 20 2007, 04:06 PM, said:

Hey man, I assume you mean the GT28bb? like from a jdm s15? Cos i've never heard of a t25 ball bearing turbo before...

From what I know the gt2871r is a step above the turbo I'm looking at the gt2860rs. The difference with the gt2860 and the standard gt28 is a faster spool time delivering more low end torque for a good responsive driving feel. With your engine and mods I reckon you would have only small gains compared to your current turbo (possibly 220ishrwkw), where as with the GT2871 i'd expect with cams and those size injectors you should pull about 240-250rwkw? With boost being evident at around 3700-4200rpm? Obvisouly with the right tune and ur PFC shuld be able to handle that easy enough.

I'd have a look into the larger exhaust housing on the GT2860RS the .86 housing as it is a little higher end pull than the smaller .64 but with little sacrifice for response. From what I know as well the GT2871r is the largest you would really want to go while minimising the lag you will get, even though the turbo is good for like over 450hp.

If anyone disagrees with me please post it constructivley.


View PostMidnightMods, on Jan 20 2007, 04:28 PM, said:

Guys i belive he may mean this turbo

Garrett GT25BB 400hp ball bearing turbo

This unit has a T25 type base flange and GT25 type rear flange for the exhaust. Features a huge .70 comp cover with smooth machined bellmouth inlet and 4" inlet. This unit has a .64 exhaust housing in the 400hp form . The comp wheel actually flows 44 LBs/Min and itself is rated near 450hp. Usual ultra reliability and superb response from the Garrett ball bearing design. Sometimes called a GT25/40. Very similar to the HKS GT25/40 but with a different comp cover and different number of blades on the compressor. Great upgrade for SR20DETs and other 2 litre's.

How much power are you after?


The 2871r would be a better turbo.
As i have heard the GT25BB is a laggy turbo.


View PostSpazo, on Jan 20 2007, 05:51 PM, said:

A friend of mine had a 25/40 fitted to his SR 180... I didn't actually drive it but apparently it was laggy and he couldn't really make use of it without forged internals. So... probably a little big, I'm going with the T2871R myself...


View Postsalad, on Jan 21 2007, 12:39 AM, said:

The GT25BB is the GT2540, or GT2876. 76mm compressor wheel driven by a GT25 turbine. Not the best combination...
The GT2871R has a 71mm compressor and is a much better match with the GT25 turine.

Can I ask why you went such big injectors?


well dude as the other guy said the JDM S15s use a T28BB, and the T25 and T25G's from CA18DET and SR20DET motors are bush bearing not ball bearing. also id find it hard to believe if you made 200rwkw out of the T25's. i was talking about a Garrett GT25BB like Midnightmods was referring to. it is rated around 400+hp.

Spazo that really doesnt help me as its on a SR20DET where as my post is about a RB20DET.

Salad, the reason for the big injectors the tuner was meant to arrive within 2weeks and needed injectors, the nismo 555cc units were going to be a 6week wait. the supplier told us as long as we have a good tuner which we do "sam cornell from Dr.Drift" the car should be alright.

the current turbo is a little laggy for what im after, hits full boost by about 4000rpm, looking for something to kick in about 400-500rpm earlier, hence why i was considering a GT28/71R.

#10 sinister

  • Joined:16-December 04
  • Location:Australia QLD
  • Car:180sx

Posted 22 January 2007 - 06:19 PM

Daniel drift007, Nismo 555cc 5 days from Japan :)

But that is too late now, whats done is done.

#11 MidnightMods

  • Joined:19-December 03
  • Location:Australia VIC

Posted 22 January 2007 - 07:09 PM

View Postsini69, on Jan 22 2007, 07:02 PM, said:

Daniel drift007, Nismo 555cc 5 days from Japan :)

But that is too late now, whats done is done.


pfft, 740cc injectors sitting next to me
next day;)

#12 sinister

  • Joined:16-December 04
  • Location:Australia QLD
  • Car:180sx

Posted 22 January 2007 - 08:02 PM

So many choices! Who would wait 6 weeks :)

#13 nismoman

  • Joined:19-May 06
  • Location:Australia NSW
  • Car:1992 Nissan S13 Silvia SR20DET

Posted 24 January 2007 - 08:47 AM

I think you will find it hard to get a turbo to spool and hit full boost before 3500-4000 rpm anyway on an RB20DET.

My brother installed a HKS GT2530 rated at 320ps on his R32 GTS-t which is considered to be one of the most responsive turbo's on the market for an RB20DET. It makes just over 221rwkw's @ 18psi but it doesn't hit full boost until 4000rpm.

RB20DET's are renown for their lack lustre response down low.
You did say you have installed cam gears, but have you installed cams?
This will provide the biggest help to improving your mid-range response and should provide more power sooner.

I recommend putting some aftermarket cams in then do another tune and see how you go before changing turbo's. I'm thinking your GT25 will still be good and deliver the response and power you want witht the cams.

#14 discopotato03

  • Joined:23-January 07
  • Car:R33GTS25T

Posted 24 January 2007 - 10:17 AM

My 3c worth .

Any GT2540R/GT2876R leaves a lot to be desired , way too much compressor for the poor little GT28 NS111 turbine . Garrett's one uses a dinosaur mid 70's tech 76mm 7/14 blade 48 trim TO4S compressor , HKS's a 76mm 6/12 blade 46 trim TO4E compressor . You could say the HKS variation is only a bit less hopeless that Garretts effort but anyway both of them have been passed over by better things .

RB20's are not very torquey mainly because of their small 330 odd cc pots . They need things like responsive turbos and good mild cams to get them going . RB20's will suffer compressor surge if you go big on the compressor side and small on the turbine housing side in an effort to get early boost rise .

Things that do work are GT2530's , GCG's BB Hi Flow and depending on how much lag you can live with maybe the RB specific GT-RS . If you can get access to a HKS exhaust housing any GT28BB based turbo will bolt up to your std exhaust manifold .

Budget and determination , cheers A .

#15 DLRIUZ

  • Joined:20-August 05
  • Car:Widebody GT30/40 S15 previously ownedT78 powered 95 MKIV Supra, 97 S14A, 93 S13

Posted 30 January 2007 - 09:37 PM

View Postnismoman, on Jan 24 2007, 09:00 AM, said:

I think you will find it hard to get a turbo to spool and hit full boost before 3500-4000 rpm anyway on an RB20DET.

My brother installed a HKS GT2530 rated at 320ps on his R32 GTS-t which is considered to be one of the most responsive turbo's on the market for an RB20DET. It makes just over 221rwkw's @ 18psi but it doesn't hit full boost until 4000rpm.

RB20DET's are renown for their lack lustre response down low.
You did say you have installed cam gears, but have you installed cams?
This will provide the biggest help to improving your mid-range response and should provide more power sooner.

I recommend putting some aftermarket cams in then do another tune and see how you go before changing turbo's. I'm thinking your GT25 will still be good and deliver the response and power you want witht the cams.

we did fit cam gears and have noticed abit more response without touching them. have done some research and ppl say adjustable cam gears can change the response up to 1000rpm difference.

#16 discopotato03

  • Joined:23-January 07
  • Car:R33GTS25T

Posted 31 January 2007 - 07:38 AM

Thats going to depend on how far away the cams are from optimal and how bad to start with . If they are spot on or very close you won't see a huge improvement .

Cheers A .





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