The Turbo BMW

 PowerLabs!

 
 
 

 

 Introduction:
  I put this web page together for my friend Robert Schmitt, who is in Iraq right now, and for his brother Joe Schmitt and Cousin Al. The three of them actually devised and put together this car; I just gave them a hand with it over the last couple days that the car was put together. I hope you find this page interesting and inspirational: Turbocharging a naturally aspirated engine is a great exercise in automotive ingenuity and if done right, the results can be quite spectacular.

 Left from right: Al, Joe and Robert. My bad guys; this photo was taken early in the morning after a couple of near all-nighters spent building, running and tuning the car.

 The Schmitt's page:

http://www.fuzionllc.com/exp.html

 

 The Car:
 Rob purchased this car while he was still in High School as his daily driver and has entered it in various Autocross competitions, ice races, and track days. The car is driven very hard and has gone through several upgrades, mostly for better handling: The fenders were rolled (by hand, with a baseball bat!) and 225 45 17" Falken Azenis RT-615 tires were installed (Rob talked so much about these that I ended up getting the exact same tires for my own car) on some 17" rims. Suspension is Bilstein Shocks and Eibach Springs, and virtually all the bushings in the car have been substituted for polyurethane ones, which are less compliant, improving handling at the cost of some added road noise. The car is still relatively quiet and as streetable as it was the day it left the factory.
 The handling upgrades on the car allowed it to place very well in several autocross events (including various 1st place wins in its class at Fox Valley Motorsports events). Still... Something was missing... The stock 166 horsepower that the factory engine produced just wasn't enough any more, and now, with a job and a steady paycheck, Schmitt decided he was going to finally make the car into the sports car he wanted...
 

 The Turbo:
Forced induction in this project comes in the form of a Garrett T3/T4 T04 Trim Turbocharger; This is a rather large turbo, and would probably be capable of supporting close to 500horsepower on a properly built and tuned engine. Also, other BMW enthusiasts have had good results using this turbo on their projects. Most importantly, however, is the fact that a brand new unit can be purchased for under 200 dollars... All the info I have available on this unit is that it is oil cooled, has sleeve bearings and has an A/R of .56. Getting the turbo to fit required a fair amount of "persuasion"... Mainly hitting the side of the strut tower with a hammer to create a dent. This is probably the biggest turbo you could fit in there without some serious modifications.
 The black rubber reducer seen in this picture was used for initial testing and melted as soon as the exhaust manifold got hot.

 

 

Oil is plumbed to the turbo via aircraft grade hoses and fittings. During initial runs it was found that the turbo leaked a lot of oil past its bearings into the turbine housing, resulting in a lot of smoke. This problem was diagnosed as being due to too much back pressure causing oil to leak past the hydrostatic sleeve bearings. I suspect that the weight of the oil chosen (20W50) may have had something to do with it as well. Either way, the problem was solved by adding a scavenging pump to the oil return line. The pump can be seen on the picture to the left of this text, and it completely eliminated the problem.

 Also notice the K&N cone air filter leading up to the turbocharger. More on this later...

 
 

 Intercooling and oil cooling:
As the turbocharger compresses the air into the engine, it also heats it up. The heating effect is proportional to the amount of boost being run and efficiency of the turbo at that boost level. For modest turbocharged applications (up to about 6PSI) no cooling of the intake charge is needed. However, as boost builds, the intake charge becomes hotter and hotter and will eventually lead to detonation in the engine. Furthermore, cooling down the intake charge has the added benefit of making it denser, which helps make power. The goal of this project is to run a lot of boost, so a front mount intercooler was the obvious choice. It can be seen under the front bumper (it looks like a radiator). This intercooler was purchased for very cheap on Ebay, together with 3" intercooler piping kit.

 Oil coolers are always an excellent idea, particularly on turbocharged cars, and much more on a turbocharged car that runs an oil cooled turbo. If the engine oil warms up too much, it will lose its lubricating properties. The plumbing for the oil on this car is all done with aircraft grade stainless steel braided hoses, and anodized aircraft grade fittings... The oil cooler is thermostatically controlled. This particular unit came stock with the car. It is slightly bent from hitting a deer. The deer died, but the oil cooler still works!

Both the turbocharger intake and the intercooler are plumbed via a 3" intercooler piping kit and silicone couplers and elbows. Initially, hitting any kind of boost caused the couplers to immediately come undone. This was remedied somewhat by double clamping all the hoses, although I am not convinced this fix will work at high boost levels. Ideally, it would be nice to flare out the edges of the pipes.
 

 Exhaust:
 The heart of this project is a completely custom made 6 into 1 exhaust header that allows the turbo to bolt on to the engine. Al designed and built it himself, and it seems to work very well.

Turboback is a full 3" custom made by a local exhaust shop, with a 3" catalytic converter and a Borla Dual tip muffler. Despite the lack of resonators, the exhaust is actually surprisingly quiet. Turbos are quite effective at dampening the sound level of exhaust pulses and I imagine that the catalytic converter does a good job as well. That cat is probably robbing some horsepower, but overall this system should be able to sustain huge power levels, specially considering that the turbocharger is externally wastegated by a 50mm wastegate. Boost is currently set at wastegate pressure (9PSI) by connecting a hard line between the turbocharger outlet and the wastegate control line.
 

 Intake and blow off valve:
  The intake is a K&N cone air filter positioned ahead of the passenger side front wheel, right behind where the fog lamp would be. This supplies the engine with cold air through a 3" diameter aluminum tube that is routed through a hole in the fender well.

 

 

 

 

 

 

 

 

 

 During boost runs it was found that lifting off the throttle would instantly cause the intercooler hoses to separate; boost was building up and slamming into the throttle plate when it closed, causing a rapid surge of pressure that blew the hoses apart. The solution for that was to install a blow off valve; the BOV is located right before the throttle plate and has a line running into the intake manifold; when the throttle plate closes, the engine continues to pull air in, creating a vacuum on the intake manifold: this vacuum pulls the BOV piston up, releasing excess boost pressure into the atmosphere with a satisfying "WOOOSH!". I did a lot of the tuning on the BOV and found it difficult to get right; the bov would frequently not open or open prematurely, leaking boost. It might be worthwhile investing in one that costs over 20 dollars ;)
 

 Engine Management:
 The stock ECU (Engine Control Unit) this car has was never meant to see boost. As such, a means of controlling the engine in turbocharged trim had to be devised. Rob opted to go with a full standalone computer; the cheapest option is Megasquirt... However, megasquirt has two downsides; it has to be completely soldered and built by the end user, and, it has no base map with which to run the car... Joe Schmitt not only assembled the megasquirt, but also figured out how to tune it while getting it to run the car. Very impressive! The tune is still a little bit rough at times, but it runs... Megasquirt also required that a Bosh wideband O2 sensor was added to the car, along with a different idle air controller, which Joe and Al cleverly adapted from a GM unit using a block of threaded delrin, and a throttle position sensor, which was removed from a Subaru.
 Tuning and data logging is performed by computer serial interface, however, installed in the ash tray of the car is a megaview: the digital readout not only displays vital engine data in real time, but also allows the user to change tuning parameters on the fly. I made the ash tray mount myself :)
 

 Results!
How about that? All the same classic looks of the original 3-series, but now with turbocharged power! The intercooler is barely visible under the bumper, and it will be further hidden in the future by a black mesh and fog lamps or covers where the plumbing runs. It also doesn't sound very different from stock.

 On the street, it feels much like any other aftermarket turboed stock car I've ridden in: you get virtually all of the original low end torque and acceleration that the car had before, but, somewhere past 3000RPMs a whine builds up and gives way to far more power than the factory ever intended! Joe reports that, at 40 miles an hour, the car will spin tires from a roll!

 I can also report a lot of on-boost wheel spin and serious acceleration, however...

 Ahhh... The joys of a modified car! Its happened to me twice before, and I tried to tell rob that there is a reason why they don't come that powerful from the factory in the first place but he just told me that "blowing up is a subaru thing"... Look at the top of the cylinders on that picture; you can see that the head gasket blew in all but one cylinder. The 6 cylinder block looks like a strong engine and a very good candidate for forced induction, but BMW actually made that head gasket out of cardboard! A further attempt to replace the head gasket resulted in it blowing again.

 Update! The head gaskets were blowing from overboost; apparently the wastegate line was not working properly, allowing the engine to see 20PSI+ of boost. With a new wastegate line, the car is now being daily driven at 14PSI... I hope to get some new videos some time soon.
 

 Videos:
 BMW On Oval Track. (Quick Time, 12mB, 1 minute).
 

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