Date: 6 Jun 2002 13:08:53 GMT From: davehinznopsamcop.net Subject: Re: Wife buying '02 9-3 SE convertible . . .what should I keep an eye on??
Someone who looks an awful lot like M. <m.cnopsamree.fr> wrote: >> Pardon me, but this is complete bunk. A few *thousand* miles? And then >> you mention it wasn't even a Saab? And, how could that possibly affect >> the engine, exactly? > Hi, I have nothing against Saab as I'm currently buying one (9-3 2.2 TID). > I'm just talking about the way a Turbo should be taken care off. Maybe I > wasn't clear enough : when I mean the engine should be idle before switching > off, I don't mean to let it idle during 30sec or mn. It just mean that the > turbo shouldn't be activated before switching it off. Yes, and then I gave direct personal experience of a Saab going a quarter of a million miles, with no such special spin-down attentions, which never had any problems with the turbo. Your message quite clearly said the turbo and engine would only last a few thousand miles if you didn't do that, which is completely, utterly, and blisteringly false. For any turbo car, not just Saab. Hell, even the Corvair turbos were far, far more resiliant than you imply, and they predate the Saab ones. And, again, if there were problems with the turbos, we'd probably have seen some messages about that sort of thing here, all things considered, and I can't recall the last time I saw someone asking about replacing or rebuilding a turbo, for anything other than performance upgrade reasons. > What happened on the engine I mentionned is that the turbo blew and the kind > of rotor which is inside broke in pieces. It's a few pieces of this "rotor" > which went throuh the engine. I'm not a mecanic so the name is maybe not a > "rotor" but the final result was still there. A turbo impeller does not shatter due to a lack of letting it spin down. It will shatter if it ingests something; if a chunk of solid material got past the filters and into it. What a lack of cool-down will do, *in turbos which are susceptable to such problems* such as straight oil-cooled ones, is that the turbo is cooled by the oil flow. When the engine is shut down, that oil flow stops, so the cooling stops. Because the thermal mass of the turbo is rather high, the temperature at the bearings will actually increase for a time, as the heat equalizes through the body of the turbo, before it eventually dissipates into the surroundings. The net effect of all that, is that the oil that is in the bearings, instead of cooling it, will start to "coke", and turn into a solid. Scorches it, if you will. This eventually reduces the oil flow to the bearings & shaft of the turbo, which results in higher wear, which will eventually lead to the bearings loosening up to the point where they are no longer keeping the shaft centered, at which point the shaft takes out the seals (in a very slow, non-exciting manner). Right about then, you start getting unusual colors of smoke coming out your tailpipe, and go and get the turbo replaced. None of this will shatter a turbocharger. > I was just replying to this post in order to give an experience of what > "could" happen to a turbo engine which is not used properly. Well, I "could" walk out of work today and find a stuffed wombat on the hood of my car as well, but it's extremely unlikely. > Regards, and please excuse my english as it's not my first language. Your English is fine, but your description of turbo failures as a result of not letting them spin down, is not. Dave Hinz