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Defrosting cars in the morning

Dryce said:
I wouldn't be inclined to redline it when cold but it's pretty clear that all the autos I've had have hung on to the lower gears and changed up later when warming up.
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The specific reason given for various Mercedes petrol models hanging on to the lower gears when cold is to rapidly raise the temperature of the catalytic converter to its efficient operating level rather than the engine itself. :dk: But that's just another reason to drive off sharpish!;)
 
Yes, I had this 'feature' on other cars (non-MB) as well.

Interestingly, this is purely an emission issue - i.e. it does not make a difference to the health of neither the engine nor the cat.

On my Vauxhall I had a 'snow' button, which meant the car started moving forward in third gear, very useful if you want to bypass this emission-reducing feature in order to make make a reasonably quiet exit at 4am...
 
Link didn't work??
 
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grober said:
The specific reason given for various Mercedes petrol models hanging on to the lower gears when cold is to rapidly raise the temperature of the catalytic converter to its efficient operating level rather than the engine itself. :dk: But that's just another reason to drive off sharpish!;)
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My diesel auto also hangs onto gears longer when cold than when warm. It is actually very noticable during the current cold weather. Joyously, I hav no DPF to warm up, either, so it has to be the engine that is being warmed.
 
prprandall51 said:
My diesel auto also hangs onto gears longer when cold than when warm. It is actually very noticable during the current cold weather. Joyously, I hav no DPF to warm up, either, so it has to be the engine that is being warmed.
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As said - it is meant to warm-up the cats, actually, not the engine (though the engine also warms up quicker this way - but this is really just a side effect), to reduce emissions... the cats are not very effective when cold, so a quick warming up will ensure they start doing their bit for the environment earlier... though you pay for this with the increased mpg.
 
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markjay said:
As said - it is meant to warm-up the cats, actually, not the engine (though the engine also warms up quicker this way - but this is really just a side effect), to reduce emissions... the cats are not very effective when cold, so a quick warming up will ensure they start doing their bit for the environment earlier... though you pay for this with the increased mpg.
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But, as I said, I have a diesel. NO cats, no DPF.
 
momomo said:
Have you had your cats removed? Otherwise you will have cats.
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S211? Will have cats indeed....
 
Yep, recent diesels do have cats, mine included as I had to have it welded recently due to one of the welds cracking!
 
My C220D has a CAT and its 15 years old, so can hardly be called latest technology!

The following is shamlessly plagiarized ;)

For compression ignition (i.e., Diesel) engines, the most commonly used catalytic converter is the diesel oxidation catalyst. The catalyst uses excess O2 (oxygen) in the exhaust gas stream to oxidize CO (carbon monoxide) to CO2 (carbon dioxide) and HC (hydrocarbons) to H2O (water) and CO2. These converters often reach 90% effectiveness, virtually eliminating diesel odor and helping to reduce visible particulates (soot), however they are incapable of reducing NOx as chemical reactions always occur in the simplest possible way, and the existing O2 in the exhaust gas stream would react first.

To reduce NOx on a compression ignition engine, the chemical composition of the exhaust must first be changed. Two main techniques are used: selective catalytic reduction (SCR) and NOx (NOx) traps (or NOx Adsorbers).

Diesel engine exhaust contains relatively high levels of particulate matter (soot), consisting in large part of elemental carbon. Catalytic converters cannot clean up elemental carbon, though they will remove up to 90% of the soluble organic fraction[citation needed], so particulates are cleaned up by a soot trap or diesel particulate filter (DPF). In the United States, all on-road heavy-duty vehicles powered by diesel and built after 1 January 2007 must be equipped with a catalytic converter and a diesel particulate filter.
 
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I have had two auto 190's in the past, both non cat models and both held on to the lower gears longer when cold. So it's not just for the cats to warm up but also the gearbox and engine:)
 
stwat said:
I have had two auto 190's in the past, both non cat models and both held on to the lower gears longer when cold. So it's not just for the cats to warm up but also the gearbox and engine:)
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Precisely. I drive off within 5 seconds or so, not just to get the engine warm, but also to ensure the entire transmission warms at the same rate......

I wouldn't want a warm engine, but a cold transmission. I think the thermal stress would be significant.
 
I just put old towels on the windows and take them off in the am , works for me.
 
Noodle-Pulp said:
I once did that and the towels ripped when I tried to take them off...
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Hopefully I wont leave them out longer than overnight, mind you if siberia comes then its back to the de-icer if this resulted in towels breaking, but so far for the last 3 years (touch wood) its worked.
 
momomo said:
Im really sorry I couldn't help but laugh out loud when I read that as a response to Speras' post,

It must have been very very cold for that happen?
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Funnily enough this was when I lived in your neck of the woods, I was living in Weybridge at the time.

I think what must have happened was that the windscreen was damp - the towels absorbed some moisture and then it all froze.. and then it snowed.
Luckily enough they were OLD towels as Spera suggested :)
 
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