Engine question?
 

Are all engines with the M104 badge the same? That is, 24V 3liter with variable intake valve timing? I ask because I often see posts where the engine is said to be M104 but then further discriptions will be 3.2 liter and only about 180 Hp as compared to the 239 Hp rating in my 300SL's owner manual. Is the valve timing truely variable and is it for 6 intake valves or all 12? It'd be great to find a link to a source of info on these engines and their heritage.

No, there's two basic types - CIS / 3.0 liter / 1990-93, and the HFM 3.2 & 2.8 liter, 1992 and later. None of them were as low as 180 hp or as high as 239 - you're getting some bad numbers somewhere.

Tkamiya is right, and to add to it:

The 3.0 liter M104 engine used the old CIS-E fuel injection system which was carried over from the 3.0 liter M103 engnie. It is basically a mechanical fuel injection system with electronic help. This M104 engine still uses a typical distributor, with a coil wire and 6 spark plug wires.

The 3.2 liter M104 engine was used in all 1994-1997 SL 320's, 1993 W124 chassis 300E/300CE/300TE (3.2), '94-'95 E320's (W124 chassis), 1996-1997 E320's (W210 chassis), and 1993-1999 S320's (W140 chassis).

The 3.2 liter M104 engine uses a different ignition system - HFM (hot-film mass air flow sensor), fully electronic, with integrated electronic ignition and sequential fuel injection. This system combines fuel injection and ignition control in one module. HFM-SFI systems use coils that are mounted directly on the spark plugs, replacing the distributor at the front of the engine. Each coil pack provides spark to two spark plugs at the same time, one connected directly to one plug, and the other with a short high tension lead to the next spark plug. So there are 3 coil wires and 3 high tension lead wires.

HFM fuel injection systems are designed so that idle speed can't be adjusted. Idle speed is completely controlled electronically. This HFM injection system also has adaptive technology that compensates for conditions such as engine wear and unmeasured intake air and is designed to maintain driveability as the engine ages.

HFM-SFI can retard engine knocking to just the knocking cylinders, unlike EZL technology, which retards spark timing across the entire engine. This keeps the ignition timing point as advanced as possible for maximum power output.

The 3.2 liter M104 engines also have variable valve timing on the intake cam, making the torque curve broad and flat, developing HP at a much lower rpm. This makes the power much more useable and noticeable.

The M104 engines also have a superior head design than M103 engines. Valve guide wear has always been a problem on M103 engines. The M104 head design has minimal vave stem/quide side force [ cam-valve swipe] . Mercedes seems to have solved the common M103 valve guide problems with this far superior design and it is not unusual to see them still tight into the 200K figures.

The early 3.0 liter 24-valve M104 engines are nice, but the advancement of technology is just so great in the 3.2 liter M104 engine, making these later engines much more desireable, IMHO.

Thank you all. That's exactly the information I was looking for. BTW, the 239Hp was my typo, sorry, the manual says 229 Hp. Tod

Actually, the number you are quoting is the hp rating for the 300SL only. The hp and torque ratings are different for the 3.2 liter M104 in all other chassis.