Quote:
Originally Posted by JTYAMSHAYIN
VipinLJ how accurate has your dragy been when compared to the Speedo. Just purchased one and noticed it was off by quite a bit. Haven't played with it to much but something I noticed when trying it out quickly this morning.
Also, where did you mount yours?
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So...
Usually, it's pretty damn spot on (the speedometer reads exactly 2mph higher than what my dragy shows, right down to when the speed changes (i.e, say I use cruise control to cruise at 70mph (as per the speedometer); dragy will show 68mph. If I increase the speed by 1mph, dragy speed also increases exactly by 1mph at the same time the speedo changes (maybe 1s slower at most)). This happens around 95% of the time.
But
Say a warning message pops up on my live cockpit. It could be something like tyre pressure change, low fuel, low engine oil (I've had those warnings pop up). I notice that the speedo suddenly shows a larger error. When that happens (it has happened many many times, with the most recent happening being today when fuel was low and the warning popped up (yellow triangle sign with less than 30 miles remaining warning)). But this larger error is also spot on (for lack of a better word). When this error is present, for speeds usually above around 40-50mph, the error becomes exactly 5mph (dragy shows 5mph less than speedo reading). Above 100 mph, it increases to 7mph. At lower speeds, it's usually 3mph. This error corrects itself after the warning goes off and the car has been driven for around 50-60 miles. I can also reproduce it (playing with the tyre settings or measuring engine oil levels brings this up too). No one will notice the error unless they're running an app on the side showing GPS speeds. I noticed it first after my tyre swap (they didn't reset the TPMS and I fiddled a lot with tyre settings). I did a dragy run a few days after the swap and realized I couldn't record a 62-124mph run (dragy stopped at 123 when speedo showed 130). If it wasn't for that, I would never have noticed the error. At first, I thought it was the TPMS sensor somehow causing the issue. Then I thought it was my JB4. Later I realised it was the idrive doing it. People thought I was crazy but I recorded videos with cruise control activated and car and dragy readings in the same frame to prove the error existed.
I know it's crazy but it's true. At least in my car. Without this freak error, it's spot on.
And I mount my dragy right behind the iDrive screen. You can keep it anywhere as long as it can get satellite signals.