I have owned my 1973 BMW 2002 for 3 years now and put in countless hours of work and changed out nearly everything, except the drive line. Two weekends ago I went up to my friends shop to finally change it all out. I have been running the stock setup from the clutch back for too long. Also, the lack of a 5th overdrive gear is hurting my gas mileage.

The install went pretty smoothly and took only a day to accomplish. While we were putting in the new transmission and driveshaft we also threw out the stock open differential for a 3.9:1 limited slip. I have said this after numerous projects before, but wow it feels like a new car! The transmission is smooth and the shift throw is much shorter and tighter. In conjunction with the new differential gear ratio the gets off the line quicker. Also, since power is put down the wheels evenly it comes out of corners like a race car. Previously with my open differential the car ‘wiggled’ as it regained traction after a hard corner due to the fact that is sends power down unevenly.

To see pictures of the installation check out the Flickr set.

Open differential versus limited slip differential

I’m not going to go into great detail regarding all of the differences because that can easily be Googled. I just wanted to show the the main difference. On left we have my stock differential which is an ‘open differential’. On the right we have my new Limited Slip Differential (LSD) with a gear ratio of 3.9:1.

The major difference and also the major weak point of the open differential are the spider gears. This allows the wheels to spin independently. With the car in the air, I can spin one back wheel and the other one will spin in the opposite direction. The limited slip on the other hand doesnt have those gears. Not only can it handle more power it also makes locks the wheels together. Putting the car in the air and spinning one wheel will make the other spin in the same direction. More information can be found at howstuffworks.com.

Its been a long time since I last tuned the car ever since I started on the new M3 motor. Just as I was getting back into practice and tuning for efficiency given the high gas prices, a friend gave me his fuel map for a similar car also with Individual Throttle Bodies (ITB’s). After about 30 minutes of tuning the car ran superbly!

It had taken me quite a long time to get where I was and from the looks of the map above it would have taken me several more outings. One of my main trouble points was coming back off overrun and right off idle. The latter is a common problem with ITB’s that normal cars dont have with one throttle body. When the throttles quickly open the pressure drops to near full atmosphere and therefore we are getting much better volumetric efficiency requiring more gas.

So far everything is performing wonderfully. The hesitation off idle is gone and the power band is strong all the way up. Also, overrun back onto wide-open throttle is amazing. The fuel efficiency appears to have improved as well. This may not make sense to some but hopefully this is useful to somebody out there (click on the picture above to see a larger image).

More photos: BMW M3 head photo set

The M3 head just came back from the machinist about a week ago and it looks wonderful but unfortunately I didnt send off the cam case and other parts to be media blasted along with the head. So this Saturday I spent the day with the parts cleaner at my friends shop A1 Imports Autoworks in San Rafael. It saved me a little bit of money and I had to inventory anyway. I cant wait to put it together!

 Recently I have concluded the bulk of the exterior work on the car. The paint isnt perfect buts its actually pretty good especially for a street car. The added side skirts and bullet mirrors help tie it all together. Now to focus on some of the electronics, as well as the new motor. (click the thumbnails for larger pictures)

Even though I havent even put 7,000 miles on my first motor install I purchased a cheap S14 2.3- liter motor from the first M3. In combination with my other parts lying around, I am going to build a 2-liter M3 motor with the bottom end (M10) from the 2002. Actually, the blocks are identical except for displacement but machining will probably be required to get all the oil and coolant passages to line up. The M10 block has been in production for over 20 years. My friend and mechanic JP Cadoux will be teaching me how to hand build my first motor and I will be teaching him to control fuel and spark delivery with MegaSquirt open-source software.

I dont want to reveal too many details yet because I am not sure what is possible but I have some very exciting ideas. This motor will be completely custom from the machine work to get everything to mate up to the pistons and rods. For what I am trying to build I dont think I’m going to find anything off the shelf. I am going to attempt to use the same camshafts and valve train as well as the M10 2.0 crank of course. Once the machinist has his hands on it I will know more.

In the past few weeks I have fallen into so many parts at such incredible prices I couldnt resist. Some of the parts I acquired are pictured below but some of the ones that arent include a 5 speed, a limited slip 3.9:1 differential, the bottom end to another 2002, and a complete M3 motor from the 80’s that needs to be rebuilt. I am going to be building some interesting things in the near future. I cant wait!

I recently wrote a letter to the editor of the Roundel Magazine, published by the BMW Car Club Of America, about my friend JP Cadoux at A1 Imports Autoworks in an effort to get the word out about what he does. I am kinda surprised they actually published considering I wrote in a serious manner but frustrated after reading silly articles about carbon fiber, xenon headlights, and other useless do-dads. Nevertheless, here it is.

I’ve owned this car for almost 2 years this August and for the life of me I have not been able to get this car to sit flat, i.e. not sag in the rear. I have replaced every bushing, removed every spacer, replaced the springs and shocks and still, the sagging continued. So I finally bit the bullet and replaced my front suspension struts with coilovers which allow for an adjustable ride height. Not only does the car sit level it handles better, especially squatting into a corner.

The Bay Area BMW 2002 car show is coming up this Saturday so in preparation to avoid flame wars I have cleaned up the car a little. Everything is coming together quite well, including the tuning. The Bay Area 2002 Show and Swap may be the biggest in the world with over 100 cars attending. Its incredible to see so many of these cars so well cared for. Here are some photos for those of you who cant make it to the show.

While having a few drinks with a buddy of mine at a local bar in San Francisco I met an editor for Jalopnik, a sister site for gawker.com. After talking to him for a while I mentioned my open source fuel injected 1973 BMW 2002 sitting out on the street. Next thing I know he is taking pictures of the car and taking down my info. A few days later some friends who read the site me this link featuring my car.