David Foley lives in New Orleans and is a good friend of mine. He tought me most of what I know about '02s when he let me work at his shop for a while in the mid 1980's. At the time I had a 1976 2002 and was learning to work on it myself. David helped me with that car as well as with the rebuild of a 1966 2000cs I purchased from him. Since then he has started to work on more exotic BMWs, including the rebuild of a Schnitzer twin cam engine:
To the less informed U.S. fan of BMWs, "AC Schnitzer" means little more than a line of aerodynamic components, wheels and engine goodies. In Europe, the Schnitzer name is highly respected and is well known for its association with BMW's racing heritage.
The Schnitzer brothers, located in Freilassing, West Germany, were dedicated to getting the most out of four-cylinder BMW motors. Josef Schnitzer, the oldest brother, had a brief stint with the factory motorsports team, aiding in the design of their racing motors. In ] 972, after about a year with the factory, Josef returned to the family business, concentrating on his own design of twin-cam power, based around the standard four-cylinder block. Unlike the factory twin-cam motors of the day, Schnitzer's engine had the intake and exhaust placed on the same sides as the production fourcylinder engines. Much of Schnitzer's success came in l 973 with Formula Two open-wheel cars.
Schnitzer twin-cam motors were used in the 2002 chassis for both rallying and road racing. The Weber-carbed rally motors produced approximately 225 bhp. For road racing, the injected motors developed around 275 bhp. These were installed early on in the same attitude as the production engines, canted 170 to the side.
The car featured here is an early Group 2 car, prepared in Germany by Schnitzer The engine is fed fuel by a Kugelfischer mechanical injection pump driven off the front of the crank in the same fashion as the road-going 2002tii. Unlike the tii, this pump has no limiter or automatic cold running enrichment device. Cold starting takes two people-one to hold the difficult to get to enrichment lever and the other to hit the starter.
Air metering is performed by an aluminum slide throttle encased in a magnesium casting complete with detachable magnesium trumpets. The slide plate glides across about 120 tiny roller bearings on one side and Teflon(g) strips on the other. At first, the use of two different sliding surfaces seems odd but not when you realize that the injectors are located upstream of the slide so that at partial throttle the injector spray is hitting the plate, causing slight pooling of fuel at idle and low speeds. I Having the Teflon strips on the pooling sides keeps the lubricated roller bearings cleaner. You can actually hear the tapping noise of the injectors hitting the slide plate at idle. Neat! Wide open, the fuel\air mixture has no throttle plates or shafts to impede its flow through the intake tract.
As the cylinder head and cam carrier was in two parts, the head was always cast in aluminum, but the cam carrier was cast both in aluminum and magnesium. There were early and late versions of the cylinder head\cam carrier assembly design changes in strengthening ribs and oil return valleys being the main differences. Also, the newer style heads were beefed up for use with turbocharging (more in a moment).
As with most twin-cam motors of today, the camshafts ride on split bearings directly on the aluminum of the cam carrier. Cam and bucket lubrication is by hollow core cams fed by the first of five split bearings. l his first bearing also serves as the thrust bearing for the cam. Pressurized oil in the cam cores is then distributed to each bearing and cam lobe through small brass oil jets. A duplex roller chain, similar to the standard production engines but longer, drives the twin cams by their standard cam gears. Here is seen a distinct difference between the factory and Schnitzer. The factory motors used a series of helical gears off the crank and cams to drive everything. Valve adjustment on the Schnitzer motors is both tedious and time consuming, since the adjusting caps can only be exchanged by removing each camshaft. This is the same method used to adjust clearances on the M1 BMW. Combustion chamber shape is that of the efficient "pentroof" design, resulting in a compression ratio of 11.5:1.
Clamping of the cylinder head to the block is taken care of by the stud and nut method, which is more effective than the standard bolts. Magnesium is the metal of choice for both the valve cover and upper front timming cover.
Pistons are of the skirted variety and have fairly low domes and shallow eyebrow cuts for sufficient piston-to-valve clearance. The low domes allow for good, even flame propagation at the ignition point. Schnitzer used two different rod lengths in its motors and also two different metals, depending on if the motor was normally aspirated or not. Turbo motors received the steel 148mm ccnter-to-center length rods, while the early atmospheric motors had 143mm titanium rods. It is interesting that both Schnitzer and the factory had problems with titanium rods early in their development. A change in actual design, it seems, was needed along with the use of the then exotic metal.
Lubrication for this particular motor is provided by a three-stage dry sump pump mounted on the lower exhaust side of the engine. Cool oil is supplied to the pump by a four-gallon tank mounted in the passenger side rear seat area. Pressurized oil is sent by the gilmer belt-driven pump via large radisized curved -10 Aeroquip line to a remote-mounted Fram racing filter and then into the engine through a very modified standard filter mount. Particular attention was paid to oil flow, both to the motor and inside it.
Excessive oil is helped off the crank and into the pan by a handmade windage tray assembly whose center piece is secured on pedestal-style mounts secured to the main cap studs. The outer one-piece tray is sandwich-mounted between the oil pan and the block. Both the windage tray assembly and oil pan with special scavenge pickups were fabricated using pieces of the original as a guide.
The car's owner approached me several years ago about the possibility of reconstructing his original Schnitzer motor, which had grenaded on its first outing. After having made numerous attempts through different repair shops to no avail, I was contacted again to evaluate the situation and devise a plan to get the car back to its original state.
As is usual in these cases, the prognosis is always worse than first imagined. It was concluded that a new cylinder head\cam carrier assembly was needed since the original was not even usable as a boat anchor. Being as rare as these engines are, you can imagine what it would take to find a "new" head. Five of these new cylinder head kits were imported into the country back in the '80s, and l had two of them. This car got one of them, so I now had a solid base to build from.
The agreed upon overall plan with this car and motor was to build the engine to stay together and keep the car in its "it has character" condition. What this meant was a lot of money was going into the motor and its life supporting systems, so there would not be much left over for a fancy spit shine.
With these marching orders to follow, the engine was built with an emphasis on reliability. Pistons were made using a Mahle racing piston from another Schnitzer motor as a sample. I incorporated modern ring, pin and material technology to this design. This resulted in a narrow, good for highrpm use, 1mm top ring and special skirt design to allow much tighter pistonto-cylinder wall clearances than called for by older forged pistons made in this country.
Since this was a later style head and was new-in-the crate, many of the bosses for the ancillaries needed machining for our intended installation. Schnitzer used these motors in several different configurations such as the upright and canted mountings. The motors were installed in the upright position for Formula Two cars and also the 1.4-liter turbo version of the 2002. In 1977, Schnitzer successfully campaigned a 1.4 turbo version of the twin cam, which put out over 386 bhp. This was an incredible car and motor! It won the German Championship in 1977, defeating the twin turbo Porsches of the time!
Along with the special engine, the Schnitzer brothers performed their magic on the car itself, especially the suspension. Originally the car was equipped with 13x13 rear wheels and 10x13 fronts. To accommodate these massive wheels, the front and rear suspension pick-up points had to be moved inward. In the rear, the half shafts were shortened, and the shock mounting points were totally refabricated and reinforced. At the front, standard diameter springs were used, while at the rear special 2.5-in. coilovers did the job. Presently, Ronal three-piece 8x13 and 9x 13 wheels, shod with Mickey Thompson road race tires, are used.
Brakes are vented discs up front and solid discs at the rear. Calipers are Porsche all around. A unique water cooling system is used along with ducted air to cool the front discs. The rear brakes are cooled by the vertical vents fabricated into the front of the rear flares. To keep the rear differential temps in check, a belt-driven pump transfers oil to a front-mounted cooler.
The first driving event was coming quick, so actual testing consisted of more than a few runs up and down a deserted stretch of road. Fuel mixture, ignition timing and oil pressure were all checked and adjusted. When everything looked good, the car was loaded up and my friend Eddy and I were on our way on a nonstop ride to Sebring, Florida. We made it there about two hours before tech! I really don't think the owner thought we were going to make it since I was up all night for three nights before the event getting the car finished. Sound familiar?
Well, the car ran great and got better at the second event in Atlanta, after an ignition glitch was resolved. At Daytona, the car sort of kissed the wall a bit too passionately but has since been repaired and is currently touring the southern HSR circuit.
So what does one do now as an encore to the Schnitzer 1 (i valve? The next project is a genuine factory CSL with the m49\2 twin-cam 24-valve, full flares, wings and all the other factory goodies.
Sounds like another story!