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Barbaraok · 11-17-2005, 08:08 AM

Now - remember we are new to diesel, so if this is a stupid question, I'm asking forgiveness ahead of time. How long to do warm up. The manual says to wait to drive until the temp is 170+. We never get there just sitting idling. We start to move at 150, but that seems to take an awfully long time.

Barbaraok · 11-17-2005, 08:08 AM

Now - remember we are new to diesel, so if this is a stupid question, I'm asking forgiveness ahead of time. How long to do warm up. The manual says to wait to drive until the temp is 170+. We never get there just sitting idling. We start to move at 150, but that seems to take an awfully long time.

EngineerMike · 11-17-2005, 08:26 AM

Not a stupid question. Ancient wisdom in the diesel world (trucker wive's tales?) had us all doing long warm-ups, idling while parked for lunch, etc. That isn't required. Idle temp, if you started the engine & never went anywhere for hours, would be about 175, so getting to 170 would take approximatley forever ± an hour or two.
If you start the coach w/no air, and wait for the bags to fill & blow off the first time, you can roll out unless you are planning to pull a major mountain in the next 3 minutes. Once you are moving the coach, engine temp comes up quickly as the exhaust being generated is now much hotter than 175. Tranny temp takes a lot longer (at first I thought my gauge was busted).

ggbanks · 11-17-2005, 10:10 AM

Ths is a good site to check out: http://www.cummins-sp.com/document_library/Support/Engi...ce_operation_isc.pdf

Cruzer · 11-17-2005, 11:38 AM

Today's diesel engines are much different than the older Cummins that I used to overhaul in the 70s. Their tolerances are tighter for efficiency and emissions. They do not recommend excessive idling for long periods. I fire mine up and after a few minutes hit the fast idle on the cruise control. Once the air bags are full I will ease out of the campsite. By the time I get to the campground office it's starting to come up. If it is close to a busy interstate and I need to floor it to mesh with traffic, I'll sit a while in front of the office (don't want to annoy any sleepy campers

) at fast idle before hitting the road. Generally traffic is light and be easing down the 2 lanes I can warm it up real well before applying full power.

The same applies for cool down after a good run. Normally, by the time I get to the campground it's pretty well cooled down. If the park is close to the interstate I'll let it run at fast idle outside the office to cool the engine and turbo down. Never shut down a hot turbo.

TXiceman · 11-17-2005, 12:44 PM

By the nature of a diesel, they develope very little heat when idleing. So, it will take forever to warm up from cold. Best way to do it is start up, and let it idle for at the most a minute, but give it time to getall of the fluids circulating, and pump up your air system and you are ready to pull out. Until you have the temp gauge moving up, don't rw-hide the poor beast. Take it easy until you are nearly up to temp.

Good suggestion to pull up by the office or out of the way if you do need to warm up and not annoy the neighbors. Now, I personally like the sound of a diesel....stink, rattle and smoke...

Ken

EngineerMike · 11-17-2005, 02:02 PM

George- Thanks for the link. That sheet covers the ISC, which is similar to the ISL tho not exact. Couldn't find one for the ISL, but did follow the links to Cummins PowerStore and bought the ISC/ISL Troubleshooting & Repair manual. There is also a subscription service for $50/year here that allows access to engine data, service bulletins, exploded parts diagrams, etc. for those who don't know how to have any real fun. Here I go down the diesel rabbit hole.

Audrey & John · 11-19-2005, 10:55 AM

I remember thinking the WRV manual as very odd in terms of this long warmup and high temp. Especially since the ISL manual specifically warns against idling for long periods.

Seems like by the time the air bags are filled, the engine is warm enough. That's just a couple of minutes. We're usually moving slowly, navigating out of a campsite, hooking up the toad, etc.

On cool down - we always check the intake manifold temperature (you need to the VMS system to read this). If it not dropping but rather is steady (usually around 124-130 degrees), then we shut the engine off. If the Intake Manifold Temperature is within 40 to 50 degrees of the outside temperature, it's safe to shut down the engine.

Audrey

EngineerMike · 11-21-2005, 10:12 AM

Random thought- I find it peculiar that an Exhaust Gas Temp gauge isn't used much on these larger (than automotive) diesels. The real issue on shut-down (or at any operating point for that matter) is heat generated vs. heat scavanged.
W/our previous diesel (Trek) engine, I was hanging w/a group of pickup jockeys who were hot-rodding & truck-pulling w/their rigs, & pushing things to the max and occasionally beyond w/"my" engine. The single most important watch item to avoid breakage was found to be EGT. That's how much heat is pushed into the heads, valves, cylinders, etc. That's how much heat must be scavanged by the coolant. And since EGT can be pushed to a multiple of 6x or 7x coolant temp, the temp scavanging gradient can become too steep for the system under some circumstances. Only an EGT gauge can identify the problem circumstance (absent some esoteric cast-in-place, in-head thermocouple device of which I'm not aware of its existence except perhaps in advanced aircraft applications maybe).
I asked Cummins if they had a sensor for EGT as an input for the engine computer, ECU (so maybe I could read it via VMS?). They said no. I suspect the reason is that as an ECU input, a) EGT is not either a power output or smog independent variable, and b) not a dependent variable from which ECU-actionable data can be gathered. In other words, Cummins can't improve performance, govern for damage control, or decrease smog by knowing EGT. When engine tuning or engine damage control is found to be ECU-controllable by knowing EGT, Cummins will add an appropriate sensor (my guess).
That doesn't change the fact that a hot shut-down can damage the turbo, induce accelerated wear and fatige on cast parts, etc. So, absent an EGT reading, Audrey's shut-down process is a good one, IMO. For use in driving, I need to add and EGT gauge.

VAGABONDMAN · 11-21-2005, 07:04 PM

E-Mike,

I checked out the link you referreed to and noticed the maximum amount of calcium carbonate (hard water) is 170ppm; that translates to 10 grains per gallon, which I'm sure you exceede at your shop. Therefore, you need to use the Vagabond purified water for cooling system make-up.

dkgreene · 11-23-2005, 11:38 AM

Engineer Mike,

I am always amazed at the knowledge base you have and on all types of topics. What kind of engineering degree do you have that gave you such a board randge of knowledge?

EngineerMike · 11-25-2005, 04:36 PM

DK- no degree, I "read" for my background in engineering (like Abe for his carreer in law). Got a degree in Forestry though. Civil, structural & electrical, mostly for cellular phone outfits like Sprint.
The above commentary was the offspring of necessity- electronic diesel coach broke down 2 days into Mexico, where the GM facility "near" me (8 hour drive farther south) said, "We never sell dat chit down here." So I either had to a)learn about electronic diesel, or b) convert my coach to a chicken coop & leave it. Chose a.