T6.1 BiTDI 204 power at higher ambient temperature

[petr_io]

While driving yesterday, I have noticed an odd reduction of power.

I was driving on a section of a motorway that goes up/down hill and while going up one of the uphills, the van simply would not go above 150km/h, which is not usually the case.

The ambient temperature was I think around 32-34C, I had the AC going relatively hard but otherwise there was just a full tank of diesel, around 150kg of luggage and me.

While this was happening, the oil was 125C and the coolant temperature was still indicating normal, though I have heard that each of the "segments" has quite a wide range so it's not particularly helpful unless something is really wrong.

The section of road where I've noticed the issue was around 10-15deg hill and was not completely straight (in case there is any influence on the power delivered based on the steering angle).

The second time I've noticed it is when I was reaching my destination at around 1500m of altitude, it definitely did not feel like it had its usual power though it was much harder to tell on the mountain road compared to the motorway as I could not do an accelleration test. Oil was also around 120C at that time as well, ambient also around 30C.

No error messages, the van just felt like it had less power than usual (no sharp decline, it slowly got tho the 150km/h top and then just did not accellerate anymore). There are no other issues I would be aware of and the van was quite happy maintaining the 130 km/h cruise control speed I had set through the hills.

It's a 12/2021 T6.1 California Beach Tour 4Motion 204hp, DSG, 80000km

Is the above normal behaviour is may something be wrong? The van is german spec and thus does not have any hot weather adaptations. It's my first summer with it here in Spain with it thus I do not have a reference re. how it had behaved before with hot temperatures.

 

[BuilderJay]

Welcome to the forum!
Hopefully someone will be along soon to advise as I have no idea but have the same engine.
Can you get hold of a reader to see if you have any fault codes saved??

 

[oldiebut goodie]

I used to notice the opposite in my old T3 diesel - cool early mornings and the engine had more oomph so I suppose what is happening there with yours could well be down to the temperature. The cooler and denser air certainly made a difference , when you only have 75 horses in the engine bay any gain is noticeable.

 

[petr_io]

Welcome to the forum!
Hopefully someone will be along soon to advise as I have no idea but have the same engine.
Can you get hold of a reader to see if you have any fault codes saved??

I will have a look, I just have the OBD port lock on so it's a bit of a faff to remove and plug anything in. the VW app that no health issues detected, the infotainment says everything is green if that means anything.

I used to notice the opposite in my old T3 diesel - cool early mornings and the engine had more oomph so I suppose what is happening there with yours could well be down to the temperature. The cooler and denser air certainly made a difference , when you only have 75 horses in the engine bay any gain is noticeable.

That's what I am trying to understand as well, it's not like it's really limiting me in any meaningful way, as I've said the van was maintaining the top allowed speed without issue I just noticed it behaved slightly differently and it's good to be on top of these things just in case

 

[kipperman]

Personally I would consider running at that speed , temperatures of that ilk and going uphill as putting rather a lot of strain on my van.

 

[petr_io]

Personally I would consider running at that speed , temperatures of that ilk and going uphill as putting rather a lot of strain on my van.

I am with you - I was not trying to maintain the speed long term, that was a "test" to see how the power was, I was maintaining normal motorway speeds otherwise.

What I am also trying to understand is whether there is some inherent protection in the van's ecu that rather than getting even hotter, it reduced power? And if so, whether that is a normal behaviour, if so, then I am completely fine with it.

 

[Samro]

This sounds really similar with what I experienced today.

In 30 -33 degrees of heat, all temps getting very hot, at altitude, at around 1500m above sea level up a dual carriageway across the Swiss Alps - Albeit towing a 2 ton load caravan.

Van is a 2022 T6.1 199 (Although VW seem unsure if it is 199 or 204!)
Van has done 22k miles.
Van ran out of puff and seemed to stay that way until oil temp reduced.
It is almost as though the oil is too thin at these high temps.

Here was what I posted before stumbling after this thread:

How hot is too hot?

Big hills and high temps! Slowed down to take load off and coolant has dropped 10 degrees in this pic! What is the maximum permissible oil temp as 137 degrees seems damn hot!

www.t6forum.com

 

[petr_io]

This sounds really similar with what I experienced today.

In 30 -33 degrees of heat, all temps getting very hot, at altitude, at around 1500m above sea level up a dual carriageway across the Swiss Alps - Albeit towing a 2 ton load caravan.

Van is a 2022 T6.1 199 (Although VW seem unsure if it is 199 or 204!)
Van has done 22k miles.
Van ran out of puff and seemed to stay that way until oil temp reduced.
It is almost as though the oil is too thin at these high temps.

Here was what I posted before stumbling after this thread:

How hot is too hot?

Big hills and high temps! Slowed down to take load off and coolant has dropped 10 degrees in this pic! What is the maximum permissible oil temp as 137 degrees seems damn hot!

www.t6forum.com

Sounds like you were putting it through a lot more strain than I did, though the behaviour looks similar.

Why are you thinking of compression issues? My initial though was software limiter that dials down power based on the temperatures/conditions, though I do not have much mechanical knowledge to know how a compression issue would feel like.

 

[Samro]

Very thin oil will not fill "the gaps" like more viscous oil and can result in a lack of compression.
(In old knackered engines, running thicker oil can bring up the compression in old worn engines.)

The thin air at 1500m above sea level could also be a factor insofar that there is less oxygen and consequently less of a "bang", causing a loss in performance.

I don't know if the thin oil is related to the loss of performance, as this could be the lack of oxygen, but something doesn't seem right.

Sounds like you were putting it through a lot more strain than I did, though the behaviour looks similar.

It is true that I was towing a heavy caravan up a steep long hill, but as soon as I saw the coolant temp rise above 90 degrees I downshifted and slowed to 40 mph.
I know that car manufacturers actually lie to us about engine temps (so that the temp always stays at 90).
This means that when the engine temp falls outside of the intended temps set by the manufacturer, the temp will appear to rise quite quickly, until the coolant temp falls back within the design operating temp.
It was therefore a shock to see the temp rise to around 110 deg c!
The van should cope with what I asked of it today and if I hadn't seen the temp start to rise and act accordingly, the temps may have climbed to a level which could easily cause issues such as head gasket failure.
I am not at all convinced that the recommended oil spec of 0W-30 is ideal for hot high altitude conditions.
I'd be interested to know an experts view.