Auto Start/Stop - Pros and Cons

anotherbaldrick

Ultrasonic wrote: »

That's really interesting, thanks. Getting the engine to always stop at particular cylinder positions seems impressive to me!

My thoughts entirely, cylinder to be detonated has to be stopped at precisely 5 deg past TDC. If it stops too soon it could backfire. Anyone apart from me old enough to remember the good old days when you could get a backfire ? You would be cranking the engine by hand and the spark would happen too early ( dodgy ignition retard ) the detonation would spin the crankshaft backwards and you over the bonnet. Why did they take the fun out of motoring ?

Richard53

anotherbaldrick wrote: »

My thoughts entirely, cylinder to be detonated has to be stopped at precisely 5 deg past TDC. If it stops too soon it could backfire. Anyone apart from me old enough to remember the good old days when you could get a backfire ? You would be cranking the engine by hand and the spark would happen too early ( dodgy ignition retard ) the detonation would spin the crankshaft backwards and you over the bonnet. Why did they take the fun out of motoring ?

My Dad's lessons to me aged about five started with 'keep your thumb on the same side as your fingers on the starting handle, as if it kicks back it can break your thumb'.

On a related note, I have seen a 15-stone bloke thrown into the air when trying to kickstart a 500 Norton single.

I'm no fan of much of modern technology, but I do love an electric starter.

almillar

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).

I don't like this - what's the car? You should be in neutral with the handbrake on if you're going to be sitting for more than 'a moment', manual or automatic, unless the car's manual says otherwise.

rpc

almillar wrote: »

I don't like this - what's the car? You should be in neutral with the handbrake on if you're going to be sitting for more than 'a moment', manual or automatic, unless the car's manual says otherwise.

Both automatics we've owned have said to leave the transmission in drive for short stops (e.g. traffic lights or queues).

almillar

Again we're very short on make and model of cars. And short time is down to interpretation, but I'd still say it's the same advice for auto or manual, into neutral and handbrake on if you reckon you'll be sitting for 60 seconds plus. Unless you have read in your manual (not heard off the internet) otherwise.

rpc

almillar wrote: »

Again we're very short on make and model of cars. And short time is down to interpretation, but I'd still say it's the same advice for auto or manual, into neutral and handbrake on if you reckon you'll be sitting for 60 seconds plus. Unless you have read in your manual (not heard off the internet) otherwise.

Honda slushbox and VAG DSG. Read in the manual, it is stated very explicitly. Stop/start on the DSG relies on firm footbrake pressure.

Honda reckon it is less wear to leave it in D (the torque converter isn't too bothered) although you can engage the handbrake if you wish. In the DSG, the clutches will be engaged but only a little so the difference between D and N isn't huge.

You can argue the toss over the DSG, but all the advice I have seen for slushboxes is to leave them in D due to the wear caused by going to N and back. Some drivers seem to insist on going to Park - which causes a nice little flash of the reverse lights!

If a long stop is expected (e.g. level crossing), I'd always be going to at least neutral and switching the engine off manually if necessary.

anotherbaldrick

rpc wrote: »

Honda slushbox and VAG DSG. Read in the manual, it is stated very explicitly. Stop/start on the DSG relies on firm footbrake pressure.

Honda reckon it is less wear to leave it in D (the torque converter isn't too bothered) although you can engage the handbrake if you wish. In the DSG, the clutches will be engaged but only a little so the difference between D and N isn't huge.

You can argue the toss over the DSG, but all the advice I have seen for slushboxes is to leave them in D due to the wear caused by going to N and back. Some drivers seem to insist on going to Park - which causes a nice little flash of the reverse lights!

If a long stop is expected (e.g. level crossing), I'd always be going to at least neutral and switching the engine off manually if necessary.

With the DSG putting foot on brake when stationary puts the box into neutral, taking foot off brake engages first increases rev's to 1200 and leaves box fighting the handbrake. Don't do it.

B00st

almillar wrote: »

Again we're very short on make and model of cars. And short time is down to interpretation, but I'd still say it's the same advice for auto or manual, into neutral and handbrake on if you reckon you'll be sitting for 60 seconds plus. Unless you have read in your manual (not heard off the internet) otherwise.

Constantly moving an auto from drive to neutral and back wears the clutch bands out due to constantly engaging and releasing them against the drums. The owners manuals for the autos I've had suggest only coming out of D if it is obvious that you will be stationary for at least 5 minutes.

If you had stop/start you would have to press the brake, wait for the engine to switch off, engage neutral but still keep the foot on the brake otherwise the engine will restart then put back into drive before releasing the brake.

almillar

Ah, I half understand the DSG system now. It works like most manual start/stops, except that the manual ones activate when you go into neutral and take your foot off the clutch. In the absence of a clutch pedal, the DSG ones rely on the footbrake. I would suggest to the VAG people that using the handbrake to activate it might be a better idea, but what do I know?!
5 minutes seems like an awfully long time to be sitting in 'D' with your foot on the brake, don't you auto drivers get cramp in your legs?! If manufacturers really do insist on staying in 'D' when stationary, they should be fitting their cars with strong enough handbrakes to hold the car.
'Honda slushbox' could be any number of gearboxes from the past few decades BTW, but the same principle applies I guess. As long as people are following the manufacturer's instructions, and not just being lazy and saying 'the internet told me so'!

27col

chevettedriver wrote: »

Wow! I am extremely jealous, as our ageing 406 automatic petrol can only manage 20mpg around town, sometimes less!

I initially thought it was faulty, and had garages looking at it until I found the original spec which confirmed Urban MPG was indeed stated at 17mpg when it was sold!

Who would buy a car nowadays with that spec!

I think you should be OK with your stop/start, it's a heavily tested system, you could always try a week on/off to see the difference.

More to the point, why would anyone put up with that sort of consumption unless they had to.