CLS 350 CDI Shooting Brake

[DaveTheDrummer]

Hi guys.
I am in a position to pull the trigger on a 63 plate CLS350CDI Shooting Brake.
I test drove it today and was quite impressed. The poke is substantial.
One thing stood out to me though: Almost zero torque converter pull.
You know when you take your foot off the brake and the autobox pulls you along so you can creep in traffic? Well none of that.
Well OK a little tiny bit, but not enough to get me over a speed bump. My ancient 200k miles E320CDI has excellent converter pull and happily goes over even those massive plastic bumps. The CLS just bounced off. I wasn't expecting that.

Is this normal for the CLS? Or normal for modern Mercs now?

I thought it might be something to do with the eco systems but I didn't have enough time to really get any info so I am a bit in the dark.
I had a brand new (15 miles!) B class a few weeks ago (MOT time nach) and the box in that wasn't fabulous. It sort of paused before taking off.
CLS doesn't do that but there's little converter pull.

It's the only thing making me wonder so I thought I'd come and ask you lovely chaps and chapesses.

Thoughts?

 

[whitenemesis]

What autobox mode were you in?

 

[DaveTheDrummer]

Good question.
It was in E and I did also try it in S.
In S it appeared to be normal (strong converter pull) for a few seconds and then went back to being a wet lettuce. Not sure though as I was reversing and turning in a cul-de-sac so the changing drive modes may have changed the gearbox mode. No idea.
The car wasn't exactly warm either. Although normally in mine the converter pull is at its strongest when cold. Fluid is more dense.

So I can really only say that it was in E mode.

 

[TheFoX]

If memory serves me, when in E the box will select gear 2 from standstill, while in S it uses all gears more ferociously.

Of course, I could be wrong, but my understanding of E is that it is trying to be economical and select a higher gear, hence the low torque pull.

I know that when I reverse it needs a little bit of throttle to coax her to move, even on a flat surface, so it is probably the same when driving forward. Next time I take her out I'll make mental note whether she idles forward or not.

 

[Peter103]

If memory serves me, when in E the box will select gear 2 from standstill, while in S it uses all gears more ferociously.

I thought the opposite, when in E it will pull away in 1st gear, and in S select 2nd to begin. Ist is such a short ratio its quicker /safer to get away in 2nd. When I owned a 335 BMW I was told, in manual mode from standstill always select 2nd gear, or you could over rev the engine.

 

[TheFoX]

If memory serves me, when in E the box will select gear 2 from standstill, while in S it uses all gears more ferociously.

I thought the opposite, when in E it will pull away in 1st gear, and in S select 2nd to begin. Ist is such a short ratio its quicker /safer to get away in 2nd. When I owned a 335 BMW I was told, in manual mode from standstill always select 2nd gear, or you could over rev the engine.

I know that if I accelerate from standstill to 60mph in E, it takes longer than if I accelerate from standstill to 60mph in S.

In E mode, the gearbox selects the highest gear for any given road speed and will only change up or down when necessary, while the S mode will change gears quicker and use a lower gear for any given road speed to allow the car to react quicker to throttle changes.

I will also say that the Highway Code suggests using second gear to pull away in slippery conditions to avoid wheel spin, whereas first gear gives the quickest take off. I would find it hard to believe E mode would select first gear for a quick getaway, then select the most economical gear for the road speed, while the S mode would select second gear for a smooth, non slip, takeoff, then select the gear best suited for a ferocious acceleration.

 

[Headhurts]

My car E350 with 9 speed auto always selects first gear regardless of Eco or Sport mode.

There are plenty of posts I have seen where owners cars do pull away in second gear so it may be dependant on which model box you have.

Mine does creep in gear but not strongly, I guess you need to see if you can test a different car to see how yours compare.


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[DaveTheDrummer]

Thanks guys, seems like I may have been concerned for nothing.

 

[DaveTheDrummer]

Had it for a while now and I think I have it figured out.
As TheFoX said it start off in 2nd in gearbox E mode. In S mode it starts off in first.
So in E coming slowing to a stop, I mean walking pace here, very gentle pressure on the pedal to avoid the dull-witted eco system cutting the engine (I know there's a switch, but for the moment...) the car stops, and then with the same pressure on the pedal starts moving again slowly.
In the instant before it starts moving again I think I can feel something change under me.

I think what's happening is that I've stopped in second in E mode, the 'box changes down to first, therefore pull at that rpm is greater (more easily transferred), so the pull overcomes the applied brake pressure. Applied brake pressure was at the absolute minimum required to stop the car.
When this happens the converter pull is exactly as I would expect.
If I apply more pressure to stop the car then the dullard wakes up and kills the engine. Ho hum.

So the converter pull in second is rubbish but in first it's completely fine which is exactly what you'd expect.
I think that me stopping the car with the absolute minimum of brake pressure is possibly confusing the car a little which is why it changes down to 1st. Although I don't have anything to back this up.

I think I'll have a controlled play with it in manual and see if I can quantify it by comparison.