malcolm

Does this bring us back to a discussion about the need for a two-speed transmisson?

James

Based on what we saw, I think the key for the Tesla Roadster is a 100% charge and being in performance mode for about two hours to get warmed up.
It is difficult to get to that perfect state and still have fun during the evening. You want to go out and do a few runs. But if you do that before you are ready, you are never at that best state for the best time.

We charged in range mode at the EV Juice Bar (Wayland's house) and all left with 100% full batteries. But it was 15 miles to get to the track, so we are already down. We had 40 amp recharging at the track for about two Roadsters at a time, so we were always trying to sneak in there and suck juice to keep our charge percentage high.

Every single run reduces the ideal range by 4 or 5 miles. So if you do 3 runs, then you need about 30 minutes at 40 amps to get back to where you started. It takes planning to get it all right. I seemed to be able to stay around 75% most of the night. But my runs while near 95% were with performance mode only recently turned on. So the Roadster Sport was never really warmed up while it had a high charge.

We produced our record 12.643 seconds with a warmed up Roadster Sport at 75% charge. So clearly there is a better time in there. Maybe 12.4 or 12.5 is possible with this car. We will find out in a few weeks.

The ideal scenario would be to have an HPC with 240 volts and 70 amps at the track. Then of course your charge could be more easily maintained at closer to 100% over the course of the evening.

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SByer

Were those runs with TC on or off? Which cars had the performance tires?

TEG

Everyone started out with TC on. Then later we realized that the times were a tad better with TC off, so the 2nd day most runs were done with TC off. Given the starts were off a line covered with rubber from the other cars, and with warm ambient temps, the tires had plenty of traction. Scotty's two foot launch (loading up the emotor with the brake on) managed to break traction a bit at launch but it looked like he 'hooked up' rather quickly. Note: NONE of the Teslas did a tire warm-up burnout in the wet area before getting to the line. I suppose there might have been an extra tenth to find if one were to get the tires even stickier with that trick. The Tango was doing burnouts before they got to the line. Note: cooking the tires like that wears the tires out quickly. All of the Roadsters were on their "daily driver" tires, so I think the owners had some limits as to just how much they were willing to "abuse" their cars at the track.

(I am still in Portland right now... It is 104 degrees today and the same yesterday... Good thing this hot spell came after the event!)

James' Roadster Sport was the only Roadster with the A048 Sport tires. All of the 2008s had the standard Neova high efficiency tires. It is hard to know how much of the ~.3s difference in the quarter mile time is due to tire differences, or 2008 vs 2010 differences or Sport vs non-Sport differences. Theoretically it should be mostly the motor power output improvements, but getting some 2008s with sport tires, and non-Sport 2010s on the track should help answer that question.

TEG

After James' Sport made the two quickest runs it went back for a 3rd but showed "Battery Error" on the VDS. After a while it cleared up and it returned to normal, but apparently if you really push hard you can overheat things. It seems that the motor, PEM and battery pack are all subject to occasional situations where power has to be reduced temporarily.

When I was looking behind the diffuser on the 2008s and the 2010 Sport, I noticed the 2010 Sport had two fans attached to the motor, compared to one on the 2008s.

I=V/R

One of those fans is attached to the motor, as with the 2008, although the airflow is routed a bit differently.

The other fan is attached the PEM - the 2008 PEM has an internal fan.

These changes are common to all 2010s, not just the Sport.

dpeilow

Apologies - I swapped an 8.7 for a 7.8 somewhere in my head.

qwk

I posted this in the other thread, but it probably belongs here. Anyway, in an ICE car the high 7 1/8th mile times @~88mph would net you high 11's @~116 in the quarter. Since the roadster only has one gear, you can tell the high rpm power tapers off because the trap speeds in the 1/4 mile are so low.

James

That makes sense. It is very quick to 90 mph. But it is a bit slower beyond that to 100+. I think the highest 1/4 mile time we saw all weekend was around 104 mph on a Roadster.

__________________
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The Roadster Foundry Mobile Connector (RFMC)

doug

Sorry, I haven't been able to pay very close attention. Is there a compelling reason for there to be two threads here. Seems they are about the same topic. Other moderators have suggested a merge, and I tend to concur.