Rested idle at stoplight no accessories - Page 2 - Scion IA Forum
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post #11 of 14 (permalink) Old 05-22-2018, 01:08 PM
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Location: Las Vegas, NV
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Originally Posted by Frishkorn View Post
Hrrm happens with a manual too? Maybe itís just the motor mounts at that RPM then. Itís not so bad that Iím worried about it. Just hoped it wouldnít break after warranty. Iíll keep an eye out and report back.
Yeah, apparently manuals and automatics are having the same "issue". That at this point I don't even think there's one after reading many of us hear the same rattle. I have it hooked to my OBD port through the Torque app and everything looks okay, just like I said before I've never seen a car idle at ~450-550 RPMs before. My 16 V8 Camaro and my 2009 Cobalt idle at 650-800 depending on temperature and engine load.

2017 Toyota Yaris IA - 6 speed manual - Sapphire
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post #12 of 14 (permalink) Old 05-22-2018, 04:44 PM
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Yeah guys it's a cheap subcompact that has direct injection and a venerable 1.5 and weighs what 2,000 lbs? it's going to idle rough
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post #13 of 14 (permalink) Old 01-19-2019, 03:54 PM
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Originally Posted by joelg1988 View Post
I get about 34 mpg with very aggressive driving (A/C off). But since it's now May and temps here in Vegas are starting to hit 100 degrees, I get 32 mpg with aggressive driving (with A/C on) and 38 mpg slow driving with A/C on.

I guess it's only easy to get 40+ mpg with the A/C off. Once you turn on the A/C compressor, you lose 5 mpg (or more, depending on how you drive) easily.

My V8 Camaro only loses about 1 mpg with the compressor on. Looks like our little FrankenMazda is not happy with the compressor on.
No fault of the frankenMazda!

On a car like a V8 Camaro...

+ You have a higher amount of air to waste power moving through ( the car is significantly wider and less streamlined, but perhaps just as tall ).
+ You have a transmission that needs to transmit over 4 times the torque, so the drivetrain losses make up a significant amount of load to move the car. The lower the load of the drivetrain is ( IE when cruising at a steady speed on the highway ), the higher % this is of the horsepower needed to move the car along.
+ That rear differential also adds to this drivetrain friction.
+ Your engine has over 3 times the displacement, and at a low load such as highway cruising, it also takes a big friction and pumping loss penalty.

The Load that comes with a ~3 horsepower compressor turning on easily disappears in the noise of all these losses.

But on our very aerodynamically optimized ( this car is smaller than a Prius ) cars, an extra 3 horsepower load is a big kick in the balls.
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post #14 of 14 (permalink) Old 01-19-2019, 03:57 PM
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The car does idle rather low, but you can thank Mazda for saving your fuel economy during city trips by running the engine at a low RPM. The sad thing is that if you upgrade the motor mounts to ones that aren't the wobble-squish units the car came with, then you get to feel this.
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