Banks says that Turbo Cool Down is a myth!

[hammersley]

Read Myth # 7



http://www.bankspower.com/tech_TD-fact-Fiction.cfm

 

[fox]

They must be getting ready to sell turbos?

It is good to let any engine to cool down for a few minutes before shut down, and a must with a turbcharger. This is to let the exhaust housing cool below the coking level of the oil. This is as low as 300 degrees for conventional oil and about 400 degrees for synthetic.

 

[R-N-R]

MYTH #7

You have to let a turbo-diesel idle for two minutes before you shut it off.



FACT

This is a current myth that has a basis of fact stemming from many years ago. It also has a kernel of truth regarding today’s turbocharged gasoline engines that operate at higher peak exhaust temperatures than turbo-diesels. In the early days of turbochargers, the turbo shaft was supported by a babbitt bearing that could seize, or even melt, if the engine was shut off immediately after sustained boost conditions where the turbocharger would “heat soak”. A two minute cool down at idle allowed the turbocharger to dissipate any remaining spinning inertia, and the oil circulation cooled the bearing and prevented oil “coking” in the bearing area. Turbochargers haven’t used babbitt bearings for over 30 years, and today’s oils resist coking. Synthetic oils won’t coke, period. With a turbocharged gas engine, it’s still good insurance to let the engine idle for 30 seconds to a minute to allow the turbo or turbos to dissipate any inertia and to cool the bearing area to prevent oil coking, especially if the engine has been worked hard just prior to shut-down. Of course, using quality synthetic oil eliminates this potential coking problem.



Today’s turbo-diesels are a different story. There is really no reason to “cool down” a turbo-diesel these days, but you won’t hurt anything by doing it either. You can still find people who swear you have to do it, but the myth is fading. Maybe they just like to sit and listen to the radio.

A couple of years ago, a guy who works at the factory warrenty center told me that coked turbos were DCX's #1 drivetrain return from diesel trucks. VPs held 2nd place.

 

[macdaddy]

Typical!!!!!

I guess we are supposed to disregard the owners manual all together. These people are amazing

 

[john3976]

A couple of years ago, a guy who works at the factory warrenty center told me that coked turbos were DCX's #1 drivetrain return from diesel trucks. VPs held 2nd place.

Really, I can't seem to find all these Turbo Failures when I do a search, me thinks someone was blowing smoke up your skirt about Turbo Failure being the number one warranty drivetrain problem.



My BS meter pegged out on that one.

 

[Joseph Donnelly]

At MM'05, Jim O'Donohoe of BorgWarner Turbo systems discussed failure analysis. Coked oil from high temperature shut downs was one of his issues. Mr. Baker can't change organic chemistry, and organics don't hang around at much over 400 deg. C regardless of what they are. You also want to allow cool down time for the rest of the engine's components, not just the turbo.

 

[SKargo]

Really, I can't seem to all these Turbo Failures when I do a search, me thinks someone was blowing smoke up your skirt about Turbo Failure being the number one warranty drivetrain problem.



My BS meter pegged out on that one.

I'm with you on that one. We almost never see failed turbos at this dealership.

 

[john3976]

At MM'05, Jim O'Donohoe of BorgWarner Turbo systems discussed failure analysis. Coked oil from high temperature shut downs was one of his issues. Mr. Baker can't change organic chemistry, and organics don't hang around at much over 400 deg. C regardless of what they are. You also want to allow cool down time for the rest of the engine's components, not just the turbo.

C J Baker may not be as far off as you are making him out to be, in fact he might be right on the money:



To convert between Farenheit and Celsius use this formula:

Farenheit Temperature = (Celsius Temperature)x(9/5) + 32



400 deg C = 752 deg F according to this formula.



If in fact I have done the formula correctly then Mr. Baker is correct and you are wrong about the oil issue.

 

[cojhl2]

In my opinion the turbo cooldown is the least of the issues. The engine internals must normalize also.



Way before turbos were a standard item on these engines we would never think of shutting an engine down immediatly after pulling it hard.



It all depends on how hard the engine has been working shortly before shutdown. I you are just driving down the street its a no brainer. If you have been on a pull like an upgrade down in the gears,, dont tell me you dont have to give the engine a chance to normalize down to idle temps!!!!

 

[john3976]

C J Baker may not be as far off as you are making him out to be, in fact he might be right on the money:



To convert between Farenheit and Celsius use this formula:

Farenheit Temperature = (Celsius Temperature)x(9/5) + 32



400 deg C = 752 deg F according to this formula.



If in fact I have done the formula correctly then Mr. Baker is correct and you are wrong about the oil issue.

Here is a link to a conversion program and according to it I was right on the money with the formula.



http://www.indiana.edu/~animal/fun/conversions/temperature.html

 

[john3976]

In my opinion the turbo cooldown is the least of the issues. The engine internals must normalize also.



Way before turbos were a standard item on these engines we would never think of shutting an engine down immediatly after pulling it hard.



It all depends on how hard the engine has been working shortly before shutdown. I you are just driving down the street its a no brainer. If you have been on a pull like an upgrade down in the gears,, dont tell me you dont have to give the engine a chance to normalize down to idle temps!!!!

I let my engine idle for 30 seconds to a minute, if I was pulling hard I would let it idle for about 3 minutes to 5 minutes depending on what my Pyro gauge is reading.

 

[Scrappy]

I have turbo temp monitor and have it set @ 300, it is usually shutting the truck off by the time I am just out of the truck. If I pull my trailer it usually takes 2-3 min.

 

[nickleinonen]

C J Baker may not be as far off as you are making him out to be, in fact he might be right on the money:



To convert between Farenheit and Celsius use this formula:

Farenheit Temperature = (Celsius Temperature)x(9/5) + 32



400 deg C = 752 deg F according to this formula.



If in fact I have done the formula correctly then Mr. Baker is correct and you are wrong about the oil issue.

are we talking about having an oil product up at 400°C??? most lube oil has flash points in the 190°C-250°C range...

 

[Joseph Donnelly]

I was stating that almost all organics decompose by about 400C. Many decompose at lower temperatures. Oxygen presence and time are also factors. As others noted above in confirmation to my post, the rest of the engine should have a chance to cool also. You can get away with a lot, but i thought the objective was to be nice to the engine. As an example, the 21cm2 housing kept the early intercooled first gens pretty hot, and every one of those housings I have tried to remove were warped tight from heat and harder to remove than 18. 5 or smaller housings.

 

[bmoeller]

I had to replace a turbo on one of our Mack trucks, that the boss' brother used to drive. He almost NEVER let the engine cool down before shutting it of. The turbo only made it 50k miles. About 200k, on the current one.



The seal and bearing on the turbine side were shot. LOTS of play. The oil leaking from around the clamp was what tipped me off. Caught it before the shaft snapped, like last time he ruined one.



You'd think as many times as I told not to shutdown hot, he'd learn. Nope. Glad he doesn't hardly drive the trucks anymore.

 

[amsoilman]

are we talking about having an oil product up at 400°C??? most lube oil has flash points in the 190°C-250°C range...

A good high quality synthetic oil such as the Amsoil Series 3000 HDD 5W-30 has a "Flash point" of 237 C. /457 F.



Wayne

amsoilman

 

[john3976]

Royal Purple has a high flash point: http://www.ro-quip.com/Technical_Docs/Royal Purple/Industrial fluids/RP Motor Oil_ps.pdf

 

[john3976]

Royal Purple Long Rider oil flash point: http://www.longrider.com/proper.htm

 

[rbattelle]

Give me a break. Anyone notice #9?

MYTH #9

Diesel fuel has less heat energy than gasoline.



FACT

Diesel fuel has almost 11 percent more heat energy than gasoline. A typical gallon of gasoline has about 124,800 BTU, whereas a typical gallon of #2 diesel has about 138,700 BTU.

Okay, that's half true. The other half is that on a MASS basis (aka gravimetric), diesel has LESS energy content than gasoline. As far as I'm concerned, then, diesel has less energy content than gasoline; its lower heating value is lower than gasoline's.



What is the coking temperature for a modern conventional oil? And what does the bearing type have to do with oil coking?



-Ryan

 

[catoiler]

Here's another reason,The speed of the turbo when it is shut off and no oil pressure feeding it.