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The above data was posted a long time ago by the author. Bottom line is that the 2013 Prius has a Road Load HP that is lower than the C-Max by around 32% at 20 mph dropping to around 23% at 80 mph as shown on the attached graph. So, one would expect the Prius to get around 25 to 30% better FE under normal cruising conditions than the C-Max all other things being equal. But according to the data by Tim, this is not the case as indicated by the table of Tim's data below. This suggests that the software algorithm for the C-Max is "tuned" to achieve FE and "beats" the Prius tuning or perhaps the Toyota M/G set can't operate in negative split mode (generator reducing ICE rpm by speeding up to keep rpm to wheels / vehicle speed constant) like the C-Max can due to operating limitations. There is a physical connection between ICE, MG1, and MG2. At 65 mph and likely higher, the Prius apparently can achieve an equivalent FE based on its lower RLHP as shown in the table below. Fuel Economy (mpg) MPH 45 55 65 2013Prius 75 65.1 57.5 C-Max 74.7 57.5 48 % diff 0% 13% 20% Here's the link to the old thread on this. At that time, most were unaware of how Ford "blew it" on the EPA fuel economy estimates and how the RLHP coefficients from coast down measurements changed. So, the natural assumption was that tuning was off or final drive ratio was wrong. Tim's post below was prior to the final correction of coefficients in 2014. Tim also did not record data for analysis to help understand how both cars were operating. All we see are four points at a specific time (scan gauge) and he doesn't have the BSFC curve for the C-Max.

I have seen that simulation for the Prius a few times, but the ratios are wrong for the C-Max. I would love to find out the speeds of each part in our cars and see what is going on at the 50 mph to 85 area where they can now go EV only. What is the RMP limits of our MG units? I have had my C-Max over 90, but obviously, it was not in EV mode with the old software and all. I race very high performance electric 1/8 scale RC cars. The motors are the exact same technology as the ones in our cars. They have very strictly defined characteristics. Any given wind / rotor combination will have a specific RPM / Volt rating and a torque / amp rating. These do not change unless the magnet starts to lose strength, which does happen from over heat and/or large over current events. When the magnet gets weaker, the rpm for a given voltage will go up, but the torque for a given current will go down. The result is the power drops a bit until the magnet is way too weak, then the efficiency goes to crap. So many new racers gear way too high to go faster, and when the motor is fresh, they seem to run great, but kill the rotor fast. This is only dealing with about 1400 watts or just under 2 HP in an 8 pound car. In the C-Max, we are shoving around 3,600 pounds with 33,000 watts of electricity. The electronics need to monitor the rotor and winding temps and make sure they don't demagnatize it in a few second if something goes wrong. The voltage limit is the battery pack at full state of charge. This limits the rpm the motors can produce any torque out. In theory, you could spin them faster and still use it as a generator for charging, but the system will have to throw away some of the power as the batteries can't accept the charge too fast or at too high of a voltage.I know the cells are just under 5 amp hour each, and even the good high current racing cells can only be charged at 5 times the amp hour, most are limited to 1 or 2 times. The pack in the C-Max hybrid it 76 cells in series, for a nominal terminal voltage of about 245 volts, and a max voltage at full charge could hit about 310 volts. Good race cells can dump out up to 30 times amp hour current, but I doubt highly our cars would ever even try to do that. Most cells are more in the range of 5 to 10 times for long life. so the battery can theoretically put out around 300 volts at 50 amps for 6 minutes, that works out to 1,500 watt hours, the spec says 1400 wh, so I am pretty close with the simpler numbers. The problem is the battery can't accept current at near that rate, which is why you need to brake gentle to get a 100% recovery score. Most of the power MG1 generates, has to go straight to MG2 to help push the car. The Battery is only seeing at most 1/2 of the power at any time. The charge rate, even at 5C is 25 amps at 300 volts, or 7500 watts, or only about 10 hp of braking force. Under maximum acceleration, they do claim 33 KW out of the 1,400 wh battery. Wow, that is about 24C rate discharge, right up with the racing RC cells that last just 300 charge cycles. And that amount of power will only last 2.5 minutes going from 10% to 0%, and the C-Max will only do 80% tops down to 30 or 40% at the bottom. So figure you get that power for just 1 minute. Well, that is plenty to get up to 80 mph accelerating onto the freeway. By the way, 33KW is almost 44 hp with a 98% efficient electric motor. So our ICE engine is also making 144 hp to get the 188 rating to the wheels. Not too shabby. My whole point of all this, the math all works, the battery, motor, gearing, etc. all has to be carefully chosen to get this kind of performance. You can't just say program this motor for more rpm and change physics. If the data Ford is gettign off real world cars in use shows an issue, they could maybe get a little better with software alone (13B07) but to make any bigger change will require different gearing and/or motor(MG1 MG2) windings to move the rpm ranges much at all. And yes, BOTH MG units can act as motor or generator depending on where in the power range the car is. MG1 is mostly generating and MG2 is mostly a motor, but the roles do change with conditions. Any time the MG1 is trying to reverse to make the engine turn slower, it is consuming energy, and adding it to the wheels through the PSD. This energy either has to come from the battery, or use the MG2 as a generator, dragging that power from the wheels, making the efficiency seems pretty weak. Without knowing all the ratios involved, I can't calculate how efficient the trasfer would be, but trying to force a big over drive sounds like a losing proposition. The goal when in this mode is to not be using any battery power. So all the power used by MG1 will be coming from MG2. When the engine is turning faster, doing a low gear, the opposite is true. The MG1 is only acting as a generator, slowing the inner gear of the PSD and therefore producing output torque to the wheels at the outer gear of the PSD. This generated power can charge the battery, or feed to MG2 to add even more torque to the wheels. This mode makes for an incredibly efficient torque converter. The fact that under drive is more efficient than over drive explains Ford going to the 2.57 final drive ratio. But I still need to figure out the PSD gear ratios to make much use of that simple ratio number. I assume they mean if the ICE and MG1 are turning the same speed, such as the PSD al turning as a single unit, then the wheels are turning just ICE speed / 2.57 ??? or is this a max ratio, with any PSD induced overdrive added in ?? I have no idea at this point. Using the Toyota PSD diagram, you can see if the engine and MG are at the same speed, the final drive to the wheels (assuming the tires roll 6 foot per revolution) works out to about 4.0, the book says 3.7, so maybe the tires are a bit smaller on that model. Doing the math backwards, I get a tire roll out of 5.45 feet per revolution, that seems really small, a 185 60 14 is 6.4 feet per revolution. Maybe they do use some of the overdrvie in the PSD to get the final ratio, or this PSD simulator is based off of a different gearing in an older Prius?? Sorry for the ramble on, I really want to use my engineering thoughts to understand how the power is being used and if it can be improved on.