Go Back   EcoModder Forum > EcoModding > Instrumentation
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 11-11-2011, 03:19 PM   #1 (permalink)
EcoModding Apprentice
 
Join Date: Mar 2010
Location: Los Angeles
Posts: 110
Thanks: 0
Thanked 5 Times in 5 Posts
speedometer off by 5 miles at 60mph

according to a gps app that shows mph, i'm doing 60,while the speedometer shows 65.if i got ,say 300 miles to a tank,what is my actual mileage?

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 11-11-2011, 04:58 PM   #2 (permalink)
...beats walking...
 
Join Date: Jul 2009
Location: .
Posts: 6,190
Thanks: 179
Thanked 1,525 Times in 1,126 Posts
...which do you "believe" is more correct, GPS or car speedometer? Both have intrinsic errors, the question though, is which is LEAST wrong?

...what vehicle? GM products are "known" for speedometers displaying 2 mph ABOVE their true value...but, the odometer is (supposedly) not affected by this difference.
  Reply With Quote
Old 11-11-2011, 05:27 PM   #3 (permalink)
EcoModding Apprentice
 
Join Date: Mar 2010
Location: Los Angeles
Posts: 110
Thanks: 0
Thanked 5 Times in 5 Posts
1987 toyota truck.
  Reply With Quote
Old 11-11-2011, 06:12 PM   #4 (permalink)
...beats walking...
 
Join Date: Jul 2009
Location: .
Posts: 6,190
Thanks: 179
Thanked 1,525 Times in 1,126 Posts
...1987 will almost certainly still be using direct cable drive from the transmission to a mechanical speedometer "head"--for these, the aftermarket sells "gears" the can be put "in-line" with the cable to compensate for tires, transmissions and axles affects on the speedometer readings.
  Reply With Quote
Old 11-11-2011, 06:17 PM   #5 (permalink)
.........................
 
darcane's Avatar
 
Join Date: Aug 2009
Location: Buckley, WA
Posts: 1,597
Thanks: 391
Thanked 488 Times in 316 Posts
Can you find a nearby section of freeway with odometer calibration markings? They have several near me in Washington, not sure how common they are elsewhere. But, you can compare your odometer to a 5 mile long section of road that is marked at precise, 1 mile increments. Use that to determine what percentage your odometer is off (which may or may not reflect the error in your speedometer).

Assuming the 60 actual miles = 65 miles indicated, you would need to multiply your indicated miles by (60/65) or .92

300 x (60/65) = 277 actual.
__________________
Past Cars:

2001 Civic HX Mods

CTS-V

2003 Silverado Mods
  Reply With Quote
Old 11-11-2011, 11:57 PM   #6 (permalink)
EcoModding Apprentice
 
Join Date: Mar 2010
Location: Los Angeles
Posts: 110
Thanks: 0
Thanked 5 Times in 5 Posts
Not where I live,near L.A
  Reply With Quote
Old 11-12-2011, 01:28 AM   #7 (permalink)
Pishtaco
 
SentraSE-R's Avatar
 
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,485

Mean Green Toaster Machine - '06 Scion xB
Team Toyota
90 day: 48.92 mpg (US)
Thanks: 56
Thanked 286 Times in 181 Posts
i used my GPS to determine odometer error. I recorded the odometer readings at 20, 40, 60, and 80 miles, v. the GPS miles. Now, when I fill a tank, I multiply the odometer reading by the % error from my testing.
__________________
Darrell

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
  Reply With Quote
Old 11-12-2011, 08:28 AM   #8 (permalink)
GRU
Master EcoModder
 
GRU's Avatar
 
Join Date: Oct 2011
Location: Windsor ON Canada
Posts: 373

silver bullet - '00 Honda Civic
90 day: 34.41 mpg (US)
Thanks: 21
Thanked 37 Times in 32 Posts
It could also be tires. If your tires are worn down about 1/4 inch which is 1/2 inch in diameter it will show a ~2% error compaired to a new tire. Another thing is make sure you have stock size tires on if you want the speedo to be accurate
__________________

  Reply With Quote
Old 11-12-2011, 09:35 AM   #9 (permalink)
Master EcoModder
 
Join Date: Nov 2010
Location: Atlanta
Posts: 403

Sweetie - '11 Hyundai Sonata GLS
90 day: 39.35 mpg (US)

My Miles - '03 Combo GLS/KLX/Ninja
90 day: 40.49 mpg (US)

Sipper' - '04 Kawasaki Ninja 250
90 day: 74.98 mpg (US)
Thanks: 1
Thanked 37 Times in 28 Posts
Quote:
Originally Posted by SentraSE-R View Post
i used my GPS to determine odometer error. I recorded the odometer readings at 20, 40, 60, and 80 miles, v. the GPS miles. Now, when I fill a tank, I multiply the odometer reading by the % error from my testing.

My mileage from odo to gps was 2.8% different on many tanks of over 600 miles distance.

Speedo reads 1 high though.
__________________
This ain't a war, anymore than a war between men and maggots. Or, dragons and wolves. Or, men riding dragons, throwing wolves at maggots!
  Reply With Quote
Old 11-12-2011, 10:04 AM   #10 (permalink)
Pishtaco
 
SentraSE-R's Avatar
 
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,485

Mean Green Toaster Machine - '06 Scion xB
Team Toyota
90 day: 48.92 mpg (US)
Thanks: 56
Thanked 286 Times in 181 Posts
On my xB with OEM tires, the speedometer was 5% optimistic, but the odometer was 3.3% pessimistic. Now I'm running tires that are 5.31% larger diameter, and my speedometer is accurate, but my odometer is 9.9% pessimistic.

__________________
Darrell

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
  Reply With Quote
Reply  Post New Thread






Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com