Product detailed description

PIII GR Corolla Airbox Intake Kit

The PIII GR Corolla Airbox Intake Kit is a complete OEM+ intake solution developed to increase airflow, improve induction sound and support higher engine performance while retaining the practicality of the original Toyota panel filter format.

After more than 12 months of development and real-world testing across multiple vehicles, from Europe imports to North America, we created an airbox that improves the GR Corolla’s intake path without compromising serviceability, fitment or OEM-style integration.

Unlike many open-cone intake systems, the PIII Airbox uses a sealed cold-air design, feeding the filter directly from the front of the car. The result is a cleaner, more controlled airflow path, improved pressure recovery at speed, and a more stable intake environment for both OEM and tuned cars.

Air Filter

The Included French-made Filter uses a race-proven, dual-layer woven cotton gauze in PIII specifications. You can easily authenticate it by checking for the laser-engraved logo on the sidewall, which ensures it delivers the exact same motorsport-tier performance trusted by WRC and 24-hour endurance OEM Teams.

In the PIII configuration, testing has shown a Filter efficiency of = 99.1%

The filter is also washable, but please follow the instructions and do not over-apply oil when priming the filter, as this may cause issues with the MAF sensor!

Designed around the OEM panel filter format

The PIII GR Corolla Airbox has been engineered around the OEM Toyota panel filter format.

This allows the car to retain simple, reliable and affordable filter servicing, while also giving owners the option to upgrade to a higher-flow panel filter for additional performance.

When paired with an aftermarket panel filter, our testing has shown gains of over +6 bhp compared with the stock airbox on OEM ECU settings, with further improvements across the power band on Stage 1 and Stage 2 EcuTek engine software.

As with any intake system, final gains depend on the vehicle specification, ECU calibration, supporting modifications, ambient conditions and total engine output.

Clean airflow, not just more noise

The goal of this airbox was not simply to make the car louder.

The PIII GR Corolla Airbox completely redesigns the intake path, making use of the available packaging space to create a sealed, unobstructed cold-air route from the front of the vehicle to the filter.

The incoming air is guided toward the panel filter in a controlled and direct way, helping maintain stable airflow before the MAF sensor and turbo inlet.

This is one of the main advantages of a properly designed panel-filter airbox. Compared with many cone-filter layouts, the panel filter format allows the airflow to approach the filter face more evenly, instead of reaching it from an uncontrolled angle inside the engine bay.

There is a reason why many high-level motorsport intake systems use large panel filter airboxes when packaging allows it: they offer excellent filtration area, controlled flow, and a stable intake environment.

OEM turbo inlet retained for a reason

During development, we tested and analysed the intake path carefully.

One of the key conclusions was that retaining the OEM turbo intake pipe from the airbox to the turbocharger was the correct solution for this application.

Larger-diameter pipes are not automatically better. On this platform, and at power levels below approximately 550 bhp, increasing the pipe volume in this area can reduce air velocity and density, which may negatively affect response, spool and torque delivery.

For this reason, the PIII system focuses on improving the airbox and cold-air feed, while retaining the OEM turbo inlet geometry where it still works correctly.

Motorsport-derived MAF sensor housing

A critical part of this system is the dedicated HP MJF 3D printed MAF sensor housing.

This component is produced with high dimensional accuracy and is designed to replicate the critical OEM sensor geometry as closely as possible. The goal is to provide stable, repeatable MAF readings for consistent operation on both OEM and tuned ECUs.

The housing is bonded seamlessly into the rear airbox duct and includes the necessary features for correct MAF sensor positioning and wiring harness retention.

The result is a clean OEM+ installation with proper sensor integration, not an improvised intake conversion.

Performance testing background

The PIII GR Corolla Airbox Intake Kit is based on the same engineering philosophy used for our proven GR Yaris airbox development.

On the GR Yaris platform, testing showed measurable improvements across different ECU configurations:

Stock ECU, OEM software
A Gen.1 GR Yaris tested on ACME Racing’s Rotronics hub dyno showed a +5.9 hp gain over the stock airbox before ECU adaptation time.

Test 1: carried out on an OEM Gen.1 GR Yaris and no changes to the electronics. Gains will be larger after the OEM ECU has time to adapt. Testing by ACME Racing on a Hub dyno by Rotronics:

Stock ECU with Stage 1 software
During testing at ProfiTuning, swapping from the OEM airbox to the PIRAS Motorsport airbox required an 8% reduction in Wastegate Duty Cycle to maintain the same power level, indicating a significant increase in airflow efficiency.

Syvecs ECU, Stage 1 software
A Gen.1 Rally R1T GR Yaris running a Syvecs ECU in speed-density mode gained +7.5 hp from the airbox swap alone, with improved power delivery from 5300 rpm to 7200 rpm and a reduction of the torque dip.

Test 3: carried out on a R1T Rally GR Yaris, with Syvecs ECU and no changes to the electronics. Gains will be larger software adaptations. Testing by ACME Racing on a Hub dyno by Rotronics:

These results are not presented as direct GR Corolla figures, but they show the performance potential of the airbox concept on the Toyota G16E-GTS engine platform.
Dyno runs have been carried out on the GR Corolla, but the environment was not controlled so we prefer to stick with our confirmed data for now.

Air Filter & Wet Weather Use

The PIII GR Corolla Airbox Intake Kit is designed around the OEM Toyota panel filter format. However, we do not recommend using the OEM paper air filter in heavy rain or very wet conditions. Please use the included filter in heay rain!

Paper filters can absorb moisture and restrict airflow when saturated. For customers who regularly drive in wet conditions, we recommend using a high-quality performance panel filter designed to withstand moisture exposure.

Technical specification table