Aero efficiency - with or without moonroof?

At low speed it would likely be insignificant because aerodynamic drag is very low. At high speed it could be much more significant but I couldn't say how much. I have the same question regarding the GenIII solar roof.

 

Crap, should have passed on the moonroof then lol.

 

Any money you spend on a passively open sunroof, will more than offset the extra cost of fuel you burn running the AC or heat. I drive mine like I stole it, my rational is that no matter what I was driving it would not get as good of MPG as my C. 36k and still running great.

 

Just drive it slow, no worries then!

 

I think the reason for the channeled roof cross-section on the Prius family is to reduce the frontal area. It's a small effect, but Toyota has used many small refinements to incrementally improve the aerodynamics and the fuel mileage. The numerous small increments add up. The boundary layer is probably tripped to turbulent by the upper edge of the windshield, so the effect of the sunroof is small. The effect of the cross-section may not even be measurable in a wind tunnel. They just did it because it's definitely favorable for drag, even if the benefit can't be quantified.

 

I've driven the same 100miles+ stretch of 65mph+ highway with my C2 and moonroof C4 and there really isn't any noticeable MPG loss/gain

 

I am sorry to tell you guys that the channels you see on the roof have nothing to do with aerodynamic or fuel efficiency but they don't. They are there for Structure.
Any time you have a flat sheet of metal the bigger you make it the flimsier it becomes. Think about holding out a thin metal sheet in your hand that is only 1ft long it probably wont bend but if you hold out in a 6ft metal sheet that's the same thickness it will start to bend under its own weight. You can either make it thicker to accommodate for this or you can press ridges into it that eventually make it smaller sections instead of one big section. This gives the roof more strength.
It almost breaks the roof up into 3 sections as opposed to 1 big section.
The reason its smaller on the roof with the moon roof is because the roof section behind the moon roof is much smaller and not as much is needed to make it sturdy.
All vehicles have this. Even in places that you cant see. Like the floor boards under the carpet and the interior door panels. This is nothing specific to Toyota.
Way back in the day in the 40's and 50's manufactures figured this out and quit making the panels on cars thicker and started to press sections in them to make them just as strong.
And with the presses going front to back along with the air flow they have no effect on aerodynamics

 

This is not an issue. Sorry, you'll have to worry about something else.

 

Isn't the one with the sunroof like a half inch taller? That shouldn't damper fuel economy that much.

 

OMG !!!!!!!!!!!!!!!!!!

 

Sunroof adds weight too. Every ounce counts in the 1/4.

 

I drove to work with snow on the top of the car. When I got there the snow was blown off the front of the roof near the top of the windshield... but had remained on the top of the car where the sunroof is. Based on this observation of airflow I doubt that the sunroof is adding any drag in comparison to the standard "deep channel" roof contour.

SCH-I535 ?

 

I wouldn't drive a car without a sunroof. Living in Seattle I am lumen starved and driving a closed cabin would drive me nuts(er). I rarely open it for air, sucker is noisy, but having light when you want it is so nice. That's why I didn't go with a full size in part, sunroofs are a high end option and push the price way up. Being said, I avg. around 48-50mpg in mixed driving.

 

Got the sunroof to blow around what hair i have left... if i get balder(er) will this reduce drag? lol-j/k

 

My experience with aero improvements on cars says the moonroof will have more negative effect on aero than the grooves; the grooves are there probably to meet roll-over standards and are parallel to air flow while the moonroof is vertical and thus will result n more drag.

 

That the snow remained on the sunroof is a good sign air flow was deflected over it and in doing so increased drag.

 

While the regular Prius has a CD of .25, the C has a .28.

Would you think the CD of .28 with an increased height of .75" with a sunroof be increased to, perhaps, .2805 or .2806?

Would that be more or less efficient than carrying around the weight of having a full tank vs half a tank? Or would it be irrelevent compared to any number of the daily variables contributing to more/less mpgs?

 

But the roofline up to the point where the moonroof starts is pretty much the same between both versions... so the same airstream coming off the windshield would probably be similar either way.

SCH-I535 ?