Grimmspeed Post MAF Intake Hose – 08-14 WRX, 08-21 STI

Some OE parts look passable and others miss the mark. In the case of the factory post MAF hose, the quicker you can get it out of your bay, the better. GrimmSpeed now has you covered with our all-new Post MAF Hose Kit which not only looks better, but fixes the performance flaws of its OE counterpart.

Our Post MAF Hose construction improves flow with 2 main features:  

The first is the smooth inner surface, removing the pockets from the OE structural corrugated folds. The GrimmSpeed Hose is made with reinforced silicone, which is flexible, but has strong structural properties that allow for a design that maximizes flow, is very easy to install, and won’t collapse under vacuum.

The second feature is a tapered center portion, making sure the inner diameter matches the OEM air box and turbo inlet. A mis-matched diameter creates steps, which will interrupt the airflow trajectories and create small vortexes in the post-MAF hose. The GrimmSpeed Hose was designed specifically to prevent these issues.

QUICK SPECS:

• 4-Ply Reinforced Silicone – Extremely durable, available in red or black
• OEM Fitment – Easy install, no modification or tuning required
• Seamless Flow – CAD optimized design
• High-Quality Breeze Hose Clamps – Included in every kit
• GrimmSpeed Logo to Represent your Favorite Brand!

TESTING DATA

The first step in improving on an existing part is to find its shortcomings. The OEM rubber hose requires a straight section in the middle, which means sharper curves on both ends. This contributes to uneven airflow through the hose with high and low-pressure spots. The GrimmSpeed hose design can support a minimal curve transition, maximizing airflow. The plot below shows the pressure through the length of the hose; the GrimmSpeed design results in a smoother transition from the airbox into the turbo inlet:

The removal of the corrugated folds adds a significant reduction in vorticity (a calculation used for flow disruption, with blue representing consistent flow and red more turbulent) between the two designs. Smoother flow will give us a more consistent air supply to the turbo:

The tapered center portion is an important design choice for contributing to even flow through the hose. A plot comparison showing vorticity between a non-tapered version and GrimmSpeed’s tapered hose shows an additional reduction in turbulence through the center where a majority of airflow will occur: