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im kinda a newbie at turbocharging, but i looked at some other posts and found out everything you would need for a custom turbo kit, and i saw that hks makes a turbo exhaust manifold for our cars now with a T25 housing, so they say it can be combined with almost any of their T25 turbochargers, now on their site i see five different turbo chargers with a T25 housing and to be quite honest i have no idea whats the difference between them, i see there are different ps outputs and some other differences, but i dont know what that means, if anyone could tell me the pros and cons or something about the five turbochargers they make with the T25 housing that'd be awesome, right now just guessing i'd guess they are bigger and smaller turbochargers, some making higher horsepower numbers but with the higher numbers greater turbo lag, so any information would be great cause then i would be able to choose which turbocharger is right for the custom kit i want to make and then i can start purchasing things, think you all in advance who will reply to this

 
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Well lets take 2 and compare

HKS GT2540R - 360/370 PS Output

COMPRESSOR:
-Wheel- 46 Trim - 51.7 Inducer / 76.2 Major
-Housing- 60 Inlet / 50 Outlet - 0.50 A/R
TURBINE:
-Wheel- 76 Trim - 53.8 Major / 47.0 Exducer
-Housing- GT25 inlet / Internal GT25 oulet - 0.64, 0.86 A/R




and


GT2835R Turbo
HKS GT2835R - 420 PS Output

COMPRESSOR:
-Wheel- 56 Trim - 53.1 Inducer / 71.1 Major
-Housing- 100 Inlet / 50 Outlet - 0.50 A/R
TURBINE:
-Wheel- 90 Trim - 56.5 Major / 53.6 Exducer
-Housing- GT25 inlet / Outlet spec:
Internal GT28 90 Trim; 0.86 A/R
External GT30; 0.61, 0.73, 0.87, 1.01, 1.12 A/R


The difference in PS (i'm assuming) is HP. But there are other differences. Here's some info taken from Honda-Tech and FSS regarding GARRETT turbos that can help you understand what some of these numbers mean.

"Turbo 101 - some info about GARRETT turbos"

Disclaimer: All of the following is correct to my knowledge. Please feel free to jump in and correct anything that is wrong or feel free to add anything. This post is pretty long, but hopefully it will help out some newbies that are getting into turbochargers.
There seems to be some confusion about there about what all of the numbers mean when looking at a turbochargers specs. Awhile back, BlueShadow wrote an excellent post on how to read a compressor map. Find that post, read it, and combine it with this one...voila, you'r a guru! (not really)

Garrett makes several "families" of turbochargers that are targeted for different sized engines, HP goals, and drivability characteristics. Crafty tuners, manufacturers, etc, have mixed and matched these components to produce hybrid turbos that can provide the benefits of several turbo families. The possibilities really are endless, but I'm just gonna list some common ones or else this post would be reeeeeeallly long.

Turbocharger families
The T25 family = super fast spooling "small" turbo that makes good low rpm torque, but lacks top end power. This turbocharger is commonly used where throttle response and low rpm torque are desired without much regard to high rpm power.

The T3 family = "intermediate turbo" that spools slower, but has the ability to make substantially more power than the T25 family. This turbocharger has been used on A LOT of production vehicles (Ford, Nissan, Volvo, Saab). They can make impressive power, but were known to be laggy.

The T04 family = "big turbo" that makes huge power, but is very very laggy. Without the beauty of being able to make a hybrid turbo, a T04 would probably not even be an option.

The 3 main components that have the biggest impact on performance are the a/r of the turbine housing, the size (aka trim) of the tubine wheel, and the size (aka trim) of the compressor housing.

Common turbine housing a/r "sizes"
T25: .64 a/r, .86 a/r
T3: .36 a/r, .48 a/r, .63 a/r, .82 a/r
T4: not listed...see why later

(CivicRyda2K's addition)
Common compressor housing a/r "sizes"
T3: .42 a/r, .50 a/r, .60 a/r, .82 a/r
T4: .50 a/r, .60 a/r, .70 a/r


In a nutshell, the larger the a/r, the later the power comes. A small a/r gives you a fast spooling turbo but limits top-end power. A large a/r gives you a laggy turbo with big top-end power.

Common T25 turbines:
DSM trim (?? not sure how big it is, but it's quite small)
60 trim (small)
76 trim (medium)

Common T3 turbines:
Stage 1 (small -- most common turbine on junkyard turbos)
Stage 2 (med)
Stage 3 (large -- most common turbine on new T3/T04 hybrids)
Stage 5 (very large)

Common T04 turbines:
I'm not gonna list any because I don't have info on them and the T4 turbines require so much exhaust energy to spin that they are practically unusable in our application unless you want insane lag and have got a motor that will spin to 10k every day.

Common T25 compressors:
I'm not gonna list any. I do have some info on them, but for the most part, a T25 compressor will struggle to stay in its efficiency range on a boosted Honda.

Common T3 compressors:
40 trim (20lb/min -- haha...don't even think about it)
45 trim (21lb/min)
50 trim (30lb/min -- probably one of the most common on junkyard turbos, works well for SOHC and LS engines)
60 trim (34lb/min -- biggest "production" T3 compressor, excellent power on D series/LS) <=== my old turbo
"Super 60" (36lb/min -- note: this is NOT the "60-1" compressor)

Common T04B compressors:
S trim (37 lb/min)
V trim (48 lb/min)
H trim (49 lb/min)

Common T04E compressors:
40 trim (36 lbs/min)
46 trim (41 lbs/min) <=== my new turbo
50 trim (47 lbs/min)
54 trim (45 lbs/min -- note that the 54 trim flows less than the 50 trim)
57 trim (49 lbs/min)
60 trim (50 lbs/min)

Common T04S compressors:
60-1 (flows a shitload, never seen a compressor map for it)
62-1 (bigger yet -- I believe this is a T04S compressor...correct this if it is wrong)


Performance (listed in order of increasing performance):
A T25 is a straight T25 turbo --> T25 turbine + T25 compressor
A T28 is a hybrid T25/T3 turbo --> T25 turbine + T3 compressor
A T3 is a straight T3 turbo --> T3 turbine + T3 compressor
A T3/T04B is a T3/T04B hybrid turbo --> T3 turbine + T04B compressor (used in Drag kits)
A T3/T04E is a T3/T04E hybrid turbo --> T3 turbine + T04E compressor (more performance than T3/T04B
A T3/60-1 is a T3/T04S hybrid turbo --> T3 turbine + T04S (60-1) compressor


Credit goes to Sonny and CivicRyda2k from Honda-Tech

 
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DSM's are 48 trim yeah its mad small i know. Don't laugh!

 
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They didnt mention that the smaller the exhaust trim, the faster the spoolup. If you have a super 60 with a .63 exhaust and one with a .48 exhaust, the one with the smaller exhaust housing will spoolup substantially quicker.

 
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Yeah...they kinda did:

It (the smaller one) will spool up quicker, but will also have been maxed out more quickly at top end. This is why the TT Supra's come w/2 turbos. One smaller for lower end and one larger for top end. The lag of a turbo that isn't exactly the smallest can be easily recovered w/a little n2o.

Guess it all depends on how much power you want to / plan to make. Some turbos will not hold as much power as others. But for a basic setup on a D17 where you most likely wont be boosting much. A T25 is just fine.

 
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im have a T25 design...i want more torque, just because i dont do a lot of drag racing and like being zippy out of turns and what not...what our civics like to do best. Plus im not trying to hit 300whp, just 200whp or less...something thats smooth but still whoops *** on other cars

 
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I would suggest something slighty larger than a T-25 like a small T3 because T-25 is easily maxed out and you'll want something bigger once you get working on it. not to mention it just doesn't have enough punch in the high end boost really starts to drop off over 5500 RPM.

 
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A T-28 would even be better pretty much the same spool as a T-25, is flanged the same but is capable of 60-70 more horse power that a T-25.

 
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I have a GT25BB on my car, spools fast as hell and according to Garrett it supports 325+ HP.

 
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A T3/T04B is a T3/T04B hybrid turbo --> T3 turbine + T04B compressor (used in Drag kits)

This is the turbo that is coming on my custom kit. Does anyone have experience with this size on our cars?

 
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GT series turbo's are a completly different story if you put a GT25 next to a normal T-25 its almost 1.5 times as big

 
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^hmm my turbo looks pretty small to me

 
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It may look small to you but if you have ever seen a normal T-25 its tiny like i am ashamed to have one

 
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ok so basically everyones sayin dont waste time on a T25 and if im lookin for a small turbo go for a T28 because it has more potential? my question is if it will fit the T25 housing though and just have the T3 turbine or compressor itself? the thing i was worried about is that the turbo header said it will fit any T25 so im not sure if the T28 will match up but be bigger in some area sorry im not the brightest in this area

 
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I believe it will fit. Please see the "TURBO 101" sticky thread i posted at the top of this forum. It should have all the info u need.

 
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it should fit up perfectly....its just a t25 with a T3 turbine

 
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yeah a its just a T-25 housing with a bigger wheel inside so it will bolt up no problems

 
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thanks for all the help everyone