Here you can see the changes in diameter and the corrugated area inside the elbow. This cannot be good for air flow, so we're thinking we should see some positive gains from the larger diameter HPS Performance Parts intake hose kit.
The HPS hoses measure in at a girthy 80mm and the diameter is even through the entire hose length. Since they are made of silicone it is easy to design them to have very smooth bends while still ensuring they retain their shape under all conditions with their reinforced 4-ply construction.
Here you can really see the difference in diameter between the OE intake elbow and upgraded HPS silicone intake hose.
The HPS Performance Parts intake hoses went on with no issues and fit perfectly. We really like the performance look the new silicone hoses along with the supplied stainless steel t-bolt clamps gave our M5's engine bay. A welcomed addition since they sit front and center in the engine bay.
Though we were not expecting astronomical gains from the HPS intake hoses, we were expecting to see some gains – and we did! 3 horsepower and about 2.5 foot pounds of torque. The best part is that the gains were across the entire power band.