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