Diesels are very efficent at idle?
 

I remember someone in the TDI fuel economy forum (tdiclub.com) telling me that when their diesels idle its way more efficent than a gasoline engine like mine idling in N. If that's the case, for a 1.7 liter like mine fully warmed up I waste around .8 liters (.21 gallons)/ hour. I wonder if their idling is much lower then it wouldn't make much sense to idle with no engine off if its really that efficent.

Damn not enough TDI'er trying to prove this theory!

Re: Diesels are very efficent at idle?
 

I love that site -- used to be a member (almost bought a Golf Diesel 5-speed). In manual operation, it's best to leave the clutch pushed in while in N, or it would have to spin something in the transmission (although bad on the throw-out bearing). I remember my old EVO would nearly stall out in the cold when I released the clutch in N because the fluid was so stiff. That was a car that I HAD to let warm up in the Winter, or else I couldn't shift gears. As for autos, it can only help. The theory should carry-over -- less fuel to turn the TC mechanism or whatever.


I wish I had a Diesel, even with the prices the way they are. During College, I used to drive one for work and volunteer (ambulances and fire apparatus) many times a week. Just so much more torque and power for the FE dollar.

over here in canada diesel
 

over here in canada diesel is around 10 cents cheaper a liter than gasoline 87. But the only choice is TDI unfortnately, and as much as I want to, VW has some high prices that just can't compare to a Honda yet. But once Honda gets smart and let us test out their diesel things can change...

A car idling at a stop light
 

A car idling at a stop light has 0 mpg, and 0% efficiency, whether diesel or gas.

HEVs and EVs us no power when stopped in traffic. That's a big part of their efficiency.

locos
 

Don't remember if it was here in this forum or not but the locomotives left running in the yard all winter - turns out they don't like getting cold when they shut down and they only burn about a quart an hour idling so the cost of leaving them running all winter is much less than shutting them and resulting engine problems/damage.

A 10 mile trip in my xB with a 44mpg fuel use drops to 40mpg when it takes a few minutes to park in my usual spot. Really makes me think about where and how I park. Pulling out with a cold engine is more of a fuel burner so I always try to park so that I can just pull out instead of backing out and manuvering with a cold fast idling engine.

Re: locos
 

what you described is part of "facing out" and "potenial parking"

you may have to walk farther to your car, but for the FE gains I think tis worth it. And if you position your car correctly you can bump start without using the starter! A much smoother cold start if you ask me and you have more juice to FAS!

Re: locos
 

In very cold winters I think people do this with most heavy duty diesels. I remember my dad talking about when he was in the Army they'd have to keep the trucks warm in the winter otherwise they'd have to use ether to try and get them to start by saturating the air inlet. They tried not to do this an someone would always put too much ether in and the filter would catch on fire.

Re: A car idling at a stop light
 

This is true, but imagine it as a negative percentage. In drive, it uses more fuel, so say it would have -5% efficiency, whereas in Neutral, it would have -2% efficiency -- so you'd be saving fuel.

I don't have an exact answer, but something to remember about diesels is that even when they are idleing, they are running wide open, there is no throttle plate to close, so they might be running at a 200:1 fuel air mix without anything other then a big air filter to create restriction.

I used to have a mazda b2200 pickup.. great truck!

Had a 2.2L n/a perkins desiel. I couldn't find parts for it though, ever.. the starter went in december and I was unable to find a new one, so I did a "real world" test on this theory - I left it running from december to march 25!

In "fast idle" it would use quite a bit of fuel pretty quickly.

In regular/warm idle it would use about 1-1.5L of fuel overnight, or around 0.10l/hour.. WAY more efficient than a gas engine.

Even the big truck i drive now (13.9L cat, 590hp/2800ftlb) uses around 1 liter/hour at idle (690rpm).. the consumption spec is in the manual for it lol

Holy cow, that's fantastic.

My friend's parent used to have that truck, he loved it, and since he's been looking for another to replace his lost childhood.

Wow, all 3-4 (counting hurts) months you left it idling.

Diesels seem like a good for city driving.

So, I guess this confirms what i already thought. Diesels are the idle masters.

yeah, I'd love to find another one too.. best truck ever. Could've used a bit more power (only has 59HP brand new) but they last forever if you keep the body alive and are so easy and fun to drive.

I know of one about 30 miles from me with 500,000 miles on it, guy takes really good care of it though and it looks brand new.

why do diesels engine last longer than gasoline engines? because diesels are much better lubricated?

I wonder how long a gasoline engine can idle for before dying haha, i'd feel so bad wasting all that gas!

on the plus side diesel is cheaper than gasoline at the moment!

bumping an old thread, but I have a TDI and once it’s warm at idle it consumes .2L per hour.

jst buy an engine block heater for at home, or switch to ev so u don't have to worry about it..

philmcneal -

I'd feel bad wasting the gas too, but maybe you could attach a DC->AC inverter and "feed" the extra electricity load it is generating into your house. It wouldn't add much, but it wouldn't be going to waste either.

CarloSW2

No big deal
 

It's no big deal with the new technology. The "glow plugs" that allow cold starts have advanced in technology, so it'll be easier to start. If it's a Diesel-Hybrid and or plug-in more solutions would be available.

Also, to answer a previous question -- diesels last longer because they're built to withstand the very high compression ratios of the combustion (thicker blocks and sleeves within the cylinder).

RH77

I am with you I very very rarely idle for any lenth of time. I do have a 120vac coolant heater for winter. By the way using the coolant heater increases my MPG by about 10% on a 11 mile trip.

wow how long does it take for you to warm up? that's insane since it takes me .8L per hour fully warmed up when idling... man no wonder them diesels don't benifit much with an auto-stop feature ;)


true but i'm too lazy to find that out.

It takes FOREVER to warm up. Last winter when it was -10F or -23C with the front completely blocked driving on highway the engine temp never got above 150F and when I would slow down coming in to a town it would drop in to the 125F range. If you let it idle it will cool down, I never let it idle to long so I don't know how cold it might get. We have heated seat in the front and an electric blanket for the kids in the back.

I typically run a 120vac coolant heater when I am at home before I leave and when I leave it might be 190F and will drop to 160F by the time I am at work.

Diesels can have no throttle plate to reduce the airflow through the engine. Reducing the air volume (generating a manifold vacuum) will lower the amount of air in the cylinder to a point where compressing that reduced volume of air doesn't produce enough compression heat to ignite the fuel. At very low fuel use (idling for example) there is little fuel burned but a full volume of air moving that heat out the exhaust. As a result the engine coolant water jacket may not heat up. The engine is effectively internally air cooled.
It's not that the combustion is all that much more efficient, it's that the excess air takes too much heat away too quickly.

I had to flush out a few Mercedes diesels in my time.

We would take a papercup with diesel detergent (I think Sensydine made it, this was over a decade ago) and put the suction and return lines into it. The 5 pot Benz motors could idle off that cup for long periods of time.

Kudos for your thinking on programmed parking!
For years, I have been parking...such that the car is ready to go downhill (a long slope) when initially started. This means I have to walk some distance, but I'm primarily concerned with engine wear and door dings! MPG is a secondary benefit! Twice a day times the number of days per work week ( 5 ) times 50 weeks per year...it adds up! 50 X 5 X 2 = 500! That's big!

Correct! Plus (and it's a big plus!), diesel fuel is a lubricant. Oil is slicker than a solvent (gasoline). This makes a tremendous difference in wear rates!

The end of May,'06 ain't the middle of December,'06! Sometime in November...the price of diesel at the local rip-off convenient store PASSED premium gasoline in price! I can easily remember when diesel was less than kerosene...kerosene being exactly 1/2 the price of gas (same station)!Oil is more expensive than gasoline? ...to refine? On what planet? It looks like the greed factor is becoming more blatant! After all, look at all the power in the tiger's pocket.Grrr...(My growl...not the "fat cat").:mad:

It could also be a convergence of factors, like...
-Holiday season, lots of time sensitive LTL freight
-Military action, plenty of demand there
-USLD requirements for the entire country
I'm betting that diesel will start to drop after new years.

The Scangage say that my Powerstroke diesel gulps down as much as 1.2 gph in winter cold. It decreases to about .4 gph in neutral when warm. The truck drops from about 17 mpg around town to 15 or so in winter.

Part of the high FC at low temp is due to oil viscosity, but Ford also installed a butterfly valve in the exhaust to make the engine work harder and warm up quicker. Another of Ford's freakin' "better ideas"? I think not.

Another low temp FC problem is the Powerstroke's belt driven fan. It has a fan clutch, but the fan still pulls cold air across the radiator and engine when the truck is warming up. Ford should have installed an electric fan. It would have helped both cold and hot FE. Morons.

You should have included this line from my post. It renders the discussion moot.:re: an earlier post about locomotives idling all night,
Massachusetts has a law prohibiting diesel idling for more than 5 minutes. The commuter rail engines used to each be left idling all night until the threat of fines made the rail authority come up with a solution. Now only one diesel electric engine is left running. The electric power from that one is connected to heaters in the others in the depot to keep them warm. The one running is not considered to be 'idling' as it is providing work.

better than gasonie but...
 

nox values go way up

Considering the the very small amount of fuel they burn at idle about 0.5 gallons per hour and the probable damage if turned off and allowed to cool the amount of fuel wasted? is not an issue - I can only imagine how much they can burn at full throttle making them idle all night to keep them warmed up is really a moot point in the over all cost of operation. How many locomotives are we talking about here. Who would like to jump into an air temperature steel locomotive on a sub zero day and wait for it to warm up?

That one loco is running at "Notch-8" or full-throttle when in energy production mode. My Dad's old railroad had huge EBHs that they would plug their locomotives into instead, which is probably better for NOx to draw off of the grid... I guess if you string them together, the lead unit could provide power, which is what their doing. MA-EPA is pretty strict on diesel idling, that's for sure.

They also do this when on their routes. Amtrak in particular does this: if two locomotives are connected, the lead engine moves the train, while the second one is left in full-throttle to power the electrical demands of passenger train cars. It's odd to hear it stopped at a station running in "neutral" at full throttle.

Starting cold decreases the live of the ICE in a locomotive tremendously, and warm-up time is quite long. Some freights are left running for a month or more before service while they run routes, wait for another trainset to be completed and back out again, etc.

GE and GM (EMD) are producing low-emission units for 2007 with AC traction motors. These should set the standard for low-emission operation.

Still, shipping tons of freight by train is FAR more efficient than truck. It's a hybrid!

RH77

Tell that to my MB 220D! It's an old-tech diesel. The injector pump has a pnuematic governor and it has a throttle plate to generate manifold vacuum. One of the methods MB used to govern the engine speed on this one was to use a throttle limiter screw, so the throttle never even sees wide open.

two down, one to go...
 

I'm still looking for something regarding a 'throttle plate to generate manifold vacuum'. I'll post what I find.
However, I did find this:
https://www.mercedesforum.com/m_18690..._1/key_/tm.htm
The diaphragm control is used for control of fuel delivery.
The stop screw is used for limiting maximum fuel delivery.
Neither of these is an air restricting throttle. That doesn't mean that there isn't an air flow restricting throttle, just that these two items aren't.

That diphragm they are talking about is a vacuum diaphragm. There is a vacuum line going from the intake manifold to the injector pump to controll it.

Diesel Tractors with Throttles
 

I have no idea if this is thru, it's something I heard many years ago but:

I have heard old diesel powered tractors have a throttle for controlling engine speed and that if the intake (and throttle) comes loose for some reason the engine will be put into full throttle possibly damaging it.

A detroit dielsel 2-stroke engine used a fuel rack controlling individual injectors inside the valve cover that could stick. Also if well worn they could run on crankcase oil and run away ungoverned. There was a large butterfly that could be tripped to cut the air to the engine to shut it off in emergencies. It was useful.

Also the 50 year old Massey Ferguson tractors I saw as a kid had an air throttle linked to the fuel control. I thought it was used to smooth the torsional shudder at low speeds but that is just a guess. They ran fine with the air throttle open but I never worked on them.

Ernie