12-29-2014, 02:02 PM | #23 |
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Not necessarily. It is the car's best guess at the actual speed, and must not be confused with what it presents on the speedometer. And unlike GPS data, it is not lagging behind.
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12-29-2014, 02:09 PM | #24 |
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When i compared my cars obd speed with the performance box speed it was off. Thats my own experience comparing a cheap wifi obd reader with an expensive gps logger. 0-200 kph obd reader gave over 1 second faster
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12-29-2014, 02:15 PM | #25 | |
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When I tested 0-100 with OBD speed data, I compared to the GPS speed from the phone I used, and they agreed about the speed. |
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12-29-2014, 02:25 PM | #26 | |
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But if you are happy with it good for you i started with obd reader then bought xgps pro and used that with racechrono and ended up with a racelogic performance box anyways. Its very reliable if you want accurate data. |
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12-29-2014, 02:49 PM | #27 | |
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Remember that the 10 Hz GPS antennas also use quite a lot of filtering and interpolation to bring you the signal. There is far from 10 times more information in the data from such a unit compared to a 1 Hz antenna. |
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12-29-2014, 02:57 PM | #28 | ||
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12-29-2014, 04:30 PM | #29 |
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Yes, that is a very nice product. At least at the time it originally came out.
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12-29-2014, 07:45 PM | #30 | |
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12-30-2014, 01:47 AM | #31 | |
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1. Record a sound file inboard the car of the acceleration, making a sharp sound when you drop the clutch, such as a short shout. Use this sound to crop the file to start at the 0.0 point. 2. Use Fourier transformation on the sound file to extract the frequencies. 3. Use pattern recognition to find the engine frequency. It is usually quite dominating and continous through the file. 4. Using the number of cylinders and the fact that it is a four stroke engine to compute the RPM from the frequency. 5. Use the dynamic tyre diameter and gear ratios to compute the RPM into speed. 6. Find the point in the file where the speed exceeds 100 km/h. I used home made software for the entire process. |
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12-30-2014, 04:17 AM | #32 |
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My best time is 4,8 with a (near) perfect start in 2nd gear (automatic box). Logged with the Torque App using the OBD2 dongle. I shifted manually @ ~6500rpm.
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12-30-2014, 05:22 AM | #33 | ||
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12-30-2014, 05:40 AM | #34 | |
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I'm guessing you are trying to produce an app, that could be used like the M-Power App, or would it require extra hardware? How does it compare with other measurement methods? Is this something you are doing to make money, or just as a hobby? |
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12-30-2014, 08:31 AM | #35 | |
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Now that you mention it, it would be possible to make this as a mobile phone app with no further hardware. Some years later, a friend and I made some GPS based data loggers. He sold some of them, but it was mostly a hobby project. During the testing, we compared different methods (including Racelogic equipment and sound recordings), and you can get pretty accurate readings with all if you know what you are doing. I would say down to maximum +-0.1 second error. |
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12-30-2014, 12:28 PM | #36 | |
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Unfortunately I don't have any way to accurately check my tachometer, so I will have to take the obd data on face value, but I would say that errors can go either way i.e. both plus and minus. |
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02-18-2015, 06:09 AM | #37 | |
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I got my 116i remapped, because never driven a fast car an really wanted to see what it is like. Here is the OBD data 0-60 mph. As you can see, it has dropped from 7.9s to 5.9s. I'll post the dyno also. sec;mph;miles;rpm #10 mph 1.00s in 2yd (2863tr/min) #20 mph 1.80s in 8yd (4792tr/min) #30 mph 2.45s in 17yd (5520tr/min) #40 mph 3.30s in 31yd (5379tr/min) #50 mph 4.55s in 59yd (4499tr/min) #60 mph 5.85s in 94yd (5372tr/min) 0.00;0;0.000;1420 0.20;1;0.000;1818 0.35;3;0.000;2085 0.55;5;0.000;2327 0.75;8;0.001;2541 1.00;10;0.001;2863 1.20;13;0.002;3303 1.40;15;0.003;3924 1.60;19;0.004;4293 1.80;22;0.005;4792 2.05;24;0.006;5317 2.25;29;0.008;6022 2.45;31;0.010;5520 2.70;33;0.012;4975 2.90;36;0.014;4859 3.10;37;0.016;5163 3.30;40;0.018;5379 3.50;42;0.020;5682 3.70;44;0.023;5799 3.95;45;0.026;5680 4.15;47;0.028;5046 4.35;48;0.031;4455 4.55;50;0.034;4499 4.75;51;0.036;4649 4.95;53;0.039;4772 5.20;54;0.043;4861 5.45;55;0.047;5021 5.65;59;0.050;5265 5.85;60;0.053;5372 |
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02-18-2015, 06:16 AM | #38 | |
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Here is the dyno before an after, with the wheels still on the car (not bolted directly). Note that there is a conversion factor showing 155 whp before and 211 whp after. Note also how flat the original power curve was i.e. restricted. |
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02-18-2015, 06:25 AM | #39 |
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But how could your car have 155 whp before the tuning? That does not sound right. With 136 hp specified on the flywheel, the wheel power should be something like 113 whp.
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02-18-2015, 06:34 AM | #40 |
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02-18-2015, 06:49 AM | #41 |
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02-18-2015, 10:55 AM | #42 |
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02-18-2015, 01:51 PM | #43 |
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02-18-2015, 05:23 PM | #44 |
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I have matched my tacho against both my phone gps and my blackbox gps. The tacho show 1kmh less very consistently.
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