Gps
Thread Starter
Pro
Joined: Sep 2007
Posts: 661
Likes: 2
From: Centerville IA
Gps
I had an eight hundred mile trip last weekend. This was the first trip that I used my GPS in the FRC. The speed on the GPS was about 3-4 mph higher than my speedometer. When driving a safe speed on the speedometer the GPS shows the speed in a range that could result in a personal visit with a LEO. Which would you place more faith in, speedo or GPS? Thanks guys.
Racer
Joined: Nov 2008
Posts: 276
Likes: 76
From: Florida
I am believing the GPS. I can see a 1 to possibly 2 mph difference at most between the HUD and the GPS on mine but most of the time it reads exactly the same. I would guess the difference is due to rounding.
Melting Slicks
Joined: Mar 2004
Posts: 2,388
Likes: 403
From: Horseshoe Bend ID
With stock wheels and stock size (non runflat) tires the GPS, HUD and analog speedo are all within 1/2 MPH. Sound like you need to get a tune (professional or Diablo or Hypertech, etc.) to adjust for non-std wheel/tire size.
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I'd also say the GPS is probably the more accurate number.
Mine too. GPS/Speedometer Dead on!
Le Mans Master
Joined: Jul 2009
Posts: 9,526
Likes: 12
From: Los Angeles California
Back when I'd changed my 3.23's out to 3.73's in my Trans Am, I knew I was 15% off for the most part. But on long trips, I used a GPS as my speedo since I never got around to updating the computer with the right gearing.
I had an idea about how to make the computer automatically recalibrate the speedo via a GPS check on regular intervals... I'm sure at some point the manufacturers are going to do this anyway.
I had an idea about how to make the computer automatically recalibrate the speedo via a GPS check on regular intervals... I'm sure at some point the manufacturers are going to do this anyway.
Safety Car
Joined: Oct 2000
Posts: 4,949
Likes: 10
From: Monticello MN
The GPS uses multiple satellite info to determine location and speed. The speedometer uses an input from the car itself to determine speed. If you change any parameters, such as tire diameter, rear axle ratio, etc., and don't let the computer know, the final determination will be skewed. With satellite info, nothing matters except rate of movement of the vehicle, as determined by that multiple satellite info fed into, and calculated by, the GPS.
Ed
Ed