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Old 03-23-2019, 09:39 AM   #15 (permalink)
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Join Date: Dec 2012
Location: Nieuwegein, the Netherlands
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Red Devil - '11 Honda Insight Elegance
Team Honda
90 day: 60.2 mpg (US)

It - '09 Hyundai I10 Active Cool
Team Hyundai
90 day: 30.33 mpg (US)
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My Insight uses double spark plugs, has EGR and a thermostatic valve that will open partially at 81 degrees Celsius (177.8F), and fully at 92.

Usually the temperatures will stay in the low (1)80's even with my partial grill block. But on longer trips the intake temp will gradually build and at some point that reflects in the coolant temp reaching to the 90s.
All is fine up to 94 degrees (200 F, indeed). Above that MPG suffers noticeably. I then set the blower to max and the cabin temp up; coolant temp drops quickly and good MPG returns.

So it depends.
You need to monitor what's going on, and don't expect miracles when you already have EGR.
I don't see anything more than a small gain (2-3%) and taking it too far does hurt. But a different car may react differently.
2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.14 Gm or 0.09 MM.

Last edited by RedDevil; 03-23-2019 at 09:44 AM..
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