Auto gearbox

[SD1too]

Originally Posted by scorpio

This cause the car to struggle to pull properly and blow black smoke ..

Peter; I am not an expert on the diesel engine but your description suggests to me that yours is in need of a comprehensive service. Engine tune has a dramatic effect upon automatic gearbox operation and I would expect this to be exacerbated with the extra load of towing.

Simon

[mileshawk56]

If it "blows black smoke" it sounds bad, needs a thorough engine service-even the dreaded diesel should not do that. Gearbox and engine performance are interrelated. Chris S.

[Comfortably Numb]

Why is the BMW diesel so different from most other diesels - especially Fords, which I regularly see billowing black smoke when their drivers floor the throttle? Most diesels do it because their turbo is unable to pump enough air into the fuel mixture at low revs and high pump demand - the black smoke indicates incomplete combustion. If the OPs car is not kicking down when he adds throttle while towing, he is in that exact situation. I've never tried flooring my CDT at 50 in 5th, but if I did, I would expect some black smoke. Is this a standard 116PS CDT, or has it had the 160PS T4 upgrade? Could make a difference when towing especially.

[Andy_with_a_screwdriver]

Originally Posted by Comfortably Numb

Why is the BMW diesel so different from most other diesels - especially Fords, which I regularly see billowing black smoke when their drivers floor the throttle? Most diesels do it because their turbo is unable to pump enough air into the fuel mixture at low revs and high pump demand - the black smoke indicates incomplete combustion. If the OPs car is not kicking down when he adds throttle while towing, he is in that exact situation. I've never tried flooring my CDT at 50 in 5th, but if I did, I would expect some black smoke. Is this a standard 116PS CDT, or has it had the 160PS T4 upgrade? Could make a difference when towing especially.

I've got the 130hp diesel and it behaves exactly like all my other diesels have done under acceleration, and that is to give out black smoke. When it's hard work is done it stops smoking.
my auto also struggles with that in between speed for 4th and 5th as has been said it is best to speed up or hold 4th manually.

[Neil1]

Originally Posted by Andy_with_a_screwdriver

I've got the 130hp diesel and it behaves exactly like all my other diesels have done under acceleration, and that is to give out black smoke. When it's hard work is done it stops smoking.
my auto also struggles with that in between speed for 4th and 5th as has been said it is best to speed up or hold 4th manually.

Mine smokes a bit if I plant the throttle but doesn't if I'm just dawdling around.
Mine has had the 160 remap which is quick off the mark for a heavy car.

[rovertone]

Originally Posted by scorpio

How many gears are in a automatic gearbox on a CDT, The reason I ask is when I am towing in Drive it drop the revs when it reaches around 52. This cause the car to struggle to pull properly and blow black smoke, if I change down to 4 the revs come back up and it tows lovely leading me to think it is a 5 speed auto box.

In my experience when towing in Drive 1500rpm (52mph) is about the lowest engine speed that the car is 'comfortable' with and that's with 160 remap. I find that it's Ok when using light throttle on fairly level roads but going over hills and dales it is much better in 4th I find using 'sport' mode is useful for very hilly terrain but generally uses higher revs than are really necessary compared to 4th.
I have done several long distance trips through France and Spain and I found that on undulating roads D4 gave marginally better fuel consumption with the engine running comfortably at 2000ish rpm than not so comfortable at 500rpm lower.
Of course given performance in any particular gear is greatly influenced by the Gross Train weight i.e the overall weight the engine is pulling along (weight loaded in the car and weight of caravan).
Black smoke is probably a separate issue and as others have said state of engine tune/servicing must be to spec.