How's your idle? (Just some idle blabbing)
 

Just wondering about the rpms and fuel consumption of different engines while idling. Share your data, and please give info on the car and it's engine.

My Peugeot 307sw has a 1.6 liter HDi turbodiesel engine with 80kW (110hp). It idles @ 820rpm when rolling and 740rpm when stopped. When warmed up (coolant temp 80°C/176°F) the fuel consumption is 0.60 lph (0.16 gph) while rolling and 0.52 liters (0.14 US gallons) per hour at standstill.

Above data is from my uncalibrated SGII. Outdoor temperature 18°C/64°F. Electric load: LED DRL's (11W total), ventilation fan (speed 2 of 8), CD player.

I've noticed that the per hour consumption can increase by as much as 10% just by pressing the brake - could this be only from the added electrical load of the stop lights (55W total), or is the brake assist adding a load to the vacuum pump on the engine?

2000 Honda Insight 1.0L L3. 0RPM/0gph once warm. 900-1100RPM if you interrupt the auto stop. The ScanGauge says something like 0.11gph at idle, but it is extremely poor at measuring the fuel consumption of my car. But I suppose I should go get an accurate reading of fuel consumption at idle by rolling down the road at 15mph with the engine idling and checking Honda's instantaneous FE readout.

I've seen other cars where pressing the brake raises the idle. I bet it's vacuum related, but you can test by turning on the headlights to create a 110W electrical load.

My last car was a 1996 Subaru 2.2L. 0.24-0.26gph, 800RPM.

Heh, Robert.

My Civic is about 0.35 gph idling, which it does almost never.
The 3.5 V6 Odyssey is 0.5 gph, or 0.6 with AC on.

My 2002 Mitsubishi Galant 3.0l v6 is .34-.36 gph in neutral, warm per SGII
The Wife's Ht Rd is .5 GPH warm per OE computer. Never checked w/SGII.

The increased consumption is most likely mostly the vacuum required to be produced not the electrical load.
You could disconnect the brake switch and see if it changes.

The Ford engine 4.0 litre six cylinder non diesel , VVT and variable intake manifold uses a between 1.5 and 2.0 litres at idle (850 rpm) in neutral for the manual variant.
Info from Ford in a release about the then "New" engine (2008 I think) and still in production.

Pete.

darn this question.
I can't even measure fuel mileage.. unless I underestimate, and that is still ok I guess.

if my voltage regulator for the alternator allowed 250 rpm I would let the old sube go there. Very content. I have bogged it to 50rpm waiting for a kick in return...I can only guess they keep it like other cars to be sounding normal, like 500-750, and make the alternator function correctly. Else, I could really set it down..

The consumption is indeed low, I camped all night in one at 0F, (needed idle for heat).. hardly an 8th guage down for 8-10 hours.

1781cc, progressive 2 barrel, 3 main boxer.

Piwoslaw -

At idle, ~850 RPM = ~1.05 LPH = ~0.28 GPH at standstill.

CarloSW2

0.11gph is pretty darned close to correct. The instantaneous fuel consumption gauge crossed 100mpg while rolling through a parking lot at 10-11mph (0.10-0.11gph).

I was referring to the 0 rpm 0 gph part. ;)

1.5L Mazda Protege. 775rpm and 0.19gph. But I think I had my foot on the brake and clutch out in nuetral. I'll try tonight with clutch in, E-brake on and minimum electrical load.

Hmm, seeing stats like this makes me hunger for that blasted ScanGauge...lol

Idle consumption of a 1.5 diesel vs engine temp
 

Measurement method:
Fuel pumped out of a bottle and weighed with 0.1 g precision. The scale was oscillating a lot though (vibrations?).

I ran the engine for a minute or so in order to expel all the air. I waited for the engine to cool down completely. I noted the value every 10 seconds the first 10 minutes and then 30 seconds until 15 minutes. I attached the raw graph (spaces are due to scale shut down, values in ml/h) and another minute by minute with engine temps but here are the most interesting values:

Avg over first minute : 976 ml/h
2nd minute : 585,5 ml/h
3rd : 571,1 ml/h
...
Avg from 13:00 to 15:30 : 393,3 ml/h

Wow, that is low. I'll think twice before EOCing.

After 15 minutes of idling, the engine wasn't completely warm (especially oil temp) so I will do another test right after a (long) trip.

No wonder my uncle says that it's not worth to shut down an old-school Diesel for short times. Well, maybe the newer-generation ones with direct injection and more advanced controls, due to their lower internal temperatures, tollerate more EOC than an IDI does.

271,4 ml/h over 6 minutes with completely warmed up engine. That seems credible, I see 0.3/0.4 l/h over the net for mid-sized diesel engines.

wow thats low. for my 2.5L engine its exactly 1L/H.

In my Insight when fully warmed up (92°C) its around 0.15 - 0.2 L/h. But in general it doesn't make any noise and its 0 L/h :).

I would assume .33 to 1.0/gls hour for most any motor, up to and including the 15L Cummins in my work Peterbilt.

But, what would be the point of idle rpm fuel consumption measurements? I'd think "engine wear without work performed" would be more useful way of thinking about it (and there are scenarios where providing heating or cooled air for passengers is if high value). Engines are designed with a number of hours of economic life as a gauge. Right down to a two-stroke weedeater (cheap one at 250/hrs) to the light duty diesel in my pickup (10,000-hrs) not just commercial calculations.

The percent idle time is a recognized metric. A mph averageotherwise. On my pickup brand engine if one keeps that average at 27-mph or higher then FE is relatively good. The 10K engine life expectation (mean time between overhaul) is predicated on a 35-mph average.

The "usefulness" of engine idle fuel consumption [EIFC] ought to be related, somehow, to performance (achieving work). In a hurricane evactuation, for example, I'd expect that -- small to large -- personal vehicles are going to do no better than 3-5/mpg in bumper-to-bumper traffic. EIFC is not important in this, it is fuel capacity that matters far more (and, as note, the ability to travel 150-miles inland to be able to re-fuel from undisturbed stocks).

On the work Peterbilt we engage "high idle" if idling is to be extended past five minutes per the manufacturer instructions. Engine longevity/reliability far exceeds reduced consumption at this low level.

So, what am I missing as to importance, here?

.

According to Torque and my Ebay OBDII scanner, 0.18 gph fully warmed up coolant at 680rpm idle for a pre 2003 Toyota 1ZZ-FE (1794cc). I didn't measure it after driving a while though (hotter oil, should have slightly less friction), but I'm using 5W-20 instead of 10W-30 so that cuts the difference a bit.

I am getting the intake cam duration increased which would lower the vacuum, hoping that can cut it to like 0.16 gph :O I want to get an Apexi Power FC and play with the idle, I feel like the car should be able to idle okay at 500rpm without too much misfiring, if the gph scales proportionally that would be a fantastic 0.13ish idle. The aftermarket ECU would also let me reduce the faster idle that comes on with AC or higher electrical loads.

Honda B18B1 (1.8L from 90's Integra):

750rpm
0.22gph

In the summer and a fully warm engine.
3.2 v6 .45 gal/h

Typically 0.4 kg/h of low caloric CNG with a warm engine.

With AC on, double that.

I'm really surprised at how quickly the fuel consumption drops off - only the first minute is really the worst.

.2 gal/hr after a 6 mile warm up, sc1 1.9L, gasoline. I try again when it's completely warmed up.

.175 gal/hr engine warned up 20 miles, inlet air temp 130F, 700 RPM, I could lower the idle 100 rpm.

Thanks, I was wondering what the norm was for the 1.8 liter Toyota engine. Scangauge bounces between .16 -.17 & Ultragauge .14 -.15 on my '05 1ZZ-FE.

Does your idle gradually drop to a low point & then exhibit a slight roughness? I always assumed the mixture was intentionally leaned out by the computer to improve idle FE. I recently replaced my intake manifold gasket & idle quality/ low end torque have noticeably improved but still not a silky smooth idle like a Honda 4 banger. MPG seems better too-425 miles & still a little over 1/4 tank left.

My Neon started out as a big pig. It would start at .45 gph until warmed up, then go between .30-.33. I then cleaned out the AIC valve, which by cleaning, I mean I broke it! After putting it back in, it lowered the idle quite a bit to the point that it has a hard time keeping idle on its own from a cold start... but it would sit around .28-.30! Even still, compared to most modern engines, seems to be more than necessary. Though, I just don't even bother to let it idle just about anywhere anyways (EOC P&G EVERYWHERE!).

As for warmups, my car has had odd cooling issues from the start. When I first rebuilt the engine, silly me put the headgasket on upside-down and it allowed oil to get into the coolant. Since then, I've been struggling to get all the oil out (though nearly 2 years and many cleanout and part changes later, it's far better than it was). In the early life of this engine, it would get up to 220*F pretty easily. Fast forward to now, after extensive grill blocking and a smaller radiator, I struggle to ever see a full warm up! Only on constant steep hills do I ever get into the 195* territory... otherwise, it likes to sit around 180*. This is through 3 different thermostats now! I can only figure that the constant pulse and glide w/ engine off coasting is just too efficient? lol.

Yea it does, the mixture is most certainly not being leaned out. The 1ZZ ECU runs rich if stumbling below idle speed, stoichiometric all conditions from idle up to ~4500rpm or so, and then open loop from there on at high throttle position.

The idle isn't as good as a Honda because the cams are single profile. The 2ZZ has a better idle than the 1ZZ, 7.2mm lift vs 9.4/8.6 intake/exhaust I think explains it. I would love to get a 2ZZ + C60 combo, raise the compression, custom grind the low cam for increased duration and fuel economy, but no money :(

My 1998 Honda Civic EX 4cyl 1.6L would be 0.2-0.22gph warm at idle, in neutral, e-brake on.

My 2005 Toyota Tacoma V6 4.0L will be ~0.35gph warm at idle

My 1990 Honda CRX HF...... I have no clue because it's OBD0:mad: I'm guessing it's less than my old civic though.

my consumption goes up when rolling downhill in N
 

VW fox 2005, 1.6L: 740ml/h (0.19gph) @730rpm, no loads, parked
VW Crossfox 2012, 1.6L: 720ml/h (0.19gph)@710rpm, no loads, parked (just 15000km rolled)


This is what troubles me:

Chrysler sebring 98' 2.5L, 1.3L/h (0.35gph)@ 750rpm, no loads, parked, auto in neutral
....
Chrysler sebring 98' 2.5L, 2L/h (0.54gph):eek: @ 1200 rpm, no loads, auto in neutral, rolling downhill @5mph Aprox.

Why does consumption goes so high when rolling? why does it need to raise rpm? :(

RPM and consumption also increase when rolling in my 1zz-fe Celica, I suspect in order to keep the brake boost and power steering topped up. When stationary at idle, just turning the steering wheel a little increases the rpm a little.

Idling
 

I am wondering how much fuel a fully warmed up 4 cylinder engine that is in good condition uses. I don’t believe that shutting the engine off at stop lights is the best idea to save fuel. The reason I think shutting the engine off at stop lights is a bad idea, besides obvious safety concerns, is that a properly running car probably won’t use enough fuel idling at a stop light to be worth wearing out your starter, among other parts like the ignition switch, risking an accident, or putting the effort into shutting the engine off and restarting it constantly. Same with EOC. I do, however, shut the engine off at railroad tracks and drive thrus. But at stop lights, I just shift to neutral and let it idle. Do you agree?

For a Civic, I've heard anywhere from 0.4-0.6 gallons per hour of idling.

My cobalt (2.2 liter) is closer to 1/3 gph, coasting in neutral at 30 mph I'm in the 90s mpg.

I've seen anywhere from 0.25-0.35 gallons per hour idling with a warmed up 1.5-2.0L Honda 4 cylinder. My Insight's 1.0 3cylinder is about 0.20gph.\

EDIT: This is measured via an OBD II dongle.

If I remember correctly, my Scanguage shows about 0.23 gallons per hour.

I never idle. I sometimes bump-start, sometimes use the starter. 244k miles. Original starter, original pressure plate, second clutch disc.
No idling for me, I like being in the #1 spots! :D
EcoModder Fleet list - EcoModder.com

A ScangaugeII will TELL you in numbers.

I use one, but I question it’s accuracy. It shows identical fuel consumption when idling in D as N. How accurate is a Scanguage?

So... all these manufacturers making hybrids that turn off the engine and regular cars that have stop start, they must be doing it wrong.

Ford and BMW are on record stating that the stop/start break even period is 3-5 seconds.

The safety aspect is a dud. There's a red light/ stopped cars in front of you anyway - where are you possibly going to go?

On a factory S/S system, the engine will be running before you can put it in gear.

MPGuino can log fuel used idling:
https://www.fiatforum.com/attachment...1&d=1391392585
https://www.fiatforum.com/attachment...1&d=1391392585

That's 4.52 litres out of 55.65 for the tank or close enough to 10%. A non eco driver spends more time stationary so would waste even more idling.