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Model S vs Roadster on the Track

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Perhaps weather and/or "traffic" on the track account for some of the discrepancies...

The 1:50 time for Roadster in 2011 and the 1:51.8 time for Model S in 2012 were both Time Trial laps (you get the track to yourself-- no traffic). At Laguna with M5 a couple of weeks ago, there was always some traffic, but it was open passing and people were trying to not hold each other up. The weather in November was a bit cooler: low 60s versus mid/high 60s at refuel in July (I just looked it up and ave temp on 7/1/12 was 64 degs).

I looked up 11/3/12 weather for Byers, CO (where Cottonwood ran his test). Mean temps 45deg with high of 57deg. So significantly cooler than Laguna at Refuel.
 
If it's not overheating, I would guess it's the lower SOC (lower SOCs tend to lower available power, since for one, the battery voltage is lower; this effect is apparent in the fact that both the Roadster and Model S have better drag times when fully charged). However, the effect there shouldn't be as significant as a drop from 320kW to 160kW.

Without actual data though, this is all (largely uneducated) guessing.

So suggestions to Tesla would be a display that at least shows why the power was reduced.
 
Great to see someone take the Model S to the track and give a real run. I have to say I'm very disappointed that Tesla wasn't able to solve the cooling issues with the addition of liquid cooled motor and PEM. While I dont expect an EV to take the same track abuse as a Porsche 911 it should be capable of handeling more than just a few laps before over heating.

This also puts a damper on the rumors of Tesla introducing liquid cooled PEM/Motor option for the Roadster, apparently it wouldn't fix the issue.
 
I am crossposting this from the MSP vs M5 forum. Feel free to scroll down to the portion I marked as "Relevant to this thread"

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Been super busy lately with the election and with work, so haven't been able to keep fully abrest of the info stream.

Current summary -

Cottonwood had a bad day, and couldn't get a single valid lap in. That's an issue, which is either particular to Cottonwood, or a limitation with the car itself.

Personally I think it was Cottonwood centric, but that is pure opinion, based on the following - MSP has now been extensively track tested, by multiple publications and independant writers as a part of the review process. Lap times have not been released, but nobody has reported a problem with the car being unable to complete laps. Automobile Magazine reported the following -

For all its high-tech novelty, the Model S does an exceptional job at the things we expect any high-priced sport sedan to do well. The electric power steering is nuanced and well-weighted, with natural buildup just off-center. Through corners, the Model S exhibits impressive body control and vacuumlike grip despite weighing more than 4500 pounds. Editors also raved about the suspension's ability to soak up bumps that tortured other test cars. It was just as impressive on the racetrack -- yes, we took it on the track. "All that speed, along with powerful braking, superflat handling, and sharp steering, gives you the sense that you're invincible," marvels Jennings.

You'd think that at some point they'd mention that the car failed to complete a lap. For background, I've met Jean Jennings. She is not a professional race car driver, but she came up through Chrysler where she was a professional test driver and mechanic at their test facility. She is very experienced at pushing a car to it's limits. Among her testers at Automobile Magazine are also drivers with professional racing experience.

MotorTrend does extensive track testing with SCCA certified testers. Sports Car Club of America sanctions road racing, rallying and autocross, for both amateur and professional racers, and I would presume that their certified testers are accustomed to measuring performance at the edge of the envelope.

Neither magazine reported problems with the car being unable to complete a lap. Both raved about it's track performance (but did not publish lap times). Both publications voted it Car of the Year because of it's performance.

Edmunds Inside Line *DID* report a falloff in straight line 0-60 performance over multiple tests, with a best of ~4.3 and eventually falling off to ~4.6. This was on a hot day, and we speculated that it might be due to heat buildup. Nobody else has reported this, but the other publications only report best times.

Edmunds itself speculated it might be because of a falling battery charge, but seemed unconvinced. Every car made has a couple of tics variation on any given run. While this is not usually a linear decrease (or increase), in any limited set of runs (in this case 3) there is a significant chance you will have what appears to be a linear decrease in performance. More testing is required before we know there is an issue, let alone determining a cause.

At the 2012 Refuel races, a pre production Model S did a 1:51. At the time I posted that M5 does 1:40's and that a 1:51 is disappointing. But based on data from Inside line I was (and still am) convinced that MSP should be able to do 1:40's at Laguna Seca. We now have more test data which points to substantially faster times than 1:51's, but that and $8 will buy you a $6 burger combo at Carl's Jr (time to change the name of that burger IMHO).

RELEVANT TO THIS THREAD

Regardless, Cottonwood *DID* have a problem. Suggested reasons are -

A low state of charge causing excessive heat.
A malfunction in the cooling system.
A design limitation that prevents the car from being operated at maximum performance for even a single lap (I'll take odds against that).
?
I'll go out on a limb and propose another possibility pulled directly from my nether regions. It's known (or assumed) that Model S will cut power when it encounters heat issues, just like the Roadster. But it has been reported by Cinergi that the Model S will cut power output in the way described when its predicted range gets down to ~30 miles.

Under track conditions ~100 ideal miles might have briefly dipped under this limit as the car looked at actual usage and predicted that it could only make it ~30 miles under those conditions, causing it to cut power. Of course, once you stop pushing it the predicted range starts moving back up to the ideal range and suddenly you get your performance back until you try pushing again.

Call it the Top Gear rule. A 200+ mile Roadster predicts it can only go ~50 miles under load. If control software shuts you down at 30 miles predicted that might be an issue when you are racing with only 100 ideal miles left in the tank. Keep in mind, if you start with a full SOC you can race for dozens of real miles before this issue crops up.

Here is the link to Cinergi's report -

Behavior when getting low on range

Personally, I'd bet on any hypothesis not relying on a design limitation which causes the more advanced liquid cooled power electronics to shut down before the air cooled Roadster does. On a cool day.

I think that the firmware reigning in the car as reported by Cinergi (which I guess *IS* a design issue, albiet software related), or a simple mechanical malfunction in the cooling system are the most likely possibilities in the absense of additional data.

Edit:

Note Post #5 on Cinergi's report about the dotted yellow line at 160kWh (normally 320kWh) starting at 30 miles projected range.

Also note Cottonwoods report of the car being limited to 160kWh in post #1

Model S vs Roadster on the Track

With its liquid-cooled PEM, batteries, and motor, I had high hopes for the MSP to hold power. Unfortunately, my hopes were dashed. In 1/2 to 2/3 of the 1.83 mile lap, the little dashed limit line came on the power display, usually reducing power from 320 kW to a little more than 160kW. This shows up in the MSP having a better maximum speed (at the end of the south straight away) before the power was limited, but having worse lap times because of the reduced power in the last 1/3 of the lap. The Roadster tells you the PEM hot is the limiting factor. The MSP just lets you know the power is limited. We don't know if it was the PEM, batteries, or the motor. We did do this at the end of the day with the MSP charge at 100 miles or so rated range.

The lowest I've gone now is 20 miles left. The battery goes yellow around 30 and power is limited. I know others have had less. Would love to document what happens as you get to 0 ... can you keep driving all the way to 0? Past 0? Does power get limited even more as you get closer to 0? Details / pics please! Here's one to start:

View attachment 11616

The only thing unusual in those pics is the yellow dotted line near the 160kW power mark. That appeared with around 30 miles left.
 
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@ CapitalistOppressor - Great post! - The one thing that I don't understand is why Tesla has not responded to Cottonwood about the events on the track. Whenever I have called they have responded pretty immediately. They can pull logs remotely and have engineering look at exactly what were the limiting factors. I guess they could take the view that the track is outside of normal recommended use - but Model S Performance is supposed to run with the best of the competitors in its class. Would love to have Tesla at least look at the logs and comment.
 
I went to the track today with my Sig P85, and outperformed a corvette Z06 by over 10%. Also collected data that fully supported the "predicted-range power limitation" theory:

Under track conditions ~100 ideal miles might have briefly dipped under this limit as the car looked at actual usage and predicted that it could only make it ~30 miles under those conditions, causing it to cut power. Of course, once you stop pushing it the predicted range starts moving back up to the ideal range and suddenly you get your performance back until you try pushing again.QUOTE]

Even at over 220 EPA rated charge left, the power would be limited to 160kW exactly when the "predicted range" fell to 31 miles. The solution was then to simply drive very slow circles around the pit area for a few minutes, until the predicted range went back up. Then we'd get another 3 fast laps with full 320+ kW power. Wish there was a "reset" button for the predicted range.

Anyway, despite what appears to be purely a software issue, it's an awesome track car. I passed everybody, nobody could even come close to keeping up.
 
That sounds very interesting. What settings did you use for prediction? I take it average, 5 miles? Did changing the 5 miles to 15 or 30 make any difference(if you played with this)?

Peter

I went to the track today with my Sig P85, and outperformed a corvette Z06 by over 10%. Also collected data that fully supported the "predicted-range power limitation" theory:

Under track conditions ~100 ideal miles might have briefly dipped under this limit as the car looked at actual usage and predicted that it could only make it ~30 miles under those conditions, causing it to cut power. Of course, once you stop pushing it the predicted range starts moving back up to the ideal range and suddenly you get your performance back until you try pushing again.QUOTE]

Even at over 220 EPA rated charge left, the power would be limited to 160kW exactly when the "predicted range" fell to 31 miles. The solution was then to simply drive very slow circles around the pit area for a few minutes, until the predicted range went back up. Then we'd get another 3 fast laps with full 320+ kW power. Wish there was a "reset" button for the predicted range.

Anyway, despite what appears to be purely a software issue, it's an awesome track car. I passed everybody, nobody could even come close to keeping up.
 
I tried all the prediction intervals, but keeping it at 30 let us get our power back more quickly when we trolled the pits. Here are a couple of videos:
http://www.youtube.com/watch?v=TUsK18XAe3k&list=UU5CCwicyAAl3kIDAMqwrWcA&index=2

http://www.youtube.com/watch?v=kdtNhHcI5tE&list=UU5CCwicyAAl3kIDAMqwrWcA



That sounds very interesting. What settings did you use for prediction? I take it average, 5 miles? Did changing the 5 miles to 15 or 30 make any difference(if you played with this)?

Peter

I went to the track today with my Sig P85, and outperformed a corvette Z06 by over 10%. Also collected data that fully supported the "predicted-range power limitation" theory: