When people learn that I work as a professional racing mechanic they often expect that I have some sort of hot hatch or something equally rambunctious at home, but most would be surprised to learn that I now spend most of my time in a Toyota Prius Prime. While the Prius Prime is almost exactly the opposite of a hot hatch out of the box, I believe that the Toyota TNGA-C platform that it’s based on allows for it to be turned into something fun without too much effort.
The goal with my daily driver is to combine my skill set as a parts manual enthusiast with my skill set as a professional racing mechanic and modify the Prius Prime to handle as well as it looks and take you guys along with me in a written build series we’re calling PROJECT: OPRIUS PRIME.
I spend a lot of time on the road between my various gigs so I’ve always sought something fun and engaging as my daily driver which is how I ended up with a new Subaru WRX in 2015 that I ended up putting over 200,000 miles on. As the WRX was reaching that 200k mark, I started looking around for my next daily, and while the new WRX seemed to offer similar handling characteristics I just couldn’t get along with the looks of all the new cladding. My attention turned to other similar cars but nothing really stood out.
The Prius wasn’t in contention, initially, but I had an opportunity to borrow one for a week in January and after just a few hours of driving I started to seriously consider getting one for myself because of how well it handled in spite of being more focused on efficiency than being an enthusiast vehicle.
I brought that borrowed Prius into my shop and quickly discovered that much of the suspension mimics that of what you might find underneath other TNGA-C based vehicles like the GR Corolla, which gave me hope that I might be able to find parts to make it drive in a more compliant manner if I decided to purchase one.
All of this consideration for the Prius really sprouted from the striking redesign which took the Prius from an oddly shaped efficient appliance to a fun modern wedge. As with previous generations, much of the design was focused on aerodynamic efficiency which resulted in a slippery body with a drag coefficient of 0.27 cD. In comparison, the Lexus LFA has a drag coefficient of 0.31 cD and my old WRX is rated at 0.34 cD. After spending a week in that borrowed Prius I decided that I needed to find one for myself but, because I wanted a fun color, the search ended up taking multiple months.
My Base Prius
Eventually, I found a Prius Prime SE in Supersonic Red near me in Charlotte, North Carolina and was pleased to find out that it didn’t have a bunch of random options tacked on as that $425 special color was the only additional charge on the window sticker, which brought the MSRP to $34,495. I ended up trading in my WRX for $4,300 and leasing the Prius Prime to get $4,500 in lease cash that was being offered by Toyota.
As soon as the lease account was created I went to my credit union and bought it out which resulted in a net cost of around $31,400 plus taxes and fees that ended being brought down to $27,100 plus taxes and fees with my WRX trade. My net financed cost after all was said and done ended up being $28,480 which I was extremely pleased with considering that I was able to find a color that I liked.
As soon as I left the lot I started monitoring the fuel economy because my competitive nature always finds new benchmarks to chase and, since the car was filled up and fully charged, I ran on EV mode for the first 39 miles so of mostly highway driving. Once the EV range was depleted, the internal combustion engine switched on and I drove around like that for a couple of days and, with my driving style, I ended with a 57 average MPG number on the dashboard.
Eventually, I started plugging the car in and it started figuring out my driving style, which resulted in that EV range hopping up as high as 45 miles, though I typically saw around 40 or 41 miles of range with the air conditioning cranked up. While my charging has been somewhat inconsistent, I’ve been able to raise that average fuel economy number to 76 MPG, which is more than a 50 MPG improvement over my WRX and has resulted in me using only 69 gallons of regular gasoline over the two months that I’ve owned it, compared to the 210 gallons of premium that I would have used in the WRX for the same period. The fuel savings are significant enough that they offset a large portion of my monthly payment.
It’s Great, But I Can Make It Great (Or Maybe Worse)
I may nerd out about the PHEV elements and the charging setup that I’m building at some point in the future, but the really fun stuff lies in what’s underneath the car and whether I can successfully turn it into a hot hatch competitor. The Prius Prime handles incredibly well for being an efficient hatchback that isn’t intended to have sporting intentions, but coming out of the WRX and enjoying North Carolina back roads pushes me to bring the Prius to higher handling standards.
One of the first things that I noticed when I took it on some back road jaunts is that the Prius is pretty compliant but tends to lean towards understeer in most situations, which isn’t unusual for this class of car. In addition to the overall handling characteristics of the suspension, it’s also pretty easy to overpower the tires as the OEM Toyos are focused on minimizing rolling resistance.
With all of that in mind, I decided to start with the rear anti-roll bar as it’s a piece that’s shared with the Toyota Corolla hatchback and the Toyota CH-R, so there were already some options on the market. Increasing the rear anti-roll bar size by a couple of millimeters would be the first step in curing some of that understeer and helping loosen up the car a bit on those curvy country roads, so I picked up a 27mm adjustable rear anti-roll bar from Progress Technology. The next step in my hunt for handling improvements was also partly cosmetic as I wanted to find some lowering springs to close up fender gaps while also increasing the spring rate just slightly.
I ended up finding some TEIN High Tech springs on Yahoo! Auctions in Japan and decided to try my hand at purchasing some parts overseas through a service called Buyee. I ended up winning the springs for around $143 and after Buyee fees and shipping fees my total cost was around $185 and I had the springs in hand around two weeks later. This was a trial run for additional purchases as there are already a lot of handling and cosmetic components available for my Prius in Japan. The springs offer a mild increase in spring rate to 146 lbs/in front and 202 lbs/in rear which should improve responsiveness, but they also introduce a bit of rake as the front gets lowered by 25 mm while the rear is lowered by 20mm which should help contribute to improving the understeer situation as well.
My initial plan was to acquire OEM GR Corolla suspension parts as my research led me to find out that most of the suspension hard points match up, but unfortunately purchasing all the individual bits and pieces ended up looking like a costly affair so the current part for the next step in this series will likely involve research for things like wheels and tires along with starting to look at coilovers. The Prius Prime rides on a 195/60R17 Bridgestone Ecopia EP422 Plus tire that’s wrapped around a 17×6.5 +40 aluminum wheel with an aero cover, and while they are functional I am looking to get something a bit more stylish and possibly larger.
They're no saladshooters, but I think they could work. pic.twitter.com/dsAuya5x8u
— McMike (@ItsMcMikeTime) June 14, 2024
The current top runners for OEM wheels that fit are the Toyota Camry TRD and Nightshade wheels, along with the Lexus SC430 pie plate style wheels. Once I find a wheel that I like, I will match it up to a tire but the current most likely scenario is that I’ll end up with a set of Michelin Pilot Sport 4S tires because I’ve enjoyed them so much in the past.
Before I start making any changes, I plan to take some measurements so that I have a baseline worksheet much like I’m used to in racing so that I can track changes as they are made and work towards my goal of turning the Prius Prime into a hot hatch.
For now, the Prius Prime is serving it’s duties as my commuter around town and for race weekend trips with excellent efficiency as I collect parts to improve the handling alongside setting up a permanent charger outside of my garage in order to improve my charging habits.
I’d do the suspension stuff and wheels and tires last. If you want it to look rad, big diameter/wide wheels are sweet, but I think you’re going to significantly pay for it compared to LRR. I’d go with the pie plates as they look cyberpunk but are very aero and not as wide.
The bigger wheels and stickier tires will absolutely have an impact on fuel economy but I’m charging the car frequently enough now that the time I am spending in EV mode should still keep me fairly ahead.
Yeah… I get it. But like…. sometimes more grip isn’t more fun. Think BRZ when it came with prius tires. Might be more fun with less grip?
You might have a different opinion if you heard the sounds that these Ecopia tires make when pushed.
haha. Maybe. I love the idea; I really don’t understand why automakers haven’t been doing this with hybrids since ever. I have a 1st gen insight, and if they had just made the exact same thing with a gear ratio from an HCH and a rear swaybar, it would have been a perfect OEM+ “Si”. Same with the older Prius’s… Priuses…. Prii? Just slap some more aggressive springs on it, change some of the colors inside, and reprogram the CVT to be a bit more aggressive, bam, TRD Prius. Seems like a really low cost way to make their lineup more fresh, and make some money.
I love this!
I love this!
I’ve done a lot of similar changes to my 2014 Corolla when I bought it in 2016. Lowering springs, bigger rear roll bar, strut bar up front, aftermarket wheels. Also did aftermarket exhaust and intake.
I even had it on coilovers for a few years before I put the lowering springs back on. With the coilovers I ended up taking it offroad in Utah, which it was wholly unsuited for.
I still love how it looks, but my back would appreciate something that can handle my city’s terrible roads with a little bit of softness. Been considering putting the suspension back to stock. Bozi’s adventures might give me the push I need to do it.
That’s partly why I’m taking a less intense approach to start especially when it comes to things like the lower springs which are only a minimal increase in rate and still rated lower than even the OEM springs on the GR Corolla.
I’ve done a lot of similar changes to my 2014 Corolla when I bought it in 2016. Lowering springs, bigger rear roll bar, strut bar up front, aftermarket wheels. Also did aftermarket exhaust and intake.
I even had it on coilovers for a few years before I put the lowering springs back on. With the coilovers I ended up taking it offroad in Utah, which it was wholly unsuited for.
I still love how it looks, but my back would appreciate something that can handle my city’s terrible roads with a little bit of softness. Been considering putting the suspension back to stock. Bozi’s adventures might give me the push I need to do it.
That’s partly why I’m taking a less intense approach to start especially when it comes to things like the lower springs which are only a minimal increase in rate and still rated lower than even the OEM springs on the GR Corolla.
Aktcshually that’s a Model Y. The council of bad panel gaps will decide your fate.
Aktcshually that’s a Model Y. The council of bad panel gaps will decide your fate.
I wish toyota would do a sportier prius from the factory! I had one as a rental earlier this year, and actually liked it.
It would be fun to see some suspension treatments to it. Even if it’s fairly basic stuff like they did for some of the special Corolla trims before the GR became available.
I wish toyota would do a sportier prius from the factory! I had one as a rental earlier this year, and actually liked it.
It would be fun to see some suspension treatments to it. Even if it’s fairly basic stuff like they did for some of the special Corolla trims before the GR became available.
do NOT alter the brake calipers on the prius. it has brake by wire and you will ruin the brakes because there is no way to calibrate the programming for the larger calipers. find you some quality performance pads like from from ECS, swapping the fluid for high temp fluid , switching to stainless brake lines and upgrading the tires will be more than enough braking for this car. the regenerative braking on the prius prime does most of the stopping on the car anyway
Hate to brake it to you (pun intended) but even changing brake pads will affect the brake by wire system, as they are all trying to calculate based on brake torque so that you can seamlessly blend the regen with the friction brakes. With more aggressive pads, you will just end up with weird discontinuities as it shifts to the friction brakes
I think there is always a little weirdness going from regen to friction brakes. Upgrading them will be noticeable but probably not dangerous. Probably…
I agree that there are additional steps required due to the nature of the braking system on the Prius but swapping brake lines or fluid requires fairly similar steps as swapping calipers because of the design and layout of the system and how the stroke simulator cut valve (SSA) and the gap hold valve (SGH) work together in order to apply the brakes.
The hydraulic pressure to the calipers is controlled with linear valves that are commanded by the ABS ECU and any time that the friction brakes are commanded, the ECU sends a specific amount of pressure to each corner of the car. There are pressure sensors for each corner inside of the brake actuator and the ECU monitors the pressure and adjusts the linear valves until it reach the target pressure.
It knows these pressure points based on a set calibration in the ECU but they can be adjusted with a Linear Solenoid Valve Offset Learning procedure in Techstream. This would be something you would need to do alongside the air bleed procedures in Techstream whether you replaced a line or a whole caliper.
It is possible to calibrate changes to the brakes to an extent with the tools available in Techstream without having an impact on the braking strategy as controlled by that ABS ECU. I do agree that there might be some complications getting there and the main unknown I have right now is how the feel will change in the transition from regen to friction brakes but we’ll find out together soon enough.
I’ll have a story in this series specifically on brakes where I’ll get into the hydraulic and electronic diagrams for the braking system and how each will be impacted with changes and what can be done in Techstream in order to compensate.
So don’t give it an ol’ “Hawk Tuah”, got it.
I don’t even know enough to debate any of what you stated, but GD, sir. Bravo!
There are definitely not pressure sensors in each corner. That would be cost prohibitive. However, we all have highly accurate corner pressure estimates. Feel free to reach out to me for some further tech details on brake systems!
do NOT alter the brake calipers on the prius. it has brake by wire and you will ruin the brakes because there is no way to calibrate the programming for the larger calipers. find you some quality performance pads like from from ECS, swapping the fluid for high temp fluid , switching to stainless brake lines and upgrading the tires will be more than enough braking for this car. the regenerative braking on the prius prime does most of the stopping on the car anyway
Hate to brake it to you (pun intended) but even changing brake pads will affect the brake by wire system, as they are all trying to calculate based on brake torque so that you can seamlessly blend the regen with the friction brakes. With more aggressive pads, you will just end up with weird discontinuities as it shifts to the friction brakes
I think there is always a little weirdness going from regen to friction brakes. Upgrading them will be noticeable but probably not dangerous. Probably…
I agree that there are additional steps required due to the nature of the braking system on the Prius but swapping brake lines or fluid requires fairly similar steps as swapping calipers because of the design and layout of the system and how the stroke simulator cut valve (SSA) and the gap hold valve (SGH) work together in order to apply the brakes.
The hydraulic pressure to the calipers is controlled with linear valves that are commanded by the ABS ECU and any time that the friction brakes are commanded, the ECU sends a specific amount of pressure to each corner of the car. There are pressure sensors for each corner inside of the brake actuator and the ECU monitors the pressure and adjusts the linear valves until it reach the target pressure.
It knows these pressure points based on a set calibration in the ECU but they can be adjusted with a Linear Solenoid Valve Offset Learning procedure in Techstream. This would be something you would need to do alongside the air bleed procedures in Techstream whether you replaced a line or a whole caliper.
It is possible to calibrate changes to the brakes to an extent with the tools available in Techstream without having an impact on the braking strategy as controlled by that ABS ECU. I do agree that there might be some complications getting there and the main unknown I have right now is how the feel will change in the transition from regen to friction brakes but we’ll find out together soon enough.
I’ll have a story in this series specifically on brakes where I’ll get into the hydraulic and electronic diagrams for the braking system and how each will be impacted with changes and what can be done in Techstream in order to compensate.
So don’t give it an ol’ “Hawk Tuah”, got it.
I don’t even know enough to debate any of what you stated, but GD, sir. Bravo!
There are definitely not pressure sensors in each corner. That would be cost prohibitive. However, we all have highly accurate corner pressure estimates. Feel free to reach out to me for some further tech details on brake systems!
They need to make a GR Prius 😀
Would be fun.
They need to make a GR Prius 😀
Would be fun.
Shoehorn the AWD system in there!
I looked at the AWD models but for me it really wasn’t worth trade-off for having a bit of traction on the rear.
Shoehorn the AWD system in there!
I looked at the AWD models but for me it really wasn’t worth trade-off for having a bit of traction on the rear.
Yes! As someone who was anti Prius until this generation this brings me great joy. I can’t wait to see what you do with it.
I always apprenticed the Prius for pushing hybrid technology forward but never really considered them for a daily driver because of the cosmetics but this generation brought everything together.
Same here. I liked the technology but not the package it was in. Especially the mustachioed rear end they brought out like 9 years ago. But now I’m genuinely considering one as my next daily.
Me too. I’m still in awe that they are a Prius when I see these new ones. I, too, want one now for my daily. This or a Bolt.
I told my friend who hates them more than I do that I wanted one of the new ones and she was like I’m going to pretend I didn’t hear that. I showed her what it looks like, she’s still anti Prius but she can at least admit that it looks sleek.
Yes! As someone who was anti Prius until this generation this brings me great joy. I can’t wait to see what you do with it.
I always apprenticed the Prius for pushing hybrid technology forward but never really considered them for a daily driver because of the cosmetics but this generation brought everything together.
Same here. I liked the technology but not the package it was in. Especially the mustachioed rear end they brought out like 9 years ago. But now I’m genuinely considering one as my next daily.
Me too. I’m still in awe that they are a Prius when I see these new ones. I, too, want one now for my daily. This or a Bolt.
I told my friend who hates them more than I do that I wanted one of the new ones and she was like I’m going to pretend I didn’t hear that. I showed her what it looks like, she’s still anti Prius but she can at least admit that it looks sleek.
You only got $4300? for your Subaru? Ouch
I found it to be a reasonable trade-in value considering the mileage and condition of the car. I might have been able to sell it privately for $6,000 to $7,000 but the time spent dealing with potential buyers was just not worth it for me in this situation.
I had assumed those cars would be worth more than that, I see similar ones at $14,000+ in my area
Sounds about right. Stealerships love to lowball you on your trade then go “I know what I got” when it hits their lot.
Mine had 202k when I traded it in and the wear to go along with that. Some of the driver seat bolstering was torn. The clearcoat on the rear lip spoiler was fading and there were chips on the front end of the car to match the mileage. In addition to that, the A/C compressor was noisy and there were other small wear points because it’s a car with 200k that while being maintained well is still a sporty take on an economy car.
I might have been able to list it for $7500 or so and then sell for somewhere between $6,000 and $7,000 but I also really did not want to spend weeks dealing with the type of people that would answer an ad for a 200k mile WRX and found the $4,300 to be fair for what I wanted out of the car based on the valuations I completed with comparable cars sold at wholesale auction.
Prius Primes had markups at most dealerships. They get you somehow. His “markup” was in the trade.
You only got $4300? for your Subaru? Ouch
I found it to be a reasonable trade-in value considering the mileage and condition of the car. I might have been able to sell it privately for $6,000 to $7,000 but the time spent dealing with potential buyers was just not worth it for me in this situation.
I had assumed those cars would be worth more than that, I see similar ones at $14,000+ in my area
Sounds about right. Stealerships love to lowball you on your trade then go “I know what I got” when it hits their lot.
Mine had 202k when I traded it in and the wear to go along with that. Some of the driver seat bolstering was torn. The clearcoat on the rear lip spoiler was fading and there were chips on the front end of the car to match the mileage. In addition to that, the A/C compressor was noisy and there were other small wear points because it’s a car with 200k that while being maintained well is still a sporty take on an economy car.
I might have been able to list it for $7500 or so and then sell for somewhere between $6,000 and $7,000 but I also really did not want to spend weeks dealing with the type of people that would answer an ad for a 200k mile WRX and found the $4,300 to be fair for what I wanted out of the car based on the valuations I completed with comparable cars sold at wholesale auction.
Prius Primes had markups at most dealerships. They get you somehow. His “markup” was in the trade.
I’m so glad you’re doing something like this! I hope it ends up being the PHEV enthusiast car we hoped it would be
I’m so glad you’re doing something like this! I hope it ends up being the PHEV enthusiast car we hoped it would be
Really enjoyed that read. I am really interested in how interchangeable those parts will be!
If I had my vote for wheels, I would go for the Nightshades.
I am excited to test all the parts an pieces. I initially started looking at the Camry TRD wheels but then found out that the Nightshade gets basically the same wheels but just coated in bronze and I felt like they would be a better match than the darker TRD wheels.
Really enjoyed that read. I am really interested in how interchangeable those parts will be!
If I had my vote for wheels, I would go for the Nightshades.
I am excited to test all the parts an pieces. I initially started looking at the Camry TRD wheels but then found out that the Nightshade gets basically the same wheels but just coated in bronze and I felt like they would be a better match than the darker TRD wheels.
Sadly given the ridiculous pricing of the GR Corolla even if Toyota did a GR Prius it would be too expensive.
In any case I am excited to see what you can do with this build, so keep the updates coming!
At first I wanted the GR Corolla drivetrain in the Prius body, but now that I’ve seen a GR Corolla up close in person, I *really* like it. At this point, my next (last?) new* car purchase will be either a GR Corolla or a Miata.
*Still plenty of cars I’d buy used – the Lexus LC500 is really tempting, but only if I replaced my Challenger with it.
The LC is a dream car and hopefully one day they depreciate enough that it falls into my price range.
Yeah, I hope they depreciate a bit more before I pull the trigger. Can’t go wrong with a naturally-aspirated Lexus, I’d think.
Sadly given the ridiculous pricing of the GR Corolla even if Toyota did a GR Prius it would be too expensive.
In any case I am excited to see what you can do with this build, so keep the updates coming!
At first I wanted the GR Corolla drivetrain in the Prius body, but now that I’ve seen a GR Corolla up close in person, I *really* like it. At this point, my next (last?) new* car purchase will be either a GR Corolla or a Miata.
*Still plenty of cars I’d buy used – the Lexus LC500 is really tempting, but only if I replaced my Challenger with it.
The LC is a dream car and hopefully one day they depreciate enough that it falls into my price range.