Prius C: thinking of developing a "70 mpg aerodynamics kit"...

[cyclopathic]

Originally Posted by BabyDiesel

I would not say this, but that it is highly likely that the Cd is greater than 0.28. If you can perform coastdown testing over Instructables.com, then we could find out for sure and settle this

The C's Cd 0.28 would match the Mitsu Mirage, and they look similar IMO

As someone who owns/driven both I am pretty sure Mirage has better Cd, that's why C Cd is suspect.

Playing with calculator shows that changing Cd in 0.28-0.31 with engine efficiency to match observed MPG at 60-65 MPH doesn't change expected ~42 at 70-75. So it looks like engine might have been optimized for lower RPMs and at higher RPMs it is less efficient.

[BabyDiesel]

The calculator is a good tool, but it is not a perfect tool. So I use it as a guide, but it cannot replace real world data gathered out on the road.

The calculator showed that my car, fully optimized with 0.15 Cd, ~30% engine efficiency, ultra LRR tires, weight reduction and geared correctly @ 45 mph should be capable of around 125 mpg. Can that be true? Maybe. Though I have the problem of having too big an engine, but that is going into deeper waters than is needed here.

I think you are correct, but in most cases turning higher rpm = more fuel use, regardless of efficiency. I still say you should do coast down testing and tell us what you find out about Cd & RRC.

Back on topic...

This 70 mpg kit would have to appear like this Dream Prius I found at either Gassavers or CleanMPG.

[freebeard]

Prius now? Here's an MX-3 ...from Ecomodder in 2008.



http://ecomodder.com/forum/showthread.php/mass-produced-car-closest-teardrop-shape-5924.html#post71608

I'm not clear on the high-tailed approach vs the 1930s tail-dragger approach. It seems like the high tail would be shedding vortexes off it's lower edge.

[aerohead]

The thing is,that we can't drive around at 45-mph.You might be legally entitled to do it on some highways,but if you impede the other motorists,you cause an efficiency loss with all their cars,then we lose overall.
The GM Ultralite was rated 100 mpg @ 50-mph.That would fall to 80-mpg pretty quick at moderate 'legal' speed.
I would use the Ultralite as a benchmark.

[aerohead]

The 1st would shed from below,the 2nd would shed from above.

[Xist]

Moderation in all things?

[aerohead]

I went over my notes from the Pate Swap Meet from years back.
One of the vendors offered a body kit for S-10/GMC S-15 pickups which included a front clip,and entirely new rear 'box,' which made it look like a 1940's roadster.
Anyway,they were asking $12,000 for the kit.
Something for the Prius would have to be as radical,and aerodynamically proven,and it would have to respect the existing unit constructed Toyota platform,unlike the body-on-frame GM pickups.
If $12,000 covered their time,trouble,development,tooling,material,labor,fi xed overhead,distribution,marketing,and a reasonable net profit,etc.,then we have at least one example of a real world price for a kit which significantly alters a body shape.