hello, how long you should leave the engine(2.0 TDI) warm  in the morning before taking the road plz? some ppl told me that it should reach 90°, others said we should run slowly before 90°. 

I can't speak for the TDI, but for my 1.5 TSI I always let it run until the idle drops.  Usually about 1min.  No technical reasons I know of but if it waits for something to happen before dropping idle I can wait 1min too

The best thing is to start the car, let it idle for a few seconds and then drive immediately off but driving gently until it's warmed up.

 

Leaving a car idling for long periods actually increases wear and takes a long long time to warm up especially on a diesel. In fact a diesel is likely never able to get up to temperature by just idling.

With any diesel I have always let it idle for about 30 seconds before driving off. That way it allows the oil to get around the engine and my dsg to get up to pressure. The same for when stopping. I allow it to run for 30 seconds to allow the turbocharger internals to slow spinning. 

@Midoutn - Depending on where you park and live, "warming up" could be performed by getting out of a driveway/car park and out of town at or below peak torque (guess at 1_800 rpm), maybe 5 minutes from engine start. "Cool down" with a diesel could be the reverse, but no need to idle it for several minutes.

From my perspective (and I own 2 x TDI184 cars - a Scout and a VRS) - I turn on the engines and wait about 60 seconds prior to departing.  That lets the oil get to all the places it needs.  I have 300 yards of short backroad and then I am onto fast 60mph road.  Its important that I let the engine oil get warm before I get to the main road.  Even when I am accelrating away, I do try to make sure that I do not progress too quickly up to speed until the engine is warm.

 

The golden rule is that until your car reaches 90C (by the coolant temperature), you should avoid reving the car past 3000rpm.  However, you will also find that the car has limitations on performance (to protect itself) until the engine oil gets warm enough (things like limiting the use of the turbo-actuator to engage the turbo) until the car is warm.

1 hour ago, Phil-E said:

The best thing is to start the car, let it idle for a few seconds and then drive immediately off but driving gently until it's warmed up.

 

Leaving a car idling for long periods actually increases wear and takes a long long time to warm up especially on a diesel. In fact a diesel is likely never able to get up to temperature by just idling.

Of course it will. Just take a longer time depending on outside temperature

15 minutes ago, ords said:

Of course it will. Just take a longer time depending on outside temperature

It just take considerably longer to get up to temperature if you leave the car to idle.  I timed it once - typical Scottish Day - 10C - took 30 mins for the car to get up to temperature on idle.

The guage may say 90°c but sitting at idle from a cold start without driving in winter the actual coolant temperature sure wont be.

 

But hey if thats what makes someone feel safe then thats their look out, by spring they should be safe to leave their driveway but they will have had to fill the tank a few times while waiting.

 

The later CR engines with the achilles heel waterpump sleeve warm up a lot quicker but a PD is really slow, on a cold day driven gently mine would take at least 5 miles and often require an uphill drive to get to 90°c on the guage which was not a real 90°c but as hot as the coolant was going to get.

Edited 24 June, 20214 yr by J.R.

Why should a diesel be different to a petrol re warm-up?  Oil still has to get around the engine.  I just start the car up, put the seat belt on, get comfortable then go.  I don’t think letting either engine idle does anything except waste fuel.

 

But see my sig below...

Edited 24 June, 20214 yr by Baxlin

Coolant warms up quite quick, as the Engineers designed the engine to have things, even when the ambient temp is cold. 

Oil gets warmed much slower more so in a TDI.  It could take 15 miles or more of driving before ever at an Efficient Operating Temp.

A TSI might take 5-10 miles.    Oil is a Coolant as Coolant / Anti Freeze / Summer Coolant / Anti Corrosion Fluid is.

 

Oil is the primary coolant.

 

Good point re how much longer the oil takes to get to operating temperature than the coolant.

 

Start the engine, clean any windows if necessary then drive off, one minute for the oil to get where it needs to be?

 

Driving gently until the engine is up to operating temperature is simply common sense but some want it spelling out, if you have sticky turbo vanes you will have already refined the practice into an art form, either that or have been taken for a hell of a lot of money by garages for new turbos.

Start up and drive off immediately.  Switch the MFD to the Oil Temperature setting. Drive the car progressively harder and once it hits an oil temperature of 90 deg C, drive it like you stole it.  

If someone is up your jacksy and wants to be where you are just wait until it indicates 50*oC oil temp and then boot it, then it will get to around an indicated 90*oC oil temp soon enough.

2 hours ago, e-Roottoot said:

If someone is up your jacksy and wants to be where you are just wait until it indicates 50*oC oil temp and then boot it, then it will get to around an indicated 90*oC oil temp soon enough.

Or do what I do. Drive even slower

Or spray your windscreen and have their auto wipers come on, it is safer than brake testing them.

16 hours ago, J.R. said:

The guage may say 90°c but sitting at idle from a cold start without driving in winter the actual coolant temperature sure wont be.

 

But hey if thats what makes someone feel safe then thats their look out, by spring they should be safe to leave their driveway but they will have had to fill the tank a few times while waiting.

 

The later CR engines with the achilles heel waterpump sleeve warm up a lot quicker but a PD is really slow, on a cold day driven gently mine would take at least 5 miles and often require an uphill drive to get to 90°c on the guage which was not a real 90°c but as hot as the coolant was going to get.

What will the actual coolant temperature be then if it's not 90c as indicated?

31 minutes ago, ords said:

What will the actual coolant temperature be then if it's not 90c as indicated?

Probably somewhere in the range 75-100. 

Watch engine coolant temperature in VCDS during warm up of your car and compare to gauge indication. You'll see it gets to 90 indicated well before the sensor says 90.

I've never played with seeing how hot it can get before it reads over 90; slightly dodgy thing to experiment with, cos you'll probably have to disable fans to get it hot enough to find out.

 

It's not a biggie though, anywhere in that range is fine to drive any way you feel like.

 

 

@ords @Wino I'd go further and say that, when the gauge "reads" 90C, the actual coolant temperature could be as low as 60C.

Anything from 60°c.

 

There are several clues that its telling you what you want to hear (see) rather than the truth, the non linear rate of climb during warm up & that once indicating 90°c it sits rock steady without any variation to be expected resulting from engine load, outside temp, airflow etc.

 

Having owned a Triumph Stag I learned the art of driving with one eye on the temperature guage and to recognise all the tiny fluctuations and what caused them and to recognise anything out of the ordinary, something that continued to serve me well until driving VAG vehicles of this century where it serves for nothing.

On 25/06/2021 at 09:16, KenONeill said:

@ords @Wino I'd go further and say that, when the gauge "reads" 90C, the actual coolant temperature could be as low as 60C.

 

Possibly, but without evidence from VCDS correlating with gauge reading I'd say that's more guesswork than anything else.

 

I took a series of photos just now showing VCDS/gauge comparisons on my Polo (see profile) during the 60-76°C warm-up section, At 60 (61, just missed 60) it's still very obviously not showing 90 on the gauge:

 

 

Edited 30 June, 20214 yr by Wino

1 hour ago, Wino said:

Possibly, but without evidence from VCDS correlating with gauge reading I'd say that's more guesswork than anything else.

Well:-

1. It's based on reading the software, not empirical observations of a petrol engine car with a different warm up profile.
2. Since I'm just reading software, I'm not making assumptions about the calibration of sensors.

So, show us this "the software"?

Is it universal?