Top Tier Imports

Technical => Engine & Transmission => Topic started by: Supra2jz94 on March 24, 2017, 11:05 PM

Title: Help on Turbo AR choice
Post by: Supra2jz94 on March 24, 2017, 11:05 PM
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Title: Help on Turbo AR choice
Post by: Vince on March 26, 2017, 12:22 AM
Solid thread.

Quote (selected)
Imagine two 3.5L engines both using GT30R turbochargers. The only difference between the two engines is a different turbine housing A/R; otherwise the two engines are identical:
1. Engine #1 has turbine housing with an A/R of 0.63
2. Engine #2 has a turbine housing with an A/R of 1.06.

What can we infer about the intended use and the turbocharger matching for each engine?

Engine#1: This engine is using a smaller A/R turbine housing (0.63) thus biased more towards low-end torque and optimal boost response. Many would describe this as being more "fun" to drive on the street, as normal daily driving habits tend to favor transient response. However, at higher engine speeds, this smaller A/R housing will result in high back pressure, which can result in a loss of top end power. This type of engine performance is desirable for street applications where the low speed boost response and transient conditions are more important than top end power.

Engine #2: This engine is using a larger A/R turbine housing (1.06) and is biased towards peak horsepower, while sacrificing transient response and torque at very low engine speeds. The larger A/R turbine housing will continue to minimize backpressure at high rpm, to the benefit of engine peak power. On the other hand, this will also raise the engine speed at which the turbo can provide boost, increasing time to boost. The performance of Engine #2 is more desirable for racing applications than Engine #1 since Engine #2 will be operating at high engine speeds most of the time.

Sauce: https://www.turbobygarrett.com/turbobygarrett/turbine_housing_AR_and_housing_sizing
Title: Help on Turbo AR choice
Post by: SavageTaco on March 26, 2017, 02:17 AM
So....what's the question?
Title: Help on Turbo AR choice
Post by: Supra2jz94 on March 27, 2017, 12:29 PM
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?

Title: Help on Turbo AR choice
Post by: SavageTaco on March 28, 2017, 06:42 PM
Originally posted by Supra2jz94
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.
Title: Help on Turbo AR choice
Post by: Supra2jz94 on March 29, 2017, 10:52 AM
A .68 seems like the right choice 595hp so ill have room to play if i want. The .81 is good for 645hp and that would require further fuel mods and other things, .68 it is.