Overview

Looking for more, for less? The all new G2x/G4x Mx40i PEX Intake delivers all the performance and sound benefits as its carbon fiber sibling -- just with less showmanship -- resulting in the best dollar-per-horsepower B58 intake system available from Dinan. The Mx40i's are an impressive lot in terms of performance and style but that is not conveyed when viewing its lackluster stock intake system swaddled by seemingly unfinished strut braces (where applicable). In stock trim, the Mx40i comes with a dry and lifeless air box housing a basic panel filter that is also accompanied by an intake resonator whose job it is to eliminate turbo/intake noises. The same noises that those in the performance world relish. Essentially BMW has seen fit to give Mx40i owners an air box that looks uninspiring, flows adequately but not ideally, and emits no noise. The exact opposite of what the platform exudes otherwise. The Dinan PEX intake for the platform corrects these wrongs and delivers a semi-open intake capable of flowing 58% more air than the stock system resulting in additional top end power and improved throttle response. At the same time revealing an enhanced OEM-like appearance that blends seamlessly with surrounding factory plastic under hood components, and an increase in sound courtesy of the removal of the intake resonator and implementation of a semi-open design. To achieve the gains in flow that set the Dinan intake system apart, the entire lower box of the system, and not just the lid, has been reworked and enlarged to make use of as much of the available real estate as possible within the engine bay. In turn, this allows a 40% larger, custom, free flowing filter to be housed within and maximum flow to be realized. However, a secondary inlet has always been desired by Dinan in order to effectively fill the volume of the enlarged air box and increased filter surface area. This desire led to a multitude of experiments being conducted on the effectiveness of a possible open-air inlet in the system. With different shapes, locations, and sizes of openings being tested, the goal was to ensure that the added secondary inlet did not cause any unwarranted side effects such as an increase in air temps in the system. This is commonplace with open-air intake systems where overheated engine bay air is employed in the intake tract. The results of these tests showed that the patterned openings present in the final iteration of the box located on the opposite side from the engine provided a perfect balance of additional volume to assist the factory inlet all the while not causing an increase in turbo inlet temperatures. This was the case regardless of testing conditions (single/multiple gear pulls, constant speed, 0-100mph runs, etc.). With more air being pulled into the system, throttle response is improved and additional power is realized in the form of max gains of +9 WHP / +8 ft-lbs of torque. The secondary air inlets also allow the intake system to be more audible so the turbo spool and BOV can be appreciated. A stark difference from Dinan's traditional fully sealed systems where induction noise is not nearly as recognizable. While power and sound are the stars, the modest PEX construction fuses effortlessly into the factory engine bay for a reserved visual that despite basic materials still manages to draw attention. It's an economical solution to form and function for a vehicle that permeates both.