Is it wise to turn off engine whilst in a queue?

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Fri 15 May 2015 14:45
Is it wise to turn off engine whilst in a queue? - mak

In answer to the above, one reader answered

"Years ago I was told that it was damaging to turbo diesel engines to leave the engine ticking over for more than a few minutes because the oil that lubricates the turbo charger drains from the bearings and the seals dry out, you should only leave it on tickover speed a little just before you park up for the day."

Is this true?



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Fri 15 May 2015 15:35
Is it wise to turn off engine whilst in a queue? - RobJP

I'd say if you're in a bad enough queue that the engine will be ticking over for a few minutes, then switch any engine off.

As to an engine ticking over making seals dry out, I've never heard of that.

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Fri 15 May 2015 16:00
Is it wise to turn off engine whilst in a queue? - FP

"...the oil that lubricates the turbo charger drains from the bearings and the seals dry out..." This assumes there is no such thing as an oil pump. Sounds like complete rubbich to me.

Could it be a confused version of the advice to let a turbo-charged engine tick over for a few seconds to cool down after a hard run? The logic there is that hot bearings will dry out unless fresh oil lubricates them while they cool.

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Fri 15 May 2015 16:42
Is it wise to turn off engine whilst in a queue? - gordonbennet

It isn't bearings drying out thats the problem with not allowing the turbo to cool down on tickover before shutdown, it's that the small amout of oil left inside the bearings will get cooked and leave deposits inside the bearings which eventualy build up enough after repeated times to prevent adequate oil flow.

Never heard of bearings drying out during tickover, if that were the case then reps cars would be pegging out at MSA's every day of the week when they sit in the car on tickover for hours on end running either the heater or air con whilst they do their paper/computer work.

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Fri 15 May 2015 16:47
Is it wise to turn off engine whilst in a queue? - craig-pd130

As FP said above, the post is a bit mixed up.

As a general rule it's a bad idea to switch off a turbocharged engine immediately after working it hard, because the turbo runs very hot. If you switch off really fast (i.e. screech to a halt after several miles of high speed driving and stop the engine immediately), the heat in the turbo can be sufficient to char the oil in the turbo bearings, leading to rapid wear.

However, it's extremely unlikely that you'd go from driving at high speed, to stopping and switching the engine off within 30 seconds - unless you treat motorway services like a Formula 1 pitstop :)

Some cars have watercooled turbos, which avoids this problem -- and in most cases, you'd drive a couple of miles through urban streets before stopping, which is plenty of time to cool everything down.

As long as the engine is running, oil doesn't drain from anywhere, the oil pump keeps it circulating.

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Fri 15 May 2015 17:38
Is it wise to turn off engine whilst in a queue? - slkfanboy

IMHO its bad idea to turn an engine off as it strains the battery. You may well find yourself with as flat battery. Cars with Start/Stop systems have a much better starter motor and battery and even then don't turn off if the battery is not charged enough ofr the power drain is too high etc.

Alex

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Sun 17 May 2015 09:23
Is it wise to turn off engine whilst in a queue? - John F

IMHO its bad idea to turn an engine off as it strains the battery.

No it doesn't. Less than 0.2 AmpHrs are used assuming it starts within 3secs. The alternator should restore this in about 30secs.

physics.stackexchange.com/questions/57794/calculat...e

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Mon 18 May 2015 13:46
Is it wise to turn off engine whilst in a queue? - slkfanboy

EXIDE has expanded its coverage of the UK car parc with new AGM and ECM batteries. The new products cover vehicles from VW, Audi, Toyota, Ford and a slew of other brands.
<*** style="margin: 3px; padding: 0px; outline: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline; float: right;" src="http://pmmonline.co.uk/files/professionalmotormechanic/Exide.jpg" alt="" width="250" height="201" />Exide’s AGM batteries are claimed to have around three times the lifecycle durability of standard batteries. Parts of “matching quality”, they are designed for cars with Start-Stop and regenerative braking systems. They are also used in standard vehicles to increase endurance and performance.

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Mon 18 May 2015 14:21
Is it wise to turn off engine whilst in a queue? - slkfanboy

>No it doesn't. Less than 0.2 AmpHrs are used assuming it starts within 3secs. The >alternator should restore this in about 30secs.

So basically my ford focus has a 60ah battery and therefore is on you maths able to start the car 300 times without charge, but in any event after 30sec will be fully recharded. That sounds like no car battery on the planet.

This because the artical fails to understand a battery under cranking. Batteries are rated in CA/CCa/HCA i.e cranking amps./Cold/Hot. So basically the amp's a battery can provide over 30sec to maintain 7.2v at a given tempresure.

The clue is in the fact the voltage drop under temp/load. So basically my ford will have a cca of 620. so that under the hard condition means i have around 30 sec of starting time and by your own calc 10 starts and the battery is dead. That is asuming a brand new battery!

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Mon 18 May 2015 18:49
Is it wise to turn off engine whilst in a queue? - John F

>No it doesn't. Less than 0.2 AmpHrs are used assuming it starts within 3secs. The >alternator should restore this in about 30secs.

So basically my ford focus has a 60ah battery and therefore is on you maths able to start the car 300 times without charge, but in any event after 30sec will be fully recharded. That sounds like no car battery on the planet.

This because the artical fails to understand a battery under cranking. Batteries are rated in CA/CCa/HCA i.e cranking amps./Cold/Hot. So basically the amp's a battery can provide over 30sec to maintain 7.2v at a given tempresure.

The clue is in the fact the voltage drop under temp/load. So basically my ford will have a cca of 620. so that under the hard condition means i have around 30 sec of starting time and by your own calc 10 starts and the battery is dead. That is asuming a brand new battery!

I'm not sure I follow your argument, s'boy, but I think you are overemphasizing the theory. In practice, most engines will start in less than 1sec cranking, they are warm and crank easily, needing fewer watts. It would be an interesting experiment to see how many times your warmed-up focus egine could be started and immediately stopped with a tip-top new 60ah battery - I might be persuaded to bet that it could indeed do it 300 times!

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Mon 18 May 2015 19:07
Is it wise to turn off engine whilst in a queue? - gordonbennet

> It would be an interesting experiment to see how many times your warmed-up focus egine could be started and immediately stopped with a tip-top new 60ah battery - I might be persuaded to bet that it could indeed do it 300 times!

When i first changed the fuel filter on my Diesel Merc i discovered that it didn't have a hand primer and the official way to self bleed it was crank it till it fired, which must have been nearly 2 minutes.

Vowing never to put the starter and battery through that unecessary ordeal again, from then on i filled the filter bowl with clean Diesel before offering it up.

However even after all that time the engine was still turning over at full crank speed.

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Fri 15 May 2015 22:34
Is it wise to turn off engine whilst in a queue? - mss1tw

I don't, it means losing oil pressure and more wear on starter motor etc.

Probably no difference in the grand scheme of things.

Idling diesels sip fuel anyway, and I paid enough for it to choose if I want to burn it or not. :)

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Sat 16 May 2015 00:22
Is it wise to turn off engine whilst in a queue? - bathtub tom

I don't, it means losing oil pressure and more wear on starter motor etc.

Do you leave your engine idling all night?

You don't need oil pressure when it ain't running!

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Sat 16 May 2015 10:06
Is it wise to turn off engine whilst in a queue? - mss1tw

Do you leave your engine idling all night?

Yes I do

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Sat 16 May 2015 10:55
Is it wise to turn off engine whilst in a queue? - the_bandit

If the wait looks like lasting for at least 5mins then yes otherwise I don't.

Sods law the minute you switch the engine off the queue moves!!

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Sat 16 May 2015 13:37
Is it wise to turn off engine whilst in a queue? - Wackyracer

Sods law the minute you switch the engine off the queue moves!!

Your not wrong there! When we had a new fleet of trucks they were fitted with a timer system that if you didn't touch the throttle for 3 mins it would stop the engine. In London traffic it used to cut the engine just as the traffic started to move again, being automatics you then had to select neutral and turn the key to the off position and back again. They were a real pain and many of the drivers would keep dabbing the throttle in traffic to stop them doing it. So it probably used more fuel than it would if the trucks were just left to idle.

I tend to only switch off the engine if there is going to be a long delay i.e. accident on motorway etc.

Years ago I worked for a company and their yard shunting vehicles used to be left running for days at a time. They were even refuelled with the engine running.

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Sun 17 May 2015 09:30
Is it wise to turn off engine whilst in a queue? - John F

Years ago I worked for a company and their yard shunting vehicles used to be left running for days at a time. They were even refuelled with the engine running.

A good example of the wastefulness of collectivization. I suspect reps and professional drivers who have their fuel bills paid for them (ultimately by the people who buy their products/services) don't save fuel wisely.

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Mon 18 May 2015 14:05
Is it wise to turn off engine whilst in a queue? - gordonbennet

I suspect reps and professional drivers who have their fuel bills paid for them (ultimately by the people who buy their products/services) don't save fuel wisely.

No generalizing there then.

I don't buy into this must switch the engine off immediately nor the immediate driving of cold engines, especially engines under heavy load, unless essential.

In my left hand i have a cupful of fuel used for warm up/cool down regime.

In my right hand a pair of turbos as fitted to my current steed also the costly downtime and even though it's a bit of a strain to support in the one mitt also a wrecker capable of pulling a 44 ton combination should those turbos fail.

I reckon that cupful of fuel is the economical choice, and though its not exactly scientific i offer 3+ million miles without a single turbo failure i can recall to my name as a bit of flimsy evidence for the defence.

Lorry, just like car, turbos have become a consumable now where they used to last indefinately with a bit sensible servicing and warm up cool down regimes.

Just saying like.

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Sun 17 May 2015 09:35
Is it wise to turn off engine whilst in a queue? - John F

Idling diesels sip fuel anyway, and I paid enough for it to choose if I want to burn it or not. :)

This attitude suggests you are overpaid. :(

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Sun 17 May 2015 13:17
Is it wise to turn off engine whilst in a queue? - mss1tw

This attitude suggests you are overpaid. :(

I do earn a fortune it's true, my 1.9 diesel Berlingo is just a cover to keep the gold diggers away. 10p extra on a journey cost every now and then is a frivolity though I agree. Starter motors are much cheaper.

(Although I do save money by never changing the oil or timing belt)

Must dash got a caviar tasting session to get to.

Edited by mss1tw on 17/05/2015 at 13:18

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