Drag HP vs mph

Do not let some fraction of a MPG prevent you from enjoying your car. Get the mudflaps, you need them and you will hate yourself if you don't.

Get a car that works for you, not one you need to pamper.

 

Thanks. Yes, have decided on mud flaps- just interested to know whether it will just be only a fraction of an MPG, or possibly a bigger hit than that, and even whether it might increase wind noise on fast roads.

Most of my miles will be local, EV, and on slower roads anyhow.

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I can see much chat about mudflaps and MPG, but no facts. I would not mar my car to save 1/10 of a MPG. (I personally stay on Paved roads, but if I was on gravel much I would get flaps)

If you mention it to Bob Wilson, he may do an A B test with and without for a 1000 miles for a result.

 

Bare in mind the mud collecting (without the flaps) also affects aerodynamics

 

59 mpg at 77 mph is great. A Mega bus is much better than a semi trailer due to the lack of ground clearance with the bus.

When you were traveling 77 mph behind the Mega bus with 1 bar on the dynamic cruise control approximately what was the distance to the bus? Did you have trouble avoiding hazards in the road due to your close distance to the bus? I may have to try this again.

 

If I remember correctly, about 2 years ago MythBusters did a test of wind resistance following a large truck. Fuel efficiency improved up to a point, then decreased if followed to closely. It was explained that fuel was wasted trying to stay too close (slight acceleration and deceleration) to maintain the close distance.

 

What is 'platooning' systems?

 

I get it. Thanks. That is what Car and Driver did when Honda asked some auto journalists to go on a long drive in a mpg competition with the then new 2 seat Insight. C&D asked if drafting was allowed. Honda said yes. So C&D used a Suburban with swing out rear doors and attached plywood to each door in the opened position to make a large air block for the Insight. I believe they used radio communication and had visibility to the inside of the Suburban. Their mpg was significantly higher than their competitors in Insights who did not draft.

 

I tried the same trick today with a semi. I set the following distance to 2 bars, 1 bar that I used on the bus was too close for comfort. The semi's that dragged me today were averaging 63mph, and my fuel economy was about 58.5 in hybrid mode. Total trip was 360mi, fuel economy for the entire trip was 62 after judicious use of EV on surface streets and regen on mountains. 1700 mi on the car in these first 2 weeks averaging 64mpg. Meets or exceeds expectations.

 

Wouldn't it be much better to use what @bwilson4web is doing (in his avatar)?

 

I can't find a magnet that big.

 

I thought that proper 'platooning' needed to be under computer control, not human control.

 

0.5% reduction in MPG.....They have did R&D on Prime......this is for rear mudflaps......

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3M plastic paint protection is much better and almost invisible

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As an exercise (to myself mainly) I have taken @lroki 0-60 test for EV on wet ground with some slip at the beginning, see here , multiplied all results by a small factor that brings the 60 mph to 11.8 seconds, which I assume would be the result on dry and no slip.
Calculated acceleration power vs speed from these results, added total drag power vs speed from the EPA data (see first post here).
Results are shown in the chart:



Vehicle mass: 1550 kg.
Max power is ~63 kW @ 42 mph. putting mass as 1590 kg will raise max power to ~65 kW.

Max power available in EV dual motors drive is 68 kW.

Just an exercise.

 

Still trying to get a handle on the raw EPA data that Bob pointed out ..

Now that the data columns are not mangled, I can see the Coefficients. I filtered for the Prius Prime and show one row below:



The colored cells are each original value multiplied by 4.5, to convert to newtons.
I know that Bob warned against attempting to pigeon hole a Coef to a real force, but I'm bothered by Coef B always being a larger contributor to the final result than Coef C since Coef C would presumably (?) model air friction.

 

Look at the headings. Set coefficients are not dimensionless, to get rolling resistance (force) at certain speed, multiply the B coefficient by mph. To get aero resistance (force) at same speed, multiply C by mph squared.
Or, work with target coefficients which are dimensionless.