On the BMW 335i with the N54 engine, Cobb Tuning has come out with a Stage 1 Plus map, that gives an option between re-flashing the cars ECU with everything being stock and the Stage 2 map which typically requires a full turbo-back exhaust. There is only one part that is required for this map, and that is the Cobb intercooler that is a direct replacement for the stock unit.
The reason for this is because on this car, the stock intercooler is the main factor limiting performance when tuning the stock car. BMW gave the car a rather small intercooler, and they also decided to put on plastic end-tanks for some reason. Those end-tanks are just crimped onto the intercooler core, and that does not offer a very reliable seal as you start to turn up boost pressure.


Cobb designed an intercooler that solves this problem by increasing the intercooler to as large a volume as will fit into the car without modification, and welding the end-tanks onto the core so that it can easily handle more boost pressure reliably.


It is worth noting that if you are looking at installing this intercooler, there are a couple other parts that would be a good idea to install at the same time, the main one being the charge pipe. This is the pipe that connects the intercooler to the throttle-body. The stock pipe is made of plastic, and just as with the intercooler, as boost pressure is increased, there is a chance that the stock pipe could fail, and as it ages, the plastic can potentially become brittle which can also lead to an potential failure.


The charge pipe is also where the factory by-pass valves connect and on the 335i, those factory pieces are made by Bosch, and are made of plastic as well. So if you are going to install a new charge pipe, it would not be a bad idea to replace the bypass-valves at the same time.


Once those parts are installed you can safely run the Stage 1 Plus map, and the increase in performance is fairly substantial.


When we put our 335i project car on the dyno to get a baseline, the car made 270 ft lbs of torque, and 243 wheel horse power. On the Stage 1 map, that increased to 345 ft lbs of torque, and 284 hp, which is a lot for just a re-flash of the ECU. It is worth mentioning that those results were on the Cobb 93 octane map, but we were running 91 octane in the car because that is the highest octane rating that we have access to here in Colorado. The car was consistent on the dyno with that fuel and that map, so we felt that this was a reasonable result for the potential gains over stock.

Cobb 335i Stage 1 Plus Vs. Stage 1


When we installed the Stage 1 Plus map, we didn’t want to risk running the 93 octane map because since it was more aggressive now, there was a greater chance that the car would not run properly with the lower octane fuel than the map was calibrated for. But even on the standard 91 octane map, the end result was 370 ft lbs of torque and 328 wheel hp. Not only did we gain about 25 ft lbs of torque and 44 whp, the overall power band was also greatly increased.


I can also tell you that after running this map for over a year now, the car has been entirely reliable at this power level, and there have been no issues with any kind of limp mode, etc. in all the time that I have been running this map.


The car just feels like this is how it should have come from the factory. The stock power levels are fine but now that we have added 100 ft lbs of torque and nearly 90 whp, the car is an absolute blast to drive. I can say with out a doubt, if you have a BMW with the N54 engine in it like the 335i or 135i, you will love the car with the Cobb Stage 1 Plus map installed.


Thanks for reading, and I will include some related links below to our baseline test on the 335i, as well as our install of the Cobb charge pipe and the Turbosmart bypass-valves.

-  Jon Cooley