Hi,

how do the engines of a 1990 300CE (M104.980) and a 1996 E320 (104.995) differ, apart from the air filter arrangement as in the pix below? They are two variants of the same serie M104.

For sure the 995 variant must have some improvements over its precedessor, which are?

__________________
1996 E320 since 1/16/08, 171K miles as of Feb 2011

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1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE

Main differences are Engine management with Full Electronic HFM and Sequential Fuel Injection. No fuel distributor/accumulator/eha system needed.

Another big change is no more distributor/rotor ignition system. Full Electronic/ DIS distributorless Ignition.
And HFM/SFI systems have variable intake runnner length system.


High Tech/Low Tech ...

Thanks Arthur,

"high tech" sounds intimidating to DIY'ler, does it. More electronic less mechanical parts.

Still the newer one is not more fuel-efficient with all that high-tech stuff .

__________________
1996 E320 since 1/16/08, 171K miles as of Feb 2011

---------------------------------------------------------
1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE

I prefer HFM/SFI anyday..

I guess a tech evolution comparison would be:

Bosch Fuel Injection Type:
[ MFI] = Mechanical Typewriter
[ CIS ] = Electric Typewriter
[ HFM/SFI ] = Computer w/keyboard

But it is more fuel efficient - the 1990 300CE EPA rating was 17 and 21, the 1995 E320 coupe was 20 and 26.

Gawd,,, that 96 is a Beeeyoutiful engine.

__________________
95 SL500 Smoke Silver, Parchment 64K
07 E350 4matic Station Wagon White 34K
02 E320 4Matic Silver/grey 80K
05 F150 Silver 44K

I took the time to write a nice piece on the difference of these engines in an old thread.

I found it and will copy and paste it here:

1990-1992 300CE's have a different M104 engime (M104.990). This 3.0 liter-24 valve M104 engine is an early version of the 24-valve DOHC 3.2 liter M104 engine used from 1993-on. The 3.0 liter version still used the CIS-E fuel injection system as 1986-1992 3.0 liter M103 engines, using a distributor with one coil wire and 6 spark plug wires. This is basically a mechanical injection system with electronic control.

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 the EZL technology of the 104.990, 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.

Early M104 engines had head gasket problems. Also, all 1993-1995 Mercedes have bad engine wiring harnesses. Last, M104 engines have an electronic throttle actuator which is notorious for failing. All three items are expensive to fix.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".