Who Should I Trust
Thread Starter
Racer
Joined: Jan 2005
Posts: 488
Likes: 2
From: Fort Lauderdale Florida
Who Should I Trust
I have a Kenwood headunit DNX9140 that has built in navigation. One of the features of the navigation is it tells you the posted speed limit and the speed the vehicle is traveling. When the posted speed limit is exceeded, it will illuminate in RED.
The problem is the speed posted on the speedometer and the speed posted on the GPS is consistently 12 miler per hour different.
That's a very big difference - I think I'm doing a 70 and I'm actually doing 82 possibly. That could be very bad.
What should I do to try and fix this?
The problem is the speed posted on the speedometer and the speed posted on the GPS is consistently 12 miler per hour different.
That's a very big difference - I think I'm doing a 70 and I'm actually doing 82 possibly. That could be very bad.
What should I do to try and fix this?
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
If you think it's your speedo, I would have it tested. Not sure who does that but surely someone does. I'm a little leery on trusting a GPS to tell me how fast I'm going personally.
Racer
Joined: Nov 2004
Posts: 261
Likes: 0
From: Appleton WI
This may be really stupid but is your GPS in the MPH mode?
Also I have seen the speed limit sign displayed on the GPG wrong to what is accually posted on the road. Or you can go 35MPH through a school zone. I'm sure the cop will tell you what your speed was!
Also I have seen the speed limit sign displayed on the GPG wrong to what is accually posted on the road. Or you can go 35MPH through a school zone. I'm sure the cop will tell you what your speed was!
Pro
Joined: Feb 2013
Posts: 565
Likes: 143
From: Bedford VA
I would trust the GPS. Had the same problem with my recent purchase. It was consistently three or four mph below the GPS speed. Checked the programming with HP Tuners and the tire size was wrong. Corrected it and now the speeds listed are spot on and based on traffic flow around me is right. Never have a problem with LEOs.
Drifting
Joined: Dec 2011
Posts: 1,422
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From: San Gabriel Valley California
St. Jude Donor '14-'15
Go out on the interstate, where they have the mileposts marked. Check two or three, as all are not exactly one measured mile.
60 mph going one mile, is 60 seconds. See which is accurate that way.
60 mph going one mile, is 60 seconds. See which is accurate that way.
Safety Car
Joined: Apr 2011
Posts: 4,260
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From: Houston TX
Find someone with a portable GPS navigation unit and test off that as a second opinion. You could also look for a smart phone app that uses GPS based speed or run past highway patrol at an indicated 100 mph to see what they think.
Drifting
Joined: Jun 2000
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From: Placitas NM
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This would be an easy way to check it - if both GPS units measured the same, I would lean towards the car speedo being off.
Team Owner
Joined: Mar 2001
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From: small town in S.E Pa. PA
St. Jude Donor '03-'04
Go to your device's preferences menu and go through the pages until you get an option called "set units". Access that submenu and select the units you'd like to have. it may be set to KPH instead of MPH.
Bill
Bill
