scruffycyclist Posted February 18, 2006 Share Posted February 18, 2006 I'm a new owner of 2005 OB XT and my friend told me that with all turbo engines, in addition to allowing a minute or two for the engine to warm up, I need to allow the engine to cool off for a minute or two before I turn it off. Any input? Is this true? Quote Link to comment Share on other sites More sharing options...
gfcrane Posted February 18, 2006 Share Posted February 18, 2006 I bought a 05 Forester XT about six months ago and wondered about turbo cool-down too. The manual is silent and the dealer says it wasn't needed. After looking at some coolant diagrams on the Forester site, it appears Subaru has a very clever design and it isn't really necessary to run the engine at idle to let it cool. There is a small coolant reservoir, metal not plastic, where the coolant returns from the turbo. This is then connected to the plastic overflow bottle. In operation, when the turbo stops at shut-down it boils and the vapors pass into the metal coolant collection tank. Boiling evaporates the coolant mixture until sufficient cooling has taken place and the pressure from steam is safely disapated into the plastic overflow tank. This is a clever design and should prevent any damage unless the coolant level gets low. The oil setting in the turbo bearings will probably see somewhat over boiling temperatures but non-synthetic can tolerate 230 F for a while and synthetics for far longer. Quote Link to comment Share on other sites More sharing options...
fishy Posted February 18, 2006 Share Posted February 18, 2006 Not sure if subaru did this very much or often but my 94 turbo legacy has a sticker right on the door panel by the handle that says "let car idle for a minute or two after extended highway driving" (or something to that effect). it rarely gets this treatment as I don't think it's really necessary and I forget about it anyway... once in a while if I've really been caning it I'll let'er cool for a minute or two though - just to be nice. Quote Link to comment Share on other sites More sharing options...
Dickensheets Posted February 18, 2006 Share Posted February 18, 2006 I say better safe than sorry. Remember that the turbo takes hot exhaust air, compresses it making it even hotter. The turbo gets stupid hot!!! Spool down time allows the unit to cool slowly with oil flowing. Shutting off right away after hard driving allows the turbo to bake in stagnant conditions and possibly cooking the oil and itsself. Instead of letting it sit, try driving the last mile of your trip like a granny - same result. rd Quote Link to comment Share on other sites More sharing options...
Megell Posted February 18, 2006 Share Posted February 18, 2006 I say better safe than sorry. Remember that the turbo takes hot exhaust air, compresses it making it even hotter. The turbo gets stupid hot!!! Spool down time allows the unit to cool slowly with oil flowing. Shutting off right away after hard driving allows the turbo to bake in stagnant conditions and possibly cooking the oil and itsself. Instead of letting it sit, try driving the last mile of your trip like a granny - same result. rd Right on! Work the turbo hard, let it cool for a minute or two. Typical errands around town, not really necessary. Either way, all the more reason to use a good synthetic in turbo engines. Amsoil, if I remember correctly is good to about 600 degrees before the oil starts breaking down. Mike Quote Link to comment Share on other sites More sharing options...
daehttub2000 Posted February 18, 2006 Share Posted February 18, 2006 OLD Mitsubishi type turbos only cooled the bearings with OIL and you HAD to run the engine for a bit before turning it off. There was an epidemic of early turbo failures. The oil literally "cooked" into what they called "coke" and it ruined the turbo. NEW Subaru turbos use coolant but I still run the engine for a bit after I have finishing flogging my WRX. I use synthetic oil. If you use regular oil, I'd run the engine just a bit if you've been leadfooting it just to be safe. Some new cars (VOLVO) still use oil only for cooling their turbos and require the use of synthetic oil. That's probably why you see so many Volvo's in the repair shop... Quote Link to comment Share on other sites More sharing options...
nipper Posted February 18, 2006 Share Posted February 18, 2006 Depends upon your last mile of driving before parking the car. if you had to gun the car in the last mile, then yes let it sit a minute and spin down. IF you didnt then you can shut off the car and go in. This is where an exhaust gas temp gauge would come in handy. It would dtell you exactly whats going on so you would know. ive only seen one person on a list have a failed turbo, and that was due to his having to floor the car to get up his dirveway. He would shut the car off immediatly. nipper Quote Link to comment Share on other sites More sharing options...
Megell Posted February 18, 2006 Share Posted February 18, 2006 OLD Mitsubishi type turbos only cooled the bearings with OIL and you HAD to run the engine for a bit before turning it off. There was an epidemic of early turbo failures. The oil literally "cooked" into what they called "coke" and it ruined the turbo. NEW Subaru turbos use coolant but I still run the engine for a bit after I have finishing flogging my WRX. I use synthetic oil. If you use regular oil, I'd run the engine just a bit if you've been leadfooting it just to be safe. Some new cars (VOLVO) still use oil only for cooling their turbos and require the use of synthetic oil. That's probably why you see so many Volvo's in the repair shop... Do you mean because of the synthetic oil use that so many Volvos need repairing or because of the turbo still being cooled with oil only? Mike Quote Link to comment Share on other sites More sharing options...
daehttub2000 Posted February 19, 2006 Share Posted February 19, 2006 Oil only for Turbo cooling. Bad idea. A lot of folks don't like to spend $50-60 for a synthetic oil change and use the regular stuff. Bad news for an oil cooled turbo. Very few people let their turbo cars idle after a drive. It's a receipe for turbo failure. Quote Link to comment Share on other sites More sharing options...
Megell Posted February 19, 2006 Share Posted February 19, 2006 Oil only for Turbo cooling. Bad idea. A lot of folks don't like to spend $50-60 for a synthetic oil change and use the regular stuff. Bad news for an oil cooled turbo. Very few people let their turbo cars idle after a drive. It's a receipe for turbo failure. Thanks, that's what I thought. Just wanted to make sure I didn't screw up by going synthetic at $40 a shot on my 91 Leg turbo sedan w/162k. Mike Quote Link to comment Share on other sites More sharing options...
Setright Posted February 19, 2006 Share Posted February 19, 2006 Dickensheets is on the money. Either idle a "hot" turbo for a minute, or take it easy on the last stretch of road. The place to keep the idling in mind is highway gas stations: Cruising at high speed and pulling up for fuel...wait a minute please! Quote Link to comment Share on other sites More sharing options...
beezer Posted February 19, 2006 Share Posted February 19, 2006 The most accurate way would be to have a EGT gauge so that you can monitor it. Giving it a minute or two will probably work too, and you'll probably be fine. If you are very concerned however, then install a gauge. It is just a guessing game without having a one. Just my opinion. Beezer Quote Link to comment Share on other sites More sharing options...
daehttub2000 Posted February 22, 2006 Share Posted February 22, 2006 EGT would be nice but...just taking an extra minute to idle is easier, and a good habit. An Exhaust Gas Temperature gauge is a bit expensive and tricky to install (you have to somehow stick a temperature probe in the tailpipe!). There aren't a lot of places to put an extra gauge on a Subie unless you install these wart-like aftermarket pods. An EGT would be nice for playing with the engine control and turbo setup though. Quote Link to comment Share on other sites More sharing options...
nipper Posted February 22, 2006 Share Posted February 22, 2006 one can dream Quote Link to comment Share on other sites More sharing options...
zyewdall Posted February 22, 2006 Share Posted February 22, 2006 Yeah, turbos (at least oil cooled ones like my diesel truck has) need to cool down for a few minutes after you come off the highway, or otherwise off high load. I always try to let mine idle for a minute at least if I have been under load. And I do use synthetic oil, though the owners manual doesn't specify it (I don't know if it existed in 1984). I remember when I learned to drive the 4wd articulated forklift at work, I was instructed that if I didn't let it idle for 5 minutes after working, to cool down the turbo, the turbo wouldn't be the only thing that was toast... ...$12,000 to replace it. Quote Link to comment Share on other sites More sharing options...
Megell Posted February 22, 2006 Share Posted February 22, 2006 Yeah, turbos (at least oil cooled ones like my diesel truck has) need to cool down for a few minutes after you come off the highway, or otherwise off high load. I always try to let mine idle for a minute at least if I have been under load. And I do use synthetic oil, though the owners manual doesn't specify it (I don't know if it existed in 1984). I remember when I learned to drive the 4wd articulated forklift at work, I was instructed that if I didn't let it idle for 5 minutes after working, to cool down the turbo, the turbo wouldn't be the only thing that was toast... ...$12,000 to replace it.[/quote Synthetic oil has been around for quite some time. I was a mechanic at an Amsoil dealer back in the late seventies and specialized in high altitude, high performance engines running on propane and Amsoil Synthetics. Pretty amazing results, Propane didn't contaminate the oil like gasoline doe's. Engine life was several hundred thousands of miles and clean as a whistle when finaly taken apart. Mike Quote Link to comment Share on other sites More sharing options...
shortlid Posted February 22, 2006 Share Posted February 22, 2006 For warm up you can also just drive like a grany till you hit operating temps. That is what i do with my '95 SAAB 9000 Aero and that has a oil and water cooled Mitsu. TD-04 turning out 16 psi STOCK!! Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted February 22, 2006 Share Posted February 22, 2006 This very discussion is useless. gfcrane in post #2 explained why idling is not needed in modern turbos like subaru. Quote Link to comment Share on other sites More sharing options...
zyewdall Posted February 22, 2006 Share Posted February 22, 2006 This very discussion is useless. gfcrane in post #2 explained why idling is not needed in modern turbos like subaru. Not every turbo out there is a "modern turbo like subaru". Therefore this discussion is not useless. If nothing else, everyone reading it now knows that there are multiple types of turbos, with different care requirements. Yes, it's off topic for the specific question that was first asked, but what thread on here stays on topic Quote Link to comment Share on other sites More sharing options...
shortlid Posted February 22, 2006 Share Posted February 22, 2006 Also Subaru produced turbos back in the early 90's that I would consider a MODERN turbo, but would be a NEW gen. Roo?? Quote Link to comment Share on other sites More sharing options...
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