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shark2k
Member
Hahaha. That's funny. I like that idea though. Get behind grandma or grandpa (the one's that drive slow) and blame them lol. Get good mileage and don't have to take the blame (of course best to be in a one lane with no passing allowed (thanks for noticing TEG :tongue:.) :biggrin:
-Shark2k
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Tesla is OK for no passing aloud (being as quiet as it is). If there is no passing allowed then that is another story... :wink:
Tdave
Member
Benefits of Drafting
If someone doesn't beat me to it, I plan to do tests of energy savings while drafting behind a big rig at a safe but close distance on the highway. This data is encouraging that the extra range possible will be considerable.
As a strategy during a longer trip, you could go along at 50-55 mph, and when an 18-wheeler passes you, pick up behind it and get the extra speed for free, or as I suspect, better than free.
Based on that chart, I'm guessing you can get close to 50% more range by drafting at 65 mph than going it alone at the same speed. In other words, 65 mph while drafting would be equivalent to 43 mph by yourself.
If someone doesn't beat me to it, I plan to do tests of energy savings while drafting behind a big rig at a safe but close distance on the highway. This data is encouraging that the extra range possible will be considerable.
As a strategy during a longer trip, you could go along at 50-55 mph, and when an 18-wheeler passes you, pick up behind it and get the extra speed for free, or as I suspect, better than free.
Based on that chart, I'm guessing you can get close to 50% more range by drafting at 65 mph than going it alone at the same speed. In other words, 65 mph while drafting would be equivalent to 43 mph by yourself.
JRP3
Hyperactive Member
Probably because that chart is steady state driving, not hammering the throttle and hard cornering and braking. Not saying JC was correct, but it is possible.
Tdave
Member
The 121 mph range number should be worst case, no? Accelerator is floored and PEM is giving it all it can muster.
Oh wait, 121 mph is at max RPM, I think. So top speed is rev limited, not power limited.
I would still guess that constant max speed uses more power per mile than multiple round trips 0-100-0. But I'm just guessing.
Mythbusters already did this. I thought someone posted the video here, but you can dig it up on youtube I'm sure. The savings are substantial, within the ballpark of what you guess.
Tdave
Member
The numbers in those graphs tell part of this story. We can calculate the rest of the story...
The chart says range at top speed is 81 miles.
A continuous sequence of quarter mile runs would run the PEM at its max 185 kW during acceleration and 0 kW during braking. It can do the quarter mile in 12.7 seconds. 185 kW for 12.7 seconds equals 0.653 kWh. Then let's stipulate that we'll take a quarter mile of slowing down back to 0. So that's 0.653 kWh every half mile before the sequence repeats. The 53 kWh battery will be able to do 82 of those runs before running out. That's a 41 mile range, for a near worst case.
The motor doesn't output 185Kw over the entire RPM band. Look atTesla Motors - acceleration & torque. You could match that power curve to Road and Tracks quarter mile graph and then do some sort of quasi-integration to determine the energy used in a quarter mile run, and then you'd have to factor braking regen(assume 27kw) during the braking portion. Assuming you tried to maximize regen, range would be alot more than this.
I'm just going to assume that Top Gear was pretty much as bad as it gets.
I don't understand this. They are shipping v1.5 to customers but still show old torque and power curves and state 248HP as max power even for v1.5 cars.
In that leaflet for european version they are promising 300HP. Will 2009 model be upgraded?
Is it possible that even current v1.5 cars have old, first version PEM with new singlespead gearbox and power upgrade will come with 2009 model year that will be sold to Europe also?
My guesses:
#1: The 300HP on the Euro literature was a mistake/misprint.
#2: Low end torque rose (from ~200lb-ft to ~280lb-ft), but not max HP, so total HP for 1.5 isn't much more than for 1.0.
#3: Perhaps they don't plan on updating the torque curve on their web site until all the first shipped 2008 cars get upgraded to 1.5 drivetrain?
I suppose they could they be planning a drivetrain upgrade for the Euro-Roadsters and the 300hp turns out to be right after all, but I sortof doubt it.
Either way, 55 or 41 miles, I like the fact that driving the freak'in snot out of it, balls the the wall, pedal to the metal as hard as I can possible thrash the Roadster...
I can still get to work and back, no problem.:biggrin:
So - I just did this journey (Southampton to Edinburgh, 430 miles) in 8 hours with 90 minutes of stops.
Thanks to JB's charts I was able to see which service stations I would have had to stop at based on the speed I was driving.
If Tesla can get a three-phase, 1 hour charger into just a few strategic locations, and if the range gains from 2900mAh cells we discussed are possible, then there is no reason I couldn't do that journey today with zero inconvenience over an ICE car. To me, this proves the issues are no loner technological.
graham
Active Member
Yes, especially if you also think of the multi-battery pack solution they have talked about with the Model S with the high-end being over 300 miles. I wonder if that is with 2200mAh, or 2900mAh cells? Very likely by 2011 when the Model S actually hits the streets with the extended range, the required charging will be very minimal. I am optimistic.
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