Turbo cooldown
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The owner's manual recommends that you should let the engine run at idle in order for the vanes of the turbocharger to slow down and prevent turbo failure. If you drove the car hard (racing it, towing or driving in a hilly area) then you should let the engine run at idle for about a minute or so before you shut it off. If you drive normally then there is probably no need for it especially if you are using synthetic oil.
Under full throttle, in the T5, the turbocharger unit can reach speeds of up to 150,000rpm so it is essential not to shut off the engine immediately. When I arrive home, I usually slow down about 1/4 of a mile from home and when I park the car I do a couple of routine items (such as turn off the radio, put away my sunglasses, grab my briefcase, etc.) before I shut it off.
Yannis
Dude, you do need to cool down your turbo after a hard run. It's true that the intercooler does cool down the turbo, but to ensure the lines of the turbo are allowed to clear of hot fluid and the air is allowed to pull through a bit, it will prolong the life of your turbo.
You do need to let your turbo cool after a hard run as previously stated. Even though Volvo utilizes a continous oil return line system since 1993, it won't cool your turbo down enough. What happens is your turbo is spinning really really fast and if you just shut offf your car it won't have a chance to properly cool. If you go race your car then park and turn it off, after a few times your turbo becomes "heat soaked". When it becomes heat soaked your turbo will "spike".
this means your merging onto the freeway and you step on it and your car hits 3500 rpm's and your turbo sputters then 4,000 rpms sputters some more. After a few times your turbo will be shot.
If you look at other imports or street racers they have a Turbo Timer, which allows your car to keep running for a desired time even after you shut it off. For the sole purpose of letting your turbo cool down.
Think of your turbo heating up like if you heat up your brakes. If everywhere you drove you waited till the last minute to brake your going to heat up your rotors right ? Well then warping occurs which means your rotors heat up and since metal is flexible at high temps it changes shape ery easily then cools down at the different shape thus forth you get warped rotors. Well you need to let your turbo cool down after you heat it up.
this means your merging onto the freeway and you step on it and your car hits 3500 rpm's and your turbo sputters then 4,000 rpms sputters some more. After a few times your turbo will be shot.
If you look at other imports or street racers they have a Turbo Timer, which allows your car to keep running for a desired time even after you shut it off. For the sole purpose of letting your turbo cool down.
Think of your turbo heating up like if you heat up your brakes. If everywhere you drove you waited till the last minute to brake your going to heat up your rotors right ? Well then warping occurs which means your rotors heat up and since metal is flexible at high temps it changes shape ery easily then cools down at the different shape thus forth you get warped rotors. Well you need to let your turbo cool down after you heat it up.
Dude, I have work as a tech specialist for Volvo for years and yes you are right the turbo should cool down after a hard run> But, what constitutes a hard run for you might be differant for others. A hard run after which you should cool down is usually when you have just run the vehicle at high RPM 5k to 5.5k for a prolonged time (racing or street rodding). However if you are driving to and from work 3.5k to 4k rpm then the vehicles intercooler will allow you to not have to do a cool down. I just thought I should clear that up.
Dude!
Dude!
Okay Cal,
While i'm sure you're right on this one, i'm just trying to keep it in the minds of those who aren't exactly sure what to do when it comes to cooldown. If you worry about it, maybe letting your engine idle for a half minute will just help a little bit more, and maybe it'll just give peace of mind.
Not trying to be a jerk, just helpful.
Thanks for the tech. info
David
While i'm sure you're right on this one, i'm just trying to keep it in the minds of those who aren't exactly sure what to do when it comes to cooldown. If you worry about it, maybe letting your engine idle for a half minute will just help a little bit more, and maybe it'll just give peace of mind.
Not trying to be a jerk, just helpful.
Thanks for the tech. info
David
Cal, no the intercooler doesn't cool the turbo, it cools the charge of air entering the intake manifold after it leaves the compressor side of the turbo. Remember that the act of compressing air heats it up. The intercooler lowers this temperature to ambient so the air is at the lowest temperature possible when it enters the cylinder.
Hot air entering the cylinder reduces efficiency and increases the propensity of predetonation.
Besides, the heat induced into a turbo comes from the turbine (exhaust) side of the engine becuase the exhaust gasses are so hot. After a 'hard run' the turbine can be red-hot. A rapid shutdown after a hot run will halt the flow of oil to the turbo shaft bearings. If the shaft is too hot, it will 'cook' the oil remaining in the bearing. The resultant sludge that remains will prevent more oil from entering the bearing to lube it the next time the car is run. The bearing will then fail, the turbo will not spin up, and the engine will not produce its advertised power anymore.
So as long as the oil flow continues to run through the turbine-side bearings after a shutdown, it will keep the bearing not only cool but prevent the oil from cooking & forming the damaging sludge.
In any case, switch to Mobil 1 because the temperatures needed to break down the full synthetic oil are a lot higher than conventional oils.
But oddly enough, I asked the Volvo reps in Sweden if it needed a turbo cooldown period and he said they'd solved the problem and it wasn't necessary anymore. The old models recommended a one-minute cooldown with the engine at idle after a long run through the desert.
Still, I'm going to switch to Mobil 1 and let it idle for a minute after a run through the desert when it's 120 degrees in the shade. Can't hurt.
cal,
how could you say this? intercooling only refers to slightly cooling off the air charge *after* it's compressed and before it goes into the engine; there's no relation to the temperature of the turbo or the oil that flows thorugh it.
seeing as how there is no change in the amount of heat energy within a volume of air as it's compressed, compressing air increases the temperature of the air becuase you still have the same amount of heat energy, only now in a smaller volume. factor in that the turbo impeller is in fact driven by exhuast gases, and it only stands to reason that turbos are going to get hot. (and as previously mentioned, these impellers can get up to some pretty extreme RPMs when being driven under load, even when not being driven fast or at high RPMs; it only seems reasonable that you would want to let them spin-down before shutting off the flow of oil that lubricates and cools them.)
FWIW, even the owners manuals for the light pressure turbos like the S40 recommend allowing a minute or 2 for the impeller to slow down and for the oil to cool it down before shutting off. (using a synthetic oil that has better heat transfer characteristics and is more resistant to heat breakdown can only help.)
in summary, i'd think that you may be able to get through the warranty period without any turbo-spindown without failure, but is that all you want to get out of your vehicle? a minute at idle to allow it to spin down and cool down seems like a small investment in performance and longevity.
cheers!
e
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I am just going to "butt in" here, in this interesting discussion and give you my opinion which has been arrived to by talking to many reps, both in the US and Sweden. As I mentioned, previosuly, unless you have been driving the car aggressively, you should not have to sit there and wait for 1-2 minutes for the turbo to slow down. Since these turbos have become WATER cooled (that means that the main shaft of the turbocharger has a "vein" in which antifreeze runs through, therby increasing the heat tolerance) the "cooling down" period has been diminished in importance. It is a good and a preventative measure to allow yourself, anytime, a few seconds before you shut off the engine anyway...such as gather your belongings, turn off the radio, raise windows, close sunroof and then shut it off. Do you have to? Most likely not. But it is the same as when the oil and filter change intervals are every 7,500 miles but you have not too much to lose by investing $25 extra every 3,750 miles and do an extra lube job!
Yannis
I actually heat soaked my turbo it was spiking for a while till I had to let it run and properly cool down repeadetly and it corrected itself. I am sure I was just about the point where it would of ruined the turbo. I didn't cool it down in the first place because the Master Volvo mechanic that had been working at the dealer for 23 years told me the anti-freexze going through it would take care of the problem.
I think it would be rare for a person to park their car immediately after running it hard. That is, the last couple of minutes should be slow if you live in a residential neighbor hood, or you are in a parking lot, etc..
The reverse works as well (for the cold engine warming up). I hate to drive hard on a cold engine. However, since I am several blocks from the highway, the engine is reasonably warm by the time I enter the highway to go to work in the morning. Same goes for leaving work at night.
The reverse works as well (for the cold engine warming up). I hate to drive hard on a cold engine. However, since I am several blocks from the highway, the engine is reasonably warm by the time I enter the highway to go to work in the morning. Same goes for leaving work at night.
I have do a lot, and I mean LOT of research on this one and came to the following conclusions about turbo volvo's. Especially if you plan on keeping your past 50,000Mi/80,000K.
1. As it states in the manual, if you drive the car hard (or even remotely hard) let the engine idle for "up to 2 minutes" before shut down.
2. Use a GOOD synthetic oil. don't buy into the BS that mineral oil is just as good, this is simply false. All turbine powered aircraft/ships/trains etc use 100% synthetic oil because only synthetic oil has the properties that protect at extreme temps and speeds.
3. I have found that Amsoil Series 2000 0W-30 is by far the best motor oil available (do the research your self), albiet very expensive at about $8.50/quart. There is no comparison with any other, even Mobil 1 which is second best. Castroil is not a real synthetic and Valvoline has poor quality additives.
1. As it states in the manual, if you drive the car hard (or even remotely hard) let the engine idle for "up to 2 minutes" before shut down.
2. Use a GOOD synthetic oil. don't buy into the BS that mineral oil is just as good, this is simply false. All turbine powered aircraft/ships/trains etc use 100% synthetic oil because only synthetic oil has the properties that protect at extreme temps and speeds.
3. I have found that Amsoil Series 2000 0W-30 is by far the best motor oil available (do the research your self), albiet very expensive at about $8.50/quart. There is no comparison with any other, even Mobil 1 which is second best. Castroil is not a real synthetic and Valvoline has poor quality additives.
This is a common misconception regarding synthetic 0W-30 oil. the 0W stands for it's winter flow index, the 30 is the "weight" of oil and therefore 0W-30 is as "thick" as 10W-30, I'll paste the response I got from a Ford engineer (who also now is an Amsoil dealer) who explained it to me a while back, when I too, thought 0W-30 was too thin, he is very kind and takes time to explain it in detail, I ended up calling him and talking for a while as I too am a mechanical engineer by training and found a lot of it interesting..... read below: The question was posed that my dealer told me not to use 0W-30, the answer follows....
Simply put, 0W-30 is the same as 5W-30 for warm weather( there are minor differences, but the fact that synth is superior to carbon based negates that), except it is better on the cold wx, especially cold starts, so the answer for cold climate would be 0W-30, however 5W-30 is also sufficient. It's just a matter of what is best. Also, the Amsoil 0W-30 is specifically designed as a year around oil for all climates, and more importantly is specifically designed for cars that REQUIRE 5W-30 and 10W-30 oils such as our 2.4T and T5's.
[This message has been edited by V70SAM (edited 12-08-2001).]
[This message has been edited by V70SAM (edited 12-08-2001).]
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Correct. What the "W" refers to (among other things) is the "pouring point under cold temperature. The higher the number, the thicker the oil becomes under very cold temperatures.
Yannis
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