Difference between two M104 variants?
 

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?


http://i245.photobucket.com/albums/g...1990_300CE.jpg

http://i245.photobucket.com/albums/g..._1996_E320.jpg

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 :confused:.

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.:D

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.

<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>

All 104 engines have variable intake valve timing.

Another difference between the early M104 vs. the later version is the timing chain configuration. The early version included an idler gear. The later M104 design doesn't use this set-up. The result was a quieter engine. A minor difference, but significant IMHO.

"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. "

all M104 had headgasket problems that were fixed with the replacements from mercedes.

In fact Workshops have generaly seen the new M104 more for a head gasket change than the old ones.
But they all wear out and leak oil with age until the replacement is done.

There are no specifix bad engine wiring harnesses, all mercedes from 1993 models with both the new gasoline and diesel engines all got this new biological brakedown wire insulation, but some engine harnness are prone to wear out much quicker due to higher temperature fluctuations.
As is a huge problem on the 6 and 8 cyl. engines as they have the ignition coils directly on top of the engine.
And it is not only the engine harnness, it is used in the whole car as well, but is no problem here as the temperature are not as high as in the engine bay.

The reason for the quiter engine, was largely as an resault of the new type of tensioner chain guide.
The 1 type was made of aluminium with a plastic rail on top of it, were the chain ran.
The aluminium guide was hold in place of the chain tensioner that were also in metal, so the chain sound from the fricktion on the plastic rail was easily transfert trough to the housing of the engine.
With the 2 gen. guiderail as also fits on the 1 gen. M104 the aluminium base was replaced with some rubber/plastic frame that did not transfer the chains fricktion sounds through out to the housing.

The other chain guide/lubrcation housing was not an isue of noice, but an isue of getting the chain lubricated on both sides.
Where on the new type you have an oilspray nossle doing the same job without a housing, but then you lose the tothwhell and get an ekstra chain guide witch in fact makes more noice as the chain runs along this and in the housing it dident.