What is the A/R ratio, and what does 1.28 mean for my turbo?

The A/R ratio, or Area/Radius, describes the size of the turbine housing's volute and its outlet. A higher A/R like 1.28 generally means a larger housing, which can help maintain boost and power at higher engine RPMs by reducing exhaust backpressure. It typically results in slightly slower initial spool compared to a smaller A/R.

What is a 'divided' turbine housing?

A divided turbine housing has an internal divider that separates the exhaust gas flow from the two ports of a divided exhaust manifold. This separation helps prevent exhaust pulses from interfering with each other, leading to more efficient turbine operation and potentially quicker spool-up.

What turbocharger compressor wheels is this housing compatible with?

This 75mm turbine housing is designed to be compatible with turbocharger center sections that utilize a 75mm turbine wheel. The specific fitment will depend on the turbocharger manufacturer's design and the mating flange dimensions.

Turbosmart Turbine Housing T4 Divided 1.28AR TS-19TH75C-D412

Name: Turbosmart Turbine Housing (75mm) T4 Divided 1.28AR
Brand: Turbosmart
SKU: turbosmart-turbosmart-turbine-housing-75mm-t4-divided-1-28ar-t14-960297
Price: 573.29 USD
Availability: BackOrder

Turbosmart Turbine Housing (75mm) T4 Divided 1.28AR

$573.29

On Backorder — Expected to ship by May 9, 2026

Order now to reserve yours — we'll ship as soon as stock arrives. Full refund if we're unable to fulfill.

Turbosmart Turbine Housing (75mm) T4 Divided 1.28AR

Key Features

This package includes the Turbosmart 75mm turbine housing.
Features a T4 divided inlet flange for turbocharger mounting.
Includes a 1.28 A/R (Area/Radius) ratio for exhaust flow management.
Constructed from durable cast iron to handle high engine temperatures.
The divided housing design helps separate exhaust pulses for improved spool.
Suitable for applications prioritizing top-end power due to the larger A/R ratio.

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Product Details

This package includes the Turbosmart 75mm turbine housing, designed for T4 divided turbocharger applications with a 1.28 A/R ratio. This housing is a key component for building or upgrading a forced induction system, directly influencing how your turbocharger spools and performs under load. The 75mm inlet size is suitable for a range of turbocharger compressor wheels, while the 1.28 A/R ratio on the divided housing helps manage exhaust gas flow for improved response and power delivery, especially in higher horsepower applications.

Crafted from durable cast iron, this housing is built to withstand the high temperatures and pressures associated with turbocharging. The divided entry design is intended to help separate exhaust pulses from each cylinder bank, which can lead to more efficient turbine operation and a quicker spool-up compared to undivided housings. This setup is particularly beneficial for twin-scroll turbo manifolds, allowing for optimized exhaust scavenging and reduced backpressure. The 1.28 A/R ratio is on the larger side, suggesting it's geared towards maintaining top-end power in applications where sustained high RPM performance is prioritized over the absolute quickest initial spool.

When considering this turbine housing, it's important to ensure it mates correctly with your chosen turbocharger's compressor cover and that your exhaust manifold is designed for a T4 divided inlet. This component is not CARB approved and cannot be shipped to California. For optimal performance and longevity, proper exhaust manifold design and wastegate integration are crucial.