Turbo Compressor Covers & Housings

Turbo Compressor Covers & Housings

The turbo compressor cover, also called the compressor housing, is the snail-shaped aluminum casting that surrounds the compressor wheel and directs compressed intake air to the engine's throttle body or intercooler. Upgrading or replacing the compressor cover affects the flow capacity of the turbocharger and is a key component in turbocharger rebuilds and stage upgrades.

Popular Turbo Compressor Cover Options

Larger compressor cover A/R ratios support higher airflow targets at the cost of slower low-RPM spool. Smaller A/R compressor covers spool faster and are better suited to street-driven applications where low-end response is a priority. Ported or map-width-enhanced compressor covers extend the usable compressor map range and reduce surge at low mass flow conditions, making them popular on applications with large intercoolers or tight boost controller setups.

When does a compressor cover need replacement?

Compressor cover replacement is needed when the housing bore shows scoring or damage from compressor wheel contact, when the inlet flange is cracked or broken, or when an A/R upgrade is performed as part of a turbocharger power upgrade. OEM replacement covers are available for most factory turbos, while aftermarket billet aluminum or cast upgrade housings are available for popular Garrett, Borg Warner, and Precision turbocharger frames.

Does compressor cover A/R affect spool time?

Yes. A smaller A/R compressor housing increases air velocity at the impeller inlet at lower mass flow rates, building boost pressure sooner in the RPM range. A larger A/R housing flows more total air at peak but requires higher shaft speeds and mass flow to maintain the same pressure ratio, resulting in slower spool. The correct A/R selection depends on the target boost pressure, engine displacement, RPM range, and turbocharger wheel sizing.

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