KATOOM

I know that shut down temp is 300* BUT what I dont understand is why shut down temp for gas motors is 400*? I understand that we need to reach this desired temp so that the turbo bearings dont cook but a turbo is a turbo and why is gas allowed another 100*? Not that I'm trying to get someone to tell me that I dont have to worry so much about shut down but I do know guys that drive there trucks (one is a Ford) without gauges and they just shutdown when they stop! I never hear of them having turbo problems, now that I mention it I never hear of anyone having a bad mechanical turbo problem unless they have done serious mods or messed around with the turbo themselves. Not complaining, just curious. [undecided]

BigBlue

Gassers run hotter temps than we do. They might not be able to get down to below 400. I know it takes my truck forever to reach 300. I usually shut it down between 350-330 depending on how hard I've been working it.

TxDieselKid

[quote author=BigBlue link=board=4;threadid=14392;start=0#135267 date=1052195664]<br>Gassers run hotter temps than we do.<br>[/quote]<br><br>You sure about that?

MCummings

I was staring at 1600* yesterday for about 1/8 - 1/4 mile while seeing how fast I could accelerate 27,000 pounds from 50MPH-80MPH.<br><br>Merrick Cummings Jr

GrandpasRam

Sorry, diesel burns hotter than gasoline - gasoline holds something like 80K BTU's per gallon and diesel contains 130K BTU's. There must be a different reason, such as the alloy of the housing on the gassers conducts heat faster, so during a cooldown can shut off at a little higher temp because it will dissipate the heat before it can coke the turbo shaft, whihle the alloys in the heavier duty turbo housings have to be allowed to cool further before shutdown because they hold the heat longer when the oil stops flowing through. Just a thought...

TxDieselKid

Plus remember our Cummins diesel will REALLY burn hotter because we use compression, no glow plugs, which are needed to ingnite the fuel. <br><br>Merrick, you are CRAZY!!!

GrandpasRam

He definitely needs a Scotty II...

MCummings

I have a Mega-Cannon (I'm in with the TDR crowd, but not here with the DTR crowd,, ah well)<br>I have a 0-35 PSI Boost gauge,, the boost was on the left &quot;O&quot; in the lettering BOOST.<br><br>It's hard to keep 450+HP Cool. (1/4 times estimate 475-500)<br><br>OH, BTW, I recall now, I WAS pulling a descent size grade. I was prepared to hear a KNOCK-KNOCK-KNOCK sound at any time from gettin' too hot. It seems to run better now??<br><br>Hey Andrew,, Hear about the possibility of a Burnout COMP @ TiM?? (as long as I don't do like Greg (Cummnzpwr), otherwise *I* will need the trailer. LOL<br><br>Merrick Cummings Jr

doug

[quote author=GrandpasRam link=board=4;threadid=14392;start=0#135472 date=1052249921]<br>Sorry, diesel burns hotter than gasoline - gasoline holds something like 80K BTU's per gallon and diesel contains 130K BTU's. <br>[/quote]<br><br>A diesel running hotter than a gasser would be true only if both engines both burned their fuel at the same unit volume per unit time. What you would have in this case is that the Diesel would do more work (put out more HP). The extra BTU's in a gallon of Diesel is available to do work, not just produce heat. So my point is that if the two engines put out the same HP, the Diesel would consume less fuel but would generate the same amount of heat. That's assuming of course that both engines have the same efficiency. You get out exactly what you put in -- as long as you remember that part of what you &quot;get out&quot; is wasted heat.<br><br><br><br>You might be on to something here. The thing about shutdown temps is that it's not about Diesel versus gas -- its about the thermodynamics of heat transfer, which is unique to the way the factory designed that part of the engine. Every engine has its own heat flow characteristics (temperature differential) across the turbocharger and every engine has its own heat dissipation (cooling) characteristics.<br><br>I have a feeling that temp differential across the turbo is the main factor. If you have 400 post turbo and 600 pre-turbo on one engine (200 degree difference), and the other is 300 post and 600 pre (300 degree difference), then what you're really seeing here is that the pre-turbo temp is the constraining parameter, not the post-turbo temp. I say that because the problem here is heat soaking -- heat from the manifold soaking into the turbo bearings after shutdown, which will cause the post-turbo EGT to rise after the engine is shut down.<br>

BigBlue

One of my friends told me that the gassers run hotter. Didn't go into detail. Just remembered that he said that.

MCummings

I think when cruising and running hard, gassers run hotter, for longer.<br><br>I've heard gassers can sustain cruise EGT of 1700*F for extended period of time, but I have no knowledge of gassers,, I'm a Diesel kinda guy.<br><br>Merrick Cummings Jr

TxDieselKid

[quote author=MCummings link=board=4;threadid=14392;start=0#135482 date=1052250885]<br>Hey Andrew,, Hear about the possibility of a Burnout COMP @ TiM?? (as long as I don't do like Greg (Cummnzpwr), otherwise *I* will need the trailer. LOL<br><br>Merrick Cummings Jr<br>[/quote]<br><br>Better make it a bumper pull after all!!!! <br><br>Andrew

HC

Could be:<br>1) One number based on pre-turbo temp, the other based on post-turbo temp...<br>2) The gasser might have a water-cooled turbo <br>3) The gasser might have thinner parts due to less boost required<br>4) The gasser engineers may be less conservative than the diesel engineers, because they don't expect their products last forever anyway<br>5) Other???

HOHN

If you shut down at 350 post turbo, you will NEVER have a turbo problem. Look at your owner's manual. It says that shut down temp for empty running around town is less than 1 minute. Where am I at exactly one minute? Right around 350. It takes forever to get to 300.<br><br>I have my pyro mounted POST turbo. I figure this tells me more about how hot the turbo is. If you gauge shutdown temp with e PRE turbo EGT, then you are waiting for the exhaust manifold and all that to cool down as well. It's all about TIT (tubine inlet temp) vs TOT (turbine outlet temp).<br><br>Generally, a gas engine WILL have higher egt than a diesel. This is because of their design: diesel is lean-burn by design, while gassers are rich-burn. Also, the diesel cycle is more efficient, so it tends to produce less waste heat (and thus lower EGT).<br><br>I suspect that the higher shutdown temp for gassers is because they can't get down to 300 ever except in extreme cold.<br><br>I am also pretty sure that gasser turbos ARE designed differently than ones spec'd for diesels. This, to accomodate the different EGT ranges. I also suspect that diesel turbos lead an easier life than those attached to gassers (less heat, less RPM range, etc.) Except for Andrew's, of course.<br><br>IN the end, it makes no sense to have different shut down temps because they are both cooled and lubed by oil, but I am sure that someone smarter than I am came up with a good reason why.<br><br>HOHN

P Kennedy

Hohn is right on the gasser turbos quite often have a pressurized oil bottle which feeds oil to the turbo bearings after shut down to prevent coking (the process of heating oil to the point of forming a hard tar like substance). Gassers with turbos also are generally designed for performance meaning that high heat is not produced unless pushing for maximum acceleration. Industrial diesels are designed to take advantage of increased atmospheric pressures through the whole RPM band to increase efficiency and pulling power. Running around empty in your CTD will not produce a lot of EGT, coming in off the highway pulling 10k lbs will have excess residual heat which must be disipated before shutdown. The industrial diesel engine will also have heavier component castings as well retaining residual heat longer. This can be demonstrated by heating a 1/4&quot; bolt red hot and a 1&quot; shaft red hot and measuring the cool down time to a set temperature (comfortable to hold). If either is too hot to hold the heat has been transferred to your hand and like oil will cause damage, one will retain that heat transferring capability longer. This now becomes an idling issue, can't afford the 3 minutes to cool down and only going to be away for 2-5 minutes leave it running. $2000 turbo vs 8 0zs of fuel is not a choice but a reality, can't afford 3 minutes cool down regularily buy a gaspot-your in too much of a hurry to own a turbodiesel anyway. PK