[Greg in Oz]

M103 for smoothness, quietness, easy "drivability", easier maintenance.

M104 for potent upper rev range and a magic sound when working hard (late HFM version).

I regularly drive both my '90 300TE (M103) and my father's '93 E320 coupe (M104). Whilst the E320 offers good performance (especially with 5-speed auto) and a lovely sound when working hard, it is intrusively noisy for daily driving. Its power delivery is not as progressive and it is possible to feel the points where the camshaft timing and inlet manifold tuning changes. The 300TE, whilst not as potent, offers smooth and progressive power delivery and is almost silent.

 

[Greg in Oz]

Single row timing chain is not an issue on the M103 (6 cyl), only on early M102 (4 cyl) and early alloy M116 (V8). On the M103 it should last the life of the engine. Oil consumption (not caused by leaking head gasket) is usually easily fixed by replacing valve stem oil seals (which can be done without removing head). Early M103s did also have a problem with oil consumption due to premature valve guide wear (head must be removed to replace guides).

 

[Greg in Oz]

cap'n Jasper - 10/29/2004 8:06 PM

i like the early 104. 7000rpm, mechanical injection ala 103, 217 horses

Amen!
230 horses without the cat (UK spec), smooth power (no variable cams), no wiring issues, less weight than 3.2, more stable idle, incredible noise at high revs[]

I believe you will find that all M104s had variable timing on the inlet camshaft. Please correct me if I am wrong but I have just checked the factory shop manual and it refers to the camshaft adjuster on both the 104.98 and 104.99 engines.

 

[Greg in Oz]

cap'n Jasper - 10/30/2004 7:59 PM

The 300-24v does not have variable valves.
The 320 does.

I have checked again. All M104s have variable inlet camshaft (valve) timing. The adjuster is mounted on the front end of the inlet camshaft and operated electrically (hydraulic oil pressure does the work). The HFM (2.8 & 3.2) version also got variable resonance inlet manifold which the CIS (3.0-24) version did not. Perhaps this is what you are thinking of. The CIS version also has a high voltage distributor driven by the front end of the exhaust camshaft. The distributor was not required on the HFM (2.8 & 3.2) versions due to the use of three ignition coils.

 

[Greg in Oz]

cap'n Jasper - 11/4/2004 2:01 AM

The 3ltr is definitely much smoother though the revs, the 3.2 has a pronounced 'step' at about 3500rpm. My vote still goes to the 3ltr 24valve(with it's variable cam timing[])

Cap'n Jasper,
I suspect the "step" in the middle of the rev range which I too have noticed in the 3.2, may be the point where the inlet manifold tuning changes. There is a butterfly valve that can open to form one large chamber or close to form two smaller chambers. This variable manifold tuning does endow the HFM engine with more low down torque than the CIS (KE) engines.

Apial - 11/4/2004 6:10 AM

Is it the case that the variable valve timing allows the engine to redline at 7000rpm on the 300-24 M104?

The extra 1000 rpm just keeps the power surging on like it is "back to the future" time!

Apial,
The variable valve timing does allow for better cylinder charging across the rev range however I believe the rev limits and recommended engine speeds are determined more by what gives an acceptable margin of safety and engine life versus usable power and torque characteristic. The M103 remains turbine smooth and will happily rev beyond its 6,200 recommended limit, however at this point you are on declining points on the torque and power curves.

The 3.0 M104 produces its peak torque and power slightly higher in the rev range so the recommended limit was raised to 7,000 despite this engine essentially sharing bottom end components (and bore and stroke dimensions) with the M103.

With the 2.8 and 3.2 (HFM) versions of the M104, the torque and power peaks were again moved lower in the rev range, allowing the recommended rev limit to be moved down a little.

A similar situation exists with the 4-cylinder M102 which is effectively a shortened M103. Here, the recommended rev limit was only 6,000 due to the M102 producing its power and torque lower in the rev range than the M103. Being a four, the M102 does not exhibit the smooth, free-revving character of the M103 six. The M102, particularly in 2.3 litre form, is much happier slogging along at lower engine speeds making use of its good torque characteristics. Of course, there were also the 16-valve versions of the M102 which displayed a much peakier characteristic with a higher rev limit to exploit their top end power as with the early M104.