What's this Auto Start Stop Thing All About?

Auto stop/start will be the first thing I turn off when I get the car. I rarely drive in stop and go traffic anyway, so it's not likely to save me many pennies.

Originally Posted by jgrasty

Auto stop/start will be the first thing I turn off when I get the car. I rarely drive in stop and go traffic anyway, so it's not likely to save me many pennies.

Take care of the pennies and the pounds will take care of themselves...or would that make one penny wise and pound foolish?

Can anyone who's driven a BMW with Auto Start/Stop confirm with certainty whether it uses the starter to restart the engine or if it just fires the appropriate next cylinder and restarts the already warmed up engine that way? I was under the impression they used the 'next cylinder' method, but comments earlier in this thread seem to imply the starter method.

Originally Posted by SoonerJohn

Can anyone who's driven a BMW with Auto Start/Stop confirm with certainty whether it uses the starter to restart the engine or if it just fires the appropriate next cylinder and restarts the already warmed up engine that way? I was under the impression they used the 'next cylinder' method, but comments earlier in this thread seem to imply the starter method.

I can't confirm which method it uses to restart the engine since I didn't really get into the technical details of the car. However, I will say that it starts VERY quickly when you goose the gas pedal. I think the delay between complete silence and accelerating was less than the turbo lag I had in my old Saab 900 Turbo... but that's probably not saying much.

Generally I found if I was driving reasonably sedately then the auto start/stop was never an intrusion. It did however mean that I was having to plan ahead if I wanted to drive it harder... something that still sits wrong with me a little. The benefit to me of buying a sports car/sedan is simply the ability to switch personality just by choosing to drive it differently. Having to hit buttons or think about how I'm driving in advance somehow just seems wrong.

So instead of a dynamic personality, I feel the auto start/stop as well as the buttons in the console give the cars more of a "switchable personality". Somehow I feel something has been lost there.

Originally Posted by thumper_330

I can't confirm which method it uses to restart the engine since I didn't really get into the technical details of the car. However, I will say that it starts VERY quickly when you goose the gas pedal. I think the delay between complete silence and accelerating was less than the turbo lag I had in my old Saab 900 Turbo... but that's probably not saying much.

Generally I found if I was driving reasonably sedately then the auto start/stop was never an intrusion. It did however mean that I was having to plan ahead if I wanted to drive it harder... something that still sits wrong with me a little. The benefit to me of buying a sports car/sedan is simply the ability to switch personality just by choosing to drive it differently. Having to hit buttons or think about how I'm driving in advance somehow just seems wrong.

So instead of a dynamic personality, I feel the auto start/stop as well as the buttons in the console give the cars more of a "switchable personality". Somehow I feel something has been lost there.

Thanks Thumper! That super-quick start is consistent with what I've heard from others. That seems to me that it must be a 'fire next cylinder' start to get it running again that quickly, but I suppose the starter could get a warmed engine running pretty quickly as well.

Regardless, I have my 335i ordered and can hardly wait for my March 1 ED. If I don't like the way the start/stop operates, I'll just grow accustomed to hitting the start button and then immediately hitting the override button next to it. :-)

I believe they use the starter (I'm not sure how you'd fire the next cylinder without using a starter to move the piston- the stroke goes fuel spray, compress, fire - so you can't simply ignite fuel that's sitting on the cylinder walls and you can't have it spray and compress without moving the piston - so no matter what you need a starter to get that going...)

Bear in mind it's not your typical ignition starter - a start/stop starter has much greater mass AFAIK

Originally Posted by JoeFromPA

I believe they use the starter (I'm not sure how you'd fire the next cylinder without using a starter to move the piston- the stroke goes fuel spray, compress, fire - so you can't simply ignite fuel that's sitting on the cylinder walls and you can't have it spray and compress without moving the piston - so no matter what you need a starter to get that going...)

Bear in mind it's not your typical ignition starter - a start/stop starter has much greater mass AFAIK

It is definitely possible to do it without using a starter motor. The computer determines the best positioned cylinder, it shoots a fresh shot of gas in, and fires the plug and then just keeps on firing the other cylinders as normal. The only good professional explanation I can locate quickly at the moment is a PDF, but here's a link: http://www.etas.com/data/RealTimes_2...6_01_34_en.pdf

Huh, I usually consider ignition at an improperly timed piston movement to be called "detonation" - but i guess it makes sense with the computer controlling the cylinder and the amount of fuel (presumably) it makes sense.