wheels

I know this horse has been rode to death, but I let my mind take over and I have a couple questions. I have a fair amount of mechanical exprerience and like to learn how things work.

Ok here is my question on idleing, right now it is cold here, the high today was 30 so lets take today for example. ( I dont plug it in, I wont plug it in till it gets below zero. I have started diesels for years without glowplugs or grid heaters or any kind of heaters well into the teens or single digits. Plugging it in is for Fords!!) I go out and start my truck about 15-20 minutes before I leave. I let it idle normally. Now my question is, my pryo goes up to around 200-250 degrees starting cold and letting it sit there idleing. Now the block and everything else is stone cold (30 degrees or whatever the ambient temp is) the cylinders are obviously seeing temps around 200-250 degrees. (pyro is pre-turbo) I realize it is going to take quite a while to warm up at this rate BUT, the pistons and valves are seeing 200-250 degrees right off the get-go, so is this still too low of temp to complete the combustion therefor creating varnish and such in the cylinders? At what temp does diesel combust completely? I have read bumping the idle up to around 1200 RPM or so should keep it warm enough to complete the combustion therefor keeping any varnish from forming, the rings from sticking, or any washing of the cylinders. When I crank it up to around 1200 RPM the pyro only comes up to a little over 300 degrees. So my question is at what temp does the pyro need to show before I can be sure it is warm enough to keep from forming varnish and such.

On a side note, I have been around diesel engines for years and never heard anything about idleing being bad for the engine. I used to drive a bull rack and let it idle all night while I was catching some ZZZZ'S as did every other trucker I have ever seen. I also worked in the oilfields running a pulling unit and they would idle sometimes all day long for weeks on end. they were Detroits and leaked oil worse than a Harley but I never had any problems with them idleing all day. (other than at the end of the day I would clear her throat out and you had to be careful and not give her full throttle otherwise she would run away from you, it smoked like a train after idleing all day but they ran like a top for well over 30,000 hours)

Keith

HC

See http://www.turbodieselregister.com/faq.htm and space down to questions 11 and 12.
Also, if you want more details on "why", Cummins has a web site and provides quick turn-around on technical questions. The folks who designed and built this engine say idling is bad for it. I've asked them before, and they clearly say idling is bad for it, even with a high idler to increase engine speed.

Edit: Found additional information: http://dodgeram.info/tsb/2000/cummins01-06-00.htm
Go to the link for full details, but, this confirms a couple of points: 1) Engine design impacts whether or not it is OK to idle YOUR engine. Quoting: "The 4 valve cylinder head on the ISB runs at a cooler temperature, which in some cases is allowing tar to condense on the exhaust valves. This may result in sticky valves and bent push tubes. The 2 valve head runs at a hotter temperature, thus preventing the tar build up."
2) You don't have to worry much about a few minutes of idling; they are talking about HOURS of no-load idling in this TSB.

doug

The only thing I would add to HC's excelent post is this: the advantage to plugging in is to reduce the warm up time. On the 24v ISB's you want engine temp to reach 140 degrees ASAP. To me, its not a matter of starting, its a matter of reaching proper operating temperature as soon as possible. For the valve train, that's 140 degrees. for the rest of the engine, thats 190 degrees. <br>

AlpineRAM

I start it up in the morning , let it idle for about 30 secs to 2 minutes (scraping ice ) and then I drive it carefully. Until the needle starts to move I try to stay below 1500 rpm. After about 3 mins of driving I go up to 1900 rpm. That's about the right lane on the highway. When the needle is up the left lane is mine!<br>Works for me, YMMV<br><br>AlpineRAM

Superduty12v

They say you want to idle at least at 1000rpm if it's going to be for long periods of time. Other wise it's not burning it all and coating the cyls.

slimchase

does leaving the ac on keep the temps a little hotter?<br>Chase<br>

phox_mulder

On my 2002, turning the defrost on (or mix of defrost and heat) turns the AC on as well.<br>Can tell by the AC clutch clicking (well, thunking after truck sits for a while) on.<br>(AC removes moisture from the air, thus, quickening up the removal of &quot;fog&quot; from the windows)<br><br>It's a load on the engine, not much, but still a load, so it might help heat up quicker.<br><br><br>phox

admin

If you have an exhaust brake, you can run that while it's idling It doesn't help much, but it helps, jut like the previous poster said.

pwabbott

Long periods of idleing increase frequency of oil changes. Remember oil is a coolant to many of the engine parts which wear most until engine is up to operating temp., ie. crank and connecting rod bearings. If the oil circulating through them is a 0 deg. they will not expand to operating tollerances until engine is warm. The heater is standard equipment for a reason on the diesel. Contrary to popular opinion, the engineers who design these engines have a goals of performance and longevity for your engine. Give your engine a break use the heater whenever possible and prolong the life of your engine.<br><br> 8)

doug

second that! consider that most of the engine wear occurs during startup, and that there are two major mechanisms:<br><br>1. boundary lubrication upon initial crank. This is arguably the biggest factor -- metal sits more directly on the bearing surface rather than being suspended in oil, which of course is the case while running. The sooner you flow oil to the bearings the more you reduce wear. developing oil pressure itself is not the goal, since cold, thick oil will show pressure (depending on where it's measured) without establishing optimium bearing lubrication. Warm oil is the goal.<br><br>2. tolerances. As Sierra Phil as rightly pointed out, engine parts are not within operating specs untail they are at operating temperature. increased wear occurs during warm-up because mating surfaces are not optimumized to each other yet. <br><br>From the standpoint of startup wear, its actually best to use the block heater all the time even in warm weather, although this probably yields dimminishing returns and a high power bill. From the standpoint of varnish buildup, the greater the percentage of time you run warm versus cold the better -- so especially if you take short trips, like commuting back and forth to work under 30 minutes, your engine will thank you for assisting the warmup time using the block heater. On the 24V ISBs, the valve train needs the engine to be above 140 degrees for more than 30 minutes (if memory serves) in order to keep things clean. <br><br>AlpineRAM your approach is pretty close to mine -- the engine needs a light load to increase warm-up time, but should not be loaded heavily until warmed up.

AlpineRAM

Doug- I think you meant light load to decrease warm up time ;D<br><br>Since I can't plug in (230Vac over here) I need to get the temps up on their own. You should drive it lightly without lugging the engine the manual says. On mine after going lots of short distance or city driving I take it for a walk up some mountain. I try to get EGT's up a bit. <br><br>AlpineRAM

HC

AlpineRam,<br>Check out http://www.220giftcenter.com/transformers.htm<br>You too can plug in, 240 &gt; 120 volt tranformers for less than $100, world wide shipping available.

TPilaske

any URL with &quot;giftcenter&quot; in it must be a good place to go! ;D

HC

Ouch; another good place to visit - www.sendmeyourmoney.com

doug

yikes, I sure did mean &quot;decrease&quot; warm up time .<br><br>by the way a 700 watt transformer is enough to power a couple of good sized TVs, and probably not to be found in a gift shop. But a true transformer is not needed -- you can get those SCR-based power convertors that work well for resistance heaters. They produce completely horrible voltage waveforms but work really well for simple heaters. If I was constrained to 220v I would surely invest in one of those.