I know this has been rehashed many times, but what is the magic number in minutes for a safe turbo cool down?

 

I have always heard 2-3 minutes should do.

 

Are any of you guys using dedicated turbo timers to do this?

 

i have my turbo timer set for 3 mins. it works perfect for what i do, and its programable to what ever time you want to set it.

 

That really depends on your particular situation. If it's just stock 2-3 minutes should be fine, if your running a tune that is pretty aggressive with fueling it might take a little longer depending on if you were just running it really hard. Turbo timers from what I've heard work pretty good, but you still have to guess on the fact that in the majority of situations 2-3 minutes is going to be safe for shutdown. Since I've added bigger injectors if I'm coming off the interstate, it has taking me longer then 3 minutes to get down to approximately 400 degrees on the egt gauge(only thing I've really used to determine save cool down, I would argue the most accurate for all situations if your stopping it at the same temp every time). So to sum up 2-3 min is a good average time to let it cool, but I think if you really want to know for sure go by the egt gauge if you have one, if not a turbo timer is better then nothing if you can't wait for the 2-3 min before you get out.

 

Hey tex, I usually let mine hit 375 before I shut it down but this only takes 30 seconds or so with the stock tune or 60 seconds with the Looney.

Is 375 to 400 a safe range to shut down? I was thinking that maybe I should be letting mine run a little longer to get it down to ~300 (if you can get this low) becuase everyone is letting theirs run for 3+ minutes.

 

It's an approximation, 400 is not really set in stone, I like nice even numbers, you let it go lower thats probably actually better for the turbo then what I do. My truck is flowing more fuel that's why it takes me longer with the bigger injectors(even though they are only stage 1's they still flow alot more then what people think and after a workout it does get hot in the exhaust, I can easily peg 1450 with half throttle with my street tune).

 

The 400F EGT temp is for Post-Turbo not pre-turbo temps. At idle the pre-turbo temps will drop quickly but the Post-turbo temps will remain high do to heat soaking of the turbo etc.

The only way to accurately know the turbo temp for cool down is a Post-Turbo EGT gauge. You can also install a turbo temp monitor that shuts the engine down at a safe post turbo temp.
www.dieselmanor.com/isspro/ttm.asp

A truck that has been towing for a period of time on the highway will take much longer to cool down than an empty truck running in the City etc.

 

That's the first time I've heard that. I would find that being a problem as 97% of the people that I know(key phrase, that I know) run pre-turbo pyros, what would be the point have having one(rather crucial number to know) that is post when the vast majority run pre. That doesn't make much sense to me. I only now 2 people personally that run 2 pyros gauges(they use the outlook monitor for that), but that's it as far as my experiance goes.

 

Don't mean to sound ignorant but I just bought my 1st diesel, 04 F250 Crew Cab 6.0, do you need to let the turbo cool down everytime before you shutdown? Great site by the way.

 

I do, it doesn't hurt it at all. However, if your just running city errands, then it probably won't need much if any cool down, it's mainly if your doing long road trips or hauling alot, or even laying down some rubber at every street light.

 

Okay, we are talking about two different things here. Yes the majority of EGT gauges installed are pre-turbo and for good reason, when you are driving, towing or just have your foot in the throttle EGT temps can rise rapidly and in order to lower the EGT temps you must be able to see what they are when they come out of the combustion chamber, hence pre-turbo. With this knowledge, the driver can lift up on the throttle and lower EGT temps before ECT, EOT, and cylinder & piston temps reach a critical point and serious engine damage is done.

Now if we are talking cool down of the turbocharger itself we need to monitor post-turbo temps. When the exhaust gas passes through the turbine side of the turbocharger not only does it provide the energy needed to spin the compressor wheel which in turn produces boost to intake air, ithe turbocharger also absorbs heat from the exhaust. This heat is stored in the metal of the turbo charger & surrounding components. When the engine is allowed to idle the pre-turbo temps (think exhaust gas) drops rapidly but the metal turbocharger and surrounding brackets, downpipes etc take much longer to dissapate heat (metal stores and holds heat much longer than air) so the post-turbo temps will take a much longer time to drop off.

If you can only have one EGT gauge then pre-turbo is the better choice, but you still have to guess at the actual temperature of the turbocharger and when the turbocharger is properly cooled to allow for safe shut down.

For maximum longevity of the turbocharger you should really run two EGT gauges (both pre & post turbo) or run a pre-turbo gauge and an Turbo Monitor that keeps the engine running until safe post-turbo temps are reached.

So when you see the number being thrown around of 400F for safe turbo shut down, that is referring to post-turbo temperatures.

With todays modern oils and bearing materials, turbo failure do to high shut down temps is rare and so most people have forgotten the proper way to measure turbocharger temperature.

 

Now there is some great, 'positive-rep worthy' information. Thanks Blackhat!

 

Thanks Blackhat. I can see the reasoning now for a post-turbo EGT guage now.

 

the magic number is not in MINUTES. it is in DEGREES.

You dont want to shut the truck off until the egt gauge reads 350 or less ideally, but worst case at least wait until it drops to 400 degrees.

depending on ambient temperature, how hard you've been running, and whether the a/c compressor is on or not, could take anywhere from a 2-3 minutes, up to 10-12 minutes.