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There’s a performance device called “dragy” that reportedly is very accurate. It’s $149.

I’d certainly like to measure my Tesla’s performance, (uncorked S75D), but once that’s done I don’t really feel a need to have that dragy device sitting years unused in a drawer.

So... What I propose is that we put together a bunch of similar minded people with various Teslas, buy one dragy, and then mail it around so we can each objectively test our car’s performance. We’d assemble everyone’s numbers then come up with real performance numbers.

The dragy is GPS based and communicates with iPhone or Android. It has been criticized because it uses a 10Hz GPS, the thought being that it cannot measure in increments of less than 0.1 second. I think it interpolates so may get accurate times closer to 1/100 sec. I’ve read that it is very close measuring 1/4 mile track times, the times closely match the track times on the printed performance tickets.

Anyway if there is interest, reply here, and if there are enough interested people maybe we can look into it further.
 
IMO these are next to worthless for a Tesla. Their value can be found in vehicles that can be and are modified where you want to get a quantifiable idea how your modifications have changed the performance. In Teslas, you already know all the stats which are going to be more accurate for your specific car than the error of margin this device offers and on top of that.. what modifications are you planning to test out? I've used these in the past for other performance vehicles but on a Tesla it just feels like a waste of money.
 
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IMO these are next to worthless for a Tesla. Their value can be found in vehicles that can be and are modified where you want to get a quantifiable idea how your modifications have changed the performance. In Teslas, you already know all the stats which are going to be more accurate for your specific car than the error of margin this device offers and on top of that.. what modifications are you planning to test out? I've used these in the past for other performance vehicles but on a Tesla it just feels like a waste of money.

There are a few comments on other threads, like the improved driving dynamics software update one. Many, like myself, are curious if anything has changed in terms of acceleration. Others wonder if the cars really do their Tesla advertised 0-60 times.

I’m on board doing some testing if the OP follows through with this purchase.
 

ICUDoc

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May 19, 2015
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The dragy is GPS based and communicates with iPhone or Android. It has been criticized because it uses a 10Hz GPS, the thought being that it cannot measure in increments of less than 0.1 second.
Interpolation can give you (at best) half the limit of reading ie 0.05sec. But I don't know if you have access to the raw reading on Dragy.
I like your pass-it-around idea. Saves resources.
 
IMO these are next to worthless for a Tesla. Their value can be found in vehicles that can be and are modified where you want to get a quantifiable idea how your modifications have changed the performance. In Teslas, you already know all the stats which are going to be more accurate for your specific car than the error of margin this device offers and on top of that.. what modifications are you planning to test out? I've used these in the past for other performance vehicles but on a Tesla it just feels like a waste of money.

Tesla has not been quite honest about the 0-60 numbers. Tesla quotes Motor Trend testing that includes a 1 foot roll out. It doesn’t sound important but it is, it introduces a huge error in a 0-60 measurement. The quicker the car, the worse the error. So when you say I already precisely know the stats, well I don’t.

Tesla says my car will do 0-60 in 4.2 seconds. Tesla says that includes the roll out. My car will be moving at about 7 MPH when it reaches the end of that 1 foot roll out which is when the time measurement starts. So my car will go from 7-60 in 4.2 seconds. What’s the true 0-60 time? You tell me.

Or we can measure it.
 
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Tesla has not been quite honest about the 0-60 numbers. Tesla quotes Motor Trend testing that includes a 1 foot roll out. It doesn’t sound important but it is, it introduces a huge error in a 0-60 measurement. The quicker the car, the worse the error. So when you say I already precisely know the stats, well I don’t.

Tesla says my car will do 0-60 in 4.2 seconds. Tesla says that includes the roll out. My car will be moving at about 7 MPH when it reaches the end of that 1 foot roll out which is when the time measurement starts. So my car will go from 7-60 in 4.2 seconds. What’s the true 0-60 time? You tell me.

Or we can measure it.
1 ft roll out is the accepted standard whether you agree with it or not. It’s consistently 0.2 sec lower than without rollout and it’s pretty standard for most manufacturers...
 
1 ft roll out is the accepted standard whether you agree with it or not. It’s consistently 0.2 sec lower than without rollout and it’s pretty standard for most manufacturers...

1. It isn’t “the accepted standard”.
2. It is needlessly inaccurate
3. Your 0.2 second is not consistent, it is only accurate for one specific acceleration profile.

If you choose to accept it, go for it. If you think you can just add 0.2 seconds to any 1 foot roll out 0-60 measurement, you can do that. You won’t be correct but you can do it if you want.
 
Tesla has not been quite honest about the 0-60 numbers. Tesla quotes Motor Trend testing that includes a 1 foot roll out. It doesn’t sound important but it is, it introduces a huge error in a 0-60 measurement. The quicker the car, the worse the error. So when you say I already precisely know the stats, well I don’t.

Tesla says my car will do 0-60 in 4.2 seconds. Tesla says that includes the roll out. My car will be moving at about 7 MPH when it reaches the end of that 1 foot roll out which is when the time measurement starts. So my car will go from 7-60 in 4.2 seconds. What’s the true 0-60 time? You tell me.

Or we can measure it.
Yeah, you can measure it using a stuck on system that will offer roughly the same "precision" is my whole point.
 
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Yeah, you can measure it using a stuck on system that will offer roughly the same "precision" is my whole point.


Are you saying the dragy system is not accurate? If so I don’t think that is correct.

Do you anything to back up your opinion? If not perhaps you might share your reasoning that leads you to this conclusion.

I don’t say you are wrong, I just want to find out what is right.
 
Are you saying the dragy system is not accurate? If so I don’t think that is correct.

Do you anything to back up your opinion? If not perhaps you might share your reasoning that leads you to this conclusion.

I don’t say you are wrong, I just want to find out what is right.

It's GPS based measuring fairly small distances. I'm skeptical too, but reports say it's accurate. You probably need to do a few runs and average them
 
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Tesla has not been quite honest about the 0-60 numbers. Tesla quotes Motor Trend testing that includes a 1 foot roll out. It doesn’t sound important but it is, it introduces a huge error in a 0-60 measurement. The quicker the car, the worse the error. So when you say I already precisely know the stats, well I don’t.

Tesla says my car will do 0-60 in 4.2 seconds. Tesla says that includes the roll out. My car will be moving at about 7 MPH when it reaches the end of that 1 foot roll out which is when the time measurement starts. So my car will go from 7-60 in 4.2 seconds. What’s the true 0-60 time? You tell me.

Or we can measure it.

Tesla uses times with 1 ft rollout subtracted only for performance cars . So if you’re quoting 4.2s for a non performance it should be spot on. I’ve always assumed the different approach is to increase the marketing segmentation and also because every other car maker does the same thing.
 
Are you saying the dragy system is not accurate? If so I don’t think that is correct.

Do you anything to back up your opinion? If not perhaps you might share your reasoning that leads you to this conclusion.

I don’t say you are wrong, I just want to find out what is right.
It's GPS based so there's inherent flaws to timing something that does 0-60 or 0-whatever.

It's relatively accurate but there's also a margin of error that's probably around 10-15% possibly even more. I didn't read the documentation or reviews but I've used these GPS based devices in the past and they're not super accurate. It's best for comparing before/after mods since whatever error exists is more likely to exist across runs.

In other words, the difference between two different measurements will be more accurate/useful than just an individual measurement. This is where these devices shine is you do some baseline measurements and then perform whatever mod you have planned and then take some more measurements to get an idea (read: estimate) of how much power you gained via that mod.

If you plan to measure your car with a $150 consumer grade GPS device and then sue Tesla over the 0.01 difference in your 0-60 I think you're in for a rude awakening.

Bottom line: It's a toy. If you bought a six figure car you can likely afford something that's $150 for pure entertainment value. If you're trying to "time share" the $150 then you don't seem to fit this category so I would say it's not going to be worth your investment on something like a Tesla. If you want an idea of what the performance #'s are just Google it and you'll get more accurate #'s than what that device will get you after you spend your hard-earned duckets.
 
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Reactions: bhzmark
It's GPS based so there's inherent flaws to timing something that does 0-60 or 0-whatever.

It's relatively accurate but there's also a margin of error that's probably around 10-15% possibly even more. I didn't read the documentation or reviews but I've used these GPS based devices in the past and they're not super accurate. It's best for comparing before/after mods since whatever error exists is more likely to exist across runs.

In other words, the difference between two different measurements will be more accurate/useful than just an individual measurement. This is where these devices shine is you do some baseline measurements and then perform whatever mod you have planned and then take some more measurements to get an idea (read: estimate) of how much power you gained via that mod.

If you plan to measure your car with a $150 consumer grade GPS device and then sue Tesla over the 0.01 difference in your 0-60 I think you're in for a rude awakening.

Bottom line: It's a toy. If you bought a six figure car you can likely afford something that's $150 for pure entertainment value. If you're trying to "time share" the $150 then you don't seem to fit this category so I would say it's not going to be worth your investment on something like a Tesla. If you want an idea of what the performance #'s are just Google it and you'll get more accurate #'s than what that device will get you after you spend your hard-earned duckets.


Sue Tesla? 0.01 difference?

The 0.01 is off by a factor of 40.

I didn’t say anything about suing anyone. Can we not just discuss the hardware and leave out all the personal comments?
 
Tesla uses times with 1 ft rollout subtracted only for performance cars . So if you’re quoting 4.2s for a non performance it should be spot on. I’ve always assumed the different approach is to increase the marketing segmentation and also because every other car maker does the same thing.

Here’s the quote from Tesla’s site:
“Performance
Performance acceleration ratings are based on maximum battery power mode and follow Motor Trend's test procedure of subtracting the first foot rollout time to represent drag strip performance.”

It’s my understanding that all claimed acceleration numbers for all Tesla’s cars include the 1 foot rollout error. I believe the error is about half a second in the Performance S. I could be off a bit. Who knows? The only thing we do know is that Tesla’s numbers are wrong.
 

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