Tesla Model S P85D owners are questioning whether their vehicles actually have the advertised 691 horsepower.
One group of Tesla owners sent an open letter to company CEO Elon Musk, challenging the American automaker’s claim that the P85D makes 691 hp.
“The P85D was marketed as making 691 horsepower. It doesn’t. We believe, based on various testing methods and tools including dynamometer testing and testing with professional performance data loggers that the maximum energy output is 415 [kilowatts], which results in a maximum horsepower of 557 before any drivetrain losses on a fully charged battery. Even without factoring in drive train loss, this is almost 20 percent less than the advertised horsepower,” said the letter. “The missing horsepower is quite noticeable at highway passing speeds. For example, from 70-90 mph, the P85D should perform like a car with a power to weight ratio of one HP for every seven pounds. Instead it performs like a car with one HP for every nine pounds. The result of this is that from 70-90 mph the P85D is easily outperformed by an Audi RS7 with a power to weight ratio of only one [horsepower] for every eight pounds.”
Since then, Tesla chief technical officer JB Straubel has taken to the company’s blog to explain a bit on how electric power is defined in terms of horsepower, saying that it isn’t very intuitive. “Electricity alone can’t generate physical motion the way a horse or a fuel-burning engine does,” Straubel explained in the post. “An electric motor converts electricity into motion.”
He also notes that to calculate the overall horsepower of a dual-motor electric vehicle, the rating of the front motor was added to the rating of the rear motor. “Where some confusion occurs is that in the 85D and 70D vehicles the combined motor shaft power is very similar to the battery electrical horsepower under many normal conditions,” he added. “With the P85D the combined motor shaft power can often exceed the battery electrical horsepower available. The dual motors utilize the battery horsepower in the widest variety of real world conditions.”
Interestingly enough, nowhere in the post does Straubel specifically confirm or correct the 691-hp figure that’s advertised for the Tesla Model S P85D.
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