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BMW 2002, 2002TI, and 2002tii - More Power Part II

In part I of this article, we explore different fuel injection and carburetor setups for BMW 2002, 2002TI and 2002TII models as part of a series on improving the 2002's M10 engine output. Part II focus on selecting the proper camshaft, ignition, and exhaust setups. This article applies for all BMW 1602, 1802, 2002, 2002ti, 2002tisa, 2002tii models.

Which cam is for me? Here is where careful research is necessary. Selecting the right cam for a 2002 depends on the intended application, and what rpm range you want the motor to make horsepower. 2002 cylinder heads contain large amounts of horsepower potential. Just by changing cams, improving the induction system, and running an OEM exhaust, 150 horsepower on an otherwise stock head (no porting) and bottom end is not uncommon.

The stock cam found on almost all 2002's (with the exception of the 49-state '76 2002) is referred to as having a 264 degree duration. This cam is a reasonable compromise between low-end torque and mid to high-end power. Also available from BMW is (was) the "sport" camshaft, with a 300 degree duration. This cam was designed for the TI's and TI/SA's (with dual sidedraft carburetors), and requires enlarged cam bearing journals.

The most well known aftermarket BMW cam manufacturer is Schrick. These are German cams made from new chill cast billets. Because Schrick cams are so widely used in BMW 4 cylinders, a brief description of the available grinds is given below. All grinds are referred to by their "advertised" duration number. This number is different from the "actual" duration of the cam, the amount of time in crankshaft degrees that the cam holds the valve open.

284 really only a mild improvement over stock, has good low end torque characteristics, no loss of driveability. Works well in conjunction with a 32/36 Weber DGV carburetor. Valve lift: 9.m intake; 7.2mm exhaust. ( a good stock replacement cam)

292 Probably the best overall street cam. Works well with either a 32/36 Weber or sidedraft DCOE's. Excellent mid range (3500-5500 rpm) performance. Power gains are seen throughout the rpm range, and the top end really benefits from the breathing capabilities of the DCOE's. This cam will yield 140-150 horsepower with accurately jetted DCOE carbs. Low end is still very impressive. Valve lift: 10.m intake; 7.6mm exhaust.

304 This is where the Schrick grinds start to get serious. This cam can be run on the street, but it is not for everybody. Low end begins to diminish, due to this cam's increased valve overlap. This cam really works well with 45 DCOE sidedrafts, and a BIG ( > 2.5") exhaust system. the power curve really begins at 4000 rpm, and continues on through 7000 rpm.

316 This cam is really suited only for the racetrack. The valve timing and duration are such that the fattest part of the horsepower curve is near 5000 rpm. This cam has been recently upgraded to provide the same lift figures as the 336 grind. Useful power is 4500-8000 rpm depending on carb jetting. (11.9mm intake valve lift)

336 This is the ultimate statement in Schrick cams. This cam has found homes in 220+ horsepower GT-3 racers here and in the saloon car series over in Europe. Only included here for informational purposes, a motor with this cam will hardly IDLE, and will easily rev to over 8500 rpm!

There are many other options for BMW cams. Re-grinds and new billets are available from various race shops, and several reputable manufacturers and tuners such as Iskenderian, and Korman. Korman offers their own version of a "300 degree" camshaft at considerable savings to versus a Schrick cam. Norris used to grind good hot cams, but they are no longer around. The best thing to do when looking beyond a Schrick is to work closely with someone who has had measurable experience in this field.

Tips for extracting more reliable performance from a BMW 2002: * A "tii" full mechanical advance distributor (008 Bosch) is a nice addition, but not necessary. This distributor features only a centrifugal advance mechanism, no vacuum mechanism. This distributor has an advance curve that cuts in slowly and maxes out with a relatively small total advance. In other words, it is ideal for motors running high compression (you don't want a quick advance curve, it would promote knock). Using this distributor on an otherwise stock non-tii motor can actually hurt performance. Cars with low compression and/or EGR need a quicker and taller advance curve to improve midrange torque and top end power. In actuality, every 2002 distributor is mechanical advance, but there is an additional vacuum assist servo which can either add advance under load, or retard the timing at idle, depending on the specific distributor. These distributors can be easily re-curved using different advance springs and weights, a variable speed drill-press, and a tachometer.

The total advance of a distributor is a function of the initial advance setting (what you set with the timing light) and the amount of advance built into the distributor itself. The main thing on any distributor, is to make sure that the advance mechanism is in good working order, that the distributor shaft has no "wobble" or runout, and that the shaft endplay is less than .006". It is also important to check that you are getting full total advance from the distributor. Many times, complaints about poor performance come from the fact that the distributor becomes worn or sticky and will not give full advance at the top end, hindering power.

Convert to an electronic ignition system. Electronic ignition systems are a wonderful replacement for the sloppy breaker points setup. It often makes a noticeable difference in top end power (mainly because it maintains proper dwell/spark energy/ignition timing at high revs), and adds tremendous precision and reliability to the ignition system. On a race car with a 300+ degree cam, and 45 DCOE Webers, the addition of a common small electronic system was worth another 500 rpm on the top end. Another widely used ignition system conversion is the capacitive discharge type. These systems typically can be fired with either points, or a magnetic/optical pickup. There are several excellent brands, which yield nice improvements in performance. Capacitive discharge (CDI) systems offer a higher voltage spark (useful when cylinder pressure and rpm numbers are high), and more precise control than standard systems. The increase in spark voltage comes tends to come with a decrease in spark duration, though. CDI systems tend to be most useful in situations where rich mixture and plug fouling are problems, and a high voltage is needed to get a spark going. The leaner fuel mixtures on newer cars tend to favor a longer duration spark for a more efficient burn.

Another ignition alternative is to adapt a Bosch TCI system from a newer car. This requires a few modifications though, and is best left to those wanting to tinker. Either way, an electronic ignition system improves the precision of the ignition system, rids the system of points, and can provide higher spark energy when combined with a bigger coil.

If you're running a downdraft carburetor with manifold, matching the ports on the manifold to the ports on the head will improve performance as well. The stock port castings on the intake manifold are considerably smaller than the ports in the head. Opening the ports up will help breathing. Remember that SCCA Street Prepared rules state that intake ports on the cylinder head may be matched ported only up to one inch from the port entrance.

A tii exhaust manifold flows quite well, and is a good alternative to headers. They last a long time, and are quiet. Also, Original BMW exhaust systems flow a lot better and are quieter than exhaust systems from the local quickie muffler shop. A 2002 Turbo system might be considered for engines producing over 150HP.

If you have a '74-'76 carburetted 2002, you might want to upgrade the clutch for any high-performance applications. These models use a 215mm clutch, whereas the earlier ones and the tii use a 228mm clutch. Changing over requires a different flywheel, clutch disc, pressure plate, throwout bearing, and the earlier longer flywheel bolts. Fichtel and Sachs (F&S) make several "sport" and competition pressure plates for the 2002 that are well suited in high horsepower applications. Also, Tilton makes an aluminum flywheel and accompanying pressure plate setup for the 2002.

When performing a total engine rebuild, ALWAYS balance the entire bottom end rotating assembly. This includes the pulleys, crank, rods, pistons, flywheel, and clutch assembly. This is crucial when building a reliable, smooth running, high rpm powerplant.

Pay careful attention to casting marks on rocker arms. These are potential problem areas on these parts. The rough edges cause stress risers along the surface of the part. The most critical area is actually on the BOTTOM of the rocker arm. The top surface (the edge that you see) is actually in compression under loading, and is therefore not as critical. Many engine builders like to "polish" this side. This is fine, but they often forget the much more important underside, where most of stress concentration occurs. Several performance outlets (Korman, Metric Mechanic, etc) offer special racing rocker arm which feature a stronger alloy, and hardened wear pads.

Total seal piston rings (or other gapless designs) work excellently on all piston applications, and are worth the extra money. Your motor will last longer, have less blowby, and make more horsepower.

When installing a 292 or 304 Schrick cam, it is recommended to also install the Schrick heavy duty single valve springs. These feature a higher seat pressure, and will provide an extra measure of insurance. They don't measurably increase camshaft or rocker arm wear, either. For the radical cams, double (inner and outer) valve springs are a must. Some people run double valve springs on the 304 Schrick cam. This is not necessary, and will result in accelerated valvetrain wear.

Don't forget the cooling system. 2002's have a tendency to run warm stock, increasing power will only increase the problem. Consider a high-efficiency re-cored radiator, a 320i radiator, or several other options (such as the Ford Pinto radiator or Volvo 240 radiator). Lower temperature thermostats are also available, in 71 deg C and 75 deg C varieties (stock is 80 deg C). It is also recommended that the stock plastic engine fan be removed and an aftermarket electric unit be installed. In the past, problems have occurred with the stock fan causing water pump failures at high rpms, because of thrust loads imparted on the pump shaft by the fan. Electric fans do a sufficient job of cooling at speeds under fifteen mph. (and they're quieter) At speeds over fifteen mph, airflow from the car being in motion is sufficient to cool the engine.

So, you can see that BMW 2002 owners have a plethora of performance modification information as their disposal. These cars' advanced engineering, simple mechanicals, practicality, inexpensive ownership, and sheer pleasure to drive make the BMW 2002, 2002ti, or 2002tii great car even today, 30 years after they were last sold new.

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