Turbo flange tech - T3 for 6cyl, T25/28 for 4cyl?

[Stefan]

Something I haven't been able to work out from researching on the net:

Single T3-flanged turbos tend to (always?) come stock on 6 cyl engines - like RB20, RB25 etc, and likewise single T25/28 on 4 cyl engines like SR20s and CA18s. The T3 flange is bigger than the T25/28, and thus so are the exhaust housings (I don't mean the A/R, I mean the size/shape).

What I want to know is:

• Is the T3 flange & exhaust housing inherently better suited to 6cyls? Or is it more to do with engine capacity?
• Will a 2 litre 6cyl tend to spool a turbo faster/earlier than 2litre 4cyl? More exhaust pulses, but smaller capacity per cyl, and thus less torquey but more revvy.

I'm shopping for turbos for my single turbo 1G which currently has a T3 flange, but the majority aftermarket T3-flanged turbos are to suit larger capacity engines like Rb25s rather than RB20s. T25/T28 aimed at SR20s are more common,and aimed at 2l engines (albeit 4cylinder ones).

[jimmmayyy]

it doesnt particularly matter, because you can get larger t25/28 turbos and small t3 turbos... its all much of a muchness.

my advice is that you research what results other people have gotten with particular turbo and go from there with what you aim to achieve.

what are your plans?

[CHB]

i thought turbo from RB20DET is a T28?

[Stefan]

i thought turbo from RB20DET is a T28?

No .

[Stefan]

it doesnt particularly matter, because you can get larger t25/28 turbos and small t3 turbos... its all much of a muchness.

my advice is that you research what results other people have gotten with particular turbo and go from there with what you aim to achieve.

what are your plans?

After something very streeetable - fast spool, low lag. I can find what I want designed for say an SR20, but am unsure quite how it will go on my 1G. Good starting point though, thanks.

[The Real Roadrunner]

GT3071r with a .63 if your after good response and up to 250rwkw or if you want something cheaper that can do 210rwkw grab an RB25 turbo, extremely responsive and reasonably priced second hand.

cheers
linden

[Stefan]

I actually have an RB25 turbo on the way, but am wondering if I would ultimately be dissatisfied with it. Have the supporting mods for more power (fresh engine, adap ecu, bigger injectors, coilpacks, forward-pacing plenum with larger TB, lightened flywheel), and have found some nice T28s that promise great response and reasonable power...

[Stefan]

Linden - have you had experience with an RB25 turbo on a 1G, or on other engines?

[jimmmayyy]

25 turbo is a very good turbo for 2L. the main thing is though they are cheap and easily replaced. if you look around on nissan forums you may even find a hiflowed steel wheeled one.

what flange do you have?

[Stefan]

As per my first post I currently have a T3 flange (with kkr430) - but it is no big deal to cut that off and replace with a T25/28 flange - have to go to the effort of a new dump pipe anyway.

[The Real Roadrunner]

Linden - have you had experience with an RB25 turbo on a 1G, or on other engines?

common upgrade on RB20DET's (done 12 as replacements when the factory turbo craps itself), a 1GGTE is very similar performance wise but i generally just fit aftermarket BB turbos as i believe they will be more reliable over time. Not to mention that i only like doing a job once, anything that comes back for warranty etc will generally cost me more than the profit on the job.

cheers
linden

[ICS]

The real roadrunner is right. Do it right first time & you will have trouble free motoring. We did the mistake of changing the turbos off a 1g with the 1j units should have just done a single.

[Stefan]

I have no doubt that a stock Rb25 turbo in good condition will last ok If I limit the boost to keep it happy - the question is whether I will be bored with it, as I have the mods to support more power if I can have my response cake and eat it.

If I get a dump made up to suit, It does give an easy upgrade path to further RB single-turbo upgrades in the future, but excludes me from anything T28 (which I'm not sure will be suitable anyway - still can't get a definitive answer on how much of a difference more smaller cylinders makes to turbo spool).