Does anyone know this car? (boat-tailed 2nd gen. Prius spotted in the wild)

[MetroMPG]

Fantastic!


Welcome to the forum.

[aerohead]

Your car is so 'worthy', I went ahead and crunched a second set of numbers.
The assumptions:
1) Af= 23.7836-sq-ft ( 2.2095 m-squared )[ I used the same proportion of net area, to gross area as Don Sherman did with the Gen-III Prius in 'Drag Queens.'
2) Cd 0.26.
3) OEM tires.
4) 3,232- pounds test weight.
5) 95.333 feet/second ( 65-mph ).
6) 43.3-mpg @ 65-mph, with AC 'ON'.
7) 1.5011-gallons/hour ( @ 111,836 Btu/gallon REGULAR Unleaded E10 )
8) 167,883.14 Btu/hour (gross )
9) divided by 2546 = 65.9399- gross horsepower equivalent
10) X 0.40 ( thermal efficiency ) = 26.3759 brake horsepower/hour
11) X 0.978 ( accessory losses ) = 25.7957-hp
12) X 0.8771 ( CVT mechanical efficiency ) = 22.6254-hp Road Load
--------------------------------------------------------------------------------------
13) 11.56782-hp aero= 95.333/550 lb-ft/sec ( 0.5 X 0.002375 X 0.26 X 23.783 X 96.333-squared )
-------------------------------------------------------------------------------------
14) 22.6254-hp - 11.5678-hp aero = 11.0575-hp rolling resistance ( a constant )
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15) 65-miles/hour divided by 60-mpg = 1.08333-gallons/ hour
16) X 111,836 = 121,155 Btu / hour
17) divided by 2546 Btu/ hp = 47.5865 hp-gross
18) X 0.40 thermal efficiency = 19.03461-brake horsepower-hour
19) X 0.978 ( accessory losses ) = 18.6158 hp
20) X 0.8771 ( CVT efficiency ) = 16.3279-hp Road Load @ 65-mph ( modified )
--------------------------------------------------------------------------------------
21) 16.3279 -hp - 11.0575-hp rolling resistance ( a constant ) = 5.2703-hp aero power ( streamlined ).
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22) 5.2703-hp = 95.333/ 550 [ 0.5 X 0.002375 X 23.783 X 99.333-squared X Cd ( unknown )]
23) 30.406 ( after algebra ) = ( 256.6833 X Cd ) after algebra
24 ) 30.406 / 256.6833 = Cd (unknown ) = Cd 0.1184 ( if all mpg gain was strictly attributed to aerodynamics )

[Talos Woten]

Originally Posted by aerohead

Your car is so 'worthy', I went ahead and crunched a second set of numbers.
... ( if all mpg gain was strictly attributed to aerodynamics )

Hey aerohead!

Here are some well known, reasonably certain Cds:
Full aerofoil 0.045
Half aerofoil 0.09+ground effect
Aptera 0.13-0.15
Aerocivic 0.17-0.19
Tesla Model 0.23
Gen II Toyota Prius 0.26

Claiming that Champrius has a drag coefficient of 0.12 is effectively saying it's somewhere between a half aerofoil and an Aptera, which it clearly is not. I don't know where the flaw is in your methodology, but it's there somewhere.

I personally feel much more comfortable claiming that v3.0 was somewhere between the Aerocivic and Tesla Model 3, which is why my guess is 0.21ish. I will boldly claim that v4.0 will equal the Aerocivic... I feel that good about the new revision.

If people are really curious about the drag coefficient, I can try to do a coast down test when I'm done. Unfortunately, v3.2 has already been taken away by the trashmen, so we'll have to wait until 4.0 is complete.

[Phase]

Originally Posted by Talos Woten

Hey all!

I'm the creator and owner of Champrius, the car pictured here.

She has all mirrors, they are just tiny. US interstate law says we need 10 sq in of area, and that's all I have. In addition, there are three rear cams: one center for backup, and two angled at 45 degrees for either lane.

The thing sticking out of the end was a flexible tailpipe. Which broke, flooded my tail with hot gas, melted my rear bumper, and destroyed version 2.0 of the boat tail. The current exhaust is under the tail, in a welded on steel pipe.

Champrius has been featured in many places including Sloppy Mechanics, Jalopnik, TikTok, and my personal favorite: ****ty Car Mods.

Parallel parking is fine. So is parking in parking spots, etc.

It is indeed a camper. She's Champrius, the Champion Camping Prius. I use her for extended road trips and camping excursions. She's got a fridge, stove, foam mattress bed, signal booster for internet, and all the comforts of home.

I used to have a flexible solar panel, under the tail canopy. Those things are crap and should be avoided at all costs. After three of them failing in quick succession and a whole lot of hassle, I slapped a rigid solar panel on the back and never looked back. I haven't had any problems with it yet, years later.

No glass has been removed. There's white vinyl on it, to reduce heat and for a modicum of privacy. Part of the roof has been removed. I made a small hole with a vent to a temperature controlled fan, to cool automatically when it gets hot. That's also where I route my signal booster.

PM me if you want my address to send me an Ecomodder sticker.

I'm unfamiliar with Judd Engles in Ohio. I'm very familiar with the Aerocivic, which was what version 2.0 was based on. In my latest version 4.0 I'm striking off into bold new territory, where no modder has gone before.

I'll post a thread once I hit 15 posts. Right now the forum isn't letting me do links, and there's a *ton* of useful links regarding Champrius.

I drive on the highway 75%+ of the time. I set the cruise control to 65 mph, and go to sleep. Seriously, I don't use any hypermiling techniques. Any mpg gains are pure aero / mechanical.

In order to make this legal in PA (my home state), I technically had to classify the tail as a trailer. Anything under 2ft can be considered a bumper; anything over is a trailer. So she has a DOT approved trailer light kit. That includes:
red marker lights at the end
yellow marker lights on the side
I didn't need conspicuity tape because it wasn't a minimum of 12 linear feet on edge. Rear backup lights aren't required on trailers, but I've decided to put them on my next version Champrius 4.0 which I'm building now.

Onward!

how do you keep the under belly pan from roasting from the muffler? im trying to do a belly pan and diffuser for my ioniq and my muffler is right in the middle! also why didnt you do a full rear wheel skirt?

[Talos Woten]

Originally Posted by Phase

how do you keep the under belly pan from roasting from the muffler? im trying to do a belly pan and diffuser for my ioniq and my muffler is right in the middle! also why didnt you do a full rear wheel skirt?

In version 1.0 I didn't. I covered everything with coroplast. Consequently, the car cabin overheated, it charred the belly pan, and I had to scrap the whole thing and start over.

In 4.0, I'm using two cat shields made out of aluminum to cover the catalytic converter and resonator, which are also in the center of my underbelly. I'm leaving the muffler exposed, because it's off to the right. If I were to cover it, it would be with a metal sheet, and I'd make sure that it had an opening in the rear for hot air to eject. Not just the tailpipe, I mean an opening the size of the muffler itself. (This assumes there's some way for air to also get into the same channel. On my car, the muffler is right behind the rear sway bar, so that's not an issue.)

I originally tried out full wheel skirts, and they definitely work. But a) the front wheels had too much flutter, negating the aero benefit, and b) they were a pain for servicing. I eventually moved to the slim fairings I have on Champrius now. They gave me 75% of the benefit of the skirt in the rear, and actually performed better than a skirt in the front. So ultimately I choose the lighter, easier to service, less hassle option that had equivalent fuel economy.

By the way, I also tried a half dozen different variants of side skirts, catamarans, wheel tails, etc. and concluded they are all crap. They don't improve mpg, and in some cases interfere with subtle aero-shaping that's already in play on the Prius (in particular near the rear wheel spats).

Last but not least, I believe that air curtains are the way to handle the front wheels, rather than a skirt of any kind. That's from multiple perspectives: performance, safety, and serviceability. That's what I plan on putting on 4.0.

[Phase]

Originally Posted by Talos Woten

In version 1.0 I didn't. I covered everything with coroplast. Consequently, the car cabin overheated, it charred the belly pan, and I had to scrap the whole thing and start over.

In 4.0, I'm using two cat shields made out of aluminum to cover the catalytic converter and resonator, which are also in the center of my underbelly. I'm leaving the muffler exposed, because it's off to the right. If I were to cover it, it would be with a metal sheet, and I'd make sure that it had an opening in the rear for hot air to eject. Not just the tailpipe, I mean an opening the size of the muffler itself. (This assumes there's some way for air to also get into the same channel. On my car, the muffler is right behind the rear sway bar, so that's not an issue.)

I originally tried out full wheel skirts, and they definitely work. But a) the front wheels had too much flutter, negating the aero benefit, and b) they were a pain for servicing. I eventually moved to the slim fairings I have on Champrius now. They gave me 75% of the benefit of the skirt in the rear, and actually performed better than a skirt in the front. So ultimately I choose the lighter, easier to service, less hassle option that had equivalent fuel economy.

By the way, I also tried a half dozen different variants of side skirts, catamarans, wheel tails, etc. and concluded they are all crap. They don't improve mpg, and in some cases interfere with subtle aero-shaping that's already in play on the Prius (in particular near the rear wheel spats).

Last but not least, I believe that air curtains are the way to handle the front wheels, rather than a skirt of any kind. That's from multiple perspectives: performance, safety, and serviceability. That's what I plan on putting on 4.0.

thankfully my ioniq already has front air curtains built in from hyundai

im going to be making a metal rear wheel skirt in a few weeks, hoping to also do a belly pan. hyundai already includes a front and center smooth under body, but the rear is totally exposed and the muffler is horizontal and right in the center!

[Talos Woten]

Originally Posted by Phase

thankfully my ioniq already has front air curtains built in from hyundai

im going to be making a metal rear wheel skirt in a few weeks, hoping to also do a belly pan. hyundai already includes a front and center smooth under body, but the rear is totally exposed and the muffler is horizontal and right in the center!

Let us know how much mpg you get from the skirts! It's helpful to compare between cars.

All I can say is that my respect for automotive engineers has gone up considerably since I started modding my car. I remember reading a paper about how a wheel spat 40mm high and placed precisely there improved mpg. I went to install them on my car... and discovered it already had them.

Anyhoo, I wouldn't put it past some clever engineer to design a virtual diffuser using the heat from your muffler or somesuch.

[Phase]

Originally Posted by Talos Woten

Let us know how much mpg you get from the skirts! It's helpful to compare between cars.

All I can say is that my respect for automotive engineers has gone up considerably since I started modding my car. I remember reading a paper about how a wheel spat 40mm high and placed precisely there improved mpg. I went to install them on my car... and discovered it already had them.

Anyhoo, I wouldn't put it past some clever engineer to design a virtual diffuser using the heat from your muffler or somesuch.

i think thats what hyundai was going for when they put the muffler underneath horizontally. its curve at a slight angle too. its like a messy rear diffuser. i mean obviously a smoother underbody panel would be cleaner and allow better airflow, but i think they did the best they could with a muffler

i need to smooth it totally out so i can add a proper and extended rear diffuser, like the mercedes eqxx has!

and from my coast down quick testing with rear wheel skirts, i saw a 1mph improvement from baseline, and from everyone elses tests of their rear wheel skirts, and even light year one/zeros tests, it seems like it only nets about a 1 mpg gain, give or take. better than nothing, but only about half the drag reduction as say, removing side mirrors

[freebeard]

Originally Posted by Talos Woten

Anyhoo, I wouldn't put it past some clever engineer to design a virtual diffuser using the heat from your muffler or somesuch.

This was just a thought experiment, it doesn't consider intake air:



The stock VW Beetle has about 1500cfm of hot, corrosive exhaust gases and 1500cfm of engine cooling air. A 4-into-1 header feeds a 90 degree elbow into a vertical stainlees steel stack perforated on it's front face. It is surrounded by a stainless steel heat shield forming a Coanda Nozzle conforming to the shape of the truncated boat tail.

The engine cooling air is open to the bottom of the stack and is entrained and sucked out of the cooling ducts, augmenting the stock fan with it's undersized pulley.

"What do you think sirs?" MST3K

[aerohead]

At 100km/h ( 62-mph ) the Beetle is displacing about 103,664 cfm of atmosphere.
We'd want to look at blown/suction slot technology, and see what percentage of total 'flow' volume is required to make a showing.
And Georgia Tech would probably be the place to contact.