My Concerns with the New Prius

we can only hope you're right. but so far, i'm seeing no signs of recession. fed needs to step up the rate increases

 

Inflation is not being caused by economic growth. It is being caused by supply-chain problems. Rising interest rates are making things only worse. In any case, the administration will keep printing money for things like student-loan forgiveness etc., which helps fuel the inflation.

 

so cars won't be cheaper this year?

 

You don't want cars to be cheaper if you have a newer trade-in.

 

Don't you mean less torque from the transmission output, not from the engine crankshaft? That usually means the same thing for fixed gear transmissions, but not necessarily for CVTs, and certainly not for HSD-eCVTs.

My understanding is that Toyota HSD's engine management doesn't make the engine spin faster unless increased power is needed. For most circumstances, without air pressure changes, power output and RPM can be used as proxies for each other.

The Prius v also has a significantly worse Cd, more air drag, so inherently needs more engine power to maintain the same speed. Wider tires too. Unlike traditional vehicles, the Prius engine control laws are to keep RPM and torque on a fixed load line as much as possible, so more power necessarily means higher RPM. See its BSFC map. I can imagine them changing the final drive ratio to better match the overall system characteristics to that higher RPM.

For fewer confounding factors, a simpler comparison would be change just the final drive ratio, or just the tire diameter, without those weight and other air drag changes.

I'm seeing more differences than that. The Wilderness is also jacked up higher, so has more air drag for a given tire diameter. "Rugged Appearance Package" has different bumpers and exterior cladding, which on other 'rugged appearance' vehicles suggests increased air drag. Transmission is from the larger Ascent. Re-tuned CVT for greater low-end off-road torque, which also makes it faster off the line than the non-Wilderness turbo. And with all this stronger low end performance, it appears to have a lower top speed than the lower-power, non-turbo Outback. Plus, I don't believe it has HSD's fixed-load-line engine management.

 

And what if you don't?

 

You want cars to be cheaper

 

Looking at used Primes, I can't find one of any year with 50,000 miles on it for under $25,000 within a 500 mile radius except two that are suspicious at $22K and $23K. Right now the cheapest MSRP for a brand new Prime is about $28,000.

 

exactly.

 

I need to stop rambling on, but my 2013 Avalon hybrid originally had an MSRP of at least $36,000. But 5 years later I was able to get ir with 50,000 miles on it for about $15,000. I was able to pay $5,000 down plus all the taxes and fees and so got a loan for $10,000 or $185 per month.

I just looked up my Avalon on Kelly Blue Book and it's now worth $5,200 for trade-in or $7,300 if sold to a private party. I still owe $1,500 on it and will have it paid off by September. If I keep saving after that then in 2 and a half years (March of 2026) I'd have enough for another $5,000 down payment, assuming the Avalon is not worth a dime by then as it very well could have over 200,000 miles on it by then. But will I be able to get a 2021 Avalon Hybrid (or Prius Prime) with 50,000 miles on it for $15,000 in 2026?

 

a lot of people have to finance cars, especially the last few years. i feel bad for the ones who just want basic trans, but not for anyone who wants more than that.

 

Assuming the new Prius has the same final gear ratio as other hybrids with that drivetrain, will the system speed up the engine to compensate for the bit of extra power needed with the larger diameter tires, or can it stay near the same engine speed while going a little farther per rpm?

 

My understanding has been that for a fixed ground speed, the wheel RPM will slightly decrease, but absent a change in drag, the engine RPM will stay constant. But since the slightly lifted vehicle should have slightly more air drag, the engine RPM should slightly increase to cover that drag power, though this change should not be directly linked to the change in wheel RPM. The eCVT's effective gear ratio changes to accommodate.

This contrasts to a fixed gear vehicle, where the engine RPM necessarily decreases proportional to the wheel RPM, requiring increased torque. But for drive-ability and customer expectation reasons, the engine is usually operated in an area of the BSFC map where there is some, or even a lot, of torque reserve available, so this RPM decrease is not a problem. In fact, it usually pushes to a more efficient operating point on this BSFC map, due to reduced pumping loss, so MPG increases. That is, as long as the RPM reduction doesn't cause it to run out of torque reserve, forcing a downshift.

Under the control laws of the Prius HSD, the engine is already running at high torque, minimum RPM, and low pumping loss. It has no reserve to reduce RPM while maintaining the same power. This is also why it is more efficient to begin with. All those efficiency gains that folks used to get by installing taller tires, the Prius has already harvested by other means.

I am ignoring a secondary issue on the HSD system. This tire or final drive gear ratio change, does change the power split between the more efficient mechanical gear path, and the less efficient MG1->MG2 electrical path. Toyota isn't ignoring this when they select that final drive ratio.

I'm probably missing other considerations, maybe someone can speak to those.

 

A friend of mine is looking at a Kia Niro. How does the non aerodynamic Niro manage to get 50mpg?

 

I know right!

But I think there's something fishy about it. How does a car that gets 53 city and 54 highway get a combined fuel mileage of 49?

https://www.fueleconomy.gov/Feg/noframes/45673.shtml

Still, imagine what that engine/transmission combo would do in a body like a Prius.

With ICEs there's still plenty of efficiency to pickup that's left on the table. Engines with efficiencies as much as 60% are possible, but getting them to work in a car and still be affordable is a bit of a challenge. If a 40% efficient engine gets you 40 to 50 mpg in a typical car, a 60% efficient engine should get you 60mpg or even better!

 

45 highway

 

it all depends on how they handle the epa test. personally, i don't trust it. i can get much better mpg's than epa in a prius, than i can in other cars.

 

Ya, I think you're right and there's a typo on the fuel economy page.

But that also is kind of like the RAV4 hybrid. Poor aerodynamics make the hybrid get worse highway fuel mileage.

I need tips on getting better fuel mileage! I'm averaging about 20mpg right now in my Avalon hybrid. Maybe I need to drive the Prius instead.

Also, any car company can try to get the highest fuel mileage score possible for their vehicle, but there's a limit. However, any car company can also put a lower number than what they really could. Any way you look at it the comparison isn't always fair. If only there were one standard test for all vehicles with no consesions whatsoever.

 

45 highway is what the fueleconomy.gov page is now showing me.

? RAV4 Hybrid showing me better mpgs than any of the non-hybrids.

 

I must be dyslecix.

Anywho, what I meant was the difference between city and highway. The Prius is like 1mpg different between city and highway, which at 56 and 57mpg is less than 2% worse fuel mileage at highways speeds. But the RAV4 hybrid is at least 3mpg different, which is over 7% worse fuel economy at highway speeds.