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 ?

Brian Carlton · #4 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 · #5 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 · #6 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 · #7 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

Diesel911 · #8 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 · #9 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 · #10 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....

Edgeofthewoods · #11 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!

Diesel911 · #12 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).

leathermang · #13 11-25-2011, 02:32 PM

Diesel911... that was about the time they started working on those ' adiabatic' (?)engines ... have not heard much lately .... they may have burned up....LOL