General question about turbos...

forgotmyname

Modern synthetic oils stand up to the heat soak from a hot turbo better. It was the older mineral oils that used to burn.

Still a good idea to let the oil flow through before giving it some welly.

Weird_Nev

OddballJamie wrote: »

Weird Nev, ask your mate why the mpg figures are so low for such an economical engine.

Err, he reports that they're not! He gets 60mpg out of his Eco boost fiesta. Obvoisuly, I can't comment on his driving style, but it's not wildly different from the EC figures.

I freely agree though, that users report wildly different results for those engines.


Re cooling down:
Modern turbos are all water cooled, there's no need to let them "cool down" or the engine to idle before shutdown. Drive them as you would any normal engine: Gentle after a cold start, don't race it or go from full boost to nothing and just shut it down. The pootle up your road before you park will be more than enough to let the turbo cool.
Subarus (and possibly other makes) even have a passive water circulation system that keeps water circulating through the bearing housings when the engine is off, to pull heat out of the turbo.

OddballJamie

He seems to be in minority
http://www.honestjohn.co.uk/realmpg/ford/fiesta-2008/10-ecoboost

vaio

Weird_Nev wrote: »

......Re cooling down:
Modern turbos are all water cooled, there's no need to let them "cool down" or the engine to idle before shutdown. Drive them as you would any normal engine: Gentle after a cold start, don't race it or go from full boost to nothing and just shut it down. The pootle up your road before you park will be more than enough to let the turbo cool.
Subarus (and possibly other makes) even have a passive water circulation system that keeps water circulating through the bearing housings when the engine is off, to pull heat out of the turbo.

yep, my '99 bi-turbo S4 has a little electric water pump to pump water (in the opposite direction to normal flow for some reason) through the turbos depending on temperature, I *think* some of the even older Audis have the same system too.

More generally, letting it cool is not something I normally bother with apart from coming off motorways/autobahn into service stations when I do let it idle for a min or two before turning off.

I suspect that decent oil and regular oil changes is why mine is now just over 220k miles

EdGasket

hoof_hearted wrote: »

it seems that turbos often seem to fail before the end of the life of the car and engine and that repairs are very expensive. I notice that some small cars are being fitted with turbos (e.g. Micra). In general, if you just needed an a to b everyday car, would you avoid anything with a turbo/ are they more trouble than the performance benefits they bring?

yes yes yes

Ultrasonic

Weird_Nev wrote: »

Re cooling down:
Modern turbos are all water cooled, there's no need to let them "cool down" or the engine to idle before shutdown...

What constitutes modern? I'm asking before a casual reader takes this to apply to their car when it may not. Do no currently sold cars have oil cooled turbos?

Weird_Nev

Ultrasonic wrote: »

What constitutes modern? I'm asking before a casual reader takes this to apply to their car when it may not. Do no currently sold cars have oil cooled turbos?

Well, they're all oil lubricated, and that does a fair amount of the cooling....
But in short, any turbo car post about 1990 needs no special treatment in terms of how you drive it. They're engineered to "work" as any other engine.
I've not looked under the bonnet of every recent turbo car, who knows, lower EGT's of diesels might mean that they don't need the same cooling mechanisms as petrol turbos. I know some diesel lorry turbos are solely cooled by their lubricating oil. However, nissans and subarus, and virtually all garrett turbos, are water cooled designs. Looks like Audi use them too, as do Porsches.

From an end user perspective it doesn't matter: It will have been designed and engineered to work properly under normal use. Letting the engine run to "cool down" or buying a turbo timer is simply a waste of time, fuel and money. You just need to know that oil quality and cleanliness is of vital importance to a turbos longevity, and should adjust your servicing accordingly.

Handy reading: http://www.gcg.com.au/index.php?option=com_content&view=article&id=116:turbo-stuff&catid=41:turbo-stuff&Itemid=99
Imprezas have no water pump to draw water through the turbo, and use "thermal wicking" exclusively. It's a pretty neat system. The turbo "pumps" it's own cooling water even after shutdown.

Ultrasonic

Weird_Nev wrote: »

Well, they're all oil lubricated, and that does a fair amount of the cooling....
But in short, any turbo car post about 1990 needs no special treatment in terms of how you drive it. They're engineered to "work" as any other engine.

I'd certainly understood that turbos now didn't need the prolonged cooling down periods of old, but hadn't though to ask why. Out of interest, will the turbo in my 2005 VAG 1.9TDI PD engine have some water cooling then? I was under the impression it was purely oil cooled. (Not wishing to contradict, I'm genuinely interested.)

Weird_Nev

Could well just be oil cooled - a bit of googling suggests that it's not as common for turbos to be water cooled as I assumed, and may be restricted to higher performance petrol cars because of the higher temperatures the turbo cores (and all the other bits) can reach.
Diesels run cooler and have lower exhaust gas temperatures, which is generally better for life of turbo bearings, BUT sooty particulate ends up in the lubricating oil over time, and forms a very fine grinding paste - BAD for turbos! They really need regular oil changes to keep them happy. I'd never exceed 10k miles without fresh oil, or one year. I certainly don't like the trend towards "extended service intervals" with long life oil. I think it's storing problems for future owners.

Ultrasonic

Weird_Nev wrote: »

I'd never exceed 10k miles without fresh oil, or one year. I certainly don't like the trend towards "extended service intervals" with long life oil. I think it's storing problems for future owners.

Fortunately 10k or 1 year is what Skoda reocommended for my car, so this is what it got before I bought it, and what I'll definitely be sticking to!