Hey guys,

I've been trying to do more reading on different turbo designs. I'm pretty green with all the nomenclature but have the basics.

So there seems to be different turbo flange sizes, designated by t25, t28, t3, etc. T25 is the smallest up to like t04.

Which part of the turbo are they describing by that 't' designation? Is it just flange opening size for the turbine, bolt hole pattern???

I ask, because from what I have read, every turbo available for our cars uses the smallest T25 setup. Why is that? There seems to be concern that sure some of the bigger turbos have compressors that will run 500 whp each, but there's no way they'll ever do that with T25 and the enormous amount of exhaust backpressure.

Also, when just looking at turbos by themselves, how do you know which 'T' model it is.

Why would one use a gt3071, gt3076, and gt3582 use the T25 flange?

Thanks!

 

the T size is just that the flange size, I believe it is rated independent of the rest of "name"......

Its very confusing to me too lol. I know mine are T3 flanges with 54mm inducers wheel, and journal bearing.......and they go pssshhht psssshhht psssshhhht

tom

 

ya seems that all of the log manifolds (used by APS, HKS, Greddy, and GTM) are all that T25 size.

Does any one know the actual dimensions of the different T sizes?

 

ill tell u this my friend,

we have a Vette C5 with an APS turbo kit, the car made 750 whp using a GT28 turbos
using a T25 flang, and there was no problems, keep in mind this is a V8 engine that flows more than any V6

the guy now is changing to a GT30 with the same flang

so u can see this small flang can flow even to 1200whp

so i dont thin its a porblem on the VQ

allso GTM did 800whp with the APS EXTREME kit

and allso Rocky did 840who with the same flang

why do u think GTM have there STG 4 5 6 with the smae flang

i talkd to sam about this befor i got my kit from him, and he told me its not an issue.

i hope this can help.

 

Don't forget the T6 flange

 

T25 flanged turbo are used because a T3 flange wont fit up against the manifold and frame rail. Most Evo's for instance run the large T3 flange...huge difference between the two. If you go to a remotely mounted turbo...either up front, or down low, then you can use a true T3 flange.

 

I have the T25 also......

 

ya and obviously we'll all be watching your build Mike to see how it runs on the dyno.

I sure hope some other people are incorrect about the amount of back pressure than small flange is going to give at high HP.

750 isnt that much. And, no we have not seen anyone flow a T25 to 1200 hp. just becuase the compressor is rated 1200 hp, doesnt mean it can do it with a T25.

Unless Sam has done that (which he hasnt or hasnt posted about), he's just guessing a T25 will be ok at >800 whp.

That APS kit was a 4.24L car.

GTM uses that flange bc nothing else will fit, not because its the correct choice.

 

Txx designates the Turbine Housing (for Garrett).

T25/T28 Both share the same inlet bolt pattern and flange dimensions.

T3 Larger housing different bolt patterns

T4 Larger housing different bolt patterns.

T6 ""

Then for each of the classes of TXX the inlet flange can vary as well as the outlet flange ( V-Band, Divided, Ported etc, 5 bolt outlet, 4 bolt outlet etc etc etc). Plus you have varying A/R across the board.

T25/28 is a wise choice for the twin VQ35DE set-ups because it is compact and fits well within tight constraints. Plus there is enough material to machine up to a true 30R with out having to upsize the compressor housing to a t04e,s, etc or turbine housing to a t3. And with a little port work it will flow close to a T3. So you can fit twin 500hp turbochargers without having to drop them and add an additional pump for oil.

A 3071R downsized into say a standard 2860rs housing will still flow 500hp and provide fantastic response. Although it wont have as much high rpm uummmph or ability to make power at high boost - it will eventually choke.

IMO, I would never downsize anything larger than a 3076 - even then the gains over a 3071 wont be seen on pump gas. The 3582 is simply too large. Without the extra room a t3 turbine housing variant supplies, you wont be able to make much power past +/- 25psi (depends on turbo) - it will choke/stall. The t3 will provide the flow for higher pressure ratios.

If the VQ was an high revving inline the story would be quite different.

Ideally, you want the largest compressor wheel matched with the smallest turbine wheel possible that will still provide a balance of power, response, pressure ratio, efficiency range etc.

The only reason companies like HKS who up-size their compressor covers on their smaller garrett based turbos is to reduce the pressure ratio needed to achieve xx hp and increase the range of applicable boost. This also reduces heat as well.

Unfortunately, the VQ engine bay is not well suited to take large compressor covers or turbine housings when the turbochargers are mounted right off the block. There simply is not enough room.

 

i just checkd garrett web site, ur right, back pressure gonna be there if u run high boost.

on Garrett website all GT3071 power is rated with a T25 flang,

for GT3076 they are using a T3 flang in garret website.

GTM use a T25 on the big turbos

GT3067

GT3082

GT35s

those should be using a T3 flang.

there will be back pressure

naaaaaaah if didnt like it ill go SP

 

^should be but no. how else would the use the same log manifold for every turbo...

Thanks for the reply Clint. Really casts a new light on trying to run anything bigger than the gt3071's with the commonly available T25 log manifolds. Might really put a damper on us that wanna run 800+ but dont wanna use a scavenge pump for low mount turbos. If only PL would mass produce they 76s kit!!

I guess Mike's kit will be very informative. If you look at the "FI's top 25" thread you start to wonder why 19 psi is the highest boost run on the T25 flanges. Thats with race gas as well. Evo and Suby forums run those same turbos out to almost 30 psi with significantly more HP/psi. Cant just be a coincidence they use the bigger T3 flange as well.

I hope the GTM 3582's really push big power, then there's no regret spending the extra money on the big turbos.

 

Yes Mikes kit will be informative!! I am looking forward to the results

IMO, 800whp is acheivable - probably with 3071 (maybe only on a stroked VQ) and definitely with a 3076 - both in a downsized T28 turbine housing and accompanying compact compressor housing. Being limited to the dimensions of the t25/t28 doesn't mean you've got use them! Garret and companies like TIAL and ATP etc make various t28 housing options which are compact but increase flow/reduce backpressure over the standard options. Good old porting works too.

Also, I have never tried, so who knows, maybe a T31 or something equivalence will fit in the "standard" position. It probably would. I think compressor housing size and the location of the VQ steering shaft and engine mounts put a more limit on turbocharger sizing than anything else.

 

I assume something like that is what you are talking about.
http://www.atpturbo.com/Merchant2/me...egory_Code=GTH

No one has really tried to string out a gt3071 or gt3076, so its hard to say what the limitations of the T25 are and if there would be benefit going to one of those ATP housings.

 

30psi on a 2l vs 19psi on a 3.5l is apples to oranges...imho

 

ya but what is apples to apples is the amount of power they can run those turbos at on pump gas. Boost does not equate to CFMs, but overall power on pump gas is a function of teh turbo and can be used as a guide for other applications.

I'm just wondering if the guys running T3 gt30 's are making alot more power per turbo than we are because of backpressure created by the t25 housing. Our community as a whole is still fairly new, so alot of info isnt known yet...

 

Very good posts guys.....great info Clint as always....


I am sure George/GTM remembers there was someone on here that made over 600whp with at single GT35r.....I am getting old...cant remember where to find it.....It was the single version of the twins I am using. I am sure George will help us out with that info..

 

i believe in one of the sp posts (maybe it was on supraforums.com) larry and a few others go over the physics of turbo's and backpressure and whatnot.....

has more to do that just the flange of course.......remember boost pressure is just a measure of the limitation of the the head/plenum to take air in.......so 20psi on a stock head/cam setup, is not going to be the same power as 20psi on a ported head, larger valve/cam setup........

by that I mean, a car with ported heads will make more power at the same boost than a car on stock heads (all else being equal).

tom

 

^^ Tom, thats correct. The burning question at what point do we outflow the T25 housing and start getting less HP return for increases in boost.....

single gt35 PL kit uses the bigger T3 housing

I guess this all boils down to the fact that turbo kits for our cars are very $$ and you want to pick the correct size from the get go. I know what my blowers dyno looks like and how that relates to power on the road. I just want to make sure that I make the most informed decision on what to buy next so that there's a night and day difference.

 

I hear you guys........Tom...I am not sure if it was SP.....I could be wrong Where the hell is George/GTM when you need him????


. That's why we went big on the cams and Heads...to be honest ... the only problem Sharif and Sam is expecting is the clutch...

If it was a 3.5L... Then I would be worried....

CJM plenum is going to be used in the end....I can't see the cosworth pushing the high note for long.

 

Here is one thread I found quickly.

I think there was another though that didn't start out about backpressure but ended up becoming about it.

https://my350z.com/forum/forced-indu...-vs-boost.html

Tom