PRL Helix Air Oil Separator for Civic/Integra/Accord/Type R

PRL Motorsports Helix Air Oil Separator - Honda & Acura Turbo

Direct-injection turbo engines have a carbon problem, and the PCV system is the cause. It routes crankcase blowby back into the intake, and that blowby carries oil vapor, fuel, and moisture that bake onto your intake valves over time. On a port-injected engine, fuel washes the valves clean. On these engines it doesn't, so the deposits just accumulate. This PRL air oil separator catches those contaminants before they reach the intake, keeping the valves and manifold clean without venting metered air or changing how the car drives.

Why This Matters On Your Engine

Worth understanding, because it's a real and expensive problem specific to how these engines are built.

Your engine is direct-injected, which means fuel sprays straight into the cylinder rather than past the intake valves. That's efficient, but it means the valves never get the fuel wash that kept port-injected engines clean.

Meanwhile the PCV system is depositing oil vapor and moisture right onto those dry valves. Over tens of thousands of miles it builds into carbon deposits thick enough to disrupt airflow, and the fix at that point is walnut blasting the valves, an involved and expensive job.

An air oil separator catches the oil vapor before it gets there. It's preventive maintenance against a problem that's genuinely costly to fix once it's happened.

It Also Helps Your Tune

A second benefit, and it matters more on a car making power.

The oil and fuel vapor going back into the intake effectively lowers your charge's octane, since you're introducing contaminants into the air being compressed. Lower effective octane means a higher chance of detonation, which is exactly what you don't want on a boosted engine.

Removing those contaminants keeps your intake charge cleaner, which supports more consistent power and reduces detonation risk. On a tuned car running real boost, that's a genuine reliability benefit rather than just a maintenance one.

How The Helix Works

The design is where this separates contaminants effectively rather than just catching some of them.

Inside the canister is a proprietary helix that spins the incoming blowby gases into controlled centrifugal motion. Heavier oil droplets, fuel, and moisture get flung outward against the canister walls, where they condense and collect at the bottom. The cleaned air routes back into the intake.

That centrifugal separation is more effective than a simple baffle, because it uses the mass difference between air and contaminants to physically separate them rather than just hoping droplets stick to a surface. More of the oil ends up in the can and less ends up on your valves.

Closed Loop, No Emissions Trouble

Important distinction, since some catch cans get this wrong.

This retains closed-loop operation. The cleaned air goes back into the intake rather than venting to atmosphere, which means it doesn't dump metered air, doesn't interfere with emissions equipment, and doesn't alter your factory drivability or fueling.

A vent-to-atmosphere catch can throws off your fueling and isn't emissions legal. This isn't that. It cleans the air and returns it, so the system behaves exactly as the factory intended, just cleaner.

You Have To Drain It

Being straight about the one maintenance requirement.

The AOS collects contaminants, which means it fills up and needs draining at regular intervals. How often depends on your climate and how you drive, more frequently in cold weather and with short trips, since moisture accumulates faster.

It's fully serviceable and draining is straightforward, but it's not fit-and-forget. Check it periodically and drain it before it fills. That's the small ongoing cost of keeping your valves clean.

Built In-House From Billet

PRL designs and machines these themselves rather than sourcing a generic can.

The canister is CNC-machined 6061-T6 billet aluminum with a hard anodized finish, in black or silver. Everything around it is built to match: billet aluminum fittings, a billet check valve, Viton O-rings for chemical resistance against oil and fuel, NBR reinforced hoses rated for the engine bay, and a laser-cut, CNC-bent 304 stainless mounting bracket.

Viton in particular matters here, since it resists the oil and fuel this system handles constantly, where a lesser O-ring material would degrade. It's the difference between a can that seals for years and one that starts weeping.

Silver Or Black

Two hard-anodized finishes, purely a look.

Silver shows off the billet machining and stands out in the bay.

Black is the understated option, blending into a mostly-black engine bay.

Both are hard anodized over the same billet, so they're identical in function and durability.

What's Included

• PRL Helix air oil separator canister
• 304 stainless steel mounting bracket
• Custom molded hose set
• Billet fittings and check valve
• All required clamps and installation hardware

Fitment

2016-2021 Honda Civic Si and 1.5T
2017-2021 Honda Civic Type R (FK8)
2022-2026 Honda Civic 1.5T
2023-2026 Acura Integra 1.5T
2023-2026 Honda Civic Type R (FL5)
2024-2026 Acura Integra Type S (DE5)
2018-2022 Honda Accord 2.0T

The FL5 and DE5 share the same part. Select your application and finish at checkout.

Who Should Grab This

This is for the owner who wants to keep their direct-injection engine's valves clean and avoid the walnut-blasting bill down the road, and for anyone tuned who wants a cleaner intake charge for consistency and safety. Effective helix separation, closed-loop so it stays emissions-friendly, and built in-house from billet with materials that last. Fit it, drain it on schedule, and protect the engine long term.

Fits: 2016-2021 Civic Si/1.5T, 2017-2021 Civic Type R, 2022-2026 Civic/Integra 1.5T, 2023-2026 Civic Type R (FL5), 2024-2026 Integra Type S (DE5), 2018-2022 Accord 2.0T. Finishes: silver or black hard anodized. Canister: CNC-machined 6061-T6 billet. Separation: proprietary internal helix, centrifugal. Operation: closed loop, does not interfere with emissions equipment. Includes: canister, stainless bracket, molded hoses, billet fittings and check valve, hardware. Note: requires periodic draining.