Somethings wrong with Helga! - PeachParts Mercedes-Benz Forum

Edgeofthewoods · #1 11-23-2011, 06:56 PM

Something is amis with Helga, my 83.240. Her acceleration is, well almost quick. On the interstate her performance Is almost well snappy. I beat a GM 6.2 diesel pick up to.the next light.The engine noise at 70 mph doesn't drone as bad. Her cold bloodiness hasn't changed but she is starting quickly. If It wasnt so cold she would still kill mosquitos in 3 counties. Is something wrong with my beloved Benz? Should I be on thr loom out for more problems?

Isn't it great when these old cars run so nice.
Have a Happy Thanksgiving from the Hudson Family in New Mexico. Safe Travels and may your Diesel be clean!

Brian Carlton · #2 11-23-2011, 06:59 PM

The ambient temperature dropped............the diesels perform better in the cold.

Presumably, they take advantage of the greater oxygen to more fully combust the fuel.

leathermang · #3 11-23-2011, 07:52 PM

There is a higher percent of oxygen in cold air than warm ?
How about the possibility of less humidity ?

Edgeofthewoods · #4 11-23-2011, 07:59 PM

Humidity is something we see on Discovery Channel in New Mexico.

Sorry I ment the post to be kind of tongue in cheek. (She IS running very well) Have a great Holiday everyone.

PS It was fun to beat that Chevy.We both put out enough smoke to engulf Albuquerque!

Brian Carlton · #5 11-23-2011, 08:21 PM

Quote:

Originally Posted by leathermang

There is a higher percent of oxygen in cold air than warm ?

Yes.

barry123400 · #6 11-23-2011, 10:47 PM

Check yourself for losing your hearing and halucinating. That highway engine noise in a 240d can hammer your brain. I have a couple of them but do not drive them that often. I have little brain material left to spare.

These engines running better in cooler ambient temperature needs understanding. Cold air of course is denser but in theory should reduce the combustion process a little.Not enhance it.

The effect may reduce milage a little by changing the burn rate. With all the gas cars out there going direct injection there may be hope yet that someone out there will makea a 240d a direct injection engine.

Soon enough the required parts should turn up in junkyards. Getting some sensors mounted on these blocks may be the challenge. Someone is going to try it at some point.

Injecting in the area of the present precombustion chamber area with the actual prechamber insert out of the block may not be the most efficient introduction point but it should help. On the otherhand it may be an impossible point to direct injection from is more likely. Indirect injection like these engines employ is not all that efficient to put it mildly.

Squiggle Dog · #7 11-23-2011, 10:53 PM

I noticed the same thing with my 1968 200D. It only had 55 horsepower but seemed like a fast car, almost like it had a V8 engine (despite warnings that it would be dangerously slow). Maybe it was because I'm at sea level and it's usually cold here. That and I ran it on B99 and the station advertised their biodiesel as having a higher cetane rating than diesel. Not only was I not disappointed with the acceleration, but I was impressed. I can imagine that a 240D would be even quicker.

gastropodus · #8 11-24-2011, 12:53 AM

Here's what I notice on my '79 240D (has about 1000 miles on the new rebuilt engine at this point): when I start it in the morning from dead cold, outside temps around 45, it's predictably sluggish.

BUT, at about a mile or two out in city traffic, with the temperature gauge showing about 60C, it seems extra peppy! Quick off the line. Zippy.

Then I'm on the highway for 10 miles. No problems, just steady speed. Once I'm across the river I'm back in city traffic for a few miles. At this point the temperature gauge is around 85C, and she's not quite as zippy. Still good, but not leaping to the touch. I think there's plenty there if I mash the pedal, but I don't typically drive that way.

Funny, huh? Could all be perception, I suppose.

Kurt

Squiggle Dog · #9 11-24-2011, 03:29 AM

Using the full range of the pedal is important. They're not like most cars where a small fraction of the pedal travel is normally used, but when the pedal is put to the floor, the engine keeps performing.

t walgamuth · #10 11-24-2011, 05:56 AM

Regarding the cooler air. It is a fact that more oxygen is available in cooler air.

I remember them talking every year at the INdy 500 qualifying about a cool day allowing the engines to produce more horsepower thereby hopefully enabling the cars to set ....A new track record!!!! (picture Tom Carnegie's bass voice).

Seriously.

barry123400 · #11 11-24-2011, 12:50 PM

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.

Diesel911 · #12 11-24-2011, 10:41 PM

Quote:

Originally Posted by leathermang

There is a higher percent of oxygen in cold air than warm ?
How about the possibility of less humidity ?

The percentage of Oxygen at any altitude and temp (in the Air) is always the same.
It is the partial pressure of Oxygen and the other gasses in the Air that is different at different altitudes and temps.

E150GT · #13 11-24-2011, 11:02 PM

Ive always found cars can be like people in the fact they have their good days and their bad days. Sometimes I'm driving and I can just feel the car is running poorer than usual. I might feel like it has a grumpy idle or its making a noise a little louder than usual. Then some days its running like a top and I'm like "damn this car is running great today!"

leathermang · #14 11-25-2011, 12:26 AM

Quote:

Originally Posted by Diesel911

The percentage of Oxygen at any altitude and temp (in the Air) is always the same.
It is the partial pressure of Oxygen and the other gasses in the Air that is different at different altitudes and temps.

That is what I think... was wondering if everyone was going to let Brian get away with that ' yes '... LOL

For gas engines when the air temperature is lower more can fit into the same bore .... thus more power is available since the ratio of air to fuel is assumed to be the same...you are both able to and do burn more fuel per revolution.

On our diesels... unless one has a ' mass sensor' to change the amount of fuel ifuel injected... I do not believe more power is made at lower ambient air temperature... I do think our machines may have a pressure sensor which will do some compensating for altitude... but do not think that is related directly to temperature ( and thus density ) of the air.
I am referring to NA engines.... I do not know about the others....

Diesel911 · #15 11-25-2011, 01:25 PM

Getting the O2 to combine completely with the Fuel is what is tough.

The other issue is that when the Fuel does burn not much of the energy gets converted to actual moation.
When I was in Trade School there was a pie chart. It showed that only 10% of the power reached the wheels.
Most of the power was lost by heat from the Exhaust and Cooling System (most of it goes out the Exhaust Pipe).