ECO mode

[firstmercedes]

I'm learning more about my new (to me) C220 all the time.
Usually, after the first few complete stops of a trip (traffic lights, give way etc) the engine cuts out until foot off brake, then automatic engine turn on and off we go. I really love this although friends have said they've turned this facility off I think it's great for saving fuel, environment etc.
Anyway, today the engine didn't start auto cut out for about 30 minutes of many stop/starts. It was a really hot day in Birmingham,UK today (very unusual) but this was the only difference I can think of as journey has been done many times but I can't believe temperature can be a factor? The air con. was also on for the first time in ages.
Any ideas greatly appreciated as I'm becoming quite unusually nerdy in my fascination of how my Merc works.

 

[Red C220]

If the air con is churning away at a fair old lick then ECO mode switched off so the engine can continue to power the AC compressor.

 

[Haven't a clue!]

Hi,
Could it be 2nd battery related, believe I read that the state of charge of 2nd battery used for ECO dictates if/when it functions.
2- I switch mine off unless in big queues as concerned that it significantly increases stress cycles on the timing chain. Therefore increases risk of early (<150k) failure. Anyone able to substantiate that concern?
Cheers, Tony

 

[christopherwk]

Did 136,000 miles in my 2013 E220 CDi. Almost always turned off the ECO, possibly hence never had a problem. Auxiliary battery went at about 100,000 miles, anyway, replaced under warranty.

 

[Auto-mobile]

Possibly battery in the boot as this keeps everything going when the engine switches off.

 

[alzieboy]

When running air con in summer or in fact the heating system in winter , the car will override the ECO function if it senses a certain degree of voltage drop . Don't know if I have explained this as technically correct , but in laymens terms I think this is what happens

 

[CaptainRAVE]

There are a long list of criteria that have to be met for the car to stop/start. Just one or more that haven't been met. If in a lot of the traffic the secondary battery will probably drain. I don't get stop/start for very long, probably because my car is so power hungry.

I don't see why people turn it off for mechanical reasons - Mercedes have engineered the cars to be able to handle this.

 

[sjmaxwell]

As above, there is a whole raft of criteria to be met that is constantly checked including power use (don't forget the fan is running on a hot day!) as well as engine and environmental temperatures all influencing the Eco mode.

 

[Haven't a clue!]

"I don't see why people turn it off for mechanical reasons - Mercedes have engineered the cars to be able to handle this."

But that is the question/concern I indeed raise, having read some issues related to OM651 engines.
See:
http://www.mbclub.co.uk/forums/general-discussion/153817-bmw-scare-stories.html

 

[Haven't a clue!]

Oops, maybe wrong link, smartphone screen not biggest, but search for 'OM651 timing chain' and several threads found about risk with the single link chain used, which presume must be stressed by (say) 6 stop/starts per journey rather than non-eco once. I'd personally just take the slight mpg reduction rather than potentially uneconomical mega-thousands repair bill.

 

[tode]

If the air con is churning away at a fair old lick then ECO mode switched off so the engine can continue to power the AC compressor.

Correct - the Stop-Start will not function if the cabin has not reached the set temperature - Mercedes puts comfort first

 

[firstmercedes]

Okay, thanks everyone for replies. After researching this a bit more, I think the way to go for me is to use ECO on longer journeys where not too many stops and switch off for short commutes with many stops and/or in queuing traffic. I still think it's a really good idea (conserving fuel, environment etc), and am still enjoying the novelty of it but concerned about potentially expensive timing chain issues over time. Thanks for helping me reach a decision on this.

 

[Deleted member 65149]

In my opinion you're unlikely to notice any mechanical problems resulting from continued use of Eco stop/start until you've covered a couple of hundred miles or more. As has been said, Mercedes have beefed up all the bits that get put under extra stress. So if you intend doing ultra mega miles you MAY save some potential repair costs a long way down the line by limiting the use of stop/start. But in the vast majority of circumstances it must be false economy.