karmikan

I've always been careful to let a turbo engine idle for 10 or 20 seconds after a highway run to allow the turbo to spool down. The reason is that a turbo can spin up to 150k RPM and shutting the car off immediately cuts off oil flow while the turbo is still spinning at a high rate, this increases wear. Also, engine oil helps cool the turbo and after a high-speed run, the turbo is hot enough to "cook" the remaining engine oil if the flow is cut off. This increases deposit build up..
Seems to me that auto stop/start can accelerate turbo wear and carbon build up by repeatedly cutting off oil flow to the turbo. This would be particularly problematic on county-type roads where speeds are close to highway levels but there are occasional stop signs and traffic lights.
Does this seem logical to anyone else?

fred9x

Sounds like a good question. I cannot offer any technical opinion but think that this issue applies many more models than our X253. Therefore I suggest you consider moving it to the Tech Talk forum for more views and replies.
https://mbworld.org/forums/mercedes-tech-talk-41/

mtberman

This is correct in theory and was true many years ago. Automakers resolved these concerns long ago. When your engine shuts off, there is no oil "cutoff" because the engine is designed so that oil and coolant continue to circulate either via electric pumps or gravity (or both) depending on the vehicle.

karmikan

Better idea, I'll do that

I know that most engines with stop/start circulate coolant when in stop mode but that is just to keep passengers warm, don't think it's anything to do with the turbo. I'm pretty sure that our cars do not have electric engine oil pumps, they seem to be used mainly in race cars. I believe there is an aux electric oil pump for the tranny, not one for the engine.

mtberman

Heat issues are always a valid concern. However, it's worth noting that automakers resolved heat management in turbocharged engines 20+ years ago. Precision fuel metering and fuel shutoff keeps exhaust temperatures low, especially in high-efficiency DI designs like the M274. Turbo cooling via oil circulation has been all but perfected by keeping oil flowing through the turbo and removing heat for two to three minutes after shutdown, which eliminates the need for post-drive idle time in most situations.

In addition, modern turbos are rarely working hard at high speeds because modern transmission tech has engines turning slowly at high speeds as compared to the past. Coolant circulation between re-starts (which is primarily to prevent heat soak and not anything to do with passenger comfort) keeps temps stable.

Post-drive idle time may still be a good idea if you do a lot of performance driving rapidly followed by shutdowns. It's also a good idea to open the hood in those situations.

dtl919

This.

After a few laps on the track, I have always let my car idle 5-10min before shutting it off to let things cool off. However, this isn't really necessary for daily driving.

400ixl

Turbo temperature sensor is one of the many feeds whicjh go into stop / start and it won't cut out if there is a temperature issue. Oil flow is also maintained to the turbo.

I would expect you to have manually switched it off on a track day, but day to day, unless you are really giving it some I wouldn't be concerned.

peet

On the street I found that when I'm entering a cross-traffic turn, I disable auto stop/start. The slight lag could mean the difference between making it or not. With the GLA, the button was close to the starter button so it was muscle memory, sit down, hit start, hit disable stop/start, click sport mode. Click click click... With the GLC, the 9 speed tranny doesn't need sport mode as much so that's good, because the mode switch is a PITA. The disable stop./start is located in an odd place that you pretty much have to look down and already getting in the car is a bit like a flight checklist. Get in, plug in phone, switch to carplay, open app, bla bla bla. I know, problems of the first world kind. LOL

Sigp232

Philamg

Same discussion taking place on BMW forum regarding new X5.

fabbrisd1

eBay ... buy the OBD module from Vladimir and put this whole thread behind you - whatever you have ECO set to when you turn your MB off - is the ECO setting on Start-Up - easy peezee... you like Off... have it on ECO Off at shut down....t's Off... if you like On.. have ECO On at shutdown... and its it's On ... after you fire up if you change profiles and ECO stays at you're preferred ECO setting ... you can live with that..

peet

This vlad module - can you share some more info on where it is etc? Also - does it remain in the OBD plug or is it one of those injectors that hacks things? I'm a fan of the latter as the OBD port is not something I want plugs hanging out of. Haven't checked the one on a 253 - but all previous cars, unless that sucker is 1cm or shorter, no way to close the cover.

fabbrisd1

You follow instruction and insert to reprogram - reprogram gets completed - turn car off and remove the module.. keep the module (which is now "paired" to your MB only) in the event you want to reverse the program ..

His "newest" module leaves the Dynamic Select in the position it was when vehicle turned off (including Indiv) ...so if you use Sport (or Indiv) when you turn the MB off it will be in Sport (or Indiv) when you turn back on... message Vladimir with your VIN# and he can tell you what functions he can do for your specific GLC...

https://www.ebay.com/itm/MERCEDES-Dy...jWBl:rk:7:pf:0

George in KG

All true. I bought the module via ebay. There was a shipping hiccup but Vlad took care of the problem immediately. Module works as advertised and auto start/stop is permanently off for me. Yea!

Tylbran

I have never had any issues with the start/stop feature in my 2018 GLC43 (nor my 2016 E63 wagon). I have never found any lag when I move forward - always power on demand, Personally I really do not pay any attention to it. There are times when it is working and other times when it does not presumably based on conditions. From my perspective it is no big deal to have the feature work in the background.

mtberman

+1, It's a non-issue for me. Some of our work vehicles lack the feature, and sometimes at red lights I find myself thinking "Why is the engine on? Why does this car not shut off by itself??"