Considering leaving my just-built P85D at the altar for an 85D

[dirkhh]

Well, went and test drove that 85D, and also talked at length with my sales advisor.

1) As I suspected, the 85D is great - it handles better and feels more planted than a 85. Acceleration lags slightly off the line, but at any speed it seems to accelerate almost as fast as the P85s did. If I drove this thing before I finalized my order, I would have stuck with the 85D.

2) It's just as east to hog the watts with an 85D as it is with a P85D. The average on the demo car was in the 700s, obviously due to spirited test drives. I managed to keep it a little above 300 on the highway, but had to really be gentle.

3) They can't transfer an existing order to someone else, and I'd lose my $5K deposit (I originally ordered when they were still 5K, and had it transferred).

The net is, I'm sticking with the P85D. Should have it in 2 weeks or so.

I'm surprised that they weren't willing to work with you. Might have been the person you talked to. Pushing this up the chain might have gotten you a better result.
But I think you won't regret sticking with the P. From the data that I have been able to gather the consumption difference, assuming similar driving style, will be <10%.
I'll admit that since ordering I have had my moments when I doubted getting the P85D over the S85D. But my car is on a truck to Portland. And I wouldn't have been able to get an S85D before mid April... and I definitely wouldn't want to wait another month

 

[Ben W]

That 328 has to be kicked upward a bit due to 5k+ altitude. At 7500 ft elevation there is only 50% of the air @sea level (the only metric I've seen) so maybe some here can come up with an adjustment factor. But I do admit to being half-gassed, usually. :smile:
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The air pressure at 7500ft is about 77% of that at sea level. (Calculator: http://www.altitude.org/air_pressure.php) This corresponds to a 23% reduction in wind resistance, which should yield better efficiency at highway speeds. The trade-off is that cooling efficiency is also reduced 23%, but for typical cruising that's probably minor. Another consequence is that if you inflate your tires to 40psi at sea level then drive to 7500ft, your tire gauge pressure will rise to 43.4psi (all else being equal), which further reduces rolling resistance and boosts efficiency.

Since at highway speeds about 2/3 of the energy is spent battling wind resistance, you can calculate that a 23% reduction in aerodynamic drag will improve your efficiency from 328Wh/mi to about 280Wh/mi. This would raise the nominal 265-mile range to 312 miles! Perhaps the official EPA range needs to be adjusted for Teslas sold in Colorado?

 

[sorka]

To the OP: I think you're overreacting to the reports of lower efficiency in the P85D. I don't dispute that there is as yet some penalty, particularly in city driving, but I've got 5300 miles on my P85D, all during the winter (obviously), with a lifetime average of 328 Wh/mi. I've successfully driven two, 251-mile legs, on a single charge, with better than 20 Rated miles remaining both times.

By all means, switch to the S85D if that's what you want: it's a great package and it's less expensive than the PD. Just thought you should have the benefit of my experience while you decide.

It would be nice. Steve, I don't doubt what you're saying but you probably have a special car. Maybe the alignment is just perfect enough to lower parasitic drag. Who knows, but most are claiming far far higher Wh / mile usage with some seeing slight improvement with software updates and others not seeing any improvement.

 

[wycolo]

> (Calculator: Altitude.org | Altitude air pressure calculator) [Ben W]

Site requires Flash to compute: 77% air = xx% O2 in hemoglobin. Maybe someone can get this figure. Perhaps that is the 50% I was recalling. Thanx.
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[stevezzzz]

Totally OT:

I've taken the Air Force physiological training program twice over the years; it includes a ride in the altitude chamber to explore your personal response to hypoxia, which varies widely from one person to the next. Some 'fun facts' have stuck in my head from the experience...

Roughly speaking, the altitude at which the ambient pressure drops to 500mB (50% of sea level pressure) is 18,000'. Above about 35,000' the partial pressure of water vapor in your lungs effectively displaces the oxygen, and so to survive above that altitude you have to resort to breathing 100% oxygen under positive pressure. Above 60,000' the ambient pressure is so low that blood will boil (if it were sitting in a container at body temperature, that is, and not confined in your circulatory system).