S/C 325i



One of my summer projects involved finding a fun daily driver.  The goal was 4 doors, 250hp, good handling and 25-30mpg with a 6k budget. I initially started searching for a 95-98 3 series BMW due to their torquey yet efficient inline 6 engines.  After driving quite a few cars that met my budget criteria I came to the conclusion that most of the people who sell older cars on Craigslist are completely delusional. Most of the piles (cars) needed a ton of work, many had body panels both inside and out hanging from their mounts.  I didn't even get to looking at the mechanical systems but in my book if you can't even keep a car looking nice on the outside odds are you aren't taking care of the insides either.

I ended up going back to a car I had originally found for my wife, we wound up trading her car at a dealer and luckily when I called back about this one it was still available. The car in question was a 2002 325i (5speed) with a few options: sports package, Xenon headlights and cold weather package. Our previous BMW was a 1999 328 which had 30 hp on the 325's smaller 2.5L inline six engine but the 99 was also optioned to the hilt and the lack of this added weight (no power seats or sunroof) in the 02 was readily apparent during the test drives.  It felt quicker in acceleration and braking as well as easier to corner than our previous 328.

The only downsides were the car had been stolen in the recent past and had some dents to reflect this along with some broken interior trim.  I deemed the damage pretty minor and if you didn't notice it the interior looked perfect save for some scratched window tint.  The tires were also in need of replacement.  Maintenance-wise the car was just about due for some of the bigger services at 63k miles so I factored that into my offer. The Craigslist ad had an asking price of 11k and I took the car home for 9k. 

Over the course of the next couple of weeks I replaced the broken interior trim, broken windshield washer pump and both front window regulators (the regulators are notorious for breaking) at a cost of $155.  www.fcpgroton.com is where I purchased the parts. I also swapped out the fuel filter (Autohaus Arizona $48).

The tires and wheels were replaced with a set of VMR 18" V710's in Hypersilver along with 4 235/40-18 Yokohama S-Drives. I could tell a slight drop in acceleration due to the slightly heavier wheel/tire combo ( a few lbs. difference) but the handling difference made up for the minor loss in performance. The new tires were also surprisingly quiet.  The tire and rim package came from European Auto Source out of California and I have to say I am usually not a fan of this style of wheel but on this car it just fits.

About this time I also had the body dents repaired.  Luckily for me my employer had a paint less dent removal vendor who dropped by weekly to take care of the dings on our products.  Two sessions and $90 later and the door, rear fender, front fender and trunk lid dents were gone.

The next phase of my project required access under the car but the factory sport package made rolling under the car impossible so ramps were in order.  I picked up a pair of Rhino ramps at the local Checker for $39 and after fabricating a base to hold them in place I could easily drive the car up and get plenty of clearance underneath.

The final maintenance item that is a must do for these BMW's is the replacement of all the cooling system parts.  The plastic expansion tank, thermostat housing and ends of the coolant lines tend to crack in hot climates which eventually leads to catastrophic failure anywhere between 70-100k miles (our previous 99 had this happen as well as my friends 3 series). I also decided to replace the water pump since it would be easy to do while I was replacing all the hoses.  total cost for all the parts shown was about $400 from various online parts houses.  I know the dealer easily gets nearly $1500 to do the same job but if you are at all handy with a wrench you can find various how-to's online and do it your self.

The hardest part of this job was separating the old coolant hoses!  Once the fan assembly was removed there was plenty of room to work and the fan assembly was only held in by one bolt and a single plastic rivet.

One of the allures of these cars is the well designed inline six engines BMW has been using.  Our old 99 328 had a 2.8l inline 6 rated for 184hp and I didn't realize how good it was power wise until we bought 2004 Nissan 350Z.  The Z had a V-6 rated for 280hp but despite the 100 hp advantage the BMW felt faster.  Part of that could have been the torque band which is much lower on the BMW vs. the Z, but even on the top end the BMW felt more solid and the engine was much quieter.  More than once I caught myself driving near redline in 3rd gear on the highway in the BMW with the sudden realization that I forgot to shift 20 miles ago.  There was no way that would happen in the Z as you had to upshift to quiet the engine down. Gas mileage was also far superior in the BMW.  While the Z managed around 25mpg consistently the BMW topped out around 33mpg if your commute was all highway!

The 2002 325i was a refined 2.5l inline 6 which was now rated for 180hp, four less than the 2.8l inline 6 from just 3 years earlier. Realistically  it was putting out 150 or so hp to the wheels.  The next upgrade would get this number up to my goal of 250 hp.  It was time for a supercharger.

I picked up a used S/C system from Active Autowerke in July and little did I know it would be one of the worst decisions I would ever make. Long story short they sold me kit with non-working parts and a supercharger that needed a rebuild right off the bat. My whole experience with their technical support staff left me feeling scammed after they claimed they did not receive any of the emails I sent requesting help despite answering some of the questions on them but ignoring anything pertaining to the bad head unit. Phone calls were no different, when I could get a hold of them their answers were vague and the mantra of "the head units are usually not the problem" was repeated over and over. Stay away, far far away from these guys.

Luckily I did the installation myself and I had a second car to use so the above mentioned hardships didn't affect me as much as a guy who relies on their car as the sole mode of transportation.  If I had been in this boat and had to pay someone to install this kit I would easily have been out another couple of grand due paying for the install only to discover the whole thing needed to be pulled apart to get the head unit rebuilt.  

The supercharger utilizes a Rotrex C30 head unit, bigger injectors, reprogrammed ECU and an air to air intercooler to make about 100 hp at 5-6psi.  The head unit mounts on a bracket that resides where the stock air box would usually occupy. The first steps in the directions involved pulling the air box and divider between the brake booster and engine bay to make more room to work.  If you have big hands, find a friend with small hands because the space in this engine bay are tight!

The directions have you pull injectors to swap them out with the supplied bigger units.  I had to pull up a how-to online to figure out the injector removal procedure.  Once they were in I also installed a fresh set of factory plugs replacing the cheap aftermarket plugs the previous owner had installed.

More vacuum lines were routed and various lines spliced or plugs.  Again the directions were kind of vague in spots so it took much longer than it should have.

The front bumper eventually had to come off which was surprisingly easy thanks to another how-to found online.

Most of the lower plastic shielding is removed to make room for the plumbing that goes to the air to air intercooler supplied with the kit.  The small heat exchanger above the intercooler is a supplied oil cooler for the superchargers self contained oiling system.

Eventually the S/C bracket is installed along with new idlers and a new tensioner.  The idlers were used units while the belt and tensioner were brand new. The power steering cable is lengthened with a supplied extension so it can wrap around the S/C bracket.

The S/C belt installed.

I wasn't impressed with the oil cooler reservoir mount, as you can see only the bottom few threads actually engage the mount. It also took a while to figure out how and where the mount attached as the directions simply said "install the reservoir" with no detailed pictures.

Another confusing spot in the directions was the hose routing from the head unit.  It took an hour to figure out how to route the outlet hose in part because they supplied a extra elbow.  Once I removed the extra elbow everything fit if I squeezed the outlet hose between the frame rail and S/C as shown above. One or two extra pictures in the directions would have really helped. 

The intake tube also presented a problem.  The only way it would fit where the directions wanted it located was if the headlight was moved forward. I eventually had to cut away a bit of the front fender to get the tube to clear with the lights pushed back.  This is also about the time I lost faith in their tech support.  When questioned on this their only response was if I had factory headlights, if so it should fit.  The xenon headlights are factory and I had to call again when I could not get the tube to fit.  They responded that the kit doesn't work with Xenon headlights and I would have to trim some sheet metal.  Xenon headlamps are kind of common on these BMWs so you'd think they'd mention this in the instructions.

With bruised and scratched hands I finally put everything back together and once the reprogrammed ECU came back the engine was fired up.  The whining noise the S/C made was incredibly loud but having never had one of these centrifugal style blowers before I really didn't know what to think.  The first test drive showed the boost bypass valve was not working so when letting off the gas after building boost the pressurized air was feeding back into the S/C making weird noises.  Again an e-mail and phone call to AA netted no useful information so I ended up troubleshooting the problem myself and buying a boost bypass valve from the local Saab dealer to get the car running.

Despite the noise the kit did seem to add quite a bit of oomph to the car. Unlike a roots style blower the centrifugal blower used in the kit generates horsepower in the upper rpm range in an exponential fashion so real power comes on around 3-4k and pulls harder and harder till the new 7k rpm redline (original is 6.5k).  The power at the top makes you wish for an extra 1k on the redline.  Comparing the power of the 325 to my wife's 3.0l 255hp 06 330i I can definitely say the older BMW accelerates faster and pulls harder in all rpms.   While more power down low would be nice I think the existing power delivery will keep the stock drive train components from self destructing since the whole car is rolling before the real power kicks in.

Over the next few weeks I continued to drive the car but the S/C head unit gradually became louder and louder eventually being heard above the radio played at moderate volume levels.  The high pitched squeal actually gave me a headache after my drive home from work.  My inquiries to Active went nowhere and I eventually sent off the head unit to a place in Texas for a rebuild (http://www.superchargerrebuilds.com/). $700 later I had a nice and quiet head unit.  

I made one last attempt to contact Active to get a partial refund and was told they never received my request for help e-mails (lies) and that if they did they would have had me videotape the problem to start trouble shooting (more BS).  The final call to the Manager of Operations Mike Hugh was the most telling, he basically never let me talk due to his constant interruptions.  The conversation was basically a fishing trip from Mike Hugh to try and find some way to deny responsibility.  Like I said, stay far, far away from these guys.

Update 2-1-11

The rebuilt Rotrex gave up the ghost a few months back.  I recently confirmed that the input shaft had sheared off, a part the rebuilder had replaced.  It took me a while to find a place that could reprogram the computer (not plugged into the car)  to take I back to stock but I finally did and the car is finally quiet again.  Even the place that reprogrammed my computer mentioned that the Rotrex head units were junk, typically ready for a rebuild around 50k miles.