I believe the additional oxygen is good for a gas car as it consumes all the oxygen introduced. A diesel is supposedly to have oxygen left over but I do not know where I heard that years ago.

Also when they quote left over may be only a very small amount of the original available oxygen. So with the denser air containing more oxygen the burn may be hotter is not unreasonable either. The fuel injection method and type impact negativley in my opinion in comparison to modern systems.

Now what has always hurt many things is my observation that the efficiency of the volkswagon indirect injection diesel of old was increased the hotter it got in ambient air temperatures.

Especially the fuel milage. The engines are of simular basic design. Yet there has to be some suttle difference or differences between it and the 616 for this discrepency to exist.

I have been thinking about the combustion chamber on these engines and the way the fuel is introduced. To me to say it is not the most efficient is an understatement. I also assume there is no other place more optimal to install a fuel injector without getting into the water passages. A modern direct injector in the pre chamber would change nothing much basically. The engine may even experience major difficulties if direct injected from there.

At some point someone may get an old head and open it up with a metal cutting bandsaw to get an internal view. This is the only way to find out if something might be changed. There may be hope if cast iron can be welded properly with todays technology as well.

Charactaristically I have never liked cast iron welds. Yet for years certain shops have been able to weld cracks etc in cast iron heads that stand up well. This I believe to be the most demanding area of turning these old engine heads into a more modern type.

If by some stroke of luck some way turned out to be manageable. The results of direct injection at a more suitable point might be worth investigation. You could leave the old chambers with the glow plugs intact and perhaps start on the original fuel injector system. Then transfer over to the newer direct injection system once running .

I also suspected the original glow plugs might not survive well without the pre chambers intact. I could be wrong about that though. There is no way the engine would start with direct injection closer to the cylinder centre with the glow plugs and pre chambers as they are now .

Although without the pre chamber installed if the glow plugs survived it might. The increase in power and milage would make it a much different engine. The compression ratio can then also be modified if benificial with changes to the pre chamber area.

Meeting tomorrrows emission requirements is not going to be possible. Yet the cars emissions should improve enough to be substantially better. This retrofit modification may be allowed by the powers that be.

Again the soon to be availability of direct gas injection systems at the wrecking yards at cheap prices. Might enable something. If the old system is left as a back up reliability on trips is still good. Failure of the electronic system would just mean you switch back on the original mechanical system.

We may have to do nothing in reality as the 616 is still being produced. It may be cheaper for the manufacturer to develop a new head to accomidate a newer system in the far east than do a complete new engine. There may be a lot of miles per gallon to gain and quite a bit of power as well.

Piston design of course would be modified in a factory issue engine. We would only need the heads and utilize others electronic fuel injection systems. Avoiding the excessive cost of new mercedes electronic components.

Unfortuatly the newer head would probably be done in aluminium as well if it came to pass. It may be an indicator that all is really not well inside the mercedes benz organization to not have done this already.

The resultant upside in publicity alone would have been worth millions to them in many other ways being very valuable as well. Between competition and volume the cost of direct injection systems are going to become very cheap.

I really believe for a company like mercedes not to modernise the current 616 is poor business. I really think it is doable at a reasonable cost. Actually it has got to be cheaper as electronics cost pennies today in volume compared to mechanical piston injection pumps and hard lines etc. In India mercedes are still currently producing the techology of the late thirties to some extent. Electronic systems can be very cheap and very reliable today if produced in China.