Auto box - How are you meant to use the 1 2 3 4 gears

[pcman_jh]

May sound like a stupid question but how are you meant to use the manually selectable 1 2 3 4 gear options on an automatic box? Do you use them as a normal gearbox, or does each position limit the auto box to that position's gear, automatically going to that as a limit, if you know what I mean.

The car is a 1999 E300TD.

I'm asking as my converted to veg oil car has fuel starvation when cold, but since the gearbox computer holds the gear selection that bit longer when the engine's cold (to aide heating it up quicker), its exacerbates the fuel starvation as it revs higher in each gear. I very occassionaly have to force it into a higher gear to lower the revs.

 

[television]

May sound like a stupid question but how are you meant to use the manually selectable 1 2 3 4 gear options on an automatic box? Do you use them as a normal gearbox, or does each position limit the auto box to that position's gear, automatically going to that as a limit, if you know what I mean.

The car is a 1999 E300TD.

I'm asking as my converted to veg oil car has fuel starvation when cold, but since the gearbox computer holds the gear selection that bit longer when the engine's cold (to aide heating it up quicker), its exacerbates the fuel starvation as it revs higher in each gear. I very occassionaly have to force it into a higher gear to lower the revs.

The option of the other gears is for different driving conditions like towing or in a very hilly area like when you want to hold a gear.
Your car locks up anyway to warm the cat as fast as possible, you could always alter the sensor to make it hold longer onto 2-3

Malcolm

 

[Blobcat]

You can also hold it in 2nd or 3rd when you want instant acceleration

 

[Hibbo]

I'm asking as my converted to veg oil car has fuel starvation when cold, but since the gearbox computer holds the gear selection that bit longer when the engine's cold (to aide heating it up quicker), its exacerbates the fuel starvation as it revs higher in each gear. I very occassionaly have to force it into a higher gear to lower the revs.

Hi again pcman_jh,

I really think your Veg oil conversion is causing unnecessary problems for you due to the may it is plumbed and the impact this has on purging.

I REALLY think you should think about replumbing it to include separate filters for the veg and derv. I remember from your previous posts that you can 'still smell some veg burning on a cold start'.

The fuel starvation due to filter plugging obviously means there is veg left in the filter after a purge. I'm not sure about the innards of fuel filters, but are they strictly first in last out or can some mixing happen inside them? The fact that you can smell veg on a cold derv start means there is veg at the injectors, if you are not purging long enough then there will be 100% veg at the far ends of the HP lines and thus in the injectors. This means you are starting on veg and completely defeats the point of a twin-tank system!

Starting on a filter still plugged with cold veg also (kind of) defeats the benefits of twin tanking. Not to mention that from a tight-arsed perspective you need to use loads of derv purging a big canister filter every time!


As for your actual question I often stick my gearbox in 3 (or S as it is on the w123) when I'm driving around town and my speed is between 20 - 30, as it stops the box constantly changing between 3rd and 4th.

 

[wscheffer]

As Malcom said but, straight from the owner’s manual!

D. The Transmission automatically upshifts to 4th gear. Position “D” provides optimum driving characteristics under all normal operating conditions.

3. Upshifts to 3rd gear only. Suitable for medium range up or downgrades.

2. Upshifts to 2nd gear only. For driving in mountainous regions. Since transmission will not shift up further, this gear selection will make use of the engine’s breaking power.

B. In this position, the engine’s breaking effect is utilized by shifting into 1st gear. Use this position while descending very steep or lengthy downgrades and only at speeds below 60km/h (40 mph).

Hope this helps!