Over the past few years, the BMW aftermarket has grown exponentially in North America, making it an increasingly popular platform to modify. Whether you’re looking at simple exterior modifications or 1,000 whp turbo kits, you can find almost any modification for the popular 3 Series. Today we’re taking a look at the HSD Coil-over setup and Sprint Booster electronic throttle power converter for the E46 3 Series coupe, provided by the guys at JRP Inc. and Bimmersport Automotive. In these pages, Martin Poplawski from Bimmersport is going to show us how to transform this 3 Series to a handling monster with excellent throttle response. 
Raise the vehicle to a comfortable working height. You can either raise all four wheels or do one corner at a time. Once lifted, make sure the vehicle is safely seated on the jack stand(s). Keep the steering wheel unlocked so you can rotate each spindle. Start with the front axles and remove the wheels (this is a good time to inspect the tire for improper wear). The sway bar link is connected to the shock, so the first step is to remove this from the shock assembly. Remove the 16 mm bolt and nut from the spindle so it can slide down – it is a good idea to use penetration grease (ie. WD40) to make removal easier. Use a small pry bar to open the sleeve as much as possible. Once it’s opened slide the spindle down the shock. A good place to grab is the rotor at the 11- and 1-o’clock position. With a FIRM grip push the top of the rotor towards and away from you to wiggle the spindle down while maintaining downward pressure. Once the spindle is loose it should look exactly like this. 
The shock tower in the engine bay has three (3) 13 mm bolts that hold the strut mounting bolts. Remove these three bolts while holding the shock to remove the assembly from the vehicle. 
Prepare the HSD front coilover strut by making the shock length a bit shorter than the original (note: the height is adjusted by threading the shock body into the lower base – DO NOT adjust the upper perch to lower the spring). Doing both sides at the same time makes fine tuning the suspension easier. The threads of the shock must be at LEAST 20 mm deep into the base of the strut.
Keep the camber adjustment in the middle. This will be adjusted later during your alignment for your desired spec. 
Once you’ve prepped the strut, install the top of the strut to the strut tower. Note the orientation of the mount (camber adjustment goes in and out of the vehicle, not front to back). 
For the next step, install the strut into the spindle. Once fitted, use a jack under the lower control arm to raise the spindle assembly. It is recommended to raise the spindle to the max height then tighten ALL bolts before removing the jack to avoid preloading the suspension. Continue to the next side and repeat the same steps.
The rear of the vehicle is a bit simpler. With the rear axles off and the wheels removed, remove the 18 mm bolt holding the shock to the spindle. The spring will have pressure, so stay clear when removing the bolt. Use a pry bar to pull the spindle down through the upper control arm. The spring will slip out, but you may need some WD40 to make it easier.
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Next, remove the trunk liner and side trunk carpets to gain access to the rear shock mounting points. You can also remove the tail light bulb holders and plastic trays on each side for ease of removal and re-installation of these panels. 
Pull the panel back to expose the body lining seal (as pointed out the shock mount lies right underneath it). Remove the lining, either as a whole or cut an incision to expose the top of the shock – this can come in handy later for easy quick shock adjustments. 
Loosen the two (2) 13 mm bolts and the shock will lower down. Ensure the shock mount bolt is tight, set your rebound adjustment and prepare the spring adjuster to your desired height. Make sure you reuse the paper gasket from the original shock – this is important to prevent any rust formation in this high-pressure area. 
Install the rear spring perch and tighten the supplied nut and bolt. Set the perch to the maximum height, and put the spring in place – it may sit loosely but that’s OK. Next have a friend place the rear shock through the mounting holes, then fit and tighten the two (2) 13 mm nuts to retain the shock to the vehicle. Adjust the shock length and raise the rear spindle enough to fit the 18 mm bolt and tighten. 
Adjust the spring-height adjuster to the desired height, and test it by putting the reinstalling the wheels and removing and jacks and stands. Roll the vehicle back and forth to seat the suspension before measuring the ride height. Make the necessary ride height adjustments to your liking. Once you find a ride height you’re happy with, shorten the shock so the vehicle has no more than 100 mm of suspension drop when being hoisted off the ground. 
Review that all bolts are tightened properly and re-install all trunk paneling and light bulb holders. Take the vehicle for a road test and make any further adjustments necessary to meet your ride quality goals.
SPRINT BOOSTER INSTALL
Today’s vehicles use a number of systems to increase fuel economy than ever before. Most of these changes are done within the ECU, but part of this technology replaces the throttle cable for drive-by-wire, which is an electronic throttle body system to work with today’s DFI technology. For the average Joe this is great, but for performance enthusiasts it translates to an unresponsive pedal. Remapping the ECU is quite costly, so thankfully there is the Sprint Booster, a small electronic throttle power module and switch kit that can be mounted anywhere with ease. Let’s take a look how…
We are mounting the switch next to the gear shifter for quick access. Remove the gear shifter by pulling upwards on the knob. 
Remove the leather boot by pushing inwards on the left and right edges. Once it’s removed you will see two (2) Phillips screws that hold the trim panel down – remove them.
Pull up and back to remove the trim panel entirely by squeezing the plug tabs and unplugging each switch.
Moving to the pedal, use a flat screwdriver to push down the retaining tab on the side of the pedal.
Pull upward and to the left to remove the pedal assembly. 
Unclip the factory plug from the accelerator module and install the inline sprint booster harness. Plug the factory plug into the harness adaptor with the switch wire. You can run the wires like this. 
Before reinstalling the pedal, feed the switch through the centre console panel leading up to the gear shifter area, getting the switch through the trim panel location. 
After feeding the wire through, we re-install the pedal by tucking the wires into the center console leading underneath the dash and pedal location. Make sure the wires are tight, then re-install the pedal to the base. Once clipped back in, you will have a clean, invisible install. 
With the switch fed through, we can re-install the gear shifter trim panel. When re-installing, note the tabs on the trim panel as shown. 
These will slide into the dash board in the upper portion of the trim before resting flush into place. Put all necessary plugs back into the corresponding switch.
After fitting the upper portion into place, rest the bottom portion onto the dash and leave just enough room to keep the switch tight without any excess wire. 
Once you find a good location, remove the tape from the switch and secure it into the desired location. You can now install and tighten the Phillips screws for the trim panel. 
Tuck all the wires out of the way and inside the gear shifter area. Slide the leather boot back into place, push the gear shifter back down the lever, and ensure it clips into the locking grove in the lever. Switch through the maps on the sprint booster to your liking. Our favourite setting is medium (red). Push the button to emit green and there you have it – maximum performance from the Sprint Booster!
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