Turbo cool-down period?

[WydRyd]

Are you guys exercising the typical cool-down procedure on your turbo's, even if you haven't driven the car hard? My understanding is that you should let the engine idle for ~2 minutes after a hard run (e.g: frequent max boost bursts), but if you haven't been driving the car hard at all (i.e: no boost), is it safe to just shut off immediately? Is this a bad thing?

[Craig 930 RS]

I let mine idle for a few minutes after any drive - the heat is just unbelievable, even after a modest run....

[sand_man]

I usually let mine cool down, too. Cool down for me is probably closer to 1.5 minutes. I use it as an opportunity to look underneath the engine, while it's running, to check for leaks and what not. My car sees mostly short bursts and I usually have an opportunity to drive it like a little old lady (low RPMs, no boost, 1st or 2nd gear) before I park it for the cool down period.

[38D]

You should always do a cool down. The length of time depends on how hard you drove the car. After races, I would idle for 7-8 mins.

[WydRyd]

Thanks... yeh, I'd have to say I take it easy the last 3-5 minutes before reaching final destination, then let it idle down a further minute and shut off.

I did that with my KKK for years and had no issues. Now that I have a GT BB turbo, perhaps I need to be a bit more cautious, since it hasn't got water cooling hooked up

[BoxxerSix]

Originally posted by WydRyd
Thanks... yeh, I'd have to say I take it easy the last 3-5 minutes before reaching final destination, then let it idle down a further minute and shut off.

I did that with my KKK for years and had no issues. Now that I have a GT BB turbo, perhaps I need to be a bit more cautious, since it hasn't got water cooling hooked up

Local garrett Dealer here Actually the BB CHRA is more durable when subjected to spin down(period between ignition shutoff and turbine stopping). They can run with less oil in this instance as ball bearings don't support the turbine shaft on a thin film of pressurized oil like floating bearing CHRA's do.......

All turbochargers should be "timed" no matter what the driving condition is for maximum longevity. If one is in a hurry and doesn't want to wait in the car, a good turbo timer module should be wired in for use to prevent coking(burnt oil residue buildup) which will eventually restrict oil flow. The HKS type I and II units are very good, reasonably priced(~$100-$120), and have an auto time function that determines the proper time down setting based on the car's recent driving situation(oxygen sensors referrenced). Takes the "how long" guesswork out of the equation

[WydRyd]

Thanks for the feedback BoxxerSix.

I do have a Greddy unit lying around, which I probably should have installed soon. That'll save me from sitting in my car in 90+ degree heat waiting for the cool-down process to finish

[A930Rocket]

There's something about walking away from my car with it running with a timer to cool down the turbo while I'm not there I don't like.

I can just see it bursting into flames while I go into the house and start watching TV...

[Craig 930 RS]

When I pull back into the driveway, I just use the cool down time to pick up leaves, get the mail, check the oil level, or even to see the jackass neighbor leaf blowing his leaves into the road.....

[WydRyd]

What happens when you get home at some unGODly hour in the morning? Wouldn't make you too popular with the neighbors eh?

[JFairman]

It's also pretty unpractical to impossible when taking girls out on a date.
They won't want to sit in the car and wait for that, unless your making out or something...

If you drive slowly and shift at lower revs and don't get into the boost at all for the last few minutes of driving and use synthetic oil.. I don't think you'll have a problem turning it off like a regular car.

I may be wrong though.

[WERK I]

Originally posted by JFairman

If you drive slowly and shift at lower revs and don't get into the boost at all for the last few minutes of driving and use synthetic oil.. I don't think you'll have a problem turning it off like a regular car.

I may be wrong though.

Nope, I think you are spot-on. Use syn-oil, drive the car home in a lower gear to keep the exhaust gas temps down, and think about the on-boost runs you had earlier.

[Tom F2]

With modern oils, especially synthetics, I wonder about the need for a "cool down" after moderate driving. After a highway run, or hard drive, I can see that one minute would be helpful. Has anyone really studied this issue, or are we working from intuition and legends from the early days of turbos?

[Craig 930 RS]

I agree. Driven 'mellowly', a shutoff should be fine.
If anything, airflow around the turbo while moving would help.

[wcc]

Yup, me too. I always take it easy the last few minutes before shut down. Just stay off boost by shifting before your turbo starts to spool.

[WydRyd]

Yeah, lately I've just taken it real easy the last 2-3 minutes before final destination, then perhaps let it idle down for a minute extra before shutting off.

I think the key to making turbo's last is religious oil servicing.

[timc]

Wouldn't letting the car idle for several minutes after taking the last 5-10 min easy (say around 2k in 2nd gear) actually cause the oil temp to go up instead of down???

By no means an expert, just asking..

tim.

[WydRyd]

Originally posted by timc
Wouldn't letting the car idle for several minutes after taking the last 5-10 min easy (say around 2k in 2nd gear) actually cause the oil temp to go up instead of down???

By no means an expert, just asking..

tim.

Good, valid question. Oil temps will rise if you idle for several minutes, especially in hot ambient climates. Which is why it's probably best to take it easy the last 5 minutes or so before reaching the destination. This, as mentioned above, lets the turbo cool down from the airflow around it whilst the car is mobile. If you do this, then you really just need to let it idle for a minute before shutting off. That's what I do.

I do notice in the hotter climates, if I sit stationary in traffic, the oil temps rise quickly and the intercooler begins to heat-soak, greatly impacting on power and response

[quattrorunner]

Your cooling the turbo in the cooldown, not the oil. The oil doesn't matter that much in this case. The turbo housing gets pretty hot and takes time to cool. getting out of the boost for a while would help keep the turbo from glowing, and such, but it's still going to spool.

[Zeroclearance]

As Quattrorunner has just mentioned, it is the heat from the turbine-housing and turbine wheel that we are trying to cool down. It is also the idle circuit that produces the richest fuel when sitting. Thus cooling down the turbine wheel the quickest vs having you foot on the throttle coming home. 1 minute is good 2 minutes great. After that you risk heat soak.. It's interesting to see who is good at cooling down turbochargers when tearing down the turbochargers during a rebuilt.. Having a blue shaft to the compressor side bearing is NOT good.