Dynolicious vs. V-Box and Dynojet
by Damon Lavrinc on Aug 1st 2008 at 7:58PM 
Click any image for a larger version.
Give us an iPhone application that relates to cars and we're all over it. Apparently, so is the crew at Motive. They took out an Audi S5, mounted a Racelogic V-Box onto the windshield and brought along a Dynolicious-equipped iPhone to see how it stacked up.
The V-Box uses both GPS and yaw sensor data to serve up 0-60 times, 1/4-mile trap speeds and lateral Gs, whereas the iPhone only makes use of yaw information to deliver the same numbers... along with estimated horsepower figures. While Motive wanted to find out how the Dynolicious would do with 0-60 times, we were interested in how close it would come to wheel horsepower given both an estimated weight and drivetrain loss. That meant hitting up the Dynojet at Modacar and strapping our own Project Track Slut onto the rollers.
Read on for both Motive's conclusions and our own.
Gallery: Dynolicious vs. V-Box and Dynojet
For $12.99, the Dynolicious software seemed too good to be true, but we were willing to reserve judgment until testing proved otherwise. While we've played with a few Racelogic boxes before, and found the data acquisition and customization capabilities to be beyond reproach, the cost of an entry-level model – around $499 – may be a bit prohibitive for your average enthusiast.
Motive turned off the one-foot rollout setting on both units – interested in only 0-60 times and not quarter-mile runs -- and performed ten seperate sprints to 60. You can check out Motive's screen shots of the results here, but the results showed the Dynolicious software was anywhere between 0.24 to 0.65 seconds behind the V-Box, which kept very consistent times throughout the test.
With our 1992 BMW 318is mounted onto a Dynojet on a 90-degree day, it put down a respectable, if not particularly powerful, 122 hp to the rear wheels. The graph above shows the last two runs (red and green) were within one horsepower of one another, while the first run (in blue), was done with the A/C on... whoops.
After unstrapping the Slut, we double-checked our tire pressures (38 psi all around for daily driving), inputted our estimated weight (2,900 pounds, with 1/4 tank of fuel and a monkey in the driver's seat), estimated drivetrain loss (17 percent) and set off to make a few passes. We ran to 60 six separate times, with semi-consistent launches (although we weren't clutch dropping for the quickest time) and recorded output figures ranging from 125 to 141 hp. Excluding the outliers, our average "Peak Horsepower" rating was 129 hp. Dynolicious' website says that its software provides both wheel horsepower and engine horsepower figures, but the only information displayed (see right) is the "Peak Horsepower" calculation. If that's supposed to be power to the wheels, its close, but far from exact.Is it worth it? For $12.99 there are worse things you can spend on your ride (see: LED windshield washer nozzles), but we're not ready to give up our dreams of V-Box ownership yet. And with detailed horsepower and torque curves (not to mention AFR), a traditional dyno is still the best means of getting accurate figures at the wheels. Neither are cheap, but price and precision are rarely mutually exclusive.
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Reader Comments (Page 1 of 2)
Chase 8:39PM (8/01/2008)
In defense of Dynolicious, the hp-meter is the least accurate of its features. The thing assumes you're on flat ground, you have a particular wind resistance, and you have a particular rolling resistance. That means the slight grade in the road, the shape of your car, the size of your car, the type of surface you're on, and the type of tire you're using are not the same as what the program uses to deduce your hp out of your acceleration.
But, in a pinch, its awesome.
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nataku83 8:29AM (8/02/2008)
My guess would be running tires at 38 psi would reduce rolling resistance enough over the specd tire pressure that it'd add at least a hp or two to the overall number. In addition, the accuracy of the weight measurement could also have a pretty decent effect.
Xcountryflyer 9:05PM (8/01/2008)
Its 12.99--pretty good for 12.99 and just an iPhone/Touch. I would like to see some more 0-60 test to see if the lag is consistent. If it is, then you can just subtract it to get the rough real 0-60.
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tankd0g 11:06PM (8/01/2008)
Here a stupid question, if it's not using the GPS, how does it know when it got to 60?
paul34 12:15AM (8/02/2008)
Tankdog, given a certain acceleration multiplied by time (constant and known), you can deduce both speed and distance.
Of course, acceleration varies in each gear and between shifts, but the accelerometer in the iPhone would detect that and the software would have to take that into account to calculate useful times.
why not the LS2LS7? 12:45AM (8/02/2008)
tankd0g:
It uses dead reckoning.
It uses the accelerometer in the phone to measure the acceleration of the car. You integrate that (sum it over time) and you know the speed of the car. You integrate that (sum it over time) and you know the location of the car.
So it starts from 0 acceleration, 0 speed and 0 position and it knows when you are at 60mph, or 1/4 mile away from where you started.
Well, it would, except dead reckoning like this is rather imprecise due to accumulated errors from all that summing.
The HP figures are even more fudged. Much more fudged. They do some math of the acceleration and speed and use that to calculate HP being applied to accelerate the car. And then it reverses that back to HP at the engine.
Don't take the figures too seriously.
m 9:06PM (8/01/2008)
Fail.
The iPhone app only uses acceleration data, there's no gyro on the iPhone, only a 3-axis accelerometer.
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Taylor 6:01PM (8/17/2008)
Well, really if you are just doing straight line acceleration, you don't need a gyro, they're basically just used to compensate for rotation.
-Taylor
Stringfellow Hawk 9:10PM (8/01/2008)
I think for $12.99 that is plenty close enough. I bought the app the second I saw it.
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Mark 9:26PM (8/01/2008)
If numbers aren't accurate, they are almost useless. IMO
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Allan 9:36PM (8/01/2008)
I wouldn't say useless... you could at least use it to compare car to car. The same inaccuracies would carry over, so it would be about as fair of a comparison as you could get for $13.
xbird 9:51PM (8/01/2008)
A gyro won't help you at all in determining acceleration performance numbers. You're just measuring axial acceleration. Does anyone even check to see what a yaw sensor is before writing? It measures yaw rate... if you don't even know what yaw is or that the iPhone has no gyros, you don't deserve to be writing about either.
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Chase 10:33PM (8/01/2008)
To put this in a nicer way, you could have just said it has accelerometers, not gyros. And anyway, no need to get fussy over technicalities.
Also, to note, an accelerometer can measure rotational velocity as long as you know how far off-axis it is, you know what the accelerometer's axis is compared to the axis of rotation, and the dot product of the accelerometer's axis's vector and the axis of rotation's vector doesn't equal 1. :)
Chase 10:42PM (8/01/2008)
Excuse me ... the dot shouldn't equal 0, not 1. I was thinking 0, but typed 1 for some reason...
why not the LS2LS7? 12:47AM (8/02/2008)
Chase:
It can only calculate rotation if you know there is no translation going on. It's difficult to know for rapid movements whether a particular reading on the accelerometer is being cause by rotation or translation without multiple accelerometers in different locations.
James Sonne 9:57PM (8/01/2008)
Well, the VBOX unit starts AFTER a rollout, simulating a 1/4 mi drag strip, whereas the iPhone Dynolicious does not do that. This is a difference in actual test parameters between the devices and can account for about a RT's worth of seconds, so there's 0.3 seconds ... now the iPhone is 0.0 to 0.3 seconds off the VBOX.
Also, the pictures show the iPhone mounted via windshield suction cup hinged arms ... which I imagine moved during launch and shifting, which would foul up the iPhone accelerometers. This might account for a negligible (certainly smaller than one standard deviation), difference in time, but systemic and thus notable none-the-less. Perhaps mounted with less flex would provide slightly more accurate (consistent, reproducible) times.
I am actually quite impressed with the HP calculation of the Dynolicious software. A difference of 8% or so is pretty good, especially considering the apparent difference in acceleration times recorded, but it could just be luck with the numbers the user entered (weight and estimated drivetrain loss).
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adam 10:30PM (8/01/2008)
And who says the dyno is dead-on accurate?
You can set two identical dynamometers next to each other and get complete different results. Set two non identical dynos (brake vs inertial) and you've got even further varying results.
James Sonne 4:40PM (8/02/2008)
Actually, I was mistaken. It would seem the VBOX has a setting to turn off Rollout, and it was used on the tests. There goes that 0.3 sec hypothesis.
YourNameHere 10:01PM (8/01/2008)
if you can find me something works better for $13 ill buy one.
I enjoy the g-force meter myself.
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Carlos 10:07PM (8/01/2008)
LOL 122 RWHP!
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