Buy now you know all about the Tesla Model S P85D and how awesome it is. The electric sedan is known for destroying any and all challengers on the drag strip thanks to "Insane Mode" and is rated at 691 horsepower. Or is it? A recent open letter from 71 Tesla owners, investors and supporters calls that power claim into question. The group's findings indicate that the Model S, on a full charge, was only capable of hitting 557 horsepower on a dyno. That's a lot, lot less than the stated 691 horses.

The open letter also notes how that horsepower discrepancy affects on-road performance. The issue is one of power to weight, with the group noting that the Model S P85D should perform like it has a power-to-weight ratio of one horsepower per 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." JB Straubel, Tesla's chief technical officer, kind of addressed the horsepower discrepancy in a post to the automaker's blog. He cited a number of factors as to why horsepower could be gimped, including additional weight from the driver and added options.

"Various situations (low state of charge, cold temperatures, etc.) can reduce this flow of electrons below the ultimate capability of the electric motor. In other cases, the potential flow of electricity may exceed the capability of the electric motor (warm battery, short duration accelerations, etc.)" Straubel never came out and said whether or not the P85D actually makes 691 horsepower, so the true horsepower of the sedan may never be known.