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Old 03-27-2013, 04:13 PM   #4057
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Join Date: Mar 2012
Location: ND
2012 2.0i Sport 5MT


Originally Posted by hemophilic View Post
This is kind of a ramble, wild speculation, and only slightly related to MPGs so, apologies.
While driving a cold engine this morning and wondering about the lack of power and high rpms, I started thinking of a conversation I had back in college with an aerospace engineer buddy. We were talking about high and low torque loads in turbine engines and car transmissions and this got me wondering about the warmup sequence we aren't so fond of in the Impreza. I'm guessing the Subaru engineers are thinking of cleanliness AND longevity by pumping a lot of fuel into the engine for a short time. As we know, the extra fuel will heat the engine, oil, and cat sooner than lean efficient burn to end up getting the benefits sooner rather than later. While the oil is cold, it offers less friction reducing ability (per that neat oil website someone put up a while back). So, if programming tells the torque converter to lockup later and the CVT to use a lower gear, the car ends up running in a high rpm but low torque fashion which greatly reduces driveline stresses until the liquids are at a happy temperature. That seems like a very thoughtful thing to do IF it's true. I hope this car lasts forever.
i made a highlight.

overall i agree with what you posted, BUT

extra fuel actually cools the combustion chamber. in a piston airplane where you can manually control fuel trim, if you start to see cylinder head temps rise, you can bump the mixture up a little and watch them drop dramatically so more fuel doesn't always burn hotter, and less fuel doesn't always burn hotter
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Last edited by flyboy1100; 03-27-2013 at 04:18 PM.
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