Quote:
Originally Posted by TexAg91
Now that I've taken delivery of my X5 50e, I have observed that while your formula for calculating ICE only MPG is correct, there are some important caveats to take into consideration. The trip computer/app data your formula is using is only for ICE fuel consumption and distance traveled when the ICE is running. So the 22 MPG estimate while technically correct, is overly pessimistic as it doesn't take into account any efficiencies gained when the engine is off due to energy recuperation.
When the PHEV battery is down to a 0% SOC, the 50e still acts as a strong hybrid and will shut off the engine when coasting, or at a stop light, or even when driving at low to medium speeds over short distances — it's being a strong hybrid and is using the energy being recuperated. Any distance traveled with the ICE off is not being booked against the ICE fuel consumption/distance traveled metric on the trip computer, it is being booked under the EV KwH/distance metric.
So that being the case, I would recommend the best way to estimate the actual MPG when the PHEV battery is at a 0% SOC is to take a trip in battery hold mode. For that trip, the overall MPG estimate will take into account miles traveled with the ICE off (due to energy recuperation only) as part of the MPG estimate. On a recent 55 mile trip on I-95 (in heavy traffic, in the rain, 34.8 mph average speed, lots of speeding up and slowing down), where the entire 55 mile distance was accomplished in HOLD mode, I averaged about 27 MPG.
So based on my observations, with a full battery at a 100% [...]
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You are absolutely correct. I have stated this situation could be a gap in other thread. However, for my own 45e, I have done about 7 tanks of gas, from Feb of this year to about June, where I didn't charge the car at all, drove I in hybrid mode. Per tank, I take the mile drive / gas put in, and I got 22mpg. I have that table post somewhere here as well. This number matches my formula up to the whole number.
Here is my observation
1. Under stop and condition, the amount of reg is very mild. Say between two traffic lights. The main regen is the part you slow to to stop. However, this portion is small, where as soon you hit the gas paddle, car is moving, ice is on.
2. In highway, the regen is even smaller at coasting. The car know the most efficient way is minimal regen. You do get some regen to when slow down, say to exist highway, but this happens far and few in between. To get the car back up to speet, it take more energy than 40i because of the weight. In pre lci, the weight difference is 800lb, or 15%. Which is significantly.
3. In my test, if regen has meaningful mount, I should see significant edrive miles. But I don't. Per tank, I was doing about 350 miles. Trip computer recorded single digital edrive mile for every tank. Single digital here mean 5 miles. So even if I factory in 5 mile in my formula, it is a 1-1.5% different.