Followers of our long-term big Bimmer have probably heard about the throttle tip-in this car exhibits right off the line. I decided to post a graphical representation of it with the help of my iPhone and the Dynolicious application. Dynolicious uses the phone's accelerometers to measure the G load, figures those loads in with their duration and gives a decent calculation of speed, horsepower, torque and braking. The graph shows horsepower in yellow, speed in red and longitudinal Gs in blue.
See that graceful sweep at the beginning of the graph? That's the tip-in, a brief hesitation upon throttle application before the car really gets moving. A good, aggressive launch will give a flatter curve, as shown in the graph below. The top graph represents a launch in Comfort mode, while the bottom graph shows a launch in Sport+ mode. Personally, I like the idea of having the choice between these modes. If I want to drive like a chauffeur, I can glide away from a stop. If I want to drive like Jason Statham in the Transporter, the Sport+ makes that possible (except for the really silly stunts, of course).
Just for fun, here's a bonus graph of a Boeing 737 taking off from Atlanta.
Mark Takahashi, Associate Editor @ 13,881 miles
foxtrot685 says:
10:49 AM, 08/14/09
i didnt know lotus made the boeing 737!!! lol, j/k
hola_dan says:
10:50 AM, 08/14/09
cool.
i wonder how accurate the HP is, probably not very...
cah11705 says:
11:07 AM, 08/14/09
The actual horsepower probably is fairly accurate because it is just force x distance over time. If it can figure out speed, it can know distance and already knows the force so the iphone can actually calculate that. Pretty impressive for such a small device in my opinion.
mtakahashi says:
11:27 AM, 08/14/09
In order for the app to calculate horsepower, the weight of the car must be figured in. I entered 4,599 for the weight -- a figure I pulled from the introductory post. I also entered a drivetrain loss of 20%, which is about average for most cars. Needless to say, the horsepower figures have the widest margin of error, considering the uncertain weight/loss data.
I really want to try this with the MiniE next.
jaguar36 says:
11:42 AM, 08/14/09
Me thinks the 737 numbers are a bit off, or it would never get off the ground.
mtakahashi says:
11:56 AM, 08/14/09
Jaguar36: Dynolicious cuts you off at the quarter mile. The speed and acceleration increased dramatically after it cut off. I figure it's because most passengers would complain iff it left like an FA-18 off the deck of the USS Nimitz. I, on the other hand, would pay handsomely for that experience!
haydenfive says:
12:17 PM, 08/14/09
This has to be the most worthless post on edmunds.
jjacquot says:
12:27 PM, 08/14/09
So that 737 only makes 175 hp on takeoff?
I'm going to go out on a limb and say that it takes more than 175 hp to acclerate 79 metric tons to 100 mph in 20 seconds.
But that's just a guess.
Josh
thundera says:
12:39 PM, 08/14/09
I'm sure the weight for the Lotus Elise was used during calculations for the 737, as it was probably in the settings for the profile shown during takeoff. Logically, it makes sense. A car the weight of an Elise wouldn't need to have too much more hp than that to reach 100 mph in the quarter mile. The g-curve is a whole 'nother story. This acutally proves that Dynolicious doesn't include air resistance in its HP calculation, as HP would increase expoentially with speed for a constant g reading.
mtakahashi says:
02:53 PM, 08/14/09
Good point! Yes, Dynolicious was set to chomp data for a 1,975 pound Lotus Elise, not a 174,200 Boeing 737-800 (Max.takeoff weight. Keep in mind, too, that jet engines increase their efficiency at higher speeds. I'm sure the initial takeoff roll is about as inefficient as these engines get.