66 mpg 2009 Totoya Prius, Champrius 4.0 Under Construction now

[Talos Woten]

Howdy all!

I'm the creator and owner of Champrius, the Champion Camping Prius. (pronounced with stress like champion, not like Prius). My last revision of her (3.0) peaked at 66 mpg @ 65 mph unladen and got 61 mpg in real world use.

In March 2022 I had a fender bender that destroyed the boat tail and decided to do a major upgrade. I thought that the ecomodders here might like to follow the engineering odyssey. It will all be posted on Instagram; here is a good place to start:
https://www.instagram.com/p/CeeL6xyFp-k/
However, if you have in depth questions about the build I can answer them here. (I often exceed the Instagram message post length. ;-)

My goal this time around is to top 70 mpg in real world use, which is basically setting the cruise control to 65 mph on the highway and going +5 over the speed limit everywhere else. For those curious, my figures have virtually no hypermiling. The most I do is long slow stops for safety, which as a side effect helps regenerative braking and occasionally helps me avoid stopping. When I was doing active hypermiling, I was able to squeeze a good +10-25% improvement, depending on conditions. But that not only required a lot of attentiveness, it's not how most people actually drive. I'm interested in "fire and forget" improvements that could reach the mainstream.

Champrius has been around for years featured several places, including this forum. This thread has some good images (some of it obsolete stuff I've removed):
https://ecomodder.com/forum/showthre...tml#post616905
while this one has tries to reverse engineer some values:
https://ecomodder.com/forum/showthre...tml#post635155

It's also been featured on Jalopnik:
https://jalopnik.com/check-out-the-a...1832590335/amp
and all over Reddit, including r/WTF and my personal favorite r/Shi ttyCarMods. There have also been some viral TokTiks, etc. (Actually, I laugh my butt off when someone in the comments on Reddit says to sort the group by most popular posts... and 3 of the top 5 end up being about Champrius.)

Last but not least, I've discovered a new ecomod that I'd like to share, which was another reason for finally joining the forum. Here it is:
https://ecomodder.com/forum/showthre...tml#post669246

Enjoy!

[Talos Woten]

I've hit a milestone! The new 4.0 version of Champrius under construction just topped 50 mpg!
https://www.instagram.com/p/Ce30CVQLQWk/

There's still a lot to do. I already know the tail will give me several mpg, and I have high hopes for the new nose cone.

For those interested, here's the current list of mods that got me from 39.2 mpg to 51.3 mpg:

DELETE: +% mpg gain [cost, time]
1.5% Rear and Passenger seats [$10, 2 hrs]
1.0% ~1/3 of the interior [$10, 4 hrs]
1.0% Antenna [$0, 2 hr]
1.0% Rear Windshield Wipers [$10, 2 hrs]
0.5% Rear spoiler [$0, 2 hrs]

REPLACE:
4.0% Tiny side mirrors, added vortex generators [$40, 4 hrs]
3.0% Smooth moon hubcaps from pizza pans (rear only atm) [$100, 6 hrs]
2.0% Max tire pressure 44 psi of low resistance tires [$0, 10 min]
0.5%+ Hood insulation (better colder / short trips) [$50, 2 hrs]
0.5% Gas Cap, Radiator Cap [$30/100k, 20 mins]
0.5% Air Filter[$20/30k, 15 mins]
0.5% Synthetic oil [$80/10k, 2 hrs] with oil catch can [$40, 4 hrs]

ADD:
5.0% Extreme grille block to 40 sq in [$20, 15 mins]
4.5% Solar Panel as partial Kammback [$500, 6 hrs]
3.0% Dual Cat Shields [$300, 8 hrs]
3.0% Windshield wiper deflectors [$40, 2 hrs]
2.5% Wheel fairings (partial skirts for easy maintenance) [$50, 4 hrs]
0.0% Shrouded ceiling vent + signal booster [$200, 4 hrs]

[Phase]

Can you go into detail about the VGs with the smaller side mirrors? I replaced my super silent factory side mirror with a hand crafted mini side mirror, but the wind noise is insane from it and really annoying at higher speeds.

[Talos Woten]

Originally Posted by Phase

Can you go into detail about the VGs with the smaller side mirrors? I replaced my super silent factory side mirror with a hand crafted mini side mirror, but the wind noise is insane from it and really annoying at higher speeds.

Hey Phase! Sure.

First of all, I bought the mini side mirrors. They came with already curved backs, and were 5 sq inches in area, which was exactly what I was looking for. So I don't know what can be done about your hand crafted mirrors except to shroud them with a smooth manufactured shaped.

As for the vortex generators, VGs are used to re-attach flow separation to a surface, like behind a mirror or to a back windshield / trunk that's concave to the airflow. They "inject" higher pressure air into a low pressure "shadowed" zone. Both airflows are turbulent, but when properly used the VG causes earlier re-attachment and thus better flow.

Each VG comes with a characteristic length L and width W. They are usually designed so the two are comparable. You want the turbulent unattached zone to be between 1L - 3L behind the VG, and if large enough, to place multiple VGs around 1W-2W apart. (Placing them closer than 1W at best does nothing and at worst interferes with each other.) Also note that we want at least 2L flat surfaces ahead of the VG for effectiveness, but often we can't get that near a mirror. (It's much easier on a roof, say.)

To give you real numbers, the gaspods I'm using have L = W = 3 inches. So I want to place them 3"-9" ahead of the separation point from the mirror, and around 3"-6" apart.

To find the separation point one can use tuft testing / smoke injection / look at the mirrors in a rainstorm / anything else that visualizes airflow around the mirrors. If you know the W and L of your VGs, place the tufts around 2L apart horizontally and 1.5W apart vertically. See where the flow becomes separated and put the VGs ahead of it.

You can see videos of me tuft testing here:
https://www.instagram.com/p/Ce13TiGFm0_/
and I'll take a pic of my current setup and post it in a moment.

Note that mirrors are notoriously finicky and you shouldn't use my setup as a template. I've seen other cars where the optimal placement was below the mirrors, they needed 3 VGs to cover the whole separation, they were placed differently, etc. Also note this isn't the optimal placement even for my car; it should be an inch ahead and both two inches lower. But there wasn't nothing to stick them to, so I had to compromise putting them on the mirror plate.

Be aware that VGs can also make a whistling noise. I originally used the gaspods on the front edge of my spoiler, where it met the rear window. It gave me a whopping +7-11% FE, depending. For an already optimized car, that's astounding. I took them off a week later, because they caused a heinous low level shriek. I'm an audiophile, and the improved mileage wasn't worth going batty from the noise.

Last but not least, if you are custom crafting your mirror, then I've seen other VG variants that might be more suitable for you. One had very tiny L = W ~ 1 inch VGs along the outside rim of the mirror. It directly injected air into the shadow (instead of onto the side of the car like I'm doing). Another is a flat flap used like a winglet on an airplane wing. That has the dual use of being a vortex stopper and a VG. Anyhoo, those might be appealing options.

Hope this helps!

[Talos Woten]

A picture is worth a thousand words. Enjoy!

[alexshock]

Originally Posted by Talos Woten

A picture is worth a thousand words. Enjoy!

Looks too big.

Haven't you tried to copy Toyota's OEM vgts?
Like this: https://m.media-amazon.com/images/I/...AC_SL1500_.jpg

[Talos Woten]

Originally Posted by alexshock

Looks too big.

Haven't you tried to copy Toyota's OEM vgts?
Like this: https://m.media-amazon.com/images/I/...AC_SL1500_.jpg

That's actually what the handmade ones I had before looked like. But from what I could tell on the tuft and mpg tests, it didn't seem to matter.

Also, I placed one higher up because it straightened out the lines that flowed over the roof, which were pretty chaotic before.

Hmmm... I wonder if it might even be better to *remove* the one near the mirror instead. Something to experiment with someday.

[Piotrsko]

For what I understand, they are mounted backwards: the blunt should be facing rearward. So what is your logic process to install them?

[Talos Woten]

Originally Posted by Piotrsko

For what I understand, they are mounted backwards: the blunt should be facing rearward. So what is your logic process to install them?

They are mounted correctly. Different VGs have different orientations. You might be thinking about triangular VGs, which are often placed fat side to the back of airflow. These are aerofoil VGs called Gaspods:
https://aerohance.com/

As for the logic process... I detailed that just a few posts ago:
https://ecomodder.com/forum/showthre...tml#post669668
Let me know if you have more specific questions.

[Talos Woten]

Well, we might be seeing the beginning of the end for Champrius:
https://www.instagram.com/p/CfHZAqXFjB3/
Something in her radiator just failed and it doesn't seem safe to drive her currently.

I'll keep peeps posted, but it's going to be a week before I can even get into a shop to see what's wrong.