Late in 2018, Dr Euro was commissioned by the owner of Michaelangelo’s Motorwerkes (later to be re-named South Coast Euro) to complete a passion project of converting his 2005 325xi 6-speed wagon into a 335xi 6-speed wagon. This article briefly highlights the process and the required necessary steps needed to make the conversion possible.
Ambition
For those wagon lovers out there, BMW unfortunately never released the E91(wagon) with the twin turbo in-line-six N54 motor within the US market. This car was released in the European markets but was, for whatever reason, one of the models that was withheld from the US market.
BMW did, however, release the E61 5 series wagon with the N54 motor, within the US market, but with significant weight and handling disadvantages. The aim of this build was to create a slightly more nimble/compact touring car utilizing the same, very tuner friendly, N54 driveline.
The Build
For the chassis we are using an E91(wagon), titanium silver, 2005 build, 325xi 6-speed manual car with a lot of great options: black leather interior, comfort access, iDrive/Nav, PDC, and more.
For the driveline we used a complete donor vehicle (‘07 production 335xi sedan 6-speed manual car). The goal was to create a final product that looked and handled as though it had been assembled that way from the factory+.
Here are the various tasks that we will be covering to complete the swap:
1.Removal of N54 motor, suspension, and differential
3. Removal/Transfer of 335xi trunk floor, Charcoal Canister, and Evap lines to allow for install of dual exit factory 335xi exhaust on E91 chassis
4. Refresh and cleanup N54 motor with new/updated parts and carbon cleaning
5. Removal of N52 motor, brakes, and suspension
6. Install of the N54 driveline into the E91 chassis
7. Install of F30 sport brakes
8. Install of ST coilovers and new suspension arms and tie rods
Removal of N54 Driveline
We choose to remove the driveline complete with the front subframe and suspension on custom made rolling tables. We actually created two of these tables specifically for this build. Other things needed from the front end of the 335xi was the carrier for the front radiator/intercooler/power steering cooler, shifter stage, and all other varying peripherals like AC lines, radiator, etc.
Since the E91 chassis shared the same rear subframe as the 335xi, we decided to swap only what was needed from the rear of the car. Starting with the rear differential – the gearing ratio for the 335xi is much lower than the 325xi. It is that way for driveability with boost. We removed the differential with driveshaft and rear axles in order to install them onto our E91 chassis.
The front and rear brakes also vary between the 325xi and 335xi. We choose to upgrade our E91 chassis brakes to F30 sport brakes (which we will cover more at the end).
The last items needed from our 335xi donor car were the rear trunk floor pieces as well as the evap lines for the charcoal canister (charcoal canister and DMTL parts are the same from model to model). These items are needed since they make it possible to install the factory dual exit 335xi exhaust on the E91 (wagon) chassis. We also would normally need the 335xi fuel pressure regulator but we decided, instead, to order a new one since it is also serves as the fuel filter on the car. It was interesting to see that the fuel pumps are the same from 325xi to 335xi and the only variance was the regulator.
Relocation of Charcoal Canister and DMTL
Our E91 chassis, just like any standard N52 vehicle, has a dual tip single exit exhaust on the left side. Next to that single exit muffler, on the right, starting from about the center of the car, is the trunk floor compartment which creates a large cavity for the charcoal canister and evap lines to sit in. There is no space to install a dual exit exhaust without changing the trunk floor and relocating the charcoal canister. Only additional modification beyond swapping parts from the donor was extending the wiring for the DMTL and re-routing it for the new charcoal canister location (DMTL is attached to canister). Install of the evap lines required the fuel tank to be dropped slightly as one of the lines routed all the way from the back left corner (charcoal canister location), over the fuel tank, to the purge valve at the front of the car under the intake.
*Picture below showing 335xi trunk floor installed
*Pictures below showing E91 with trunk floor removed, showing stock N52 evap line location (charcoal canister removed):
*Picture below showing 335xi evap hoses installed on E91 chassis with charcoal canister relocated to new location:
*Picture below shows the finalizing of the rear end conversion (for dual exit exhaust):
Refresh and cleanup N54 motor
Now, with everything needed removed from the 335xi donor car and the entire N54 driveline exposed on a table, it is time to replace/refresh/cleanup the motor.
*Picture below showing new valve cover, index 12 fuel injectors, and Vacuum lines installed:
*Pictures below showing walnut shell Intake Valve Cleaning (before and after):
*Picture below showing new high pressure fuel pump (also, not shown, new low pressure fuel sensor installed):
*Picture below showing oil filter housing reseal and new plugs and coils:
*Picture below showing Factory Turbo R&R:
*Picture below showing new tensioner, pulleys, front seal, and some clean-up (also, not shown, new belt):
*Picture below showing new Front Driveshaft from our friends at Driveline (AWD FTW):
Removal of N52 motor, Brakes, and Suspension
Title is pretty self explanatory here. We used a secondary table for the stock N52 driveline/suspension/brakes. Once we dropped everything out, we were able to slide the primary table over with the N54 driveline and essentially bolt it right up!
Install of the N54 driveline into the E91 chassis
Now, time to get down to business. This conversion was, for the most part, a direct swap BUT by no means was this a plug and play deal when it came time to make everything work together. Thanks to help from our close friends at Bimmerscan, we were able to team up and make all the necessary changes needed with both hardware and software to make everything work like it should from the factory. Not only did they assist in getting everything working, we also upgraded from MSD80 to MSD81 and got an M3 instrument cluster installed! Thank you Bryce @Bimmerscan!
*Picture below showing M3 instrument cluster installed (mileage reflects original N52 motor as this picture was taken prior to exchanging some of the main control modules and programming for the new N54 driveline)
Install of F30 sport brakes
Thanks to some of the members on the forum, we were able to discover that the F30 sport brakes bolt directly up to the E90 front hubs and work with the factory backing plates. It was as easy as installing the new calipers, pads, and rotors with of course a nice system flush/bleed. Also, worth noting, it did require 15mm wheel spacers to clear these calipers with the stock wheels.
Install of ST coilovers and new suspension arms and tie rods
Just to be thorough, we replaced every single front suspension arm and both left and right steering rack tie rods. Since this will not be used as an all out track car, we decided that ST coilovers fit the bill for our intended purposes. We have had great experiences with their products in the past and find them to be a great option if looking to retain good ride quality while gaining height adjustability from a reliable product – ST is owned by KW afterall.
Overall, the car handles and performs exactly to our expectations. Driving behind the wheel, you quickly forget that you are driving a wagon and the performance and handling resembles that of a stock 335xi. Best part is that it is still a wagon!
Stay tuned as we have more in stock for this build to come!