RPM Limiter

Near as I can tell, the computers dial up as much torque or power as needed to go as fast as you want.
"Red Line" is 5000 RPM because that is the Horse Power Peak (The Otto version has a red line at 6400 RPM, so the engine is not near a limit at 5000.)

Toyota NZ engine - Wikipedia, the free encyclopedia

I hope this reassures you you are not risking fragmenting your engine.

 

Why would anyone take their car daily to 5000 RPM? How about slowing down during these mountain climbs? Redline maybe another 1000 RPM, but does not mean you are not abusing your engine. Next your going to say you change your oil every 10,000 miles, please tell me that I am wrong! This is why I can't buy used cars any more.

 

5K rpm not a big deal, it's OK and safe to do that for 3-4 minutes per day. If you're worried just slow down during those climbs and you'll be out ... what an extra 4 minutes?

 

based on what jimbo said, though, that lets say he dailed it down to 65-70. the engine still may rev up to 5K just might not have as much load on it.. being its a CVT transmission, The prius does not downshift/upshift. to find the proper gear, like a conventional tranmission.

I have a couple spots on my daily commute that have a few steep hills and to maintain the speed limit of 35 the engine winds up pretty good. a few glances at torque its been in the high 4000 range...

 

I'm missing something here.

If the engine load doesn't change, why would you want the RPM to decrease?
Work is work.
If you want to decrease the RPM. decrease the speed.

Purposefully lowering the RPM (presuming that you could do such a thing) in this case might cause more engine damage than a 5,000 RPM excursion.

Have you ever ridden a Mountain bike?
You know why they have so many gears?
Imagine if you will, forcing a rider to climb a similar hill maintaining the same speed without being able to down shift so that you can work the pedals a little faster.

The idea that RPM = death comes from the dark days before the modern EFI, and it bears little on the longevity of the modern engine.....and besides?
How many Priuses are blowing engines out there?
If this happened in proportion to the worry level then the Toyota dealers would be jammed with open hood Priuses awaiting an engine transplant.
Instead.....and despite a 10,000 mile oil change interval and a population that almost never touches an oil dipstick.....Prius motorectomys almost NEVER happen!

I drive a G3.
It's fly-by-wire.
Meaning: When I STOMP on the accelerator pedal, there is no physical link between my foot and the throttle body. My foot becomes the automotive equivalent of Captain Kirk on the bridge yelling at Engineer Scott for more power. If you've ever been on a ship (star or otherwise) you'll notice that the bridge is usually a long way from the Engine room.

All of this means that I can start my car....put a brick on the accelerator pedal...go to lunch....come back and the motor will be just as healthy as before minus an hour's run time.
In fact?
My motor will probably last longer.
I check my fluids and filters.

 

I am not following what drive by wire has to do with RPM or engine wear. Drive by wire is just a modern engine control, but does the same as past throttle set ups. As to engine longevity have you seen the threads on oil burning in Prii? Don't you think daily high RPM may be a cause of oil burning in older engines?

 

The simple and easy answer is right in front of your nose........or foot in this case.

If you don't want the engine to race to 5000 RPM, just simply turn OFF the cruise control and use the gas pedal
to make it run at whatever speed you want.

Simple, cheap and easy fix.
Of course, your land speed will slow down accordingly.

 

Not exactly. To boost MPG, softer valve springs are used in prius. Thus, valves will float at lower RPM.

 

I treat climbing hills in my Prius G2 T Spirit the same way an airline pilot flying a twin turbofan airliner might do during take off. Approaching a steep hill, I build up speed to about 55 - 60mph. I climb the first 3rd of the steep hill at this speed - I can hear my Prius engine at full (or near full thrust - probably at 4,000 RPM), after climbing approximately one third up the hill, I reduce throttle with my foot - you can audibly hear the engine thrust reduce to a lower level, but my speed barely changes as somehow, the G2 just carries on whizzing me UP the hill at slightly reduced power. I've also noticed at this reduced stage, the HV starts to contribute to the power needed to keep climbing.

I notice some turbofan airliners using the same concept while climbing. Manual throttle control makes the difference, and I save more fuel climbing manually than I do using the cruise control (auto-throttle? Hahaha).

As I approach the crest of the hill, I can usually reduce throttle even further and let momentum carry me over the hump of the hill. I can then reduce power completely, feather the throttle and still fly down the other side of the hill often reaching 60 - 65mph while the ICE is still running, but at 99mpg. There's a faint resonant hum coming from it by now, not unlike a twin turbofan coming in to land with throttles literally at idle.
Often, coming off a hill like that with momentum, I do travel quite a long distance with the ICE running between 84mpg and 99mpg.

Presently, there are 2 hills on my regular 18 mile each way commute to work, and I'm achieving a not inconsiderate 63.3mpg (UK) at the moment. And that's with keeping up with the traffic driving, while exceeding speed limits slightly coming off the hills. I've long since stopped driving like a snail in the G2. Thanks to sound advice from the PriusChat Forum, I'm really enjoying getting about at much faster speeds, while STILL saving fuel.

 

Two things:
If that is true, then lowering the RPM limit likely would force a slowdown that is too much to be safe
AND
The "real" redline for the engine, that is the point after which damage is likely to occur, I think is probably a good bit higher than 5K.

As with a lot of things discussed on here, I think it is best to not worry about it and trust that the engineers would not let something happen that is really bad for the car.

 

Whatever.

Something has to give, if something is to change.
If I'm reading the OP's original post correctly they are asking for a scenario that simply doesn't exist in the realm of physics.

A vehicle is still energy being used to create momentum, and there is always a cost for that, even in a Prius. Limiting the RPM's but demanding the same speed over the same route and expecting less strain on the engine, is really impossible. Cruise Control isn't magic, it still uses the vehicle, engine, transmission, the whole thing to create speed. If a greater incline makes momentum harder to obtain, as is in the case of hills, then the engine is going to work harder. No way around that unless you demand less speed. The best RPM limiter, is your foot.

If you "hate it when it's redlining like that"...then slow down.

Personally, I think 80 mph, up mountain roads, with cruise control set is ridiculous. I don't know where you live, but where I live mountain roads are usually winding and turning, and there is no way in a Prius I'd routinely want to take them at 80 mph, because separate from engine strain, it's a safety issue.

But people don't do what they don't want to do, if they have the choice. So you don't have to bother telling me how safe it is, or necessary to your commute.

For me however my answer needs to be, I think what you need is a MPH limiter in the form of your foot, not a RPM limiter that doesn't exist, and couldn't create the results you are looking for if it did.

The other perhaps more fundamental truth is, you're driving a hybrid Prius, with a 4 cylinder atkinson tuned engine. This is a machine designed for efficiency, under "normal" driving conditions. It's not designed to eat up hills and spit them out. I suspect even slowing down considerably, which I still would recommend, wouldn't totally remove the engine struggling. Again just physics.

It all depends on what your driving priorities are....efficiency, safety....or record breaking runs to work, and 80 mph jaunts up mountain roads. The choice of what priorities to embrace are entirely yours.

 

Good Luck decreasing those RPM's...while trying to increase the Speed demand, over the exact same driving route.

If anyone can do it...I believe it's you.

 

The engineers designed the engine to be driven at near redline? I don't think so, it was designed to be driven around 2K RPM, if you want to drive near redline it will, but it can't be good for it.

 

I am sure they designed it to cope with all sorts of drivers and routes, the thing they do assume is that it is serviced regularly and driven some where near legally

 

Leave five minutes earlier and drop your speed to create an acceptable rpm at the worst points, or accept 5k rpm.

Pretty simple, really.

 

The truth is the Prius Gen II was not designed to be a sports car or be treated like one - no more than the Boeing 777 would be expected to be thrown around recklessly in the sky like a highly manoeuvrable Russian Sukhoi Jet Fighter.

The Gen II Prius was designed to get you from A to B at appreciably legal speeds in considerable comfort and relative quiet. I'll confess to relegating myself to the so called slow lane on the few times I'm on a motorway. Here, I will blissfully drive along at 65mph. Why? It's not because the Prius is slow - it will travel at 70mph quite happily. No, I chose to do this because the vehicle was designed expressly to reduce emissions by using much less fuel than the average car. It's an amazing piece of engineering! And I respect it so much, that apart from the rare moments when I might call upon the combined acceleration and torque of the ICE and Electric Propulsion Motors to get me swiftly out of a fast developing sticky situation on the road - I really, REALLY enjoy cruising at lesser than the national speed limit (mostly on cruise control) and welcome the lack of a white knuckle ride all the way to my destination.
I used to have an MX-3 Sports car, and yes, occasionally went on motorways at 90mph+.....but no more.
I consciously chose the technologically advanced Prius II as my next car - and believe me when I say I'm enjoying every minute of having completely re-evaluated my driving style.
I'm also acutely aware that if I take care of the drivetrain of this over-engineered, dual-engined technological marvel on wheels, it will reward me with very many years of flawless reliable service.