So you just got your new BMW 335I or 435I for that matter and you want to “tune” it up.  You don’t just want to throw some bits and pieces on their, but you want to make the car respond better under throttle, give you a growl and feeling as if it is no longer tamed, and of course stay reliable.  Without being cliche, this is the right place.  Not because we sell parts, but we have had the opportunity to put our hands onto this exact scenario.  A long time customer of ours got this new 2014 BMW 335I and wanted to get more out of it the way he did his old E46 M3.  As a business professional and newly family man, he did not want to risk reliability and functionality for a vehicle that might shuttle clients, head to the grocery store, or flogg his friends on the streets.  So with that in mind, we took to the drawing board.

The N55 twin scroll turbo of the 335I puts out 335bhp and about 332ft/lbs of torque according to numerous online sources.  As the successor to the previous N54, which we owned a 135I and 335I, the twin scroll single turbo offers up more performance and useability.  Like any turbocharged car, a simple formula of more air in and more air out with changes to the cars air/fuel mixture, boost, and timing is all it needs to make power.  Unfortunately, many of the newer vehicles have very strong tuning encryption which do not allow the read of the ECU data.  This inhibits the ability to tune the car and gain more performance out of it.  Luckily, VR Tuned has a product designed specifically for turbocharged vehicles to gain in some cases 40% more horsepower.  The tuning box kit plugs into the cars boost sensor, manifold pressure sensor, and cam angle sensor to alter the stock ECU signals providing a predefined map to put the car in a tuned state.  The OEM style connectors means there is no cutting or splicing of wires and can be easily removed or put back to stock.  On the 335I F30 engine, the horsepower increase is rated at 61bhp with 120nm of torque gained.  So as a first step to the mod process, this would be the biggest “bang for the buck” in modifying the 335I chassis.

A turbocharger is in very laymans term, a blower, trying to get the air in the intake side and out of the exhaust side.  If the backpressure impedes the flow of exhaust gases, the turbo cannot achieve its full potential.  The best way to reduce or eliminate any restriction on a turbocharged car is have a simple straight pipe coming off the exhaust side.  But if you like being able to think or even hear a thought in your head, this is not ideal.  An exhaust system for a turbocharged car requires a fine balance of resonation and flow to create a unique sound that can still produce power without droning a migrain into your head.  The exhaust system is made up of the downpipe and then a catback system.  The downpipe on the 335I has a catalytic converter on it for emissions.  Obviously depending on your state, removing this can be illegal.  The factory cat is restrictive and by going with a high flow cat or catless downpipe, the performance of the turbo will greatly increase.  Because of the reduced backpressure, the turbo will spool up and come into power much quicker.  As this is a street car that we wanted to stay check engine light free and emission friendly, we went with the Agency Power stainless steel downpipe with high flow cat.  This downpipe is a direct bolt on to the stock exhaust and turbo to be used in a modular way.  The high flow cat gives the O2 sensors the appropriate readings it needs to keep the cars signals happy, and the turbo pressure happier.

But if you are going to push out air as fast as you can, you can’t do it for 10% of the way and expect the performance to be there.  So this is where we designed a unique catback exhaust that delivered an incredible sound.  The exhaust is called a “catback” because it starts at the catalytic converter, in this case the downpipe, and goes to the back of the car.  Again, a straight pipe would be insanely loud so we needed to design the exhaust in such a way that the tone would be elegant, unique, and deliver performance.  Utilizing 3 inch stainless steel tubing and 2 resonators, we created a unique Y design that swapped sides similar to that of a Porsche 997 Carrera exhaust out to dual 4 inch tips.  The criss cross design with horizontally mounted resonators gave one of the most unique tones we could have ever expected.  To complete the styling of the exhaust, a flat stainless plate supported the resonators with TIG pulse welded AP logo for branding.

The final component to our BMW 335I project was the cold air intake.  The air intake kit can always be improved upon on a vehicle from the piping to the filtration.  Some factory intakes have narrow tubes, corregation, or flat panel filters that just dont deliver the best air flow possible for the turbocharged engine.  Having already designed a intake that was dyno proven for the 435I, a slight change to the mounting system was done for the F30 335I.  Featuring the signature Agency Power cone air filter, an aluminum intake tube and heat shield box was developed to maintain cool air from the nose of the car.  The cone filter also has a front inlet so the intake is breathing in an absorbanent amount more of air than stock.  With its wrinkled black powdercoat finish and AP name plate bracketing, this was one of the finest parts to come out of the Agency Power fab team.  With the 4 piece package together (tuning box, downpipe, catback, intake) completed, it was time for some dyno testing.

Here at Vivid Racing in Gilbert, Arizona, we utilize a Mustang All Wheel Drive Dyno.  Because of the sensitivity of many new vehicles traction control systems, we choose to run the car in all wheel drive to avoid any faults or failures.  With hot summer temperatures of 100F and pump gas of 91 octane, we have a mixture of low readings in general.  However what is really important is the delta between the runs.  With enough time in hand, we were able to test each of these products to show you the difference in horsepower and torque that is realized.  In addition, to the gathered dyno data, we put together this video showcasing the car, the newly designed Agency Power parts, and its performance in action.  As quoted by the owner, “This thing is a rocket!

The final outcome of ALL modifications versus the stock car.

VR Tuned Tuning Box Kit for the F30 335I N55 BMW

The high flow cat downpipe installed by Agency Power

Downpipe with high flow cat product photo by Agency Power

Agency Power catback exhaust system with dual 4 inch tips and unique Y design

Midpipe of the Agency Power exhaust.  It is a “burnt” gold color from being used.

Agency Power Cold Air Intake Kit for the F30 335I BMW

Dyno Graph showing the stock 335I as compared to the Agency Power cold air intake performance

Dyno comparing the AP Intake, AP Intake with VR Tune, and the stock car performance

This is a dyno comparing the Turboback exhaust (downpipe and catback) versus just the VR Tuning Box versus the fully stock car

This is a dyno comparing the Turboback exhaust (downpipe and catback) versus the Turboback with the VR Tuned Tuning Box


About The Author

Dan Mermelstein - Co-Owner, Blogger, Porsche Enthusiast, VRTuned Marketing and Technical Support. Available to make your car faster!

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