Can we bring up Power Mode again?

How can this be done without causing pre-ignition as the compression ratio rises toward the relatively high expansion ratio of an Atkinson cycle?

Can you point us toward any technical papers explaining it?

 

Only Toyota's comment that the Prius engine construction is no different than their other engines. It is not built as a Atkinson engine. They get the same low torque, higher efficiency effect via electronic controls. They can take it in and out of Atkinson mode or more correctly have it in variations for performance from PWR mode, standard engine to regular mode, mild Atkinson, and ECO mode, full Atkinson.

 

I'm also convinced that PWR mode does more than just remap the throttle response. I think it also delivers more power and torque to the electric motor while accelerating. In NRM mode if I push the pedal down harder to compensate for the throttle response, I notice the ICE revs higher with less net torque when accelerating from a stop than it does in PWR mode. In PWR mode you get less ICE RPMs and more net torque. That's either because they are changing the ICE timing to deliver more power or giving more power to the electric motor. I also find that my average mileage is better in PWR than NRM or ECO.

 

PWR mode turns on the ICE sooner than Normal or Eco Mode during an acceleration cycle/phase/event ( i.e. there is less of a delay between the time you press the accelerator and the time the ICE engages the transmission) - Engaging the Prius' ICE sooner than later helps to keep up with the power demands (of moving forward) when driving environment's power requirements are over and above what the NiMH battery will allow for (the NiMH maximum battery load is the power limiting factor not the electric motor - this is somewhat addressed by the Plug-in Prius by using a more powerful Li-Ion battery ). This is useful when the Prius is going uphill or accelerating from a stand-still or trying to maintain superhighway speeds (or little bit of everything above). One way around manually setting the modes in the superhighway scenario is to use Cruise Control(CC) to automatically handle the throttle. For example, in ECO mode because of the delayed throttle, I have trouble keeping the Prius speed at a constant fixed 55 mph going uphill - I tend to over compensate on the accelerator because of the delay response and end up going too fast or I under compensate on the accelerator because of the delay response and end up going too slow. Using PWR mode which has a faster throttle, makes it easier for me to adjust and control the throttle so i can maintain a fixed superhighway speed going up hill. The alternative Superhighway method is to set the CC to a particular speed when going uphill and let the Prius' computer control the throttle going uphill. At superhighway speeds with no elevation advantage, top speed is the determining factor in MPGs (especially when going on a uphill phase in a uphill-downhill cycle ), so anything that helps a driver limit the Prius' top speed helps in improving the Prius' MPGs. The only exception where the Prius MPG can slightly improve if its top speed is allowed to momentarily increase while slightly going downhill when that newly generated momentum/speed is needed to immediately to go back uphill (this technique is called Driving with Load or DWL among hypermilers)- during this following uphill climb the Prius sheds this extra speed/momentum gained during the previous downhill stretch as it climbs to the top of the next hill - DWL is suppose conserve the Prius' potential gravitational energy. With respect to the energy efficiency of any fixed/standardized vehicle, a hypermiler is manipulating four factors: conservation of momentum, consevation of potential gravitational energy, rolling resistance, and aerodynamic drag.

hope this helps

Walter

 

My 2012 Prius Four is always in the Eco mode at startup. No button-pushing necessary.

 

This isn't getting enough love. This is actually pretty brilliant and I now have something else for my hypermiling arsenal. Thanks!

 

There will be no reference here as it's impossible to use 87 octane gas in 13:1 compression ratio without engine knocking to death. The whole Otto cycle under demand idea is nonsense, even if it sounds great on a surface.

 

Holy cow! Are you all engineers?

 

I submit that if you feel the need to use power mode all the time, then the Prius may not be the optimal car for you.

 

^^ Thanks for the new valve angle map, it is slight different than Hobbit's Gen2 valve angles.

If I'm computing the simple static geometry correctly, I'm getting compression ratios of 10.28 at 61°, and 5.95 at 102°. But a previous discussion indicated that this static result answer isn't the complete answer.

 

Its been reported as 9:1 maximum compression that can go down to 6:1 and averaging 8:1. There is a fairly aggressive cooled egr taking place also. The engine should run much cooler than a normal 4 cylinder ice.

I don't know on the toyotas but honda leaves all the valves closed. That provides the lowest pumping losses.

Yep But I can't remember the math.

 

" and that compression ratios are linear"

Piston movement should be sinusoidal, yes?

 

Yes, I think that is it. In PWR mode I would think the ice would be on earlier, but not producing much power unless the battery was low. The aggressive cooled EGR makes this low power situation more efficient and the ice on allows the prius to deliver power quicker when called upon. Has anyone confirmed this with a scan guage, that the ice turns on easier?

I assume EGR is also used as engine temperatures get hot to allow stoich mixtures without pre-ignition.

Thanks I did not know the details of the system.

 

Sorry, my comment was directed at ProximalSuns who boldly stated that Power=13:1 compression full Otto cycle and Eco= standard compression full Atkinson cycle.

 

insane. Almost 40 replies to a guy that can't drive out of a parking lot without PWR button. LOL

oh, original poster has ONE post.

 

But on the bright side, only one person who replied gave incorrect data, and he always does and never learns.