10-11-2012, 06:13 PM
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#11 (permalink)
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Master EcoModder
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Quote:
Originally Posted by Sven7
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I've been looking around for stats on pre-warmup emissions on gas engines but can't find any numbers. (Trying to justify a block heater to someone on the local forum). So, how much less efficient are they when cold? Are they only inefficient during those five seconds of high idle at startup, or do they chug more gas until the temp is up?
Edit
The big question is this: Which emits fewer greenhouse gases: 800Wh of coal-fired electricity or the amount of extra gas your cold engine burns?
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MetroMPG included some stats on his page:
In praise of the lowly block heater - MetroMPG.com
I haven't done the comparison vs the grid, but I agree that's a key point. (Still pretty sure the block heater is favored, just thinking back of the envelope - % smog blamed on coal vs gasoline.)
The effectiveness of the block heater is not all about the cat though. Cat light-off temperature (50% efficacy) is like 300°C, so pre-warming the engine doesn't shorten cat light-off a ton. I'd bet the effect of the block heater is equally for fuel vaporization and cold-idle speed. (See section 1.2.3 in "Modelling and Control of Automotive Coldstart Hydrocarbon Emissions".)
This should give you an idea how a cat behaves vs temperature:
Unfortunately this chart is just a model, not real data.
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10-11-2012, 06:21 PM
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#12 (permalink)
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Years ago I posted on this topic; the Canadian govt had boatloads of info on cold start emissions, idling, plugging in, etc.. Last time I visited my post many of the links were dead. Might be worth it to search again.
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10-11-2012, 06:35 PM
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#13 (permalink)
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Master EcoModder
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Quote:
Originally Posted by Sven7
The big question is this: Which emits fewer greenhouse gases: 800Wh of coal-fired electricity or the amount of extra gas your cold engine burns?
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Hands down the coal-fired electricity. Cold engines are ridiculously inefficient and coal plants, while filthy, have a much higher thermal efficiency.
I am willing to admit the comparison between efficiencies does not address the entire question as the 800Wh is not a watt for watt replacement in powering your vehicle.
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10-11-2012, 06:53 PM
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#14 (permalink)
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Corporate imperialist
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Best thing you can do to reduce start up tail pipe emmissions is attach the converter to the exhaust manifold.
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10-11-2012, 07:33 PM
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#15 (permalink)
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Cyborg ECU
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10-11-2012, 08:05 PM
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#16 (permalink)
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Master EcoModder
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Just talking out of my ass here but NOx emissions are a result of high combustion temperatures, I dont think they are as big a problem when the engine is still cold as CO and HC.
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10-12-2012, 12:45 AM
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#17 (permalink)
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Master EcoModder
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as cat efficiency increases C02 % increases as well
on a cold engine
nox is zero
and
as cat efficiency goes up so does the percentage of C02 in the exhaust gases
about 12 to 13% cold and
about 15 to 16% when the cat is hot and operating as designed
lets be clear
the EPA is wrong when they claim that C02 is a pollutant
it is not , science and facts do not conform to political nonsense .
plants need C02
they grow better in higher concentrations of C02 ,
as the plants use up
the C02 , their waste gas is
02 , humans have a need for 02
the 02 percentage in our atmosphere is stable ,
therefore we can see that
the system we exist in is able to regulate
minor inputs made by the foolish mortals
thanks God
it is fun to watch those who do not understand , attempt to make something more efficient , when by so doing they will actually cause what they falsely perceive to be a problem , stronger (output of C02 )
i am standing beside myself
Last edited by mwebb; 10-12-2012 at 12:54 AM..
Reason: foolish mortals
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10-12-2012, 01:14 AM
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#18 (permalink)
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I think the "CO2" was a mistake; I certainly wouldn't want to sit in a room filled with carbon monoxide and I don't think plants would like it either.
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10-12-2012, 04:32 AM
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#19 (permalink)
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aero guerrilla
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I've wondered about putting a heating pad on the cat to prewarm it, but I'm not sure if the pad would survive the temperatures once everything got hot.
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10-12-2012, 06:06 AM
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#20 (permalink)
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Master EcoModder
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Quote:
Originally Posted by Sven7
Are there any relatively simple mods one could do to reduce a car's CO2, NOx, etc. emissions?
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Nothing easy, I'm afraid.
Keeping the engine warm seems to be the easiest theoretic solution, though it's not exactly practical.
CO2 is not a problem as such - it's just a problem it comes from depleting , un-renewed stocks.
On a cold engine, the main issues are unburned or partially burned, unhealthy hydrocarbons.
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