Just curious, ever hear of anyone frying their turbo? I haven't and I know guys that tow heavy with their CTD and don't even realize that they are suppose to wait to shut it down after a hard drive. Don't get me wrong, I cool mine down but I just have never heard of anyone frying their turbo (unless they did it on purpose so they could tell the wife they needed a new HX-40 or B-1 or you got the idea)

 

I run a pre/post EGT setup on my truck. The first thing, I cool mine off to 320-350 POST depending on how impatient I am. Pre turbo cools down to 300 ALOT quicker than the post can reach 350. I never trust my pre reading for shut down. I can work my engine hard and the pre turbo will read 350 fairly quickly. I switch to post, it's still sitting at 400. Not good for shutdown. Also, the 300* difference between Pre and Post only really applies to crusing speeds. I have seen a 450* difference between the two at WOT with comp on/off (pump wire unhooked). Idle temps are about the same. I can cruise at 55 in 3rd gear and see 650 (+/- 10) and 500 (+/- 10) post. I don't know bout normal accelerating.

 

[quote author=BigBlue link=board=4;threadid=14777;start=15#140725 date=1053554633]<br>I switch to post, it's still sitting at 400. Not good for shutdown. [/quote]<br><br>seems like 400 would be the upper limit, but ok for shutdown, since the oil won't flash until 450. Or is there a big temp drop from turbo housing to the post-turbo thermocouple location?

 

I don't know bout that. All I know is that I would not want to shut my motor down at just a little bit before the flash point. Cause remember. While your engine is running, the oil is circulating and cooling off. When you turn the truck off, the oil quits circulating and it becomes stagnant, soaking up heat. I've shut my truck down at 350 before and gone back out like 10 or so mins later and it was sitting at 400. IMO, the reason you shut down at 350 or so is to give yourself a little play just for that reason.

 

[quote author=BigBlue link=board=4;threadid=14777;start=15#140746 date=1053557719]<br>I don't know bout that. All I know is that I would not want to shut my motor down at just a little bit before the flash point. Cause remember. While your engine is running, the oil is circulating and cooling off. When you turn the truck off, the oil quits circulating and it becomes stagnant, soaking up heat. I've shut my truck down at 350 before and gone back out like 10 or so mins later and it was sitting at 400. IMO, the reason you shut down at 350 or so is to give yourself a little play just for that reason.<br>[/quote]<br><br>well, you've answered my question perfectly! Simple laws of thermodynamics say that heat will always flow from high temp to low temp, so the goal is to find and measure the highest temperature in the system. your experimentation shows that post-turbo temp is still not an accurate measurement of the energy source capable of heating up things after shutdown. Its better than pre-turbo of course, which is a terrible approximation of this, to be sure, but what this important piece of data says is that post-turbo temp at idle is not even within 50 degrees of measuring the correct energy source.<br><br>so you have me convinced that 350 post turbo is the right answer. hey this is good stuff: experiments like yours are valuable, so keep it up! Every truck (and every post turbo thermocouple installation) may be different, too!<br><br>P.S. still, I'm aware that many guys run pre only and are pretty lax in shutdown procedures, yet their turbos still run. that can only mean that the oil flash point and other parameters may have some additional margin in it.

 

I can shut down at 350 post and my pre temps will be around 330. Idle temps are about the same for the two (in park at least).

 

If I may add something here. I belive its Holset that says 300* is the appropriate shut down temp. This must be some kind of rule of thumb and I dont think its so we dont light our turbos oil on fire! If that was the case then every time we pull anything over 500* EGT we would have to break out the extinguisher. I have NEVER heard of a turbo fire. Its because the oil that is left to sit on the bearing will cook and turn to a nasty ugly goo. Net result will be a bearing that will have nasty ugly goo caked on it and not be able to perform at the optimun level required. Maybe even early failure. Oil doesnt light unless subjected to open flame, and at that its not easy.<br>The best solution I have seen is the Turbo Saver. Simply a bottle of oil that fills upon running the motor and when you shut down the oil slowly drains back through the turbo, keeping the oil from laying on a hot surface. It cost some money and is more complicated than I just described but you get the idea.<br>So far the cheapest is just a little idle time.

 

Just curious, ever hear of anyone frying their CTD turbo?

 

I wasn't saying that it would catch on fire. I was talking bout oil coking. Sorry if I confused anyone. I wonder what a turbo on fire would look like?

 

[quote author=KATOOM link=board=4;threadid=14777;start=15#140841 date=1053579539]<br>I belive its Holset that says 300* is the appropriate shut down temp. This must be some kind of rule of thumb and I dont think its so we dont light our turbos oil on fire! <br>[/quote]<br>is that pre or post? yea, I'm sure you're right about it being a rule of thumb. consider that for a manufacturer to make such a statement, there has to be large amounts of wiggle room (margin) in the number, or they would be open to lawsuits. So you can be this is a very safe number. and the failure mode is bearing failure, not fire, which I can see you already understand <br><br>this is not correct. oil will light when it reaches the right temperature, and if oxygen is present. The flash point is defined to be the temperature at which the oil spontaneously flames. Quite literally, to find and spec this temperature, they raise the temperature of the oil until it flames. has nothing to do with open flame, which is not itself requried to start the fire. now then, oxegen is required to support a flame, so the oil in the turbo doesn't actually flame, as there is precious little oxygen inside a pressurized oil system ;D. so the flash point of oil is only a guideline to indicate the point at which the molecular structure breaks down. (makes coke)

 

<br>Sorry I shouldnt have been so hasty. You are right that oil will catch a flame but the temps are very high. Usually it just cooks away before it lights, thus leaving the dreaded goo. <br><br> This one I never understood and I posted it awhile ago. Diesel advised temp is 300* were as gas is 400*. I know some guys said that gas motors arent built as strong as diesel so as not to hold the same heat but it still doesnt make sence. I think there is a better reason but temperature is temperature and its still cooled by oil.

 

I think gassers can stand up to a higher heat longer.

 

[quote author=KATOOM link=board=4;threadid=14777;start=15#141223 date=1053667441]<br>You are right that oil will catch a flame but the temps are very high. <br>[/quote] Not &quot;very high&quot; at all when we're talking about turbo shutdown. This is the 450 degrees I've been talking about. Actually 446 degrees F for Delo 400, and only 415 for Rotella. Guess which one I use <br><br>this is a good point. I've been using the flash point as a guideline but additional margin must be allowed for the &quot;coking&quot; temperature which may be a few degrees lower than the flash point. especially for Rotella users, who's flash point is 31 degrees cooler than Delo.<br><br><br>yup, you got it. to be sure, a diesel engine has considerably more stored energy, meaning that a Diesel engine at 400 degrees contains a lot more energy than a gasser at the same temperature. But I'm with you on this, and don't see how this affects turbo shutdown temperature, especially if both engines are measured post turbo in the same way. could be that the diesel engines' exhaust design allows for better thermal coupling from block to turbo, or just the fact that there is more energy available to transfer into the turbo housing. I dunno -- i thought that the problem was heat stored in the turbo housing, not the block. Maybe heat flows from block to turbo -- at least there is more liklihood of that happening in a Diesel. at least the real diesels ;D

 

&quot;Flash point&quot; is actually the temperature at which a fuel produces sufficient vapors to flash, but not sustain combustion when in the presence of an ignition source. &quot;ignition point&quot; is the temperature at which a given fuel spontaneously combusts (burns) independent of an ignition source. The former is typically much lower than the latter. For example, diesel fuel has a flashpoint somewhere around 130 degrees F, and an ignition temp. around 600-700 degrees F. All this pertains to the combustion of a fuel, which is irrelevent to the discussion at hand, because the oil does not &quot;burn&quot; in the engine. It does off-gas the lighter distillates in the oil, leaving behind the heavier, less lubricating distillates behind. This is a function of time as well as temperature. In all likelihood, the turbo would have to be very hot for an extended period of time without the oil moving for this to happen. <br>I'll get off my soapbox now.

 

thanks cowpie for the reminder. been too long since I read the test definitions .<br><br>seems like the flash point is still a good indicator of oil breakdown at high temperatures -- with regards to bearing failure and coking. And the 30 degree differenece between Delo and Rotella, for the purpose of determining a shutdown temperature, seems like a difference worth noting. We're talking about a 350 degree shutdown temperature, post turbo, and Delo gives you an approximately 10% additional margin.