Interesting peice on turbos...

http://en.wikipedia.org/wiki/Turbo

In it, it talks about idling te engine for a short time (30 secs - 3 mins) to allow the turbo to cool and prevent 'coking' of the oil. Would this apply to an Octavia 1.9TDi?

Yes, though not as important as other cars with bigger turbos.

Either idle for 30 secs and then turn off OR just drive sedately for the last few miles before parking up... Apparently the oil can solidify if heated too much, so would cause problems... (soz, limited tech knowledge - im sure someone far more wise and savvy will be along soon)

HTH

Yeah, exactly as Sonic says: for all turbos it's a good idea to let it sit a little after you end a journey - don't get into the habit of belting it home, and immediately turning the engine off.

When starting a journey, it's also worth keeping revs lower until engine warms up, or you might be running the turbo hard before it's oiled itself up.

For the petrol cars (e.g. 1.8T) I've heard people say to keep under 3000rpm until temp guage is at 90', but some people have said you should wait longer than that, as they have seen the oil takes longer to heat up than the water.

Its a common misconception that you should idle your turbo'd engine for a while before shutting it off so that you allow the turbo to slow down before you cut the oil feed, this is utter nonsense as if you ever get the chance to see a turbo spinning as soon as the exhaust pressure is gone the turbo will slow down almost instantly.

As for letting it idle if you have been thraping it within an inch of its life, well yes you shouldn't turn any engine off after giving it a bashing as heat soak in engines can do all sorts of nasty things to your block, head, pistons all sorts.

also, just how much do you think a lump of cast iron is going to cool in 30 seconds? not very much i dont think!

Fair enough. What about warm-up at start of journeys?

In terms of a normal journey you probably won't need to let the engine idle to cool the turbo.

If you're doing a track day, where you are actually giving it some, then "yes" letting it idle is fine.

The Octavia Owner's Manual says:

Do not switch off the engine immediately after operating it for a lengthy period at high engine load, but allow it to run at idling speed for about 2 minutes to avoid any build-up of heat.

That advice applies to all engine options, ie petrol or diesel, turbo or normally aspirated.

warm up of every engine is very important!!

Although some rovers say not! and you can apparently thrape them from ignition.. but then what does rover know they have gone bust!

Your engine oil has whole different characteristics when its not warmed properly, and remember your turbo shaft floats on a bed of oil so until its nice and warm that shaft aint gonna be floating very well.

Its a common misconception that you should idle your turbo'd engine for a while before shutting it off so that you allow the turbo to slow down before you cut the oil feed' date=' this is utter nonsense as if you ever get the chance to see a turbo spinning as soon as the exhaust pressure is gone the turbo will slow down almost instantly.

As for letting it idle if you have been thraping it within an inch of its life, well yes you shouldn't turn any engine off after giving it a bashing as heat soak in engines can do all sorts of nasty things to your block, head, pistons all sorts.

As for cooking the oil, i work with turbo's engines all day in my line of work and we never have this problem![/quote']

You're right on the misconceptions about letting the turbo slow down. They rev down as soon as you lift your right foot. The point of idleing for 1 - 2 minutes after a HARD drive is that the turbo, while on boost, spins at speeds beyond 50,000rpm, which generate a lot of heat. Also take in consideration that the turbos are pushed by the already infernally hot exhaust gases. After a hard run, if you turn off the engine immediately, you'll stop the fresh oil flow on the very hot bearings in the turbo, allowing the oil to settle on them. This will literally cook the oil, forming a heavy sludge around the bearings and cooking the bearings themselves.

That's why it is recommended to wait for a bit after a hard or long run. And that is even more importante for our engines, since the 1.9tdi and the 1.8t use very small turbochargers, which are boosting all the time (hence the lagless response of our engines).

The point is that after a hard run, you should turn off the engine right away. It'll eventually reduce the life of everything, but since the turbo is one of the first things to go, it's often the most popular part to take care of (hence the names like "turbo timer" etc).

But i could be wrong, so....

warm up of every engine is very important!!

Although some rovers say not! and you can apparently thrape them from ignition.. but then what does rover know they have gone bust!

Your engine oil has whole different characteristics when its not warmed properly' date=' and remember your turbo shaft floats on a bed of oil so until its nice and warm that shaft aint gonna be floating very well.[/quote']

Absolutely true. I have this neighbor who "warms up" his Mitsubishi 2.8td every morning by turning the engine on and applying full throttle. Needless to say, the vehicle has been in the shop more times that i've been at the gas station. Imagine youself waking up every morning, and starting to jump and run wildly as soon as you open your eyes. Your body would eventually collapse. Same principle applies to engines, although i've been diagnosed with extreme mechanical sympathy, so...:(

You're right on the misconceptions about letting the turbo slow down. They rev down as soon as you lift your right foot. The point of idleing for 1 - 2 minutes after a HARD drive is that the turbo, while on boost, spins at speeds beyond 50,000rpm, which generate a lot of heat. Also take in consideration that the turbos are pushed by the already infernally hot exhaust gases. After a hard run, if you turn off the engine immediately, you'll stop the fresh oil flow on the very hot bearings in the turbo, allowing the oil to settle on them. This will literally cook the oil, forming a heavy sludge around the bearings and cooking the bearings themselves.

That's why it is recommended to wait for a bit after a hard or long run. And that is even more importante for our engines, since the 1.9tdi and the 1.8t use very small turbochargers, which are boosting all the time (hence the lagless response of our engines).

The point is that after a hard run, you should turn off the engine right away. It'll eventually reduce the life of everything, but since the turbo is one of the first things to go, it's often the most popular part to take care of (hence the names like "turbo timer" etc).

But i could be wrong, so....

Ok so for example, you have just been out on a good run and your turbo housing was about 700 degrees c, maybe hotter, i dont think that 30 seconds or even 2 minutes is going to cool a turbo by very much when its covered by a heat shield in a warm engine bay!

I would be more worried about the heat soak in your block and head from the lack of coolant flow causing horrible heat spots and what not.

In terms of a normal journey you probably won't need to let the engine idle to cool the turbo.

If you're doing a track day' date=' where you are actually giving it some, then "yes" letting it idle is fine.[/quote']

I thought coolant was pumped around the engine when its turned off.

There is something wrong with my turbo!! :(

When I switch the ignition off I can physically hear my turbo still spinning for a good 10 seconds.

There is something wrong with my EGT gauge as well because the temperature starts to drop immediately when I come to a stand still/or idling. I really must get all these problems fixed.

After a lengthy thrashing, the 350Z loosens up a lot, even the transmission sounds different, more race car than road car

The demo car was ticking and smelt rather warm when I returned it to the dealer.

how is coolant pumped around the block and head when its off? the crank is no longer turning so no belts will be spinning to drive the water pump...

magic, have u not heard the 'gulping' sound when the engine is turned off.

how is coolant pumped around the block and head when its off? the crank is no longer turning so no belts will be spinning to drive the water pump...

I don't think any of the Skodas can pump coolant around after the engine has stopped but there is a mini pump on the TT that does. It sits just behind the rad fans.

very fancy, as for your turbo delcac.. aint got a clue whats up with that! where is the drive to keep it spinning coming from?

momentum

very fancy, as for your turbo delcac.. aint got a clue whats up with that! where is the drive to keep it spinning coming from?

His turbo is probably the same size as the engine block

The coolant will flow to a bit due to thermosyphon. Also a turbo will take a good few seconds to stop spinning, you can see this when we test engines in our run up bay.

His turbo is probably the same size as the engine block

Not probably....................It is...

I thought coolant was pumped around the engine when its turned off.

HOW !!!!

HOW !!!![/i']

Who do you think you are "Jack Hargreaves or Fred Dinnage".......:P

Younger members may not get this..