idle warm-up experiment

[MetroMPG]

i realize this is probably preaching to the choir here...

<img src="http://www.ultralightnews.ca/westach/images/squarewatertemp.jpg" width="180" align="right">

we all know that it's better to drive a cold engine gently than to let it idle after a cold start. it's generally accepted that driving uses less total fuel than idling to warm up first. driving also warms the motor up faster than idling (not to mention the drivetrain, tires, bearings, etc., which idling alone doesn't help.)

but how much faster? i didn't really know. time to get me some data!

<b>the test:</b>

i did a really basic experiment: i timed how long my car took to reach operating temp (195 F) idling, from a cold start.

(have some fun... before you read any further, take a guess at how many minutes it took, from 19 F ambient...)

<b>the test conditions:</b>

- ambient: -7 C / 19 F
- NO electrical accessories on
- cold soak (hadn't driven it since the day before)
- WAI in place
- didn't touch the accelerator at all - left the ECU to do its thing

<b>the data:</b>

note: a couple of minutes into the test i dope-slapped myself because i realized this was also a perfect opportunity to monitor changing fuel enrichment as the engine warmed up. so you'll see those figures start part way down the table - "liters per hour" of fuel consumption.

the acronyms:

FWT: coolant (water) temp in degrees F
FIA: intake air temp in degrees F
Lph: fuel consumption in liters per hour

<TABLE CELLSPACING="0" BORDER="1" CELLPADDING="2"><TR><TD><B>time (min)</B></TD><TD><B>FWT</B></TD><TD><B>FIA</B></TD><TD><B>Lph</B></TD></TR><TR><TD>0</TD><TD>19</TD><TD>22</TD><TD><P></P></TD></TR><TR><TD><P></P></TD><TD>30</TD><TD>19</TD><TD><P></P></TD></TR><TR><TD>1</TD><TD>42</TD><TD>21</TD><TD><P></P></TD></TR><TR><TD><P></P></TD><TD>57</TD><TD>21</TD><TD><P></P></TD></TR><TR><TD>2</TD><TD>73</TD><TD>21</TD><TD><P></P></TD></TR><TR><TD><P></P></TD><TD>83</TD><TD>21</TD><TD><P></P></TD></TR><TR><TD>3</TD><TD>96</TD><TD>22</TD><TD>0.8</TD></TR><TR><TD><P></P></TD><TD>105</TD><TD>24</TD><TD>0.8</TD></TR><TR><TD>4</TD><TD>110</TD><TD>24</TD><TD>0.7</TD></TR><TR><TD><P></P></TD><TD>118</TD><TD>26</TD><TD>0.7</TD></TR><TR><TD>5</TD><TD>127</TD><TD>28</TD><TD>0.7</TD></TR><TR><TD><P></P></TD><TD>132</TD><TD>30</TD><TD>0.7</TD></TR><TR><TD>6</TD><TD>137</TD><TD>30</TD><TD>0.7</TD></TR><TR><TD><P></P></TD><TD>141</TD><TD>30</TD><TD>0.7</TD></TR><TR><TD>7</TD><TD>146</TD><TD>31</TD><TD>0.6</TD></TR><TR><TD><P></P></TD><TD>150</TD><TD>33</TD><TD>0.6</TD></TR><TR><TD>8</TD><TD>154</TD><TD>35</TD><TD>0.6</TD></TR><TR><TD><P></P></TD><TD>157</TD><TD>37</TD><TD>0.6</TD></TR><TR><TD>9</TD><TD>161</TD><TD>37</TD><TD>0.6</TD></TR><TR><TD><P></P></TD><TD>164</TD><TD>37</TD><TD>0.6</TD></TR><TR><TD>10</TD><TD>166</TD><TD>40</TD><TD>0.6</TD></TR><TR><TD><P></P></TD><TD>168</TD><TD>42</TD><TD>0.6</TD></TR><TR><TD>11</TD><TD>172</TD><TD>42</TD><TD>0.5</TD></TR><TR><TD><P></P></TD><TD>173</TD><TD>46</TD><TD>0.5</TD></TR><TR><TD>12</TD><TD>175</TD><TD>46</TD><TD>0.5</TD></TR><TR><TD><P></P></TD><TD>179</TD><TD>48</TD><TD>0.5</TD></TR><TR><TD>13</TD><TD>181</TD><TD>48</TD><TD>0.5</TD></TR><TR><TD><P></P></TD><TD>182</TD><TD>51</TD><TD>0.5</TD></TR><TR><TD>14</TD><TD>184</TD><TD>51</TD><TD>0.5</TD></TR><TR><TD><P></P></TD><TD>186</TD><TD>51</TD><TD>0.5</TD></TR><TR><TD>15</TD><TD>188</TD><TD>53</TD><TD>0.5</TD></TR><TR><TD><P></P></TD><TD>190</TD><TD>55</TD><TD>0.5</TD></TR><TR><TD>16</TD><TD>191</TD><TD>55</TD><TD>0.5</TD></TR><TR><TD><P></P></TD><TD>193</TD><TD>57</TD><TD>0.5</TD></TR><TR><TD>17</TD><TD>195</TD><TD>57</TD><TD>0.5</TD></TR></TABLE>
<img src="http://metrompg.com/offsite/warm-up-chart.gif">

<b>some observations:</b>

- how'd you do with your guess??

- it was shockingly slow to warm up, wasn't it. way off my guess. it only takes 3 or 4 minutes to reach operating temps when driven, though i'll have to wait until the ambient is the same and do a repeat test for a proper comparison.

- a larger engine might warm up quicker than my 993cc alumninum powerhouse, since it will be using more fuel (though it's also a larger heat sink...)

- since doing this, i have watched the Lph figure and have seen <b>2.0 Lph</b> (!!!) immediately after start-up. i'm curious to see how fast it tapers down to 0.8. the plot suggests Lph tapers faster in the beginning, which makes sense. it steps down relative to FWT at 110, 146, 172 F