Wayland Invitational IV Electric Drag Races!

[tomsax]

More Wayland Video

I know I'm pretty late posting this, but in case there's anyone out there wanting to see more, here are some more videos from Portland.

This video shows my first run Saturday night, a race between me in my Roadster vs. White Zombie. Richard shot the video which shows how WZ totally outlaunched the Roadster, but then the Roadster matched speeds. As I was flying down the track, I was slowly gaining on WZ but not nearly fast enough to catch up in the 1/4 mile. Still, it was pretty exhilarating. Later that evening, I believe WZ put in a sub-12 second time, I'm sure that would have not felt so close.

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This is my second run on Saturday night, against ScottFe, a very close and exciting race.

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Later that evening, Richard drove my Tesla against ScottFe:

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Saturday afternoon, we converged on John Wayland's house, aka the EV Juice Bar, and charged up for the races. We had three Teslas, a Tango, White Zombie and more all charging at the same time. TEG posted my video clip earlier (thanks!), but if you missed it, here's the link:

YouTube - EV Power Bar Power Meter

The Tango was buried three cars deep in the driveway when it was done charging and wanted to head out. We were still working on clearing the way when he just made his own route:

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A half dozen Seattle-area owners are planning to converge on Pacific Raceways Friday evening for some more drag racing fun closer to home. I'm sure you'll be hearing more about that soon.

 

[tomsax]

Wayland Results and Observations

This is my best timeslip from the event, which I believe is the best time recorded with NEDRA for a 2008 Roadster: 12.982 second 1/4 mile ET at 103.48 mph.

My best 1/4 mile speed by a tiny margin was later that evening: 13.085 second 1/4 mile ET at 103.65.

I've entered the data from all of my time slips here: Time slip data in Google Docs Spreadsheet

My runs on Friday started with a state of charge around 50% in performance mode, and dropped to about 30%, with Richard and I both taking a bunch of runs and no time charging. My highest speed run Friday was a two-footed start which finally got me into the 100 mph club at 100.07 mph. My best time was on another run, 13.318 second 1/4 mile ET at 99.82 mph. I only tried the two-footed start twice, the first time with a terrible 0.789 reaction time, the second slightly improved at 0.516. I need to practice that some more. While this affects who crosses the 1/4 line first, it doesn't hurt the ET.

Ted Merendino told James that the two-footed start won't hurt the car, despite the terrible sound it makes, but I wasn't confident enough to really push it until I heard that Scotty did it full on, both feet on the floor, getting the best Tesla time by a good margin in James' Sport. I'll definitely be trying that some more Friday.

My times Saturday were better by a huge margin, over 0.3 seconds faster. RichKae had the same experience in my Roadster. So, something made a big difference. At first I attributed this to starting with a higher SOC, 215 ideal miles in performance mode, compared to the 100 down to 50 range we were in on Friday. But then Scotty turned in the best time of the weekend in James' Sport with the SOC down in the range Richard and I were running on Friday. So now my theory is that the battery pack being warm is also a factor. All of my runs on Saturday were with the car recently off the charger and/or on consecutive runs. My last, and worst, time of the night was after the car had been off the charger for at least an hour and also idle after the previous run for over 30 minutes. My time on that run was off by nearly 0.1 seconds from my best time, but that run was my best speed of the weekend. Curious.

On Friday, Richard and I together ran 16 times, so you'd think the battery pack would have been warm for some of those runs. I don't have Richard's times, but I made four runs in the first hour and I think he did two runs in the middle of those, so six runs in one hour, and still we were 0.3 slower than our times on Saturday.

Another difference between the two days is that we started runs as soon as we could, at 7:11 pm, with the sun still beating down on the track. It was especially nasty with the track aligned so that we were driving straight into the sun for those early runs. On Saturday, we waited (and charged) until sundown, then started our runs at 8:47 pm. The charging area was also cool on Saturday, with the Killacycle support RV providing some shade. So, perhaps there's something with getting the battery pack warm from charging, but not cooking the PEM as much.

I'll try to watch both temps more closely next time, but I know I was getting the PEM up to the first yellow bar very briefly, right after a run, on Friday and didn't see that at all on Saturday.

 

[TEG]

How much of the improvement in times do you attribute to running with traction control off vs on. Generally speaking was it on for Friday, and off for Saturday?

 

[Palpatine]

How much of the improvement in times do you attribute to running with traction control off vs on. Generally speaking was it on for Friday, and off for Saturday?

I would attribute about 0.1 second lower to traction control being off.

 

[TEG]

People seemed particularly interested in 1/8 mile times too.

From what I have seen, a good 2008 time is ~8.3s for 1/8 mile, and ~8.0s for the 2010 Roadster sport. It appears that the advantage of the 2010 Sport model shows up more at lower RPMs and as you approach top speed it isn't as pronounced. In other words, you gain the ~.3s advantage right away (even as you get to 60MPH) then it is more of an even race up to top speed (which turns out to be not much higher for the 2010 sport) so you end up just holding onto the lead you got at the start.

It will still be interesting to learn how much is Sport vs non-Sport motor differences, 2008 vs 2010 differences and A048 vs Neova tire differences.

 

[tomsax]

Traction Control

How much of the improvement in times do you attribute to running with traction control off vs on. Generally speaking was it on for Friday, and off for Saturday?

I never turned off traction control. I may try that tomorrow night.

 

[Palpatine]

More pictures from the Wayland Invitational IV...

2009 NEDRA - Portland - a set on Flickr

Crazy Horse Pinto (Mike Willmon) vs Tesla Roadster Sport (James Morrison)

 

[TEG]

Yeah those were my professional photographer friend's photos I mentioned before:

My friend's photos:
2009 NEDRA - Portland - a set on Flickr

I stayed with him for a few days in Portland but I was hogging his computer uploading my pictures so it took him a while to get his online.

 

[electrabishi]

I'm a newbie drag racer but if I correctly understand what I was told by other drivers at the event they have a way to engage ONLY the front breaks, leaving the rear wheels free for tire burnout. Without such a mechanism I think the rear breaks would make it hard to spin the tires even with traction control off. And I was never able to get them to spin or slip during a full-on raw acceleration in any case.

Hey guys it was great having you down in Portland. I had a blast watching the Teslas breaking into the sport. I know I'm a month late in getting something posted here about the EVent, but better late than never ;-)

Wanted to comment about the line lock thing. They are totally legal on the drag strip, and not illegal to have installed while driving on the street (just don't use it on the street ;-) )

Basically it is a solenoid in the rear brake line that closes with the push of a button on the dash, steering wheel, or other convenient location. With this line "locked out" the foot brake only operates the front brakes. This lets you hold the front brakes and let the rear ones spin. I noticed all you guys were going around the water box. Its there to promote tire spin for the burnout and keeps you from shredding the tires while doing so. I noticed all of you had enough traction with cold tires that heating up the tires any more wouldn't have helped much. However if you were getting even so much as a chirp it would affect your 60 foot times by a couple to a few tenths of a second. Every 1/10th you gain on your 60 ft time will net you a 2/10th's gain at the top end.

SO if you are hearing even a chirp on the launch I'd go for trying to do at least a compromise burnout in the water box. You may not be able to hold the front brakes, but give it a shot by letting the staging crew wave you into the water box. Most of them will wave you through until your rear tire has made a complete revolution in the water. Then just goose it once for as long as you can without accelerating past the starting line (this will "red light" you and you will lose your run). Even if you are able to get a couple spins without having a line lock it would put enough heat in the tires to let you launch without chirping. The 1/10th you save could get you 2/10ths at the top end.

One other thing to try, and I don't know if they had you do it at the Wayland invite is to drop the air pressure in your rear tires slightly. 0.5 psi can make the difference between doing an uncontrolled burnout while launching and hooking up hard and getting a good launch. I would just go in 1/2 psi increments until any chirping stops. I can't say how low is safe to go because I don't know what tires you are running. But typically 1-2 psi low won't hurt anything for a straight line run. Just remember to air them back up before you take the snaking back roads home ;-)

Mike Willmon

 

[Palpatine]

I can't wait until Mike moves from Alaska to Seattle. I need a driving coach.

There is clearly a lot more to this than just stomping on the accelerator and driving straight.

 

[doug]

FYI, Mike was recently on NPR
Scalding A Quarter-Mile In An Electric Ford Pinto : NPR

 

[vfx]

... I noticed all you guys were going around the water box.

I wasn't there but I guess I would have avoided a water box to not get my tires wet and make them slippery. Is that a problem? Not getting enough spin/heat and actually ending up on the line with tepid wet tires and a worse chance of traction?

 

[electrabishi]

I wasn't there but I guess I would have avoided a water box to not get my tires wet and make them slippery. Is that a problem? Not getting enough spin/heat and actually ending up on the line with tepid wet tires and a worse chance of traction?

Thats a very real possibility. But as quick as those things launch anyway, surely they make enough torque to spin the tires on wet pavement :wink:

I haven't heard yet if any of the Teslas racing lately have been noticing any tire chirp on launch, or what the 60 ft times have been on average. Once folks running them at the track regularly you'll start to see the trends with the 60 ft time and the ET and the Trap speed.

Its likely that if there is only a wee bit of tire spin the lower air pressure route would be the best to take and skip the water box.

Mike

 

[TEG]

I wasn't there but I guess I would have avoided a water box to not get my tires wet and make them slippery. Is that a problem? Not getting enough spin/heat and actually ending up on the line with tepid wet tires and a worse chance of traction?

Yes, that was the idea - if you aren't going to do a burnout to steam up the tires, then it is better to go around the water box and keep the tires dry and warm.

I think the battery box weight on the rear tires helped the Roadsters do OK traction wise even without cooking the tires first. If someone installs a line lock someday it might provide a slight advantage though.

 

[donauker]

I wasn't there but I guess I would have avoided a water box to not get my tires wet and make them slippery. Is that a problem? Not getting enough spin/heat and actually ending up on the line with tepid wet tires and a worse chance of traction?

Thats a very real possibility. But as quick as those things launch anyway, surely they make enough torque to spin the tires on wet pavement :wink:

Having never drag raced but heading to The Power of DC this weekend I must ask some possibly stupid questions.

Given the open differential on the Tesla, what is the possibility (probability?) that you would only get tire spin on the lighter loaded tire and be left with one cool wet tire? I do know the TC light can be readily induced to frequent flashing on wet roads. :wink:

Recommended rear tire pressure (for lower rolling resistance, increased range) is 40 PSI. Accepted reduction to 36 PSI is for improved comfort and handling. At what point might rolling resistance increase affecting higher speeds offset launch gains?

 

[electrabishi]

Having never drag raced but heading to The Power of DC this weekend I must ask some possibly stupid questions.

Given the open differential on the Tesla, what is the possibility (probability?) that you would only get tire spin on the lighter loaded tire and be left with one cool wet tire? I do know the TC light can be readily induced to frequent flashing on wet roads. :wink:

Ahh, its open? Or is it a limited slip? These are things I do not yet know about the car. If someone were to be able to (somehow) :wink: test this they could tell us if the car leaves a single black strip, two solid ones, or a combination of one short and one longer than the other. You could also jack up the rear end and spin one tire by hand and see if the other one rotates the same way or opposite than the one you are spinning. Its probable that its an open differential with a traction control that brakes the torque from the spinning tire. But I'm not intimate with the systems designed on the car.

Having never drag raced but heading to The Power of DC this weekend I must ask some possibly stupid questions.

Recommended rear tire pressure (for lower rolling resistance, increased range) is 40 PSI. Accepted reduction to 36 PSI is for improved comfort and handling. At what point might rolling resistance increase affecting higher speeds offset launch gains?

My Hoosier Drag Radial are the same pressure spec's. I run 32 on the street and 40 psi is the max rating. On the drag strip I run them at 11.5 to 12 psi. They are however a lot larger tire than your low profile tire so running that low may not be advised. But dropping them to as low as 25 lbs likely wouldn't change the straight line handling performance of the tire. The very slight increase in rolling resistance would be well over come by any partial spin you get from a launch. Its likely that if you hook harder (and leave slightly quicker) your trap speed will be slower. It seems counterintuitive that the quicker you accelerate, your trap speed would be slower.

Take for instance two 12.5 second cars. My Pinto does 60 feet in 1.7 seconds and traps out at 103 mph. My friends Jeep CJ that he runs a 454 Cu. in. gas engine does 60 feet in 2.2 seconds, finishes right at the same 12.5 seconds but at 115 mph. I know that this difference can be explained by the different Torque profile and power curve between our cars. However , if I air up my tires too much where I get a little chirp when I launch, my 60 foot time goes up to 2.0 seconds and I trap out at 105 mph. I still don't have a full understanding on why this is so. But it is consistently so.

Another one is that between me and Hank (who has over 80 lbs on me) the car will run 0.1 to 0.2 seconds quicker with me in it, but will trap out at 0.5 to 1.0 mph faster with Hank in it. Another one to ponder when you're tuning your Tesla's. Losing 100 lbs off the car will in general make about 0.1 second better ET. So leave the extra water bottles, i-Pods and overnight bags in the pits :biggrin:

Mike

 

[doug]

Ahh, its open? Or is it a limited slip? These are things I do not yet know about the car.

The Roadster has an open diff. An LSD option would be nice, though. :smile:






.

 

[Tdave]

Ahh, its open? Or is it a limited slip? These are things I do not yet know about the car. If someone were to be able to (somehow) :wink: test this they could tell us if the car leaves a single black strip, two solid ones, or a combination of one short and one longer than the other. You could also jack up the rear end and spin one tire by hand and see if the other one rotates the same way or opposite than the one you are spinning. Its probable that its an open differential with a traction control that brakes the torque from the spinning tire. But I'm not intimate with the systems designed on the car.

It's an open diff. And the traction control reduces power from the battery to control traction, so it reduces power to both wheels to the point that neither wheel slips. This results in horribly underpowered exits from turns according to my few days of experience in my new Roadster Sport. I've discovered turning off TC fixes this problem. In dry conditions, I'm turning off TC regularly for spirited driving on the street. Even for moderate radius turns, power induced oversteer is not possible. And for tight turns, it's easily controlled with the instantaneous digital-like control of power. I only recommend this for the experienced.

Off-topic tangent: This is exactly why I want to see separate motors per wheel, with the TC software controlling the slip independently for each wheel. Make it all wheel drive and we have an unbeatable winner.

 

[TEG]

Take for instance two 12.5 second cars. My Pinto does 60 feet in 1.7 seconds and traps out at 103 mph. My friends Jeep CJ that he runs a 454 Cu. in. gas engine does 60 feet in 2.2 seconds, finishes right at the same 12.5 seconds but at 115 mph. I know that this difference can be explained by the different Torque profile and power curve between our cars. However , if I air up my tires too much where I get a little chirp when I launch, my 60 foot time goes up to 2.0 seconds and I trap out at 105 mph. I still don't have a full understanding on why this is so. But it is consistently so.

Seems like the wheelspin has you starting out slowly (wasting some of your ET), but once the tires hook up you suddenly get jolted forward to a higher speed. In other words, the spinning wheels let your motor get the tire revs up quicker and so you get to a higher max speed, but you wasted some time at the start not moving much at first. Having a graph of speeds and acceleration forces covering the whole quarter mile would probably make this easier to visualize.

 

[electrabishi]

Seems like the wheelspin has you starting out slowly (wasting some of your ET), but once the tires hook up you suddenly get jolted forward to a higher speed. In other words, the spinning wheels let your motor get the tire revs up quicker and so you get to a higher max speed, but you wasted some time at the start not moving much at first. Having a graph of speeds and acceleration forces covering the whole quarter mile would probably make this easier to visualize.

Someone reasoned that since it takes you longer to get there you have a longer time to accelerate to a higher speed. Don't know if I buy that until I can get some data like you mention. :biggrin:

Another way to look at the lower trap speed is to look at the extreme case of instant acceleration (or cheating by getting a head start before you cross the line). If you could instantly be going 72mph when crossing the starting line you would do a 12.5 second run, and your trap speed would read 72 mph. So you can get an initial (relative) measure of a cars acceleration by gauging how low its trap speed is compared to a comparable time from another car. This assumes fairly constant acceleration (which a power limited electric is pretty much).