Im going for a 61mm turbo for my Supra, now the AR choices are .58 .68 .81. What i want is a fairly quick spooling turbo. And ive decided im only going to use pump gas so max hp ill get will be under 550hp.
Im a bit lost on the AR and what it means and how it would affect my turbo power?
Im ordering the kit soon so i need to make the right choice.
Would there be any huge difference between a .68 or a . 81?
I think you probably understand the basic's enough to make a decision. As i'm sure you know, the smaller turbine housing is going to be more restrictive once you start going into higher pressure ratios, pushing further out of its efficiency range. With the larger AR you will shift the map slightly to obtain more efficiency in areas while loosing it in others (compromise is always a factor). You've probably heard the saying "get the smallest turbo for your horsepower goals". This is so that you don't end up with a laggy pig of a turbo that barely gets into its efficiency range for what you're trying to do with it.
If you really want to make an informed decision, see if you can get a compressor map of both AR's on the same Turbo. Then with a few simple calculations you can plot out where on the map you'll be using it the most.
Worst case scenario, you can always switch out the Turbine housing.