Is this too big or what?

Let's say... for a Civic... :confused:

http://cgi.ebay.com/ebaymotors/ws/ebayISAPI.dll?ViewItem&item=1823558827&r=0&t=0
GT25R Roller Bearing Turbo (400 hp)
T04S Compressor (48 Trim) .70 A/R
T28 Turbine housing (76 Trim)
44 lbs / min (Includes Internal Wastegate)

Damn! Ball bearing turbos do cost a lot! :eek:

yes... waaaay too big for a civic. lemme break it down:

the GT25 series turbo is a T2 series center section and T2 series turbine. this is designed for small displacement motors.

the T04S compressor side features a .70 A/R ratio housing... this is a LOT of flow. about 550cfm of air rushing thru at max load. it should be stable up to 20psi, considering the T2 turbine combination.

the 76 trim exhaust i dont fully understand, as Garrett turbines are usually classified by stages, i.e. stage 1, stage 2... etc. i'll assume it's a .76 A/R ratio turbine housing with a stage 2 trim and an undivided tang. (normal config for T2 series)

the .76 ratio turbine housing would have no backpressure whatsoever... but that means most of your exhaust energy will flow through it with little resistance to make the turbine spin. this will create enourmous amounts of lag... especially with an S trim compressor and 46 trim wheel.

to give you an idea, the T04S housing features a 4" inlet, 2.5 inch outlet, 3" diameter compressor wheel major with a 2.75" compressor wheel minor. this is HUGE. more than enough to cause resistance to spin quickly, and add the low resistance turbine housing, and you'll reach 8 psi of boost at redline due to lag.


your best combination for quick spool up, optimal compressor flow, minimal backpressure, and thermal efficency during compression would be a T04B with a T3 center section and Stage 1 turbine. the compressor A/R should be .60 A/R and the exhaust should be .48 A/R, but no larger than .63 A/R this will create a turbine that will spool up to your desired boost before 3000rpm, and create a pressurised charge of air with enough volume without overly increasing the air temperature. it will be good for 20psi, and support over 450hp.

even a full T3 .60 A/R compressor with a T3 stage 1 turbine and .48 A/R ratio housing would be more than enough to produce VERY responsive low end performance, very good top end flow, and probably outdo anyone with a T3/T04B hybrid setup or larger due to faster spoolup and still be efficient enough with intercooling to take them at the end of the 1/4 mile. the best combo is to get the smallest turbo you can that works with your setup for better efficiency. bigger is not always better unless you're looking for an all-out drag car. this is all considering you're putting this on a 1.6 litre SOHC motor.

also, ballbearing turbos are a sort of witchcraft. they make very little difference in the performance arena. the turbonetics system is worse as they use only one bearing for thrust loading, but leaves the turbine shaft essentially unsupported... giving no useful purpose. most performance designed chargers will use a 360 degree thrust bearing, substantially increasing the thrust loading capability of the turbine shaft and extending the life of the turbocharger. plus at 100k+ rpm, the friction of riding against a ballbearing would hamper proper spoolup times, create heat from friction, and in the long run, possibly be more troublesome. standard cartridge turbine shafts ride on oil... no contact, substantially less friction... as long as you change your oil religiously.

yes... waaaay too big for a civic. lemme break it down:

the GT25 series turbo is a T2 series center section and T2 series turbine. this is designed for small displacement motors.

the T04S compressor side features a .70 A/R ratio housing... this is a LOT of flow. about 550cfm of air rushing thru at max load. it should be stable up to 20psi, considering the T2 turbine combination.

the 76 trim exhaust i dont fully understand, as Garrett turbines are usually classified by stages, i.e. stage 1, stage 2... etc. i'll assume it's a .76 A/R ratio turbine housing with a stage 2 trim and an undivided tang. (normal config for T2 series)

the .76 ratio turbine housing would have no backpressure whatsoever... but that means most of your exhaust energy will flow through it with little resistance to make the turbine spin. this will create enourmous amounts of lag... especially with an S trim compressor and 46 trim wheel.

to give you an idea, the T04S housing features a 4" inlet, 2.5 inch outlet, 3" diameter compressor wheel major with a 2.75" compressor wheel minor. this is HUGE. more than enough to cause resistance to spin quickly, and add the low resistance turbine housing, and you'll reach 8 psi of boost at redline due to lag.


your best combination for quick spool up, optimal compressor flow, minimal backpressure, and thermal efficency during compression would be a T04B with a T3 center section and Stage 1 turbine. the compressor A/R should be .60 A/R and the exhaust should be .48 A/R, but no larger than .63 A/R this will create a turbine that will spool up to your desired boost before 3000rpm, and create a pressurised charge of air with enough volume without overly increasing the air temperature. it will be good for 20psi, and support over 450hp.

also, ballbearing turbos are a sort of witchcraft. they make very little difference in the performance arena. the turbonetics system is worse as they use only one bearing for thrust loading, but leaves the turbine shaft essentially unsupported... giving no useful purpose. most performance designed chargers will use a 360 degree thrust bearing, substantially increasing the thrust loading capability of the turbine shaft and extending the life of the turbocharger. plus at 100k+ rpm, the friction of riding against a ballbearing would hamper proper spoolup times, create heat from friction, and in the long run, possibly be more troublesome. standard cartridge turbine shafts ride on oil... no contact, substantially less friction... as long as you change your oil religiously.

WOW :eek:

Alot of information, and it was definitely worth repeating :D

You rock drift.

You make an interesting point when it comes to the ball bearing turbo. I was under the impression that these where better overall (for less lag, durability, etc.). As a result, I have been very heavily favoring the APEXi turbo kit, the ball bearing design being one of the factors. The other factor was the slightly larger size, giving it what I assumed more power potential over a GReddy kit. I clearly have alot to learn about the technical aspect of turbo's, Ive been reading alot, but it has yet to fully sink in and be realized. Im just wondering what your opinion is, drift, on the APEXi vs. GReddy turbo kits, is the APEXi really worth the extra dough?

After all the info you spewed, and a trip to the turbonetics website, I realize I have a whole lot of homework to do. Im starting to wonder if the turbonetics custom route is better in the long run.

Originally posted by piscorpio
WOW :eek:

Alot of information, and it was definitely worth repeating :D

You rock drift.

You make an interesting point when it comes to the ball bearing turbo. I was under the impression that these where better overall (for less lag, durability, etc.). As a result, I have been very heavily favoring the APEXi turbo kit, the ball bearing design being one of the factors. The other factor was the slightly larger size, giving it what I assumed more power potential over a GReddy kit. I clearly have alot to learn about the technical aspect of turbo's, Ive been reading alot, but it has yet to fully sink in and be realized. Im just wondering what your opinion is, drift, on the APEXi vs. GReddy turbo kits, is the APEXi really worth the extra dough?

After all the info you spewed, and a trip to the turbonetics website, I realize I have a whole lot of homework to do. Im starting to wonder if the turbonetics custom route is better in the long run.


apexi makes a very good setup for hondas. their use of IHI ball bearing turbos are kinda questionable. considering that Garrett turbo designs are the most popular, you'd be a bit pressed to find someone who can tweak the IHI turbo should you go that route later on down the road.

all in all, you wont get much more performance from the Apexi kit over the greddy kit... but Top Fuel is about to arrive on our shores with their own distributor, so if you're not buying a setup now, you may wanna hold out for Top Fuel. if you're in Cali, just get the greddy kit... it's the only one that's CARB certified

Sounds like the APEXi is better, but maybe not $1000 better.
I can wait plenty of time, this turbo is not going to happen too soon. I'll have to look out for this Top Fuel kit you are talking about, but what makes it better?

Speaking of prices, its hard to tell exactly how much a custom set up from Turbonetics would cost. Any clue as to whether the price is generally more or less than one of the name brand kits out there?

Like I said before, I still have alot of researching to do, so far this thread has helped me get some new ideas as to what to look for. It took me close to a year to decide turbo over supercharger, I would guess it would take at least as long to decide which turbo! :D

Thanks again drift!

top fuel has been known for producing turbo systems for more than just honda preludes.

they also use top shelf parts and produce much more power than an equivalent setup from other manufacturers

Ill be watching for it.