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

[botsapper]

http://ecomodder.com/forum/showthrea...tml#post215758

That'd be nice.

[basjoos]

A quick way to test the Prius C (or any other car's) aeromod mpg gain potential is to note what the mileage improvement is when drafting, as that is the mileage improvement you could get by reducing the Cd. When drafting, the only thing that has changed is the wind load (which is the only thing being changed by aeromods) because of the reduced wind speed behind the drafted vehicle. Rolling resistance, engine/transmission rotational losses are unchanged.

[user removed]

Originally Posted by MetroMPG

Old Mechanic - fortunately in this case, the car has a CVT type of transmission. So it should automatically compensate for the reduced load by reducing RPM.

Aeromodding a CVT equipped vehicle is a 2-birds-1-stone type of deal.

I have owned two cars with CVTs. They both had a range of ratios between minimum and maximum limits (600-700% range). I'm not sure about the Toyota Hybrid Synergy Drive configuration and whether it has similar limits.
On the other hand an IVT would be capable of 120 MPH at idle speed, even 1000 MPH at idle speed. No limits to the range of ratios.

regards
Mech

[MetroMPG]

Old Mechanic: I don't know the Prius well enough to say.

However, relating to basjoos' idea, a quick search turned up this:

(Edited for brevity...)

I typically set the cruise at 65 and achieve about 49 mpg per trip. Tonight I got behind a 18 wheeler running 70-75 and followed him for about 175 miles or so - following at about 25 ft or closer (not recommended but mildly amusing). My average went from 44.5 MPG (at 65 mph), to 63.5 MPG (at 70-75) [40 miles later] - and it's an uphill run.

I couldn't believe how many 5 minute segments of 99.9 MPG I saw. The battery was 10 bars full green the majority of the way. Several times (at speeds up to 72 mph) the car went into "super-golfcart" mode where the electric motor was providing the sole source of power. I imagine you could achieve better than 75 mpg traveling cross-country using this technique.

From: "Drafting" experiment... 50 mpg to 65 mpg, easy! - PriusChat Forums

[aerohead]

Please see the thread 'Prius to get full boat tail w/ faired trailer', #25,and #27 permalinks

[mort]

Originally Posted by Old Mechanic

I'm not sure about the Toyota Hybrid Synergy Drive configuration and whether it has similar limits.

I'm assuming the Prius C eCVT is similar to the other Synergy drive units. Also I note that everybody except Toyota says the "C" has an Atkinson type engine. (Toyota says intelligent VVT.) The range of equivalent ratios in the eCVT is from about 4:1 down to about 0.5:1 The gearing limits are set by MG1 maximum rpm
[final drive is 3.19:1, rolling radius about 12 in. 1500 rpm cruise at 65 mph is about 0.525:1 gearing and maximum rpm pull at 30 mph is 3.6:1 gearing]
This PDF has some info. One limit on Prius economy is that the engine doesn't run below about 1500 rpm, but assuming Atkinson like torque, at 1500 rpm the "C" engine could produce about 22 hp. According to the ecomodder MPG calculator the "C" needs about 12 hp to cruise at 60. So the engine is throttled, which lowers efficiency, but lowers output more.

Originally Posted by Daox

In order to get the 45% increase in mileage to get 70 mpg, you'll need to reduce the Cd down to roughly .167!

I don't think that's likely without major body work.

-mort

[Rokeby]

Re: the BSFE graph in post#10

This graph may be more useful as it shows both the Gen II and Gen III for
comparison:




FWIW, I saw a Prius c in the parking garage at work today.
Gave it a good once over. Clearly a smaller car than the Prius.
I'd guess sizewise closer to the Insight I.
Impressive FE numbers being reported at PRIUSchat.
Unfortunately too small for us.

Nonetheless, I like the idea of going after all the not-so-low
hanging fruit with aero bits. I'll be watching closely.

[California98Civic]

Sven7, those images are cool. I went looking for more info and found this:
http://www.leblogauto.com/wp-content...Prius_oeuf.jpg

On Prius Chat someone claimed that the car design you posted was for sale by Toyota in the Japanese domestic market in 2010.

[MetroMPG]

Originally Posted by todayican

I am excited to be picking up my Habenero Prius c tomorrow ...

So... today is tomorrow! How do you like the car?

I build custom trikes and have access to a pretty good fiberglass guy and what not so just how hard (possible?) would it be to do a "package"

Question: are you mulling this over for yourself, or as a commercial venture? (Not 100% clear).

[user removed]

Originally Posted by mort

I'm assuming the Prius C eCVT is similar to the other Synergy drive units. Also I note that everybody except Toyota says the "C" has an Atkinson type engine. (Toyota says intelligent VVT.) The range of equivalent ratios in the eCVT is from about 4:1 down to about 0.5:1 The gearing limits are set by MG1 maximum rpm
[final drive is 3.19:1, rolling radius about 12 in. 1500 rpm cruise at 65 mph is about 0.525:1 gearing and maximum rpm pull at 30 mph is 3.6:1 gearing]
This PDF has some info. One limit on Prius economy is that the engine doesn't run below about 1500 rpm, but assuming Atkinson like torque, at 1500 rpm the "C" engine could produce about 22 hp. According to the ecomodder MPG calculator the "C" needs about 12 hp to cruise at 60. So the engine is throttled, which lowers efficiency, but lowers output more.

I don't think that's likely without major body work.

-mort

It would seem that you could do a very slight P&G with the Prius C. Just enough to get to 22 HP on the pulse then all electric on the very slight glide. Maybe a 5 MPH speed variation, with engine off 50% of the time. This would be the secret to getting very high mileage with lower overall drag numbers.
Get them low enough to get your P&G ratios above 2 to 1 or even 3 to 1 and you will see magic numbers.

Drafting in my Insight was interesting, even with the .25 ratio. I found that I could get the same mileage at 70 MPH on the Interstate as I could on a deserted 55 MPH road running parallel to the Interstate. On one trip of 650 + miles I managed 70.2 MPG while averaging 55 MPH. In the VX on one trip I managed 68 MPG at 64 MPH and that was mostly drafting at 3 stripes in the right lane of I 64 and I 95, in the late spring of 2008.

regards
Badger