2020 Prius Prime- Looking for tasteful Highway aeromod
 

Like the subject says, I've got a 2020 prius prime LE for work, and 45 miles of my commute is at a speed of 76-80 just to keep from getting run over on California interstate. I do a lot of IT stuff so I'm constantly going in and out of the car between customers etc. The rest of my commute I do very well at slower speeds. But that part of my commute I'm only getting 40-45mpg and I'd like to get closer to the 65+ I get on the rest of the time when I'm not covering high speed highway. My average on my over 200 miles of daily driving is around 63.5 plugging it in every night which nets me 30-40 miles of electric or roughly 5 mpg daily average increase.

I'm looking for some simple yet not intrusive mods to help out with the highway if it's possible. I figured I'd check and see if you all have any ideas.

-Kevin

To get the MPG you're talking about, we're talking serious boat-tailing, and even then it would be difficult at 80 MPH.

Minor mods will improve efficiency a minor amount. Major mods will improve efficiency a major amount.

All the usual mod options exist for your vehicle: partial grill blocking, moon disc wheel covers, rear wiper delete, aero treatment to the rear, increase tire pressure...

https://ecomodder.com/forum/member-f...7-12-29-57.png
Ignore the 911 cooling fan, that was to make a different point. This shows Moon disks and wheel spats.

Are those snorkels on the front active air curtains or no? I can't find any discussion. It's fairly well optimized from the factory, adding length with a boat tail or boxed cavity would help the high-speed aerodynamics but compromise parking, etc.

Else, stance it.

https://i2.wp.com/www.toyotacarsq.co...80%2C460&ssl=1
https://i2.wp.com/www.toyotacarsq.co...80%2C460&ssl=1

Everything they said above... also, you don't have to do moon discs, which you might imagine are not "tasteful." There are effective alternate designs. See this thread: https://ecomodder.com/forum/showthre...s-37690-2.html In post #12 of the thread I showed some data and some studies indicating certain other designs can be about as effective as moon discs.

If aesthetics are a problem, just add googly eyes

https://i.imgur.com/DhDzaAk.jpg
https://i.imgur.com/DhDzaAk.jpg

Googly eyes solve that. Beam me up Scotty, no aesthetics here ;)

There's little low-hanging fruit left for aero improvements on a 2020 Prius...
Maybe a small air dam or front splitter like lip.
Just do the other stuff. Remove weight and air up the tires, nobody sees that and it helps a couple of %.

Paint it black with white doors and JAPD in big golden letters (for Just A Prius Driver) so you can drive as slow as you like without getting bothered. Oh, aesthetics?

BTW- buying the Prius is like paying for a factory ecomodded vehicle. They've done the heavy lifting already. Heck, my wife gets nearly the same fuel economy as me trying, which means they've removed most of the simple techniques to save fuel.

I disagree with a lot of the above; Toyota claims a drag coefficient of 0.25 for the Prime, identical to the 3rd gen 2010-2015 Prius. There's room for improvement.

The Prime has active grill shutters, but a permanent partial grill block might still be helpful. There's no rear wiper on the Prime already, and no air curtain ducts. Trying to add internal ducts would be quite difficult since Toyota puts the signal lights right where the inlet should go. If you don't mind the look, I added external air curtain ducts in front, and am fabricating a similar design for the rear this weekend.

As far as other unobtrusive modifications: remove the passenger mirror (I think California requires the driver's mirror). Swap on some lowering springs. Enlarge the wheel air dams. Add fairings to those air dams from another car (I used the fairings from the 2014-2018 Ford C-Max Hybrid). Move the antenna inside the car and fill the hole in the roof or wrap over it. Increase the closed area of the wheel covers. That's about it for the easy stuff; then, you're looking at building a spoiler extension or tail, maybe like this guy.

Well, I'm thinking that it's already so efficient, it won't take much to increase it by much at that speed. I'm okay with the idea of the racing discs if I can actually get 2mpg out of them at speed.

76-80
 

The Tesla Model X has the same drag coefficient as your car.At 55-mph,it's road load is 15.9-horsepower.At 80-mph,that grows to 36.2-horsepower,more than double.It experiences the velocity-cubed relationship for power consumption.
As mentioned by others already,speed is your enemy,and no token effort will make any appreciable difference.'AeroCivic-ing' your Prius would be your only option.

2 mpg
 

You'll never see it.

Your speed is the biggest mod you can make. Aero drag goes up fast as speed increases gradually. A quick google search gives the below graph.

I commute on California freeways in my modified 1998 Civic daily, and I average 60-65 mph. Sometimes I am as slow as 55. I can pull around 60 mpg on average doing that (lots of technique involved). I do not get run over or cause a backup. I am in the slow lane, usually with other vehicles like trucks and other pokey cars. I imagine you are in the HOV lane and there, you get pushed by other drivers even at 70 mph, drivers who have no lawful way around you.

https://ecomodder.com/forum/attachme...1&d=1582400276

What tires and pressure in them? My 2005 gets similar numbers at that speed with the tires at about 40PSI; even with snow tires it's still pretty close.

I have driven on California highways. Slowing down is a bad idea. Good way to get ran off the road by someone with no insurance.

This is on interstate 5 basically going between 152 and 580. Headwinds are painful. However, some days, like yesterday, I can stick to 76mph and do pretty well. I averaged 108mpg over 72 miles using electric and gas and still had 7% of the battery left when I got home. I keep my pressure at whatever the dealer sets it at. I gotta say Toyota did a pretty good job with the Prius prime 2020.

So, what are your modding plans?

I own a 2017 prius, not a prime model and don't see the problem. Yesterday i drove two hours non stop with the cruise set on 80 mph and averaged 57 mpg. Any car that returns mpg numbers of over 45 mpg at those speeds should be nothing to complain about. Aero mods may get your more mpg at those speeds but at what cost versus payback?

Please stop depending on the dealership to set your tire pressure. The odds are very high that they set your tires to the wrong pressure. A nice digital tire gauge costs less than 10 bucks and properly used can easily improve your mpg at all speeds. Ignore what tire pressure is “recommended” by Toyota and read your tires themselves and set at max psi listed on them. For example, my prius recommends 42 psi, tires max is 50 psi. I get a 4 mpg bump at 50 vs 42.

I ask shops not to mess with the tires. They are happy to not do something and charge full price.

My 2017 came with free oil changes for the first 3 services. 5 weeks after buying it i took it in for the first one. Yes, 10k miles in 5 weeks. Hour drive to the dealer, 2 hour wait and hour drive home. The salesmen tried to get me to pay for an alignment on the first service as in his words “toyota recommends and alignment at 15k miles”. I smiled, handed him the owners manual and asked him to show me where it says that. Furthermore, i told him that the car was just purchased 5 weeks ago and if the alignment is off it should be covered under warranty. Got a free alignment that day and the car has never been back to the dealer, even for the “free” oil changes. I can do them myself for roughly 30$ and 30 minutes of my time vs a half a day using toyota filers and mobil 1. The stealerships can pound sand.

I drive a van at work. The placard in the door says (I believe) 44psi front, 48psi rear. The dealer fills them to 32.

Aeromods in heavy traffic?

Seriously, if you have to stay in the high 70s to keep from becoming a statistic, the surrounding traffic is your aeromod. You've got the corridor effect going on: cars in front, behind and all around. Not that it's a cure-all. I've found (in my car, on my roads, YMMV) that drafting a good 18 wheeler is good for 10 mph. That's best case- drafting behind a big rig at steady speed, I get the same mileage as I would hypermiling in open air at 10 mph less. So behind a truck at 70, I'm getting what I'd see on my own at 60.

Except your corridor isn't made by professional drivers at steady speeds, it's made by psychopaths that make it unsafe to drive more slowly. So you're not going to get optimal results from that corridor. But in traffic that heavy, I think aeromods are a waste of time.

Back when I could go out on the Interstate (;)), I found the best result with a full-widith half-height load on a flatbed. Less buffeting than with a full-height box van.

Update, I did digging, worked out some visuals. I installed a few vortex generators around the center behind the antenna in the back plastic piece with a separation of about 11 inches at the farthest points. Gave them about 20 degrees angle. Doesn't really change the fuel mileage much if at all, but certainly seems to increase the wind envelope stability when passing trucks, etc. I didn't have a ton of cross wind today. But I'm hoping to see how well it does in the nasty crosswinds we have been getting as of late.

18 wheelers going 70 mph? :eek: That even sounds dangerous. On the other hand, driving behind such a monster at that speed is some serious hypermiling! In Europe they're all limited at 55 mph.

As mentioned in other posts, not much to be gained from increasing mileage from that point. If gas is $4/gal and you make the MASSIVE change from 45mpg to 60mpg, over a 180 mile trip you'll save $4.

The question becomes: at what effort/cost?

70 mph? Going down a mountain on a straight highway you better keep an eye on your mirrors no matter what speed you're going. The semis use gravity to get to extreme speeds. Something you have to be aware of if you rent a car in the States as an European. Some I've seen fly by must have hit 100 mph or more.
Also, if you are on an incline near the crest of a mountain and there's a semi climbing slowly up ahead, better not pass but stay behind it.

Once when I was 15, I was driving the family van north on i-5 coming down the Grapevine at 80 MPH, and was passed on the right like I was standing still by an 18 wheeler.

Generally the speed limit for tractor/trailers is 55 MPH and they do 60. On roads where the limit for everyone is 75 or 80, I see the truckers going 70 or more.

The grapevine is a dangerous place for truckers. The one that passed you may have very well lost his brakes or other serious issue.

As for where trucks tend to speed, it's kind of the same as we cars. Where it's plain and simple safer for them to do so they will. Where it's not, they won't. Truck drivers in general are significantly safer drivers than car drivers. It's not 100 percent, but statistically, they are a lot safer per mile than car drivers. The big thing with car drivers, they need to be aware of what trucks will need to do in a turn etc. Aka, if you are on a wide freeway exit, don't pass them on the right. Wait...

Okay, my vortex generators were apparently more effective than I thought they would be. Consistently, I just recorded two back to back record fuel mileage days doing the same 80mph speeds on the same route. Even going directly into the wind I'm getting well into the 40s where before I'd be in the 30's. Going with the wind is better too, the window in the back seems to stay a bit cleaner too. I think I'm going to make something like the toyota prius TRD roof garnish, but a bit smaller as it's become apparent that I can use the small window bubble down effectively to achieve the result I want.