Engine/Transmission (1998.5 - 2002) How much fuel burns at idle??

[KBalzuweit]

I use my truck as a OTR RV hauler and was wondering if anybody knows how much fuel is burned an hour when the truck is just sitting at idle. Since its cold now I leave it run all night so I have heat and want to see what my costs are. Thanks!



Karl

 

[Ncostello]

Extended idling does not use alot of fuel per se. What it does do is cause the engine to cool down to temps too low for efficient operation. In 24V engines it will cause varnish build up on push rods eventually resulting in a sticking... and later bent rod. It also causes deposits on the injectors thus ruining them.



If you are serious about keeping it warm... get a diesel fired engine heater such as the popular espar heater. Otherwise you'll need an exhaust brake to leave engaged to build the heat or a high idler... which will consume more fuel than an Espar.



Cummins recommends against extended idling.

 

[GeneA]

Karl: I was doing the same thing you are doing. My solution was to rig up a bunk of sorts in the back seat. I got one of those sliding brackets which adjust your pedal to whatever idle speed you want--I would set it to run at about 1200 to 1300 with the heater on full and a winter front. It would get so warm in my sleeping bag that I would just shut off the engine after a few hours. As for fuel consumption it is so negligent that you don't even need to worry about it. I thought about the espar heater but it would take about 50 years to make up the cost. Gene

 

[KBalzuweit]

As far as temp I have no problem. The truck maintains a good temp. A little below what it is when driving, but warm enough to set the heater temp contol at half, fan on low, and I am comfortable. So should I still look at raising the idle??

Karl

 

[Ramafid]

I read somewhere that a diesel engine is 300% more efficient at idle than a gas engine. It won't burn much fuel.

 

[Sticks]

When you say it stays just a little cooler that when you are driving,is that EGT or coolant. 160 or 170 EGT may very well be too cold, and still be the same as the coolant.



I guess the question should be, at what EGT's does the diesel no longer build varnish, or risk cylinder wash.

 

[Ncostello]

Karl... at least consider an electronic plug in idler box from a source such as Practical Solutions Diesel. Their box is adjustable so you can toggle up to say 1000 rpm. Heat from the heater is not the problem... its heat in the cylinder head. I know on ISC's, there is a low coolant temp limit of something around 157 degrees. Below that for long durations causes problems in the future. Our ISC has a high idle switch that goes to 1200 rpm. If I know it'll be idling for longer than 5-10 minutes... I kick it on.



Even cheaper would be an "stick" between the wheel and the pedal. I think Geno's sells an adjustable one so you can at least keep it off idle a little bit. No load at those rpm's shouldn't consume alot of fuel.

 

[JohnE]

You need a higher idle speed. At low idle, coolant temp and combustion chamber temps are not related. The coolant temps may stay up, but the engine runs too cool to completely burn off the fuel. E-brake is a good suggestion. As long as you're towing for a living an exhast brake would supplement those service & trailer brakes.



As Neil mentioned Cummins demands high idle (100-1200 rpm) on the IS* series engines in cold weather.



It would be very easy for Dodge to have a manual high idle switch in the cab, too. Switch it on and the PCM tells the ECM to go to PTO mode (high idle). Step on the brake or shift into gear and the high idle disables even if switch is left in high idle.



Thinking of in gear, what's the thoughts on idling an auto in park? I don't winter or summer even though my trany was modded for park circuit cooling.

 

[Coalsmoke]

I read on the TDR (by a member) that you shouldn't leave an e-brake on for more than ten minutes? Is this the case or is there a difference between 12V and 24V in that regard?

 

[CPjMech]

In response to the original question:



How much fuel burns at idle??



About 0. 4 - 0. 7 GPH depending on the engine load.

 

[nwinters]

Ebrake & High idle.



Can you run the idle up at all with an ebrake engaged? Assuming you don't go above the 60psi limit what other dangers are there?



Nate

 

[KBalzuweit]

Thanks for all the info. I am going to get a high idler. My question is what rpm should you set it at and what is the target EGT?



Thanks, Karl

 

[HoleshotHolset]

IMHO: I'd like to see at least 300°F pre-turbo if I were going to let her idle for any prolonged period.....



Maybe a complete exhaust brake isn't necessary... . even though it really makes towing much easier... . perhaps you could do like Eddie Murphy in Beverly Hills Cop and 'put a banana' in the tailpipe.



Seriously - the exhaust doesn't need to be totally blocked off to keep her warm... . just a little backed up.



Matt

 

[RustyJC]

The temperature problem that bends pushrods (push tubes, in Cummins terminology) is in the valve stem & valve guide area. Low temperatures in this area generate varnish from the lube oil that causes valve sticking that causes bent pushrods/push tubes. In effect, the 24V head is too efficient at transferring heat from the valve stems to the head & ultimately the coolant at idle conditions, thereby causing the valve stems and guides to run too cold.



I always use my exhaust brake during extended idling, even though this requires more frequent cleaning of the IAT sensor.



Rusty

 

[Makensmoke]

I just bought and installed a high idler from Diesel Services Group in Canada. Dieselservices.com So far 1000rpm has kept it toasty warm and has made warm up time alot shorter, but you can ramp the idler all the way from sucking it down below factory speed up to 1500rpm which is what they say to stay below to keep from setting off check engine lights. (confusing the ECM) Good luck!

 

[KBalzuweit]

What I want to know now is why is the diesel services box over $400 and the other box mentioned only $199. Am I missing something??

 

[Makensmoke]

$400 is Canadian money, so its actually about $50 bucks cheaper. Verses the others i've seen, theirs ramps up, and is very adjustable, and uses a tap of the brake to shut off. Just seemed like it had a little better fit and finish. Which i'm very happy I spent a few extra bucks on. Installing it was easy, there instructions even told me what size wrenches were needed in each step. Explained everything very well.

 

[HeavyHauler]

Well I've only seen one reply here that answered the question so I'll back him up. The ISB will consume on average about 1/2 gallon of fuel and hour while bigger engines like in the Pete's will burn from one gallon to a gallon and a half an hour.



There's a lot of debate about extensive idling, some guys idle several hours a day and don't ever have problems but I would do the safe thing and rig up a cheap high idle switch. Probably setting it for 1100 to 1200 RPM would be plenty, or do the trottle stick like the others have suggested.



Don't waste your money on an exhaust brake just to keep you warm. You're looking at a minimum of $1000 bucks for something that you didn't need as far as towing purposes. But if you've already been considering a brake, kill two birds with one stone.

 

[Ncostello]

According to Schneider National, their research shows a diesel will idle away 7/10ths of a gallon per hour while a Webasto heater uses 7/100ths of a gallon. That gives you some idea of why they have been working on installing them. For them its cost efficient in the long run and cuts emissions.



Info from: Newport's Heavy Duty Trucking magazine.

 

[mberry]

Originally posted by Ncostello

... their research shows a diesel will idle away 7/10ths of a gallon per hour...

Ok. But which diesel? Can you be more specific please?