Myth or truth? Big engines question

[Smartbear]

I’d say that an engine which only just reached its normal temp by the end of the journey wouldn’t have had time to burn off all the condensation produced, it would have to operate at optimum temp for a longer period of time before that’s accomplished.
It’s all guesswork but I’d be uncomfortable using my car for regular journeys of less then 30mins even though it reaches normal temps after about 10/15mins or so
Don’t forget that the e85 displays water temp which reaches normal long before the oil does.
Rob

[Pondrew]

Kinell fella, I think you're missing my point and the same point somebody else made that ALL engines, no matter what size will need to reach optimum operating conditions before any detrimental phenomena occurs.
The simplest/dumbest way to measure if a 'big' engine is going to suffer more on the same journey as a smaller engine is to drive the journey in both cars the journey and see if the temp gauge reaches the middle position - usually assumed as the optimum operating temp.
If they both do, no problem! If they don't, well there's your answer.

So your answer is to conduct a very expensive and long-winded experiment?
Thanks, I'll think about it.
PS I get the feeling you may have some anger issues.

[mgrlane]

I think you have 1st got to define the definition of "warm".

Many people will look at the water temp and think the car is "warm" as soon as it "gets in the middle".

The reality is (in my (often) stupid opinion) is that this water temp means very little.

I think you have also got to ask the temperature of "what" contributes to "warm". Is it water temp? Engine oil temp, gear box oil temp?

My AMG I don't believe shows water temp (not easily anyway) but I drive it in AMG setting and it displays at all time engine and gearbox oil temp (other settings are sat nav, direction, speed etc).

When the engine oil hits 80 degrees the colour of the temp setting changes from white to blue and all systems are go (basically like an M where you get the extra couple of 1000's on the rev cycle). An interesting point is the newer 63's (w205) tolerance for being warm is 10 degrees cooler than the w204.

In terms of getting to optimum running temp my car will get there within 3-6 miles (the engine is a 6.2- I might have mentioned it). So it looks like it heats up considerably quicker that your iron block M's on here?

[BeeEmm]

Views please on this real life scenario. I have read on this forum, that a lot of people start the engine, then leave the car to 'warm up' before moving away. I always believed that this was wrong and that you should drive of immediately with reasonably low revs in each gear. I have also read the manufacturers instructions which advised the same. I have a BMW plug-in hybrid car with a 3.0 straight six petrol engine as well as the electric motor. The electric motor easily takes me to the M25 where I can build up speed to 70 mph (I know, unusual for the M25). The cold 3.0 litre engine will then 'kick in' at that or slightly lower speed and cruise happily. The change from electric to ICE is barely noticeable.

[mgrlane]

The electric motor easily takes me to the M25 where I can build up speed to 70 mph (I know, unusual for the M25). The cold 3.0 litre engine will then 'kick in' at that or slightly lower speed and cruise happily. The change from electric to ICE is barely noticeable.

I have thought about these engines before. I am interested to see how the petrol engine lasts. My understanding is that when you need extra power it will kick in the petrol engine so there are various times that you will be driving on electric and need that extra shove so a petrol engine is started and then put under load with effectively no warmth in the engine.

Is that the case? Is it an electric car that gets assisted by a combustion engine?

[TitanTim]

I would always go by 10/15 miles minimum regardless of engine size to get the engine upto maximum operating temperature and sooner you move off from cold the better.

I'm always betwixed when storing a car over the winter months that it's really doing it much good verses exposure to the elements, salt etc. The engine might be in fine fettle but sitting in a rusty shell or vice versa. Once my M140i is stored its not started again unless I know it will go out on at least a 45 minute run to heat everything up. Not just condensation in the engine if that's still a factor these days but water sitting in the exhaust system etc.

I think idling a cold engine is the worst thing you can do unless cooling down after hard use.

Tim.

[PDJ]

I have read on this forum, that a lot of people start the engine, then leave the car to 'warm up' before moving away. I always believed that this was wrong and that you should drive of immediately with reasonably low revs in each gear. I have also read the manufacturers instructions which advised the same.

With the S54 engine now running 10/60W oil the oil pressure at start up is very high over 120pis even in the summer so it is wise to let it tick over until the oil warms a little and thins out a bit and the oil pressure drops

Mine will start from cold (Cool summers morning) and the oi pressure will go round to 120 psi then after a minute it will start falling to around 60psi Takes a further couple of minuets at this time the water temp is around 40degC (remember you are only warming the thin layer of water around the block) after a couple more minuets I will drive the car with light load and a max of 3,000rpm until the oil is at normal temp, at this point the oil pressure is around 20psi at tick over the BMW red lights around the rev counter have long since gone off (way tooo early if you look at the other temps and pressures) The red lights where probably designed for the cars first set of rod bearings when it ran thinner oil etc.

[BeeEmm]

Is that the case? Is it an electric car that gets assisted by a combustion engine?

The electric motor will run completely on it's own for about 25 miles at lowish speeds and gentle acceleration or less distance if you accelerate a little harder. The car can be set to 'Electric Only' in these situations. If it is set to 'Hybrid' then as you say, the petrol engine will take over when you accelerate quickly or 'kick down'. In 'Sport' mode it uses only the petrol engine.

[Chris_D]

Kinell fella, I think you're missing my point and the same point somebody else made that ALL engines, no matter what size will need to reach optimum operating conditions before any detrimental phenomena occurs.
The simplest/dumbest way to measure if a 'big' engine is going to suffer more on the same journey as a smaller engine is to drive the journey in both cars the journey and see if the temp gauge reaches the middle position - usually assumed as the optimum operating temp.
If they both do, no problem! If they don't, well there's your answer.

So your answer is to conduct a very expensive and long-winded experiment?
Thanks, I'll think about it.

If you think driving 30 minutes to the same destination in both cars is ‘very expensive and long-winded’ then I would suggest with all sincerity that you don’t forget to clean up the broken pieces of your piggybank after raiding it for the petrol money. Also don’t forget to pack some sandwiches and a flask for that super long journey!

[sars]

Given the same atmospheric conditions, how quickly a car warms up is dependant on two things, the first is how much energy you put in and the second is how much mass there is to heat up (there are others like thermal efficiency etcetera, but let’s keep it simple as modern engines are quite thermally efficient). An easy way to determine heat input is by how much fuel you can burn and thus BHP is a good indicator. You can have two engines producing 300 BHP, one is a 2L turbo charged four cylinder and the other is 4L V8. Obviously the mass of the four cylinder is going to be two thirds of the mass of the V8 and as such the four cylinder will get to operating temperature sooner.

However that is not it though, to get 300 BHP from a 2L the engine is going to be stressed more than the 4L V8 and even though it takes longer to reach operating conditions it’s life will be longer.

[Argyll Andy]

Given the same atmospheric conditions, how quickly a car warms up is dependant on two things, the first is how much energy you put in and the second is how much mass there is to heat up (there are others like thermal efficiency etcetera, but let’s keep it simple as modern engines are quite thermally efficient). An easy way to determine heat input is by how much fuel you can burn and thus BHP is a good indicator. You can have two engines producing 300 BHP, one is a 2L turbo charged four cylinder and the other is 4L V8. Obviously the mass of the four cylinder is going to be two thirds of the mass of the V8 and as such the four cylinder will get to operating temperature sooner.

However that is not it though, to get 300 BHP from a 2L the engine is going to be stressed more than the 4L V8 and even though it takes longer to reach operating conditions it’s life will be longer.

sars, I was waiting for your answer and hoping I could understand it

As an aside, the M40i water temperature takes very little time to go from COLD to normal, much quicker than the 35iS.

[sars]

Given the same atmospheric conditions, how quickly a car warms up is dependant on two things, the first is how much energy you put in and the second is how much mass there is to heat up (there are others like thermal efficiency etcetera, but let’s keep it simple as modern engines are quite thermally efficient). An easy way to determine heat input is by how much fuel you can burn and thus BHP is a good indicator. You can have two engines producing 300 BHP, one is a 2L turbo charged four cylinder and the other is 4L V8. Obviously the mass of the four cylinder is going to be two thirds of the mass of the V8 and as such the four cylinder will get to operating temperature sooner.

However that is not it though, to get 300 BHP from a 2L the engine is going to be stressed more than the 4L V8 and even though it takes longer to reach operating conditions it’s life will be longer.

sars, I was waiting for your answer and hoping I could understand it

As an aside, the M40i water temperature takes very little time to go from COLD to normal, much quicker than the 35iS.

You failed to mention that you did though

……the only way I can make it easier to understand is if I use crayons

as an aside is it an oil or coolant gauge in the M40i? The difference being that oil tends to take longer than the coolant to indicate temperature and that could be the difference.

[Argyll Andy]

Given the same atmospheric conditions, how quickly a car warms up is dependant on two things, the first is how much energy you put in and the second is how much mass there is to heat up (there are others like thermal efficiency etcetera, but let’s keep it simple as modern engines are quite thermally efficient). An easy way to determine heat input is by how much fuel you can burn and thus BHP is a good indicator. You can have two engines producing 300 BHP, one is a 2L turbo charged four cylinder and the other is 4L V8. Obviously the mass of the four cylinder is going to be two thirds of the mass of the V8 and as such the four cylinder will get to operating temperature sooner.

However that is not it though, to get 300 BHP from a 2L the engine is going to be stressed more than the 4L V8 and even though it takes longer to reach operating conditions it’s life will be longer.

sars, I was waiting for your answer and hoping I could understand it

As an aside, the M40i water temperature takes very little time to go from COLD to normal, much quicker than the 35iS.

You failed to mention that you did though

……the only way I can make it easier to understand is if I use crayons

as an aside is it an oil or coolant gauge in the M40i? The difference being that oil tends to take longer than the coolant to indicate temperature and that could be the difference.

Yes I’d did , for once

Yes a water temp gauge on the M40i but even so seems really quick to get to temp. Loaner was the same so not specific to mine.

[Pondrew]

Yes a water temp gauge on the M40i but even so seems really quick to get to temp. Loaner was the same so not specific to mine.

It will be quicker cos it's new too. More friction in a new engine, while it 'beds in' and grinds off all that excess metal.

[Argyll Andy]

Yes a water temp gauge on the M40i but even so seems really quick to get to temp. Loaner was the same so not specific to mine.

It will be quicker cos it's new too. More friction in a new engine, while it 'beds in' and grinding off all that excess metal.

The sympathetic first 1200 miles it was treated too will hopefully help.

Have you had any of you recent purchases for 1200 miles