Turbo Sizes Explained - Does Size Matter?

Turbo Sizes Explained Does Size Matter
Reader BEWARE!! If talk of turbocharger sizes, inducers, exducers, turbo housings and compressor wheels bores you. This article is not for you, just give us a call and we can answer your questions.

You have probably heard of someone referring to a turbo as a something like a 66mm, or something similar. Generally, this is referring to the turbos compressor inducer diameter.

This diameter will give you a very general overall size and flow of the turbo. The compressor inducer is what you see when you remove your intake piping and look at the inlet of the turbo.

What you can’t see is the compressor exducer, or the outer diameter of the wheel hidden inside the compressor housing.

The relation between the inducer and the exducer of the compressor wheel (called trim) also has an impact on flow and pressure.

Increasing the exducer size will increase air velocity which translates to more pressure at any given shaft speed.

Turbo compressor wheels with the same inducer and exducer size can also have different overall heights or thicknesses (distance from the front to the back of the wheel) which will also impact the performance of the wheel.

The exact same wheel will also perform differently in different sized housings - stock vs race housings for example. Two wheels of the same size can also have different flow and surge characteristics depending on the length and height of the veins themselves.

What does all of this mean?

It’s not necessarily the size of the wheel that counts, it is how the wheel performs.

The best way to gauge wheel performance is with a compressor map which outlines the overall flow, efficiency, surge characteristics, and maximum pressure ratio (boost).

The compressor map can be used in conjunction with the specific requirements of your particular engine setup to properly size a turbo for your application.

Looking at installing compound turbos on your truck?

Things become a little more complicated when there are two compressors involved, and they must work efficiently together.

As general rule of thumb, the primary turbos compressor wheel must provide enough airflow to meet the engines power requirements, and the secondary turbos compressor must be small enough to be responsive, and also large enough to not restrict the primary turbos airflow.

You may now be wondering, “What about the turbine wheel and housing?” Well, that is another topic!

We offer a complete line of turbocharger options from stock replacement upgrades, to full race applications and everything in between. We can provide you options for your truck and help you select the best option for your application and budget.

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