Gas engines will draw air from the exhaust manifold in the winter, primary reason to prevent icing.
Old 240D seems to run so much better in mild weather, I wonder if it makes any sense to rig something up to draw warm air into the intake manifold??
Anybody ever try something like this?

Not 100% sure if that was the purpose, but I recall seeing a ford pick up with a 7.3 diesel engine from Canada with an electric fan heather (squirrel cage type) fitted to the air filter intake hose for winter driving, That was the answer I got when asked about the fan, I saw the truck at the body shop about 2 years ago.

__________________
2000 430 ML
2005 S500
87 300 D
61 300 restoring

All engines will work better with cold air intake. The air is denser the colder it gets (same reason planes fly around 36,089 feet, it is at the bottom of an isotherm..). Other evidence to this is the pocket-rocket tuners try to draw their air from outside the engine bay, it is also the reason that intercoolers work.
There is a much more complicated thermodynamic reason, enthalpy/entropy diagram and stuff, but I drank a lot of beer since college, and I am pretty sure those brain cells are dead now.
That said, what kind of cold are you concerned about? what is the temp like at the engine intake? The internal routing will warm the incoming air up some.

__________________
Mercury is a boxer

1984 300d
1999 Prelude
Medici road bike
Klein touring bike
Klein mtn bike

I'm not so sure about the hot air theory on gas engines.

So far as I knew, the gasoline engines are fitted with an air heating device on the intake for two reasons,(general not MB specific)
1. The bimetal spring operated choke on some old models needs the heat to release the choke.
2. Emissions requirements, trying to get the engine heated up faster to reach operating temp sooner, thus reducing the CO & NOX emissions and such. (This was also attempted with the use of a "heat riser" flapper plate on a bimetal spring restricting exhaust flow to hold heat in the engine longer)

Usually you will find the "hot air intake" systems are passed thru a type of thermal damper door that will bypass the system once engine is warm. (Such as the GM Thermac air cleaners used for years on carb models)

I do agree with mercury about the denser air and cold intakes. What you are experiencing is just normal cold cylinder walls and intake passages acting as refrigerators condensing fuel until the engine is warm, as heat helps to better evaporate and atomize fuels.

Emissions. The faster the engine gets warm and the faster the cat lights off, the lower the emissions.

Air temp of 25 degrees as opposed to 60 degrees. Just seems to run much better with the warm temps, even after a 45 minute ride. (Nothing wrong with engine temperature, steady at 90 after 2 miles)
'Dense air' - A diesel should run better in the cold? More air?

I took Thermo as well, got an A........however, simply consider this.....why do folks bother with "Intercoolers" between the Turbo and the intake.......cooler air, denser air charge, allows more fuel to be burned efficiently.....

Now if you were to be operating your Diesel in Antarctica......

SB

__________________

Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

On gasoline engines the thermostatic air cleaner is designed to maintain a specific air temp. If the incoming air temp on an a gasoline engine is too cold especially on carb or throttle body injection the gasoline wont atomize proporly. Resulting in incomplete combustion and high hydrocarbon emissions.
Heat risers were designed to force hot exhaust gases through a passage in the intake manifold. This heated up the area under the carburator promoting fuel atomization at low engine temeratures.
Anyone that has owned a carburated V8 dodge in the northwest can probably talk all day about carb icing. Heated intakes can help with this but there is that first few minutes where you wonder if that stupid thing is going to stay running.

My Dodge Ram has the 2 'toaster elements' in the intake manifold, and no glow plugs.

__________________
91 350SD
14 F150 Eco
19 Fusion Hybrid
11 GT500

Uhh... that's not correct. Air temperature, density, and pressure decrease as you increase in altitude. Planes don't "fly around 36,089 feet" because of an existence (or lack theof) of an isotherm. "Best range" and "best endurance" airspeeds and altitudes vary based on aircraft design and gross weight, and you can't usually fly at the most optimum altitude anyhow due to Air Traffic Control (ATC).

Warm air might help to get it started at 20F and below. I thought about trying a hair dryer for that purpose this coming winter but I decided to just hook up the block heater.
I think if the compression is low due to excessive wear (high milage), it's probably just not getting hot enough inside the cylinder to ignite. Maybe warm air helps.

__________________
'99 S420, 155k
'91 VW Vanagon GL, 150k
'85 VW Vanagon GL, 120k
'82 VW Westy, aircooled, 165k

Heating the intake air helps, big time, for cold starts.....

Cummins/Dodge use the "toaster elements" as mentioned in another post in this thread, they simply heat the intake air......just never, ever use ether with that system.....

I use a heat gun (industrial hair dryer) to start my tractor on cold mornings, my German schlepper (tractor) has no glow plugs...does have a fuel cold prime pump that squirts a bit of fuel just ahead of the intake valve.....I just stick the heat gun into the air intake, leave it to warm the air cleaner for a bit......and then start......

SB

__________________

Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

a warm air intake on a diesel will help it in the cold air -- period -- its a play and fuel ecom ( IT will go up ) -- only in a racing deal do you want cold air for more power -- pre heating the fuel will also help as big a deal as warm air into manifold -- ALASKA will teach you things that the 50 other states have no idea about -- jz

Big diesels don't typically have glow plugs, but they often have heated intakes instead. The heated intake runs much like the later glow-plug circuits with afterglow for easier cold starts and to lower emissions in the first few minutes of running.

My 10.2liter CAT doesn't have either, starts well down to 0*F. Of course the lower surface/volume ratio helps to not lose as much heat to the cylinder walls etc. on starting. Small diesels almost always need some help with cold starts.

__________________

Gone to the dark side

- Jeff