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MPG calculation wrong because speedo off?

Discussion in 'General Automotive' started by rizzo20, Apr 30, 2011.

  1. Apr 30, 2011 at 5:12 AM
    #1
    rizzo20

    rizzo20 [OP] Active Member

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    My TRD Sport reports my speed 2 mph faster than I'm really traveling. (speedo says 60 when my GPS says 58). It's accurate to assume that my odometer is incorrect because of this, correct? How can I figure out my true MPG?

    I haven't modified a single thing with the drive train and the speedo is wrong straight from the factory. I haven't talked to the dealer yet but shouldn't they make this right?
     
  2. Apr 30, 2011 at 5:16 AM
    #2
    Brunes

    Brunes abides. Thor

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    Inside: Tint, Wet Okole 1/2 Piped Red/Black Covers, Black Weathertech Digital Fit Mats, URD Short Throw w/ TWM Weighted Knob, USA Spec iPod adapter. Outside: 4300K Retro w/ Angel Eyes and Red Shrouds, 5000K Blazer Fog Light Retrofit, Debadge, Bed Locking Handle, Satin Black Rims Performance: TRD/Steigmeier Blower w/ 2.7 Pulley. 668 Injectors and 320 LPH AEM Fuel pump. URD UCON and 7th Injector. DTLT Headers, URD Y-Pipe, Wicked Flow Muffler. Suspension: Both: OME Shocks Front: 886X's and TC UCAs Rear: Dakars Armor: Relentless Front Bumper Relentless High Clearance Rear w/ Tire/Rotopax Swing Out Relentless Front, Mid, and TCase skids BAMF Diff Skid Recovery and Spares: Fullsize Spare Tire 2x2 gal Rotopax 1x1 gal Rotopax 1x1 gal Water Rotopax Warn 9.5XP-S Winch Hi-Lift Extreme 60" Ironman Off-Road Recovery Kit Upcoming: ATO Gas Tank Skid and Sliders w/ kickout. ATO Shackle Flip Kit. Down the line: Front/Rear ARB Lockers w/ OBA. 4.56 Gears
    Don't plan on it. There is a tolerance for the speedo-They legally don't have to be "perfect" I believe folks have found the computer registers the right speed and distance but the needle is the part that is off.
     
  3. Apr 30, 2011 at 5:25 AM
    #3
    rizzo20

    rizzo20 [OP] Active Member

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    Does that mean the trip counter and odometer are correct?
     
  4. Apr 30, 2011 at 5:32 AM
    #4
    Brunes

    Brunes abides. Thor

    Joined:
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    Inside: Tint, Wet Okole 1/2 Piped Red/Black Covers, Black Weathertech Digital Fit Mats, URD Short Throw w/ TWM Weighted Knob, USA Spec iPod adapter. Outside: 4300K Retro w/ Angel Eyes and Red Shrouds, 5000K Blazer Fog Light Retrofit, Debadge, Bed Locking Handle, Satin Black Rims Performance: TRD/Steigmeier Blower w/ 2.7 Pulley. 668 Injectors and 320 LPH AEM Fuel pump. URD UCON and 7th Injector. DTLT Headers, URD Y-Pipe, Wicked Flow Muffler. Suspension: Both: OME Shocks Front: 886X's and TC UCAs Rear: Dakars Armor: Relentless Front Bumper Relentless High Clearance Rear w/ Tire/Rotopax Swing Out Relentless Front, Mid, and TCase skids BAMF Diff Skid Recovery and Spares: Fullsize Spare Tire 2x2 gal Rotopax 1x1 gal Rotopax 1x1 gal Water Rotopax Warn 9.5XP-S Winch Hi-Lift Extreme 60" Ironman Off-Road Recovery Kit Upcoming: ATO Gas Tank Skid and Sliders w/ kickout. ATO Shackle Flip Kit. Down the line: Front/Rear ARB Lockers w/ OBA. 4.56 Gears
    As I've been told...Yes. Mine is off by about 1.07 because of tires-so I use that to calculate mileage...but I don't worry about it too much.
     
  5. Apr 30, 2011 at 8:07 AM
    #5
    jgraham

    jgraham Active Member

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    Weathertech Digitalfit Floorliner, locking gas cap (Stant 10504), tailgate antitheft mod, DRL override switch with LED lamps and my Original Anti-Hyperflash Mod(TM), Original, pre-recall, full length accelerator pedal!
    I've checked the speedo against my Scangauge and GPS. Scangauge data from the computer matches the GPS. It's the speedo needle that is off. Scangauge miles traveled have matched up to odo miles traveled and GPS miles traveled exactly as well, during trips of over 300 miles.
     
  6. Apr 30, 2011 at 6:34 PM
    #6
    rizzo20

    rizzo20 [OP] Active Member

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    Thanks for the info, thats all I need to know.
     
  7. Apr 30, 2011 at 6:43 PM
    #7
    slmgt

    slmgt Well-Known Member

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    This simple thread rocked!

    Thank you OP, Brunes and jgraham. It was something I too was wondering about and with 7 posts, the answer was given with proof! :yay:
     
  8. Apr 30, 2011 at 8:15 PM
    #8
    jgraham

    jgraham Active Member

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    Weathertech Digitalfit Floorliner, locking gas cap (Stant 10504), tailgate antitheft mod, DRL override switch with LED lamps and my Original Anti-Hyperflash Mod(TM), Original, pre-recall, full length accelerator pedal!
    You're welcome. I'm glad I could help.

    I should also note that I'm running the stock Firestone Destination LE 215/70R15 tires on stock wheels.
     
  9. Apr 30, 2011 at 8:18 PM
    #9
    JLink

    JLink Well-Known Member

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    stock tires on my trd sport were 265/65/17, I just upgraded to 265/70/17's and my speedometer is now spot on.
     
  10. Apr 30, 2011 at 8:57 PM
    #10
    slmgt

    slmgt Well-Known Member

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    Yet another fascinating revelation. I wonder if Toyota calibrated the speedometers with 70/17s instead of a 65/17s, changed and then forgot to re-calibrate. :confused:

    I think I will be switching to 70/17s as well once I see no more use out of my Hockeypucks (aka Dunlops).
     
  11. Apr 30, 2011 at 9:13 PM
    #11
    bocna

    bocna lifer

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    no cal.
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    trex lids,magnaflow exhaust,bhlm,bilsteins 5100 front @ 1.75 and back. aal @1.50,17x8.5 atx thug,bfg ko 265 70 17
    same here.
     
  12. May 1, 2011 at 5:14 AM
    #12
    Brunes

    Brunes abides. Thor

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    Which means you need to look at the computer outputs. Cause the discrepancy at the speedo needle comes from the digital to analog conversion and is a percentage. If your needle that means the input is off (at least I think it does...)
     
  13. May 1, 2011 at 5:38 AM
    #13
    JLink

    JLink Well-Known Member

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    I'm not sure what you are saying.. all I know is that the speedometer now agrees with the gps and the scan gauge, but before I got new tires the gps and scan gauge were the same and the truck's speedometer was off by a couple mph's
     
  14. May 1, 2011 at 5:47 AM
    #14
    Brunes

    Brunes abides. Thor

    Joined:
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    Vehicle:
    08 Red/Graphite and Satin Black
    Inside: Tint, Wet Okole 1/2 Piped Red/Black Covers, Black Weathertech Digital Fit Mats, URD Short Throw w/ TWM Weighted Knob, USA Spec iPod adapter. Outside: 4300K Retro w/ Angel Eyes and Red Shrouds, 5000K Blazer Fog Light Retrofit, Debadge, Bed Locking Handle, Satin Black Rims Performance: TRD/Steigmeier Blower w/ 2.7 Pulley. 668 Injectors and 320 LPH AEM Fuel pump. URD UCON and 7th Injector. DTLT Headers, URD Y-Pipe, Wicked Flow Muffler. Suspension: Both: OME Shocks Front: 886X's and TC UCAs Rear: Dakars Armor: Relentless Front Bumper Relentless High Clearance Rear w/ Tire/Rotopax Swing Out Relentless Front, Mid, and TCase skids BAMF Diff Skid Recovery and Spares: Fullsize Spare Tire 2x2 gal Rotopax 1x1 gal Rotopax 1x1 gal Water Rotopax Warn 9.5XP-S Winch Hi-Lift Extreme 60" Ironman Off-Road Recovery Kit Upcoming: ATO Gas Tank Skid and Sliders w/ kickout. ATO Shackle Flip Kit. Down the line: Front/Rear ARB Lockers w/ OBA. 4.56 Gears
    That was the info I'm looking for...Not the answer I expected up-but it helps.
     
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