the4g4d

i understand a/r values but i cant seem to get a strait answer on the web about trim selection. i understand what trim is and the ratio between inner and outer wheel size. my question is do you find more usable torque from a smaller trim turbo with a larger comp. a/r or do you get more tq from a larger trim smaller turbine a/r and smaller compressor a/r.
a little simpler and less to read for examples:

60/63 60 trim vs a 60/63 57 trim "which would make more torque + spool faster and why" on the same set up

60/48 60 trim vs a 60/48 57 trim "same setup

of these the 60/48 57 trim would spool faster but would it run out of breath befor say 7800 rpm?

is your spool time faster on a 57 trim vs a 60 trim or does it just flow more at the same psi?

is the relationship between trims the same as turbine a/r values?

this isnt for a specific application but if you needed one to compare or use lets pick a gsr or lsv. i more intersted in the principle of this.......

samson

Good question for a n00b.


The trims are like you said inducer squared over exducer squared as a formula and the examples you gave of a 60 trim T3 and a 57 trim hybird the 57 trim flows a fair bit more. With that said the trims come into play with the same A/R values, but different inducer and exducer sizes that either draw more air in or expel more air out or perhaps both.


For example: The hybrid turbo T3/T04B "S" Trim will flow 37lbs/min of air at a standard 60 compressor and 48 turbine (I believe the number is derived from the 48 turbine and NOT the 63, but I could be wrong). So we can leave those 2 as constants. NOW, the biggest "H" trim STILL has the same compressor/turbine A/Rs, but flows ALOT more simply because of the size wheel and how much it takes in (induces) and expels or gets rid of to the motor (exduces). Simply seeing that the A/Rs remain the same and the wheel sizes differ give you completly different outcomes and applications.


To get a good overview, just go to a website with compressor maps or try Blaast's website because he has flow ratings on his turbos. That will give you an idea on the affects of trim. Even in a sticky in FI I think there's a thread with flow ratings in it.


JP

the4g4d

from what i have read a larger trim turbo generally spools slower than that of the same size but smaller trim and like a/r values larger trim will flow more but spin slower. like a smaller fan vs a larger one in the wind. the small one will spin faster sooner but the larger will spin and blow more air.
so the trick is finding the best a/r value for a responsive turbo and still having enough air in high rpms.
has any one on here used a 60-1 with a .70a/r cold side and a .48a/r exhuast side. it seems like a very effecient turbo for a stock ls or b16 on 10-15lbs. but i cant find any one using this turbo. they sell it on phoenix turbos

samson

TunerToys.com has them and I looked at them today acutally. I wouldn't be afraid to snag a .63 on a B-Series.


JP

BLAAST

The spool up will not be greatly affected by such small variation of the compressor trim. Spool up is mainly dictated by the turbine trim and a/r.
now as far as your 60-63 t3/t04e, the 57 trim is very similar to the 60 trim, in theory, the 57 trim will spool up quicker so it will make the same torque a bit earlier in the power band than the 60 trim but on the other hand, the 60 trim will be able of more max torque because it flows more.

now, Before we discuss when a .48 a/r turbine equipped turbocharger will run out of breath, you need to specify what the turbine trim is. you did not mention that anywhere. Of course, if the turbine trim is stage 1 with .48 a/r, this turbine combination being the smallest one, will spool up super fast but it does get out of breath around 250 hp regardless of the compressor side you use. on that same stage 1 wheel, if you increase a/r to .63, you bottle neck the exhaust gases much less, therfore increasing flow a lot, allowing for more power to be made at the expense of some spool up.

now about the trim to a/r relationship, in both cases, bigger means more power at the expense of response but they don't have the same effect: larger wheel will generally spool up more gradually because of it's inertia but the spool up may still start very early if a/R is low enough and don'T forget the same specs turbocharger may be overkill and laggy on some applications and it may be a super fast spooler on other applications.

on the GSR example:
.48 stage 1 turbine is too small.
.63 stage 1 turbine is good for some 300 whp.
.48 stage 3 turbine is also good for the same power but with a more gradual power delivery because boost will not shoot up as fast.

compressor wise, a/R doesn'T affect spool up as much as people think. actually, a higher a/r is claimed by garrett to be better at exploiting a compressor wheel at low boost. so if you're boosting 6-12 psi, you're definitely better off with .70 a/r and if boosting 25 psi on a forged engine, you might prefer .50 a/r. concerning the compressor trim, you simply select the one that can support the desired power without falling under 70% efficiency.

now you can go and order a drop shipped turbo from phoenix or tunertoyz.
(or i can custom make a better one with a bolted down thrust and watercooling for around the same dough.)

rexsk8er

GOOD READ