Custom Automobile Accessories

Factory specifications are simply unacceptable, at least in my opinion. Because of this, I decided to make a few modifications to my 1992 BMW 525i. Since I did all the labor, I was able to make all these modifications for slightly less than $800.

Car PC System

In the trunk of the car is a Mini ITX computer in a custom-built box. Attached next to the amplifier on the back trunk panel, the computer is wired to a Datalux 10.4 inch color LCD touch screen monitor mounted over the center console. In addition, a wireless mini keyboard can be used, but most tasks can be accomplished with the touch screen.

(Above and below) is the Datalux mount I fabricated. Since the screen is slightly too large to fit anywhere on the front console, I used two lengths of one-inch steel piping, a 45 degree elbow coupler, and two flanges as a mount. After finding solid metal to mount to on the floor, I drilled four prep holes and then used self-tapping screws to fasten the flange to the floor. The carpet on the E34 525i easily lifts after one removes the plastic panels by the door. The website is a great resource for anyone who wants technical information on the car or wants to do modifications and/or repairs.

By lifting the carpet, one can place the flange out of sight (see picture of mount below). I found some scrap carpeting to cover the piping, and used beige zip ties to secure the carpet around it. Where the Datalux screen attaches, I cut a piece of Lexan to fit the screen, and then drilled holes to accommodate both the flange and the holes on the screen for mounting. Since the bottom flange is threaded, the entire mount is rigid, but can still swivel if desired.

While it slightly obstructs the passenger side seat, the encroachment is very minimal, and the large screen is worth the tradeoff from using a smaller, dash-mounted screen.

With a custom GUI, the car computer system does the following:

GPS Navigation

A GPS receiver connected to the car computer allows real time map data to be displayed on the screen. While this is standard issue in new cars these days, it certainly was not in the early 90s when the car was produced.

Wireless Internet Access

Using a 7dbi WiFi antenna mounted to the roof (see picture below), the car computer can access the internet. The antenna wire was fed into the space between the rear window and the frame. By lifting the plastic sealing, I was able to run the wire through to the trunk where the computer sits. Since the point of insertion of the wire leaves a slightly exposed hole, I used silicone sealant to ensure a water-tight seal.  

DVD Playback

The DVD loading mechanism is mounted to the top of the trunk and wired to the computer using a 36 inch IDE cable (see pictures below to view the computer enclosure and black IDE cable) 

Rear Camera

In the rear bumper there is a web cam wired to the computer system. For increased visibility and safety, this can be turned on while in reverse.

MP3 Playback

Thousands of MP3s can be stored on the 60 GB shock mounted hard drive and then played through the stereo system. This renders the need for CDs useless, and via the WiFi connection, I can upload new songs to the car from my home computer wirelessly.

Above are the bare brackets drilled into the particleboard backing of the trunk. These brackets hold the Mini ITX system in the trunk. The cables hanging below include VGA, serial for the touch screen mouse, IDE for DVD playback, PS2 for the wireless keyboard, power button, reset, and 12v input. Not pictured are the GPS and WiFi antenna cables.

Above center is the Mini ITX system. The case is made from an old computer case that I cut and then used sandpaper to rub off the sandblasted coloring. This leaves a shiny metallic finish to the metal. The top and sides of the case are part of the top and upper sides of the computer case. This then bolts onto the bottom, which is two parts of the side of a computer case bolted together (see diagram below for more info on making this type of case). The red denotes locations to cut.

Stereo System

I installed a Pioneer 7400 head unit into the dash, replacing the OEM cassette unit. The new head unit plays MP3 CDs and an infrared remote. I replaced the OEM Nokia speakers from the rear shelf with 6 inch JBL woofer component speakers, and I replaced the front tweeters with high-performance JBL component tweeters. I then installed a 1000 watt amplifier in the trunk, and strapped a 10-inch Bazooka subwoofer in the trunk. The 525 has a spacious trunk, so fitting the bass tube and still having plenty of extra space was not a concern. BMWs come with heavy noise blocking insulation, which improves sound quality and prevents other motorists from having to listen to your music. The system sounds very crisp, has deep bass, and even at high volumes cannot be heard outside of the car.

Power for the amplifier is fed directly from the battery terminals (which happen to reside behind the back seat). I made a single wiring harness going from the front to the back, and this is where I ran the RCA audio cables to the amplifier.

Above is the Pioneer head unit.

Alarm System

I installed a Venom keyless entry/remote-start/alarm system combo into the car. The main unit fits nicely under the rear seat cushion where the car battery and pre-wired alarm system connector rest. Wired into the alarm system are strobes in the rear shelf, and a 140db siren inside the cabin (in addition to the exterior one). The interior siren has enough power to deafen someone, should they try to steal the car or anything in it. The remote start feature allows me to wirelessly start the engine, which also turns on accessories such as the heater and radio.

Above, I used the accessory blank to install an LED to indicate alarm system status. The black button is also custom - it resets the computer should there be some problem where I need to restart.

PA System

Inside the cabin of the car is a mixer. This mixer allows me to mix the music from the stereo system to a microphone clipped onto the dashboard. Hidden behind the front fender is a loud PA speaker hooked up to an amplifier. The audio feed from the mixer goes to the amplifier, where it is then fed through the firewall to a bullhorn speaker. 

Above, location of the concealed PA speaker is behind the front fender.

This was accomplished by drilling a few mounting holes in a piece of metal behind the left fog light.

A microphone sits atop my dash in case I feel the sudden urge to have myself heard.

The mixer (above) can mix audio from the stereo with the pre-amplified microphone and then send the signal to the PA amplifier (a standard 30-watt car amp with bridged outputs) underneath the driver's seat.

Rear Horn

Have you ever been at a "no right turn on red" intersection, waiting for the green light to make a right hand turn, and someone behind you honks? Well, I have, and now I can do something about it. Facing the rear of the car are dual tone 135db tractor/trailer truck air horns wired to a switch to the right of the drivers seat. Next time someone honks when they shouldn't, they will surly be in for a noisy surprise.

Control Console

Below is the accessory switch panel I made. The large red lighted button to the right is the reverse horn switch. Going from left to right, the switches perform the following tasks: 1) PA on/off, 2) LCD monitor on/off 3) Police siren on/off, 4) Police strobes on/off, 5) Reverse horn.

There is also a police siren and flasher strobes in the vehicle. The siren is very loud, and makes the car seem like an undercover squad car. When used in conjunction with the strobes, it makes for a very convincing police vehicle. When in a tight jam, traffic does move aside when activated.

(Above) Pictures of the car at El Mirage, California dry lake bed during a day of racing and cone-course driving. The car hit 145mph that day.