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boosting in progress
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Discussion Starter · #1 ·
this might seem like a noobish question but here it goes. this is going to be my first turbo build so ive been doing some research. ive learned a lot asking as little questions as possible but i still dont understand turbo sizes to well like to go ahead and buy one. when i say turbo sizes i mean turbine wheel trim housing ar compressor wheel trim housing. i know if the turbine wheel is to big it'll make it spool up slower but other than that i dont konw to much about sizes. i would like to make about 300-350 whp but definatly want to make more once i build the block. so i want to get a turbocharger that i do not have to upgrade to soon once i build the block. i was thinking of a gt30r in this size,
Turbine -Wheel: 60mm w/ 84 trim -Housing: .82 ar
Compressor -Wheel: 76.2mm w/ 56 trim -Housing: .60 ar

thanks in advance
 

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boosting in progress
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Discussion Starter · #2 ·
AR is the rated volumetric efficiency of a turbos 2 sections, so to speak. imagine if you have a garden hose spraying water out, at a pinwheel......................

with the hose open ended the pinwheel spins okay......

but put a nozzle on it an the pinwheel will spin like mad................

but there is issues, with the nozzle on the end, you lose volume but gain pressure. with the nozzle off you gain volume but lack pressure and cant turn the pinwheel as much..............

real simple, on small displacement motors, a smaller AR is nicer, on larger obviously larger due to exhaust volume.

A larger AR will spool later and provide a higher power band, if you motor is capable of reaching the RPMS it should be used in.

The A/R ratio basically chooses your operating RPM range of a motor, the more flow(RPM's) you're trying to push, the larger the A/R ratio you need/want. You can't cross compare different types of housings and wheels, but if you have a typical T3/TO4E 57 trim with a stage 3 exhaust wheel, with a .48 A/R housing it might have a powerband of 3000-7000, with the .63 it might be 4000-8000, and with a .82 A/R housing it might be 5000-9000. If you have headwork and cams that stop pulling at 8000 RPM's, it's smart to run the .63 A/R housing. If you have a fully ported head and huge cams that will make power till 9000, the .82 A/R housing would be a better choice.






 

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boosting in progress
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Discussion Starter · #3 ·
i got the A/R down, can u guys explain the "trim?" i cant understand the way it was explained where i got that info from
 

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i got the A/R down, can u guys explain the "trim?" i cant understand the way it was explained where i got that info from
the class of the compressor wheel usually defines the exducer diameter. meaning all t04e compressors have the same exducer diameter. but the different trim to4e wheels have different inducer diameters. higher trim has larger ind diam, lower trim has smaller ind diam.

higher trim flows more air, and is more efficient at higher rpm and/or higher boost, but is more prone to compressor surge.
lower trim flows less air, and is more efficient at lower rpm and/or lower boost, and is less prone to compressor surge.

when determining what turbo is right for you, learning how to read a compressor map is the most important thing, to determine the efficiency range the turbo will be in under the conditions of your setup. that will tell you what compressor side to get.
then choosing an exhaust side will depend on what rpm you want spool to start at and how high you'd like it to be able to flow to.
usually, exhaust wheel trim doesnt vary much, so dont worry about the exhaust wheel trim. more important is the actual size of the exhaust wheel, and the a/r of the housing.

lower a/r spools faster and sooner but restricts it at a lower rpm as well. higher a/r will spool later and slower but will still flow more freely allowing more power in higher rpms.
same goes for exhaust wheel size, smaller spools faster and sooner but dies faster, larger spools slower and later but will hold out longer into the rpms allowing more higher rpm power. exhaust wheel size refers to the class and stage. ie: t3 stage 1, t3 stage 2, t3 stage 3, t4 stage 1, t4 stage 2, t4 stage 3...
 
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