5
Q. Who are the manufacturers of the M3 transmissions?
A. There are two manufacturers and both are German. Getrag produces the European six speed manual gearbox and Zahnradfabrik Friedrichshafen
(commonly abbreviated ZF) produces the US five speed manual and automatic transmissions.
3
3
.
.
E
E
N
N
G
G
I
I
N
N
E
E
Q. How do I calculate horsepower at the crankshaft when given horsepower figures at the wheels?
A. When running a car on a dyno (dynamometer), one measures horsepower and torque at the wheels. To precisely calculate your actual
horsepower at the crankshaft (also known as brake horsepower (bHP)) is close to impossible due to the unknown drivetrain losses (bearings,
gears, couplings, shafts all account for loss of HP). No two vehicles are alike, i.e., some have stronger engines with high drivetrain losses and
some have weaker engines with low drivetrain losses and so on. Through testing and experience, a safe approximation is to assume between 15-
18% drivetrain losses. To calculate, simply use the following equation (assuming 17% drivetrain loss):
bHP = ( (wheel HP) / 0.83 )
.
Q. Why should I be concerned if my water pump has a plastic impeller?
A. Model year 1995, most, if not all, 1996, and even some very early 1997 M3s were equipped with the plastic impeller water pump. The unofficial
build date cut off for the plastic impeller is 10/96 (check driver side door jamb to verify build date). If you have a 1996 or early build 1997 M3 and
are unsure if the improved metal impeller water pump has been installed, consult your dealership as the water pump needs to be removed to
determine the impeller type (there is no other way of verifying). Plastic impeller water pumps have commonly failed without warning at around 60K
miles and up. The result is sometimes a badly overheated engine that can cost thousands of dollars to repair if your warranty has expired. Note
that in 2001, BMW has reintroduced an improved durability plastic impeller water pump for all vehicles.
BMW Water Pump (metal impeller; remanufactured)
P/N 11.51.7.504.040
Water Pumps: Plastic Impeller (left) and Metal Impeller (right)
(image courtesy of Ben Liaw)
Q. How long should I wait for the engine to warm up?
A. Because an oil temperature gauge is not provided with the vehicle, it is impossible to determine the precise engine temperature. However, it is
possible to approximate a safe operating temperature. As a general rule, engine oil is most efficient at 180° F and up. Using an ambient
temperature of 32° F, start by letting the vehicle idle for no more than one minute. Begin driving, using as little throttle as possible (no more than
half throttle), while keeping the engine speed below 3000 RPM. The coolant temperature should slowly creep up and level off at the midpoint. At
this point your engine oil should be above 100° F, however it will still be relatively cold so stay below 4000 RPM with no more than ¾ throttle
usage. Depending on your driving conditions, an additional five to ten minutes may be required to reach the magic 180° F mark. After that, full
throttle and limited high RPM visits are acceptable, but it would be a good idea to wait a few additional minutes to ensure you are at maximum
engine operating efficiency.
Q. What is the firing order of the M3 engine?
A. The cylinders fire in the following order: 1 & 5, 3 & 6, 2 & 4.
Q. What OEM spark plugs are used in the M3 engine?
A. Depending on the engine type, the two OEM brands are Bosch and NGK. For the proper spark plug part number, refer to the spark plug
application chart at the Unofficial BMW site
http://www.unofficialbmw.com/images/sparkplugchart.jpg.
Q. What is the oxygen sensor fault code?
A. One of the more common causes of the check engine light is a failing or failed oxygen sensor (also referred to as a lambda probe). The 1995 M3s
had only one oxygen sensor (located before the catalytic converter) due to OBD I and the 1996-1999 M3s had four oxygen sensors (two before
and two located after the catalytic converter) due to a more stringent OBD II standard. In short, the oxygen sensor measures the air/fuel mixture
and transmits the signal to the DME which attempts to achieve the stoichiometric air:fuel ratio of 14.7:1 (or a Lambda of one). Running the
vehicle with a failed oxygen sensor is not overly harmful, but efficiency is reduced because the vehicle will be running excessively rich; a default
setting of the DME to reduce any probability of damage when no signal is present.
