I am sure this has been covered on a thread somewhere but i couldnt find it when i searched, so no doubt i will get the thread link. However, in the event i don;t find it I would like to have opinions, more technical than opinionated would be better on:

Turbo Cool Down - yes or no?

Reason I ask is: I have a number of turbo cars down through the years and own not just the scoob I have but a Zafira GSi (2l turbo) and my daughter has a 2003 GSi Astra Turbo. The vauxhalls and fords I have/had were all near enough driven as designed - quickly (but safely) and I never (nor my daughter has) let the turbos warm up nor cool down; never. And, never had to replace a turbo in my life and have kept and run the turboed cars for 1000's of miles.

However, it seems to be the norm during pub talk, forums and the like that all scoobs (or ohter turbo cars like porsche etc) that turbo cars should be up to temperature and if driven hard, allowed time to cool down - thus the invent of turbo timers.

Can someone tell me technically why we feel turbo's should be left to cool down.

I work in the aero industry and we don't have to let our aero turbines cool down

I don't want a wad of expletives please, just genuine response, because if I am doing it wrong I need to know, but as to date I have had no issues whatsoever with turbos!

Thanks in advance...

John

 

The turbo gets extremely hot up to 800 degrees celcius (correct me if im wrong someone) when driven hard, since oil is circulating it might begin to boil if you just shut of the engine after a hard run, letting it cool down simply means that oil circulates and allows cooling down of the turbo

This means that you will let the car idle for a couple of minutes before shutting the engine of, using a turbo timer simply means that you can leave the car imidietly and the turbo timer will shut down the car after a couple of minutes idling

 

Basicly what happens is when you shut the engine off, the turbo keeps spining for a time, without an oil feed to cool it down, the turbo bearings then get mega hot and selfdestruct!!!!!!!! I would buy a turbo timer if i was you, this lets the engine idle, while still being able to lock the car, letting the turbo cool down.

 

Let it cool down certainly, but a few minutes driving 'off boost' should achieve this. (Correct me if i'm wrong!). On my daily commute, I come off the motorway then through ~2miles of 30mph zone to home- all off boost driving. See no need to let turbo cool any further. Think the main area of concern would be after a long stretch on the motorway then just pulling into services and parking up. I would give my motor a couple of mins idling or 'take my time looking for a parking space' in these circumstances. Hope this helps.

 

Well, I'm no expert but I'll put my tuppence worth in anyway
I let the engine in general warm up before driving enthusiastically, especially when its v cold, just to make sure the oil has had a chance to warm up and start flowing properly. The turbo would obviously benefit from this a little as well.

As for turning off, I agree with driving 'off boost' for a couple of minutes to let the turbo (and the rest of the engine) cool down a little, especially if its been working hard.

However, the impreza has an oil / water cooled turbo, and I think (correct me if I've got this wrong) that this allows the turbo bearings to be cooled after the engine is switched off due to the coolant continuing to circulate a little due to thermal activity of the coolant itself. I don't know how effective / true this is, but given that subaru see fit to put a sticker on the door advising you to idle the engine after heavy highway driving, it may be either nonsense or not effective enough to make a difference !

Also, I've had a couple of experiences with other turbo'd cars regarding warm-up. One weird one was a land rover tdi that a friend had - it was almost unuseable above 2000rpm until it was warmed up a little in deep winter, we guessed that the turbo was actually frozen (it was extremely cold at the time). Also, I had an old (1984 ish) legacy turbo that used to be a dog 'on boost' before it was warm.

Also (promise to shut up after this ) I believe that more modern cars are built to be driven in what we would call a 'normal' manner, i.e. not requiring any particularly specialised startup / shutdown sequence, and as long as you're sensible I don't think you need to do anything differently that if it was NA.

Hope that helps a bit, and if in doubt print this off and keep it with you. Read it when you park and switch the car off once your finished reading - that should make sure it's cooled down

Pete

 

That is the only time I let mine idle during road use, I never rag it from cold either - but that is true for any engine. BMW automatically lowers the rev limit and slowly increases it as the engine warms up on (IIRC) the later M models

 

Thanks guys, this is my belief also and I would never rag a car until up to temperature but the scoob gets hot fairly quickly anyway compared to say my Zafira.

Heavy motorway stuff, yes, few seconds idling or slowish driving would suffice. I'm glad my own thouights are the same as everyone elses...cheers

 

I have some Defi gauges in my car and after seing how oil breaks down over a period of time and how long the oil takes to warm up and cool down I have made the following observations.

1) Change you oil regularly. It does break down over time and my oil pressure is completely erratic after six months of normal driving. My oil pressure was always constant when I first changed my oil but this is no longer the case. I have doen about 8,000 miles on this oil.

2) Oil heats up a lot quicker when you are on the motorway. It is no good saying leave your engine for ten minutes before using boost. My journey used to be local and it took the oil 10-15 minutes to get to operating temp. Now it takes me 2 minutes to get up to temp on the motorway.

3) I believe the minimum reasonable temperature you should have in the oil is about 70 before going mad on boost.

4) A local drive will help the turbo cool down and no need for the turbo timer. I have very rarely got the temp over 100 and only then on a very hot day after being on the motorway. Saying that I have a turbo timer and 30 secs should be more than enough after a blast on the motorway on a normal day.

These are only my observations but I think pretty good ones.

Hope that helps!

 

I'm no expert, but I recon it's good to let the car warm up properly:

I've got a set of Defi's with boost, oil pressure and oil temp gauges. When I start the car up from cold, the oil pressure shoots to about 7 BAR, even though the revs are only 1500 rpm. I think this is because the oil is thick, so the pressure is higher when the oil pump tries to force it around the engine.

After a couple of minutes driving round town at 30 mph the water temperature says it's fully warmed up, but the oil temperature hasn't even reached 50C (the minimum on the Defi's) and the oil pressure on tick over (at traffic lights) is still around 6 to 7 BAR. When the oil temp rises above 50C, the oil pressure on tick over gradually comes down until it gets to about 2.8 BAR when the oil temp is around 85C. So I recon the oil is only up to temperature at around 85C, where the pressure seems to stabilise at 2.8 BAR on tick over. I use Mobil 1 15/50 and I'm sure the pressure will be different for every oil viscosity there is.

As for turbo cool down, my mate knackered his GTI-R turbo when he stalled the car after a hard run. He started the engine seconds after, but turbo would only boost 0.3 BAR (previously 1.2 BAR). Not sure whether his turbo was oil cooled or oil/water cooled.

 

As you say 'Homerjunior' Change the oil often. The snag is you say you have run your oil for 8,000 miles. Subaru recommend oil & filter change at 7000 ish, I think, If you read some of the magazines and probably a number of threads on here you will also find many people change their oil halfway through. I do a oil change at 3500 followed by flush followed by oil and filter change at 7000 - 8000.
Regarding the comment on cooldown it is a good idea to let the car idle for a while whilst stationary. yes the water cooling of the turbo helps it cool down buit if you look into a kettle as you turn it on you will see that bubbles form round the element as it heats up. In a confined space like inside the turbo this would cause cavitation to occur resulting in damage to the water jacket. So on this ground it is better to keep the engine turning so the water keeps circulating.
On both these topics there are a number of different opinions this is my view and it seems to work for me.;

 

Quite right. I look to change my oil every 5-6000 miles usually but due to finance restirctions and other personal circumstances I haven't done this yet.

In some ways this is good because I have now witnessed oil breakdown first hand and am taking it eaiser then I would normally. It also means that I can pass the info onto other Subaru owners firsthand rather than inherited knowledge that gets fragmented.

I was really surprised as I had heard about the phenomenen but didn't actually believe it. I have seen the proof as my oil pressure is much more erratic then it used to be and especially at idle once the engine has warmed up.

I have used a variety of mechanics and they have all warned me of engine flush for the subaru. Because of the turbo's dependancy on oil and the general layout of the engine I have been warned off it. There are definitely mixed opinions on here and some people use it with no problems. Personally, I wouldn't touch it with a barge pole!

 

As you switch the engine (and oil pump) off the same oil will stay in the turbo bearing so is exposed to its heat for a prolonged amount of time. Its viscosity plumets so it can't support the load of the bearing adequately, also if it gets hot enough it cokes so you end up with hard carbon deposits floating about in it. If you idle the engine for a while it gives the turbo chance to slow to its idle speed (so it will stop more quickly after switch-off) and cool as the turbine is only exposed to idle temperatures.

I don't even have a turbo to worry about but am doing a uni project about oil-free turbo bearings

 

Care to read the owners manual then? It even tells you in there to let the engine warm down after enthusiastic driving.

Steve

 

The engines are better than they used to be and so is the oil, but most still use solid bearing turbos which should be left to cool down.

 

Im not being funny, but i wouldnt recomend using an engine flush, these remove the film of oil that coats the bigend shells, thus causeing metal on metal when starting up after the oil change. A good quality oil ei silkolene, should be used eliminateing the use of flushes.

 

When I say flush I mean filling with a cheaper oil then IDLING the engine for 10 to 15 mins, or however long it takes for me to make and drink a coffee. With a couple of blips on the throttle. Then drain, remove oil filter, fit a new pre-filled oil filter and then fill up with oil and start allowing to idle for a while. This is all done with the car on the ramps so no load is placed on the engine.

 

Theres no need to flush engines when using modern oils, they are choc full of detergents.

 

Always surprises me that my old '93 Clio 16v had an anti-percolation system and my Scoob doesn't. A very simple idea really. If the engine was hot enough for the fans to cut in after you'd switched it off, an inline water pump in one of the rad pipes would turn on, and carry on circulating water to get rid of any hot spots for as long as necessary to get the water temp below critical level.

 

Its all about cost saving though, your talking about the same company that didnt fit lock solinoids to the drivers door to save a few £...

Also I doubt the clio had very good airflow around the block being such a small car with a big lump so probably needed the aux pump.

 

The auxillary water pupmp was fitted to a few 16v models built by Renault. I had one on my 19 16v what a damn good idea, even though it was a pain in the butt when I fitted my MOSS alarm (the days before Thatcam lets up the price). Only snag is it circulates coolant not oil which would be of more benefit on a scooby.
Might be cost saving for Subaru on one hand but money MAKING on the other!!

 

May as well throw in my bit.
In my opinion, it would be a bad idea to drive hard then immediately turn off the engine. Have any of you guy's ever stripped down a really old engine that hasn't been looked after properly? You get a build up of oil that is burnt onto the internals. In this case, the turbo. In time, just turning off the engine, you will start to get the same kind of build-up in the oil lines of the turbo. This, in turn makes the walls thicker. I'm sure that after a certain amount of this build-up, the oil that then circulates around the turbo to cool it would be much less efficient. Think of it as cholesterol causing a build up of crap in your arteries. Restricts the blood flow, leads to a heart attack.

I'll stop yapping now. I hope my example isn't missunderstood and I hope this helps.

Chad.

 

The ONLY* poster almost talking sence...

Nothing to do with giving bearings time to spin down or cool down.

When you switch off the engine,the oil is not circulated, if the turbo is red hot the non circulatiing oil will boil, each time you do this it leaves a deposit of burnt oil stuck to the inside of the pipes / core / bearing. Over time this deposit builds up enough to block/ reduce the diameter of the oilway leading to little or no oil pressure when running.
No oil in the turbo when it's running... it's kinda obvious what's going to happen next.


*= with the exeption of Chad.

Andy

 

Kin ell, Chad beat me to it.

Andy

 

Hahaha! Sorry.

 

No problem, at least you know what you're on about.

Andy

 

There seems to be two issues being talked about on this thread: warming up and cooling down.

The short answer is that you should so both! Warming up an engine before enthusiastic use is especially important if you value your engine's life; the vast majority of engine wear occurs when cold.

Ns04

 

LOL I don't know about cost-saving. I think Renault just prioritise perormance over anything else with their faster models. They didn't try to build a car that was all things to all men, instead focussing on being exceptional at one thing at a time - look at the 5 Turbo, the Clio Williams, the Espace, the Sport Spider, the Clio V6, even the A610 etc. All arguably the best of that kind of car that you could buy for that price at that time.

They spent their money on building bomb-proof engines that revved to 7500 all day long, and unlike in my Scoob where it feels edgy getting up close to the redline, on a Renault 1.8 or 2.0 16v, it loves it. I saw a lot of Clio 16v and Williams engines in my time and hardly any had major engine blowups at all. It was always electrics and ancillary problems. And obviously, flimsy, rattly interiors.

 

hi right i have just got my wrx an wont 2 no how u do ya oil change coz there is 2 ways on ere can yaz let me no thanks

 

Eh?

 

Yeah you're right, there's also a sticker on the door as well - I was referring to normal vs enthusiastic driving