So I been driving Turbo cars for donkey year and it was always drilled in to me that a car should tick over for 30 seconds before switch off to make sure the turbo has stopped turning and does not loose oil pressure.

 

Has this changed as I don't see anything in the manual. My query really is if you come off the motorway to a roundabout with traffic lights and put the car in natural, the engine is going to shut off and the turbo could still be spinning .

 

Just my thoughts

Very much changed.

Stop / Start was introduced a long time back and there can still be cooling done to an engine when you switch off.

 

If you want just switch off stop / start in a situation like you are mentioning, but i would imagine that you are likely doing no more than 90 down a motorway and not really going to cook the engine / turbo.

Many turbos these days are water cooled, with a pump than runs on when the engine isn't.  As far as I know the problem was that the oil in the turbo could overheat unless you gave it a few seconds pushing oil through while the heat dissipated.

As a rule, it's good practise to let the turbo spool down before switching off; likewise let the engine idle for a couple of minutes before setting off from cold. On old cars, this was critical - I'm not sure about newer cars. Even at low speeds, turbos can spin as much as 100,000+ rpm. For the sake of 2 mins (which is better than not doing anything at all) I wouldn't bother risking potential turbo/engine damage further down the road.

In the same way stop/start can be auto-inhibited on a stone cold engine, you could argue that would also apply when it is at the upper end of operational temps (if you manage to cook the engine that much you can get it into an inhibit state).

 

After conducting hot climate cooling testing at OEM level early 2000’s, you need to really rag an engine in top gear on full throttle for at least 20+ mins without lifting to get anywhere near maximum temp limits. The mid engined cars I ran back then would de-rate the engines a little until the oil temps dropped sufficiently to allow max power again so it should easily be the case now to have more control limits in place. Front engined cars back in the day couldn’t even trip the upper temp limits due to efficient cooling systems. 
 

So don’t worry, it’s not going to cook itself if stop/start cuts in. 

Edited 18 June, 20205 yr by BigEjit

When I've been on a Motorway or been "pressing on" and come to a standstill, I try to remember to disable Stop/start. Either b pressing the button or holding the clutch down. I don't know if it makes a difference, but I feel it should.

I would expect the stop - start system to have enough intelligence in its design not to damage the turbo or other car parts through its normal operation.

 

On 18/06/2020 at 22:46, BigEjit said:

In the same way stop/start can be auto-inhibited on a stone cold engine, you could argue that would also apply when it is at the upper end of operational temps (if you manage to cook the engine that much you can get it into an inhibit state).

 

After conducting hot climate cooling testing at OEM level early 2000’s, you need to really rag an engine in top gear on full throttle for at least 20+ mins without lifting to get anywhere near maximum temp limits. The mid engined cars I ran back then would de-rate the engines a little until the oil temps dropped sufficiently to allow max power again so it should easily be the case now to have more control limits in place. Front engined cars back in the day couldn’t even trip the upper temp limits due to efficient cooling systems. 
 

So don’t worry, it’s not going to cook itself if stop/start cuts in. 

 

When everthings only freshly warmed up the lower gears (2/3) do seem to pull better than after some spirited driving. I always ensure oil is at very least around the 75c mark (coolant needle already at 90c long before that point) before i go for it.

I'm not sure if it's it making less power without boost when cold, so the boost coming in hits harder, or when it's warm it's pulling timing because charge air temps are higher. Ultimately doesn't seem to make too much of a difference though.

 

As for full throttle without lifting, longest i've done that for is about 10-15 miles, about 5-7 minutes at the speeds i was doing, at that time, in winter oil temps never went past 106c, now it's summer i can see them as high as 109c, never seen 110c though. Coolant needle never changes from 90c though, wish there was a way to change it to show actual coolant temps.

1 hour ago, FabiaGonzales said:

 

When everthings only freshly warmed up the lower gears (2/3) do seem to pull better than after some spirited driving. I always ensure oil is at very least around the 75c mark (coolant needle already at 90c long before that point) before i go for it.

I'm not sure if it's it making less power without boost when cold, so the boost coming in hits harder, or when it's warm it's pulling timing because charge air temps are higher. Ultimately doesn't seem to make too much of a difference though.

 

As for full throttle without lifting, longest i've done that for is about 10-15 miles, about 5-7 minutes at the speeds i was doing, at that time, in winter oil temps never went past 106c, now it's summer i can see them as high as 109c, never seen 110c though. Coolant needle never changes from 90c though, wish there was a way to change it to show actual coolant temps.

You are probably experiencing lower intake air temps when the engine is warming up or just at 90 then when it has been at 90 for a longer periods of time  and the thermostat has been opened.

 

Highest I have seen on my Fabia is 114c on the coolant and 129c on the oil. (Through OBDeleven logging) This was (relatively) low speed 2nd and 3rd gear full throttle uphill to over 2000m. Ambient temp was just under 10c.

coolant gauge kept showing (very near) 90c.

It took me quite a few years to understand that driving everywhere at shall we say "top speed" was a really dumb,costly and pointless thing to do. I think I finally became "mature" when I got to the age of around 55.