Luxurycars take ages to warm up. So stop start motoring (esepecially in and out of garag to wash and polish) does no good to MAF sensors etc.
And people who own these cars have more money than sense of mechanical sympathy so a new engine is far more profitable than cleaning out the injectors .. says I cynically..
madf
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>Luxurycars take ages to warm up. So stop start motoring (esepecially in and out
>of garag to wash and polish) does no good to MAF sensors etc.
Would you care to explain how "Luxurycars take ages to warm up" and where that relates to the MAF sensor?
I'm honestly intrigued.
Kevin...
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They are huge. The engine is huge, the coolant reservoir is huge. At the same time, they aren't likely to have any work to do (getting up to a relaxed 120mph cruise etc) in their normal lives.
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Tha average small car (Fiesta) has 4 litres of oil in its sump. A typical 4 litre engine has 8 litres plus. Ditto Fiesta Gearbox 3 litres oil, auto transmission 5-8 litres.
Think how long to warm that lot up alone.. plus exhaust system and engine itself, let alone coolant (7-8 litres versus 20+).
Then there is gearing : typical small car does 3,000rpm at 70 mph. Large car will be only at 1,500-2,000 rpm - all in top gear.
So twice size, twice volume to htta up but only doing half the work. A recipe for longevity if used a lot (See Mercedes diesels with 300k + miles) or corrosion and wear if low mileage
madf
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Tha average small car (Fiesta) has 4 litres of oil in its sump. A typical 4 litre engine has 8 litres plus. Ditto Fiesta Gearbox 3 litres oil, auto transmission 5-8 litres. Think how long to warm that lot up alone.. plus exhaust system and engine itself, let alone coolant (7-8 litres versus 20+).
The bigger car will be burning fuel and so producing heat at twice the rate too. Why should that be less proportionately?
I should have thought the most likely explanation, apart from specific bore wear problems, would be that luxury cars tend not to do such long runs. I bet a R-R that did 50,000 miles a year of motorway commuting would last forever.
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Talking of warming up. My wife used to be a nanny in the leafy suburbs of Surrey. Her employers owned a Rolls Royce Silver Mist (quite rare as Mist means something rude in German!) 'E' reg I think. The car wasn't used that often as hubby used the train and wifey had a Merc Estate, but when it did make an appearance the driver had to come to the house, start the car and leave it for 15-20 minutes before driving it. I was always told to drive a car straight away, but apparently the RR needed this to warmt hrough components and prevent problems in the future.
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>Tha average small car (Fiesta) has 4 litres of oil in its sump. A typical
>4 litre engine has 8 litres plus.
In fact a 'typical' 4 litre engine (BMW and Jaguar) take about 7 litres but have twice as many cylinders and much greater swept volume. By your logic the oil in the bigger engine would warm up quicker.
>let alone coolant (7-8 litres versus 20+).
Most of the coolant is in the radiator and hoses which are bypassed until the thermostat opens.
>Then there is gearing :
Twice as many cylinders again.
>So twice size, twice volume to htta up but only doing half the work.
I think you'll find that an engine pulling a large car is actually doing more "work".
>A recipe for longevity if used a lot (See Mercedes diesels with 300k + miles)
>or corrosion and wear if low mileage
The only Mercedes diesels you'll find with starship mileage are the older pre common-fail units and how low mileage will affect a big engine more than a small one has me puzzled.
In short, all the statements you gave were non sequitur.
Kevin...
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The number of cylinders is a bit if a red herring.
The amount of heat energy warming up an engine is related the amount of fuel burnt, and to the thermal efficiency of the engine.
Even though a four litre engine in a manual transmission luxury barge is four times that in a manual transmission shopping trolley, the large car may not be using four times the fuel at low/town speeds.
This is because the power required to push the cars along at, say, 30mph isn't magically split in a four to one ratio. This power is largely dominated by transmission losses, and rolling resistance (too slow for aerodynamics to have a big effect).
Another wy to consider this is that the engine in the smaller car is usually (particuarly at lower speeds) producing more power (when compared to its maximum power rating) than the large car's engine.
So, the larger car will be burning less fuel (per unit engine capacity), and may therefore, assuming the engine, oil, and coolant are sized proportional to c.c., heat up more slowly.
Number_Cruncher
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>So, the larger car will be burning less fuel (per unit engine capacity),
>and may therefore, assuming the engine, oil, and coolant are sized
>proportional to c.c., heat up more slowly.
Err, no.
The ECU maintains the same stoichiometric mixture irrespective of engine size. The difference in fuel consumption between a large engine and a small engine, with the same efficiency, is mostly RPM and internal friction.
Also, as I said in my earlier post, oil and coolant capacity are very obviously not proportional to the engine cubic capacity.
The two 'typical' 4 litre engines I mentioned take about 7 litres of oil. A typical 1 litre shopping cart (Polo or Fiesta) takes what, 4 litres? So, four times the displacement for less than twice the oil capacity.
I deliberately didn't mention the 5.7L Chevy motor which takes only 4.5 US quarts (4.25L) of oil.
The engine in a 'typical' small car doesn't warm up any quicker or slower than the engine in a 'typical' luxury car. It all boils down to engine design.
Kevin...
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I don't intend getting into an argument here, but;
The fuel flow rate into an engine is roughly proportional to the power it is producing - the amount of air injested isn't directly relevant to how an engine warms up. Once the thermal efficiency of the engine is know, you can estimate how much heat power is being rejected to the engine, its oil, and its coolant.
The power an engine produces to move a vehicle along a particular path under a particular profile of speeds *isn't* related to engine size - at all! It's purely the power required to overcome the rolling resistance (which isn't related to engine size either) in its various forms, transmission friction, rolling resistance of the tyres, and aerodynamic force.
If, on the other hand you don't do a real life journey comparison, but you academically compare how the engines behave injesting the same amount of air - then owing to the three way cat requirement, an almost identical amount of fuel would be burnt, and the engines would warm up at a rate inversely proportional to their thermal efficiencies. i.e., this is the scenario you have described.
So, on a typical journey, a small engine in a small car is working harder (i.e., producing more power as a proportion of its maximum power) , and will therefore (other things being equal)* tend to warm up faster.
Number_Cruncher
* (other things being equal) - which, of course, they never are, but you have to start somewhere!
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>>The only Mercedes diesels you'll find with starship mileage are the older pre common-fail units
Common-fail??? Freudian slip, perhaps?
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As Cheddar pointed out (but got the wrong way around), the problem with late '90s Jags, BMWs etc. was bore wear caused by high sulphur fuels destroying the Nikasil liners.
Yeah, thanks I knew that, just a bit hasty in posting, I guess the relevant point was made though.
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Rolls-Royce Silver Mist? RR never sold a car called the Silver Mist although that is what the Silver Shadow was going to be called until it was pointed out about the rude meaning in German!!!
Never mind, Ford haven't done too badly with their 'Oh, my God' range - 'Mon Dieu!'
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'RR never sold a car called the Silver Mist'
Oh yes they did and at least one company still has one.
tinyurl.com/s5pr7
The name was indeed changed, but not before a few escaped from the factory!
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"The only Mercedes diesels you'll find with starship mileage are the older pre common-fail units"
Hmm so all these CDI E class Mercs I see on Autotrader with 150k - 250k miles are not common rail?
I did not realise Mercedes had not switched to common rail until 2006:-)
The above two sentences could have been replaced by a one word reply which is unsuitable for use on a family website:-)))
madf
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I am very wary of Merc CR Diesels. I had a bit of a 'close call' with a siezed glow plug in a CDI that I bought at auction. I then found out, from a 'contact' of mine who works in the local MB dealer, that this is a very common problem and often ends up with a near £1k head-removal job. He tells me that they have had a lot of 'difficult' repair jobs on the CR's and he's not a fan of them. Apparently the fuel rail pressure sensor and fuel pump are also rather prone to failure. The CR's don't seem to be anywhere near as reliable as the old Diesels, but on the other hand they have a much higher specific output.
On a more general theme, I must say that its a bit naive to think that a 'luxury' car should necessarily be any more mechanically robust than any other car. Almost by definition the luxury car will have added equipment that could make it less reliable. Moreover, the gradual consolidation of component suppliers means that many of the parts on a Merc are made by the same people who make parts for GM. Obviously different quality standards and defect rates may apply, but we are not talking about a vast difference.
My experience is that electrical failure is the most common likely reason for a breakdown. Japanese electrics seem to be by far the best.
Actual failure of the main engine components is rare - where an engine has needed replacement it is usually due to failure of some ancilliary part - often a timing belt or some part of the cooling system - which has lead to 'consequential damage'.
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>The above two sentences could have been replaced by a one word reply
>which is unsuitable for use on a family website:-)))
Don't be shy madf, you can say what you think.
Kevin...
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The Toyota MR2 sold surprisingly well (bearing in mind its name) in France.
The old ones are always the best.
Sleep - it´s overrated.
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