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We all know that our hybrids are more efficient than a gas only car, but have we really thought about why? I believe that understanding why will make all of us more efficient drivers. There are 3 main ways that our hybrids increase efficiency over a gas only car: Driving in EV modeTurning off the ICE when not neededRegenerative BrakingI will examine each method and how it increases the efficiency of the car. Driving in EV mode Given that all of our energy comes from gasoline, why is driving in EV mode better than driving with an ICE only? The answer can be found from examining the EPA ratings for PHEVs or BEVs. The MPGe ratings of these vehicles are often around 100 MPGe combined, with numbers as high as 120 MPGe in city driving. So, what is MPGe? Saying that the Fusion Energi gets an EPA rated 108 MPGe city means that on 33.7 kWh of electricity a Fusion Energi can go 108 miles on the city test cycle. 33.7 kWh is the amount of energy contained in a gallon of gasoline as measured in kWh. Each gallon of gas contains 125,000 BTUs, or approximately 31,000 calories if we think about it as a source of energy like we measure food. 125,000 BTUs equals 33.7 kWh of electrical energy. Why are the MPGe ratings so high? Electric motors are much more efficient than gasoline engines. According to the Dept of Energy (http://www.fueleconomy.gov/feg/atv.shtml) only about 15% of the energy in each gallon of gas is converted into kinetic energy in city driving and about 26% in highway driving. Using an electric motor to provide propulsion means that about 60% of the energy is converted into kinetic energy according to the Dept of Energy (http://www.fueleconomy.gov/feg/evtech.shtml). This is why driving in EV mode is better and why PHEVs and BEVs can drive much farther on a lesser amount of energy. The battery pack of the Nissan Leaf stores less energy than is found in a gallon of gasoline and can still carry that car almost 100 miles between charges. The C-Max Energi and Fusion Energi store 6.5 kWh of energy in the battery to drive about 20 miles; that is equivalent amount of energy to 1/5 of a gallon or 24.7 ounces of gasoline. With that tiny amount of electrical energy those cars can go farther because an electric motor is much more efficient. Electric motors do not waste as much energy as heat losses compared to an ICE. They are also not affected by varying atmospheric conditions since they are not using air to initiate combustion. Since as much as 75% of the energy in a gallon of gas is converted to heat energy by the ICE this is a big advantage for the electric motor. What does this have to do with a hybrid? Our cars do not plug in to an outlet to charge and get EV only driving, but they do run for upwards of 50% of the miles in the city using only the energy stored in the battery. This means that when we are running in EV mode we are seeing much higher efficiency than if we were driving an ICE only car. When designing a vehicle the ICE must be large enough to provide sufficient power for maximum acceleration conditions. This means that the ICE is much too big for everyday driving and that there is a lot of inefficiency when running an ICE with a low power demand. The hybrid turns the ICE into an electric generator by artificially increasing the power demand when driving with the ICE to a level where the ICE is more efficient. Hybrids also include a smaller ICE that is able to more often run at its peak efficiency. This means that the car is most efficient in EV mode at lower power demands, and more efficient running the ICE under higher power demands. For us to maximize our EV mode driving and our fuel economy we want to use EV mode as much as possible when the power demand is low, and use the ICE when the power demand is higher. Turning off the ICE when not needed Since our cars can turn off the ICE when it is not needed we don’t waste fuel idling unnecessarily. When decelerating there is no need for the ICE to run and burn gas, yet in gas only cars it does. When stopped there is no need for the ICE to run and burn gas, yet it does in gas only cars. This doesn’t mean that we can sit and leave our cars turned on for long periods while stopped because this will use up the hybrid battery and make the ICE come on to generate electricity. Regenerative Braking Another big inefficiency with gas only cars is braking. Brake pads and rotors turn momentum into heat energy, effectively wasting that energy. The regenerative braking system in our cars seems to recover about 70-80% of the kinetic energy the car has when we begin braking. That is a huge improvement over the 0% recovered by traditional friction brakes. This helps our efficiency in city driving. Driving conditions for peak efficiency Based on the above information we see that for peak efficiency we want to accelerate using the ICE, then back off once reaching cruising speed and use the electric motor to maintain our cruising speed. Since the electric motor’s efficiency advantage over the ICE is highest at lower power demands we see the highest results at lower speeds in the city. At 25 MPH the power drawn from the battery to maintain that speed is minimal. I’ve cruised for miles without using the ICE when cruising at 25 MPH without stopping. This is the logic behind the hypermiling technique known as DWB (driving without brakes). The DWB technique involves trying to drive in a manner than you brake and stop as little as possible. While braking is much more efficient in our cars than in a gas only vehicle, it’s still better to brake as little as possible since an electric motor only converts 60% of the electrical energy stored in the battery into kinetic energy and regenerative braking only converts 70% of the kinetic energy back into electrical energy. For example, 1 kWh of electrical energy pulled from the battery would only get you 0.6 kWh of kinetic energy and the 0.6 kWh of kinetic energy would be converted into 0.42 kWh of electrical energy back into the battery through regenerative braking. It is much better to use that 1 kWh to drive 5+ miles without stopping than it is to stop and only recover 0.42 kWh of electrical energy. There are certain routes I have found where I can consistently get better than 60 MPG because I don’t have to stop very often and I can maintain a constant rate of speed. Such routes are the pinnacle of efficiency for a hybrid. I imagine that on those same routes I could get 75 MPG out of a Prius and over 130 MPGe in a C-Max Energi or Fusion Energi.

I recently bought and installed a ScanGauge II in our FFH. After driving a 100+ miles with in installed over the past few days I have a number of observations and a number of questions... Observations Horsepower - the generator can place about a 15 horsepower load on the ICE when the battery is low and the ICE is doing maximum recharging. This is good for about 18 amps of current flowing into the HVB. In other situations it seems that each hp of ICE output to spin the generator is good for slightly more than 1 amp of current flowing into the HVB.Amps - the maximum regen braking charge seems to be about 30-35 amps. I've never seen the regen braking charge go above 35 amps while still getting 100% brake score. That seems to be the limit for the generator. When driving in EV 1 bar on the Empower screen is about 20 amps of current flowing out of the battery. The max current I have seen flowing out of the battery has been about 50 amps. This happened when I was accelerating in EV at 1.5 or 1.75 bars and then it kicked over to the ICE. Since one motor/generator must spin the ICE up to speed (like a starter motor in a conventional car) there is a momentary spike in amps flowing out of the battery to start the ICE.Recharging - The computer likes to charge the battery with a 15 amp current flow when the battery SOC is low to maybe about 75% of the display. This seems to be in the most efficient range of the ICE as well as the LOD will often be 85+ when this load is placed on the ICE by the generator while accelerating. When the battery SOC is higher than 75% of the battery icon the amps from the ICE generator drops to 5-8 amps. If the battery is almost full the current flow drops to about 3 amps.Coasting - when coasting with your foot off the gas pedal the generator places about a 3-5 amp load to gradually slow the car down.Idling - when idling the current draw to run the computers and charge the 12V battery is about 0.55-0.60 amps. This amount of current is drawn whether the car is in Park, Reverse, Neutral or Drive as long as you are not moving. The brake lights pull a minimal amount of current, but enough to make this range 0.59-0.64 amps when you are stepping on the brake.Lights - the headlights/taillights draw about 0.25 amps. The park lights and fog lights draw the same amperage as the headlights. If you combine headlights and fog lights the current draw is about 0.40 amps.HVB temps - the HVB temp quickly increases when driving from the current flow in and out of the battery. The past few days each morning the HVB temp showed the same as the exterior temp when first starting off (between 75 & 80 F) but quickly warmed up about 10 degrees within the first few miles of driving. Only on Friday where we did a lot of driving in the city in 95 F outside temps did the HVB temp go above 100 F. The HVB fans ran non-stop on Friday. Other days I noticed that at about 85 F HVB temp the fans would kick on at a low RPM (about 750-1000 showing on the display). On Friday I saw the HVB Fan RPMs as high as 2000. Even when running at that speed I still couldn't hear the fan when I got out of the car to listen with it "running" and with the SGII indicating a fan speed of 2000. I imagine that when we hear the fan running from outside the car after the car is off it must be running much faster than 2000 RPM.Current draw when off - after turning off the car in the few seconds before the SGII turns off the power draw shows 0.04 amps. This is likely to run whatever computers are still active to display the Trip Summary and Lifetime Summary screens.AC amp draw - the AC will draw 15-20 amps from the HVB when first turned on with a hot car. Once the car has cooled down the AC continues to draw an extra 2-3 amps minimum that we observed. This puts some numbers to the effect of AC on gas mileage. That is a lot of current that must be replaced by burning gasoline.Battery display on dash without charge/discharge arrows - It is very hard to get the battery display to show no arrows for charging or discharging. It appears that while moving the car displays no arrows when the current flow is less than 1 amp in or out of the HVB. However, sometimes the current flow will be less than 1 amp and the dash will still display arrows for charging or discharging. Also, when stopped a current flow of less than 1 amp displays as the HVB is discharging. No matter how hard I've tried I have never been able to get the display to show 0.00 amps as the current flow. With steady pedal pressure it is possible to keep the amp flow steady for many seconds though while driving as long as the slope of the road doesn't change.Warm up stages - when the ICE is in S1a the power demand on the ICE is very low, less than 10 hp and a LOD less than 60, this is quite inefficient and shows why skipping stage S1a improves fuel economy so much as discussed hereQuestions :headscratch: What exactly is LOD (Load)? The car often shows 95-99 when accelerating slightly more aggressively such as accelerating onto the freeway, when accelerating in the city it often shows only 80-85. When the ICE is idling in warm up the LOD is as low as 50. Is this the % of maximum power output of the ICE at the current RPM?How do I understand the ignition timing screen (IGN)? When the ICE is off it shows -10. When the ICE is on I've seen values anywhere from 5-8 (when ICE is under load accelerating) to 30+ (mostly when the ICE is under a light load but still on such as freeway driving where the Empower screen shows the power demand being just above the EV threshold.Why does the car show 1.2 horsepower when the ICE is off? I tried using the adjustment in the setup but even decreasing the reading by 10% only lowered the display when the ICE is off to say 1.0 horsepower. What does the default value of 1.2 hp when the ICE is off mean for the numbers that the SGII displays for hp while I'm driving?As I think of more items I'll continue to add to this thread. As it stands now I hope that my observations will be of benefit to others and that those with more experience and knowledge than I will be able to shed some light on my questions. Thanks in advance for that help! :worship:

So, it's starting to get warm in the Southern States and the A/Cs are starting to run hard. We have found from another thread that a large improvement may be made to economy when the A/C is under low load. Tint can help to keep the temps down, but enough to see a significant increase in economy? I had hoped to maybe document this over the summer by getting tint halfway through, but maybe others can chime in. Thoughts/Opinions? Admittedly, it would be pretty weird to see a 5+ mpg improvement just by making the windows darker, but maybe there's some proof out there.