Selecting Your Turbo For Detroit Diesel Marine Aftercooled Engines (6V92,8V92,12V92,16V92) Video

This short video shows you how to verify if this turbo is the one that you need to replace your old one. Please check your old turbo to be sure that you have the correct compressor housing ratio and turbine housing ratio, as shown here. The turbo in this video has a compressor housing ratio of 0.75 and a turbine housing ratio of 1.13.

Understanding the Turbocharger on Detroit Diesel 92 Series Engines — And What 0.75 Compressor & 1.13 Turbine Ratios Really Mean

Introduction to the Detroit Diesel 92 Series Turbocharger System

The Detroit Diesel 92 Series is a powerful family of two-stroke V engines used widely in marine, industrial, and heavy-duty truck applications. These engines, including the 6V92, 8V92, 12V92 and even the massive 16V92, are known for their robust design, high torque, and ability to handle continuous heavy loads.

Unlike naturally aspirated engines that rely solely on atmospheric pressure to draw air in, most Detroit Diesel 92 Series engines in serious applications come equipped with turbochargers, are combined with blowers (Roots-type superchargers) because of their two-stroke design. This combination provides:

Improved volumetric efficiency.
More power from the same displacement.
Better fuel economy and lower exhaust smoke.

But to understand how these systems truly work — and what compressor and turbine housing ratios like 0.75 and 1.13signify — we need to dive deeper.

Why Turbocharging is Essential for the 92 Series Two-Stroke

The Role of the Blower vs. the Turbo

In Detroit Diesel two-stroke engines, the blower (mechanically driven supercharger) is essential. Unlike a four-stroke engine that uses piston movement to help expel exhaust and draw in fresh air, a two-stroke design needs forced scavenging — pushing fresh air in to sweep out exhaust gases.

The blower handles this primary scavenging. However, as power demands grew:

The blower alone became insufficient for higher horsepower needs.
Enter the turbocharger, which uses otherwise wasted exhaust energy to compress additional air and feed it into the blower intake.

This allows the engine to burn more fuel efficiently, increasing horsepower and torque without needing a larger displacement.

Benefits of Turbocharging for the 92 Series

With the turbocharger feeding denser air to the blower, you get:

More complete combustion. With more oxygen, fuel burns cleaner, reducing soot and unburnt hydrocarbons.
Lower exhaust temperatures, prolonging valve and cylinder life.
Greater power output, critical in marine, mining, and heavy haul applications.
Improved fuel efficiency, as you can get more power for the same amount of fuel.

This is why nearly all high-output versions of the Detroit Diesel 92 Series use turbochargers in tandem with their blowers.

Anatomy of the Turbocharger on a Detroit Diesel 92 Series Engine

The turbocharger on a 92 Series engine has two primary sides:

Compressor side (cold side): This is where outside air is drawn in, compressed, and sent to the engine. It houses the compressor wheel, which spins at high speed to pressurize intake air.
Turbine side (hot side): This is driven by the engine’s exhaust gases. Hot exhaust gases spin the turbine wheel, which is connected by a shaft to the compressor wheel, driving it.

The turbocharger effectively harvests energy that would have been lost out the exhaust pipe and uses it to push more air into the engine.

What the Compressor Housing Ratio (0.75) Means

The Compressor Housing Ratio For The Detroit Diesel 92 Series Turbo Is Marked On The Turbo Itself

When we say a turbo for a Detroit Diesel 92 Series engine has a compressor housing ratio of 0.75, we’re referring to the A/R ratio on the compressor side.

What is the A/R Ratio?

A/R stands for:

A = Cross-sectional area at the compressor inlet volute (scroll).
R = Radius from the center of the compressor wheel to that same cross-sectional area.

So, the A/R ratio is:

A/R = Area of the scroll cross section / Radius to the center of the wheel

In this case, 0.75 means that the ratio of the area of the volute (the spiral chamber) to its radius is 0.75.

How Does This Affect Performance?

A lower A/R ratio (like 0.75) on the compressor side typically means the turbo will spool up (start making boost) at lower engine RPMs. The smaller volume allows exhaust energy to accelerate the wheel faster, which is helpful for applications needing torque at low to mid ranges.
It also means less potential airflow at very high engine speeds, since the smaller cross section could slightly limit peak airflow.

For a Detroit Diesel 92 Series engine, which often runs in the 1800-2100 RPM range in marine or industrial settings, a 0.75 compressor A/R strikes a good balance, providing:

Quick boost response, aiding acceleration under load.
Sufficient airflow for the typical operational RPMs of these engines.

What the Turbine Housing Ratio (1.13) Means

The Turbine Housing Ratio On A Turbo For A Detroit Diesel 92 Series Engine Is Marked On The Turbo Itself

On the turbine side, the A/R ratio is also critical. A ratio of 1.13 means:

The area of the turbine scroll divided by the radius to the center of the turbine wheel equals 1.13.

Why a Higher A/R Ratio on the Turbine Side?

A 1.13 A/R on the turbine side indicates a larger volume around the turbine wheel. This has several effects:

Allows more exhaust flow at higher engine speeds without excessive backpressure. That’s critical to prevent overheating pistons and valves and to keep exhaust flowing efficiently.
Slightly slower spool-up at very low RPM, since it takes more exhaust energy to build turbine speed. However, for large displacement two-strokes that usually operate under heavy load and stay in mid to high RPMs, this is an ideal trade-off.

In essence, a 1.13 turbine A/R on a Detroit Diesel 92 turbo balances:

Sufficient exhaust energy extraction to drive the compressor.
Controlled exhaust backpressure to avoid choking the engine.

Matching Compressor and Turbine A/R for the 92 Series

The combination of a 0.75 compressor A/R and a 1.13 turbine A/R is a typical setup for many Detroit Diesel 92 Series turbos because it offers:

Good low to mid RPM response, ensuring the turbo helps fill cylinders quickly once load comes on.
Strong high-load, sustained operation, preventing excessive exhaust restriction that could damage components.

For example, a fishing boat using twin 8V92 engines needs consistent power under heavy load without risk of overheating. This turbo setup provides that balance.

What Happens If Ratios Are Incorrect?

If someone installs a turbo with significantly mismatched A/R ratios:

A too-small turbine A/R (like 0.65) might spool up very quickly, but cause excessive exhaust backpressure at cruising RPMs, overheating the engine.
A too-large compressor A/R (like 1.2) might flow massive air at high RPMs but lag so much at low RPMs that the boat or truck struggles to get on plane or moving.

That’s why Detroit Diesel engineers — and aftermarket specialists — carefully choose these ratios to match the unique operating band of the 92 Series two-stroke.

Function of the Turbocharger on the Detroit Diesel 92 Series

Turbocharger For Detroit Diesel 12V92

Pressurizing Intake Air

The primary job of the turbocharger is to:

Draw outside air through the compressor side, compress it, and force it into the blower intake.
This increases the mass of air entering each cylinder, even though the volume stays the same.

More air mass means more oxygen, allowing the engine to burn more fuel — resulting in higher power output.

Assisting the Blower

Detroit Diesel Blower for 6V92 Non- Turbo

In Detroit Diesel two-strokes, the Roots blower still handles scavenging — pushing fresh air into the cylinders and sweeping exhaust gases out. The turbo helps by:

Feeding pre-compressed air to the blower, reducing the work it needs to do.
Allowing the blower to maintain scavenging flow while the turbo focuses on boosting pressure.

This dual system is why Detroit Diesel 92 engines can maintain high horsepower without dramatically increasing engine displacement.

Improving Fuel Efficiency and Reducing Smoke

By ensuring there’s ample oxygen to completely burn the injected fuel, the turbo:

Reduces visible black smoke.
Cuts down unburnt hydrocarbons.
Keeps exhaust temps lower by reducing incomplete combustion.

This improves overall fuel economy — a critical factor for marine or industrial operators facing high fuel bills.

Managing Temperatures

6 ft Engine water temperature gauge mechanical with alarm switch

Turbochargers also spread the heat load:

Some energy that would become excess exhaust heat is converted into compressed intake air, improving thermal efficiency.
This keeps more heat out of the pistons and valves, reducing the load on the cooling system.

Conclusion: Why This Matters for Your Detroit Diesel 92

If you operate or maintain a Detroit Diesel 92 Series engine, understanding your turbocharger specifications is crucial:

A compressor housing ratio of 0.75 ensures the turbo builds boost quickly to support the blower and engine under load, maintaining power through acceleration or throttle-up events.
A turbine housing ratio of 1.13 ensures exhaust flows freely at high power, keeping backpressure controlled and temperatures safe.

Together, they keep your Detroit Diesel two-stroke running in its sweet spot — producing reliable power with efficient fuel burn and manageable exhaust temperatures.

When replacing a turbo, always verify these ratios along with your engine model, application, and expected operating RPM. Matching these specifications protects your investment, maintains your engine’s designed performance, and ensures the legendary durability of the Detroit Diesel 92 Series lives on for thousands of hours more.