Diesels are very efficent at idle?

[philmcneal]

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!

[rh77]

Originally Posted by philmcneal

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!

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.

[philmcneal]

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...

[Sludgy]

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.

[JanGeo]

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.

[philmcneal]

Originally Posted by JanGeo

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.

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!

[mtbiker278]

Originally Posted by JanGeo

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.

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.

[rh77]

Originally Posted by Sludgy

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.

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.

[Ryland]

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.

[Terrh]

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

[SVOboy]

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.

[kickflipjr]

Diesels seem like a good for city driving.

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

[Terrh]

Originally Posted by SVOboy

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.

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.

[philmcneal]

Originally Posted by Terrh

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!

[Brock]

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

[Rstb88]

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

[cfg83]

philmcneal -

Originally Posted by philmcneal

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!

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

[rh77]

Originally Posted by Rstb88

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

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

[Brock]

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.

[philmcneal]

Originally Posted by Brock

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

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

Originally Posted by CarloSW2

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.

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

[Brock]

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.

[Lug_Nut]

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.

[Spule 4]

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.

[Ted Hart]

Originally Posted by JanGeo

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.

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!

[Ted Hart]

Originally Posted by rh77

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

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!

[Ted Hart]

Originally Posted by philmcneal

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

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").

[omgwtfbyobbq]

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.

[Sludgy]

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.

[Lug_Nut]

Originally Posted by theclencher

... it seems to me that throttling back that excess air would be a sensible way to prevent overcooling... no?

You should have included this line from my post. It renders the discussion moot.:

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.

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.

[70 mpg jetta]

nox values go way up