Winter cold start & idling warm-up experiment

[MetroMPG]

I'm sure nobody here still idles their engines to warm them up. Aside from being a colossal waste of fuel, it does nothing to warm the other critical parts of the drivetrain that affect fuel economy: the tires, transmission oil, bearings, differential, etc.

So I did a mini experiment to chart the relationship between coolant temp, intake air temp (warm air intake in place) and fuel consumption in Litres per hour according to the ScanGauge.

The test conditions:

• ambient: -7 C / 19 F
• cold soak (hadn't driven it since the day before)
• all electrical accessories off
• WAI in place
• didn't touch the accelerator at all - let the engine computer do its thing

Observations:

One of the most astonishing things I saw was how long it took the little motor to warm up. Holy crud: 17 minutes!!

I heard back from a Metro driver on the Canadian prairies (not Peakster) who told me his Metro actually starts to cool down from normal operating temperatures at stop lights on really cold mornings with the cabin heat running.

Anyway here's the chart I was after:

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For those who want a more detailed & polished report, there's a post about this test at MetroMPG.com : Mini-experiment: cold start fuel consumption and warm-up time

[Peakster]

Nice experiment MetroMPG! Now imagine the same experiment in -25 C weather . Yup, I can also attest that the Geo's temperature gauge drops like a rock (almost right back to the 'C' mark) when stopped in traffic and simply idling in cold weather.

[metroschultz]

One of the mods I won't do is removal of my A/C. I specifically looked for this metro because of that feature. My summers can reach 100f. @ 100% humidity. I'm old and need my A/C. Sub-zero start up LOL.

[RH77]

What I'm trying to determine is the engine-on coast warm-up. (I don't use any heat until TC lockup)

Example:
From my workplace (no EBH), I can coast down a long hill for about 2 minutes before needing to go up another steep hill, down another one to a light and onto the highway.

I've tried a few things in the Winter -- latest temps are 10-20F.

• The car's is in high-idle, so I force 2nd gear and let 2000 RPM keep things moving, then...
• Coast down the hill in neutral, engine-on, or
• Nearly the same speeds are attained with "D" selected, and just let 'er go to the light/corner at the bottom

Temps have varied this week, but theoretically, which would provide the best heating action? The coolant is too cold for decel injection cut, so it might only help the transmission warm up a bit from friction ???

Then at long lights, I shut it off and wait. No sense in futile idling.

My biggest concern is to get up to the highest temp before I have to get on the highway, which is about 7-10 minutes of driving (typically takes 15 minutes of stop-and-go city driving or 15-20 minutes of near-immediate highway driving to warm up in sub 30's). Even with the grille block, the engine seems to cool itself better at higher RPMs (I observed the same in the Summer).

There's a second route that requires lots of stop-and-go, but heats things up rapidly. With some consistent temps, I'll have to log outputs to see if driving on the highway cold or taking the time to heat up, is most beneficial.

RH77

[budgenator]

It's the fuel economy thing, used to be that an engine lost 33% of it's energy to heat. now with the federally mandated pathetic millage requirements, there is simply less waste heat to use for creature comfort now. What I've seen is in the Wife's jeep, one second of driving is worth 60 seconds of idling warm-up wise (untested). I've installed the low-temp, rain-repellent washer fluid to save fuel by making the snow and ice much easier to scrape off and I'm thinking about putting in an electric heater to pre-warm the cabin in winter. I could easily see a lot of you guys installing, engine, block, transmission and differential heaters or using synthetics with extreme viscosity ranges to help with cold temp millage numbers.

[Piwoslaw]

With my coolant heater installed and winter approaching I thought I'd do a test similar to MetroMPG's. I plan to test warm-up times both for the heater, and for idling (starting with cold engine) to see the difference. Yes, it's a waste of fuel (and a source of pollution), but it is in the name of scientific research. Plus I'll do it before a planned drive, so that should partially offset any bad side effects.

To make the results as comparable as possible, I'm waiting for temperature to drop to around between -5° and -8°C. In the meantime, I'm thinking about what I need to pay attention to while performing the test. Every 30 seconds MetroMPG took readings of Intake Air Temperature, Coolant Temperature, Fuel Comsumption (in LPH). I plan to note a fourth parameter, either Engine RPM or Total Fuel Used, probably the latter is more useful.

Does anyone have any suggestions? Maybe I should pay attention to something else?

I wonder: Will my engine get up to temp in less, or more, than 17 minutes? On one hand, it's a super efficient turbodiesel. On the other, it's 1.6 liter 4-banger with an aluminum block and 110hp, so there's a lot more going on in there than in a Metro's 1.0. I'm taking bets

One thing I should add is about my air intake. It's not a short, straight-forward affair, but instead partially feeds from the engine bay, snakes around to the air filter behind the engine, then comes back up front to the turbo, passes through the intercooler (no cooling when not moving), and finally enters the manifold. This essentially makes it a WAI when the car's not rolling, with lots of pumping loses. When moving, the IAT is usually 2-4°C above ambient air temperature, but when stopped it grows pretty fast, like up to 50°C (with outside temp around 10°C) in less than a minute. A turbodiesel is more efficient with a CAI, but maybe this won't matter in this test.

EDIT: I just remembered that I recently installed an EGR/coolant heat exchanger, but this probably won't have any effect in this warm up test since the EGR valve supposedly doesn't open when idling.

[MetroMPG]

I'm betting your engine warms up faster. Based on nothing

[Daox]

I bet its slower, based on it being diesel.

[bestclimb]

my 1.6l vw diesel warms up almost twice as fast as my 1.5l honda.

[Piwoslaw]

Originally Posted by MetroMPG

I'm betting your engine warms up faster. Based on nothing

Originally Posted by Daox

I bet its slower, based on it being diesel.

I love situations like this: Someone always wins!