Auto Start/Stop - Pros and Cons

AdrianC

scaredofdebt wrote: »

Also, I always thought starting an engine used more fuel than normal idling

Just starting an engine doesn't use any extra fuel at all.

Starting and running an engine from cold uses a considerably more fuel than a similar run with the engine warm - I suspect confusion with that is where this urban myth started.

DKLS

I had the stop/start in a Mercedes C class, and there was a noticeable pause before the engine started and you could pull away, I didn't like the interference so disabled it.
Economy wasn't as issue as work was paying for the fuel.

motorguy

londonTiger wrote: »

these are relatively new innovations, who knows how these cares will fare after 30K+ miles. Lots of stop starts in a diesel in the city - likely to be trouble.

They've been around for years. From memory from the early 1980s / 1990s and on mainstream BMWs from 2007 and mainstream VWs from not long after that.

Theres cars around with it fitted with 150K+ miles.

almillar

I find the Mini system very reliable. How much do you save? That depends on how much time you spend sitting stopped in traffic, doesn't it? I'm the kind of person who would turn my engine off when stopped for a while anyway (once the engine's warm of course) so it's just doing it automatically for me. It cuts the engine far more often than I would, and sometimes, sometimes, when I don't want it to, but overall it's great. The engineers have decided lots of parameters for when it should switch off, like engine temp, air temp etc, and it doesn't happen much in the winter, but I like it.
Of course the number of people on the road who just sit there with their feet on the clutch and footbrake, that will never use stop/start, is still shocking. Use your handbrake people!

motorguy

almillar wrote: »

Of course the number of people on the road who just sit there with their feet on the clutch and footbrake, that will never use stop/start, is still shocking. Use your handbrake people!

My wifes z4 has it and i dont think shes ever had it engage yet!

It comes as complete surprise to her when i'm driving it and the car knocks off.

InsideInsurance

It does take a bit of getting used to but once you do it stops scaring you. Likewise the few I've been in with it all fire up very quickly from stop so no real issue with pulling away.

Car tax saving is the main reason to have it in my opinion. I suspect there is a fuel saving but how notable it is if you dont regularly drive in a major metropolitan area I'm not sure. Unfortunately when they introduced it to our car they also changed the engine so its not possible to say which part introduced the big fuel economy improvements.

When the engine goes off the A/C and heater do continue but at a lower level than when the engine was on. Not sure if the climate control is struggling if it will cause the engine to switch back on as the car has a number of additional triggers for it compared to a normal one

jaybeetoo

As I have an automatic, to enable the stop/start you have to keep the brake pedal depressed which means the brake lights are annoying the driver behind (especially at night).

InsideInsurance

jaybeetoo wrote: »

As I have an automatic, to enable the stop/start you have to keep the brake pedal depressed which means the brake lights are annoying the driver behind

What do you do at traffic lights then, out of curiosity? Engage Park or use the handbrake if you have one? Doesnt stop start work with either of these? I know ROSPA recommends leaving automatics in Drive when stationary at lights etc.

Ebe_Scrooge

InsideInsurance wrote: »

What do you do at traffic lights then, out of curiosity? Engage Park or use the handbrake if you have one? Doesnt stop start work with either of these? I know ROSPA recommends leaving automatics in Drive when stationary at lights etc.

Slightly off topic, I realise, but an interesting question. When I drive my wife's auto ( which I hate, incidentally, and try to do as little as possible ! ), I tend to sit with my foot on the brake and left in Drive if I know it's only going to be very brief. More than about 15 seconds or so, I stick it in Neutral and handbrake on - the way I was taught to in a manual, oh-so-many years ago. To my mind, sitting in Drive with your foot on the brake has got to be causing a fair amount of wear somewhere in the transmission. I know autos work differently to a conventional manual, but still, there has to be a lot of wear taking place if the engine is effectively battling against the brakes ?

AdrianC

Ebe_Scrooge wrote: »

To my mind, sitting in Drive with your foot on the brake has got to be causing a fair amount of wear somewhere in the transmission. I know autos work differently to a conventional manual, but still, there has to be a lot of wear taking place if the engine is effectively battling against the brakes ?

On a manual, with your foot on the clutch (whether in N or gear) you're holding the clutch pressure plate open against the spring pressure, with the release bearing under tension, and the friction plate rubbing lightly against driven and pressure plate.

On an automatic, with your foot on the brake and the 'box in D, you're merely warming the fluid up a bit. Which is fine, because the cooler will shed any excess heat anyway. No wear, no great loss.