Prius Offroad 1.5" Lift Spacer Review

My goal was improving cross winds that frequently exceed 40mph. It achieved that, and increased my fuel mileage, also oddly enough keeps the bottom of the window a lot cleaner when it rains as well as the channel around the hatchback that used to fill up a lot with stuff. I'm guessing it's not necessarily about lift in this case, but about keeping the air sticking to the car down the middle of the window. In turn that helps keep the air separation down such that it's a reduction of drag enough such that I'm seeing a 3-6mpg difference. The biggest effect oddly enough is when the car is at higher speeds. 40 miles of my 70 mile commute I'm traveling 80mph in a 70 or whatever traffic is doing which is sometimes 90mph on long straight on the interstate and I'm still averaging 60+mpg every day on michelin defender tires no less. BTW my daily driving is anywhere between 140 miles and 230 miles a day. When new, if I traveled any faster than 75mph I would net less than 55mpg average.

 

Also, they did put these on the Prius. See Prius TRD of which, parts can be ordered online and oddly enough the reason I was inspired to buy these by someone else who had those TRD parts and loved the effect on cross winds. But I didn't feel like spending 300 bucks for an experiment. Mine were still easily removable, but since they achieved the exact purpose they were designed to fix which was the cross winds and also assisted with the fuel mileage. It's kind of a no brainer spend of 20 bucks and 20 minutes dialing it in. They've paid for themselves many many times over in the last 100k miles. Seriously, I drive 50k miles a year.

 

If you want to know what's actually going on with the airflow over the rear window, here's an easy test you can do. Cut some yarn tufts, 2-3" long, and tape them in a grid pattern on the window. Wait for a windy day, then go for a drive on a road perpendicular to the wind direction. Try it with the vortex generators removed and then taped in place; better yet, try it with the VGs in various spots. Have someone take pictures or videos of the tufts. No guessing required.

What you'll end up with are images like this. Attached flow:


Separated flow:


If you didn't test/observe/measure, then you don't actually know what's going on with the airflow over a car. I've been testing for a few years now (and went back to school to get an aerospace engineering degree), and 9 times out of 10 my guesses are wrong. One test is worth a thousand opinions.

 

Why would I go back and test what's already working as an improvement? My car used to try and pull me like hell off the road in 30+ cross winds. It no longer does that. The channels around the hatch and even the seal used to require a lot of cleaning of leaves and whatnot. Guess what, it no longer does. I can also see the increased dust accumulation behind the generators going down the window which leads me to my guess.

 

I understand your reticence to test; I was the same way for a long time, and most home aero modifiers are. But it's quite easy to fool yourself into thinking something has changed in how a car feels to drive or ascribe a change in gas mileage to a certain modification with no controls on other variables like the weather, traffic, routes, speeds, winds, etc.--and equally as easy to get actual evidence that what you think is happening with the airflow over your car is or is not in reality.

In addition to a simple tuft test, you can measure crosswind stability by logging steering angle as you drive in a crosswind with various modifications (example here). Either of these will give you objective data beyond what you feel is happening.

Example: tuft testing with and without fins--




(Also note: in areas of attached flow, you will generally find less dust/dirt accumulation, and in areas of separated flow, more accumulation).

 

How many miles do you have on your shocks and struts?

 

Just over 171k as of this week. Still have the original spark plugs too.

 

Your shocks are worn out which causes your car to sway more in the wind

 

I'd believe you except, when I installed these about 3 years ago, I had less than 40k on the car back around december of 2020. I've had it since it rolled off the lot in December of 2019 as a new 2020 prime. It achieved the purpose then and still now and I've been saying the same story since.

 

May I inquire which gen is the "turd gen", and I have just placed an order for this lift kit. I was visiting a friends house and got stuck in his gravel driveway because of the angle of ascent... yeah that was embarrasing

 

3rd. Put it in maintenance mode do a good burnout the whole way up the hill

 

I'm curious if you've done anything to improve your fuel economy and what it was. I like the approach you're using. I do notice that the passenger mirror has been deleted.

 

huh? what? where?