Go Back   EcoModder Forum > EcoModding > General Efficiency Discussion
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 08-02-2013, 08:12 AM   #1 (permalink)
Master EcoModder
 
justme1969's Avatar
 
Join Date: Dec 2012
Location: ff
Posts: 459
Thanks: 59
Thanked 38 Times in 30 Posts
Test your mpg results. (odometer accuracy)

Thought I would put this out there as an officer of the law stopped me to discuss his modding efforts. His records were wrong because of tire dimensions, and a ring and pinion change.
Test your mpg by using an online trip calculator against your recorded odometer/ other distance measuring device.
Gps equipped vehicles can record close enough for most applications but if you have not corrected your speed sensor readings or the speedo gear your mpg may be way off.
I use yahoo maps myself and never even consult the odometer as my Oversized front drive tires have seriously altered that reading. You may find your mpg is better or worse than you believe.
It is simple math to follow and if you keep reciepts from your stops the addr. is on them so you can plug them rite into the trip calculator.
mi2centz.

  Reply With Quote
The Following User Says Thank You to justme1969 For This Useful Post:
101Volts (08-14-2013)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 08-02-2013, 10:29 AM   #2 (permalink)
Master EcoModder
 
doviatt's Avatar
 
Join Date: Mar 2009
Location: Utah
Posts: 388

Grey Goose (Retired) - '89 Geo Metro LSI 4 door hatch back
Last 3: 57.16 mpg (US)

Tweety - '91 Geo Metro Convertible -2 Door convertible LSI
Team Metro
90 day: 43.97 mpg (US)

Shadow - '02 Honda Shadow VT1100
90 day: 43.46 mpg (US)

Sonic - '07 Honda CBR1000RR
90 day: 42.69 mpg (US)

Filmore - '84 Volkswagen Vanagon
90 day: 20.9 mpg (US)
Thanks: 47
Thanked 44 Times in 31 Posts
I was discussing MPG improvements with friends at work and realized most don't even think their odometer/speedometer might be off and so haven't checked it. They rely on the multifunction MPG display. I've never seen one to be correct. Tall tires on my Metro make mine off by quite a bit. I still use my speedometer and odometer but multiply by the constant I came up with during my calibration. I mentally remember where my needle needs to be for my standard commute target speeds of 50, 55, and 60 which of course reads lower. The last thing a hypermiler needs is to drive faster than he intends to. I use my multiplier constant when resetting the trip odo at my fill ups.

My calibration included 4 trips of at least 60 miles each (round trip to work). I took 2 GPS (one on my phone and a portable aviation unit) and also verified my route distance with google maps. I averaged out the GPS trip distances and then came up with the multiplier to try against my odo reading. Worked quite well. I check it again every few months and every time I change tires.
Use the inverse of the percentage delta as a multiplier if your tires are big and your speed reads low. I guess it would just be a percentage if the opposite were true.

Oh BTW good thing to note is any scan gauge or eco trip meter in your car will always be off for the same reasons as it gets its data from the same sensor.

Last edited by doviatt; 08-02-2013 at 10:47 AM..
  Reply With Quote
Old 08-02-2013, 11:18 AM   #3 (permalink)
Corporate imperialist
 
oil pan 4's Avatar
 
Join Date: Jul 2011
Location: NewMexico (USA)
Posts: 11,175

Sub - '84 Chevy Diesel Suburban C10
SUV
90 day: 19.5 mpg (US)

camaro - '85 Chevy Camaro Z28

Riot - '03 Kia Rio POS
Team Hyundai
90 day: 30.21 mpg (US)

Bug - '01 VW Beetle GLSturbo
90 day: 26.43 mpg (US)

Sub2500 - '86 GMC Suburban C2500
90 day: 11.95 mpg (US)

Snow flake - '11 Nissan Leaf SL
SUV
90 day: 141.63 mpg (US)
Thanks: 269
Thanked 3,522 Times in 2,796 Posts
I have to add 3% to my suburban due to a diff gearing change and tire size swap.
I used mile markers and map quest and they came well with in 1% of each other.
On top of that the speedometer reads about 3mph fast at 60mph.
__________________
1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014.
  Reply With Quote
Old 08-02-2013, 12:40 PM   #4 (permalink)
Master EcoModder
 
doviatt's Avatar
 
Join Date: Mar 2009
Location: Utah
Posts: 388

Grey Goose (Retired) - '89 Geo Metro LSI 4 door hatch back
Last 3: 57.16 mpg (US)

Tweety - '91 Geo Metro Convertible -2 Door convertible LSI
Team Metro
90 day: 43.97 mpg (US)

Shadow - '02 Honda Shadow VT1100
90 day: 43.46 mpg (US)

Sonic - '07 Honda CBR1000RR
90 day: 42.69 mpg (US)

Filmore - '84 Volkswagen Vanagon
90 day: 20.9 mpg (US)
Thanks: 47
Thanked 44 Times in 31 Posts
The MPGuino has speed calibration in the setup screen.
Can you do this on a ScanGauge also?
  Reply With Quote
Old 08-02-2013, 12:50 PM   #5 (permalink)
Administrator
 
Daox's Avatar
 
Join Date: Dec 2007
Location: Germantown, WI
Posts: 11,203

CM400E - '81 Honda CM400E
90 day: 51.49 mpg (US)

Daox's Grey Prius - '04 Toyota Prius
Team Toyota
90 day: 49.53 mpg (US)

Daox's Insight - '00 Honda Insight
90 day: 64.33 mpg (US)

Swarthy - '14 Mitsubishi Mirage DE
Mitsubishi
90 day: 56.69 mpg (US)

Daox's Volt - '13 Chevrolet Volt
Thanks: 2,501
Thanked 2,585 Times in 1,553 Posts
Yes, the SG has speed calibration.
__________________
Current project: A better alternator delete
  Reply With Quote
Old 08-02-2013, 02:47 PM   #6 (permalink)
Master EcoModder
 
Diesel_Dave's Avatar
 
Join Date: May 2011
Location: Indiana
Posts: 1,194

White Whale - '07 Dodge Ram 2500 ST Quad Cab 2wd, short bed
Team Cummins
90 day: 37.68 mpg (US)
Thanks: 112
Thanked 511 Times in 213 Posts
My odometer was off by ~2.5%. Here's a copy of my post from a while back:

Quote:
Update:

After the kill switch install it became clear that my odometer was off slightly. Before the kill switch there wasn't much sense in correcting the odometer (nor an accurate way to do it).

In the past, I made a couple attempts to use my GPS to determine the distance accurately, but I had issues with my GPS "assuming" my route, rather than actually measuring it. This was particularly true in one area where I typically cross through a vacant parking lot, and also in my neighborhood, which is only a couple years old and not updated yet in the GPS.

I finally gave in a got a smartphone and found a great free app called Runkeeper. It's intended for running (which I do use it for) and it measures your true distance (not assumed) on-road or off-road. I first used it over 10 trips ove various lengths (totaling 284 mi) before touching the odometer:

Min error: -2.6%
Max error: -2.4%
Avg error: -2.51%

So I got out my Smarty programmer and checked the tire size in the computer. It had been set to 30.55 inches, so I moved it up to 31.30 inches (2.45% increase). This is very reasonable since I looked up the nominal diameter of my actual tires and it's 31.40. Here are the results on the next ten trips (totaling 280 miles).

Min error: -0.4%
Max error: +0.4%
Avg error: -0.04%

In every case the error was within the decimal precision of my odometer, so now I know I'm spot on. There's also a marked 5 mi speedometer course check on my way to and from work that I've checked myself against. Every time I'm within the precision margin.

So, to summarize the kill switch gained ~6% and the odometer another 2.5%. So all told I wasn't accountng for ~8.5% of my miles in the past.
__________________
Diesel Dave

My version of energy storage is called "momentum".
My version of regenerative braking is called "bump starting".

1 Year Avg (Every Mile Traveled) = 47.8 mpg

BEST TANK: 2,009.6 mi on 35 gal (57.42 mpg): http://ecomodder.com/forum/showthrea...5-a-26259.html


  Reply With Quote
The Following 2 Users Say Thank You to Diesel_Dave For This Useful Post:
101Volts (08-02-2013), doviatt (08-02-2013)
Old 08-02-2013, 10:11 PM   #7 (permalink)
Master EcoModder
 
mcrews's Avatar
 
Join Date: Oct 2009
Location: Texas
Posts: 3,523

The Q Sold - '02 Infiniti Q45 Sport
90 day: 23.08 mpg (US)

blackie - '14 nissan altima sv
Thanks: 2,203
Thanked 663 Times in 478 Posts
Quote:
Originally Posted by doviatt View Post
The MPGuino has speed calibration in the setup screen.
Can you do this on a ScanGauge also?
as mentioned in scangauge II threads, yes. the key is to switch to the metric setting on the sacngauge and the gps you are setting it from. This will give a much more accurate adjustment. Then switch back to miles when set.
__________________
MetroMPG: "Get the MPG gauge - it turns driving into a fuel & money saving game."

ECO MODS PERFORMED:
First: ScangaugeII
http://ecomodder.com/forum/showthrea...eii-23306.html

Second: Grille Block
http://ecomodder.com/forum/showthrea...e-10912-2.html

Third: Full underbelly pan
http://ecomodder.com/forum/showthrea...q45-11402.html

Fourth: rear skirts and 30.4mpg on trip!
http://ecomodder.com/forum/showthrea...tml#post247938
  Reply With Quote
Old 08-03-2013, 10:22 AM   #8 (permalink)
Master EcoModder
 
Join Date: Aug 2010
Location: Philippines
Posts: 2,173
Thanks: 1,739
Thanked 589 Times in 401 Posts
In the years I've been testing using a Racelogic V-Box GPS system, I've found most odometers to be witihin acceptable tolerances on standard tires... about 1-2%.

It's speedometers that are way off. Some over-reading by over 5 mph.

Pays to keep a GPS device in your car... or at least calibrate against a GPS device.
  Reply With Quote
Old 08-03-2013, 02:40 PM   #9 (permalink)
...beats walking...
 
Join Date: Jul 2009
Location: .
Posts: 6,190
Thanks: 179
Thanked 1,525 Times in 1,126 Posts
I just take my car to the local speedometer shop and have them test it on their chassis dynamometer at exactly 60 mph and compare their value against the simultaneously read ScanGauge II value, which then gives me a "scaling coefficient" for the ratio between "actual" and what the ECM "thinks" the wheel is turning (which includes tire diameter).
  Reply With Quote
Old 08-06-2013, 07:48 PM   #10 (permalink)
Master EcoModder
 
alvaro84's Avatar
 
Join Date: Jul 2010
Location: Fehérvárcsurgó, Hungary
Posts: 384

Teresa - '04 BMW F650CS
Motorcycle
90 day: 80.53 mpg (US)

The YARDIS - '99 Toyota Yaris 1.0
90 day: 59.52 mpg (US)
Thanks: 4
Thanked 11 Times in 10 Posts
Not having a GPS I check odometer accuracy whenever I get to travel continuous highways with reliable km signs (old roads patched with bypasses won't cut it). I also keep an eye on my normal commute trips' measured length. This was that showed me that the new to me car had wrong sized (too small diameter) tires, so I corrected every distance by -3% until I got new (winter) ones. Then the commute length became pretty much the same as our 'unit bike' (Ciliegia, Hyosung GV250 - has the most accurate odometer among our vehicles).

My bike (Teresa, BMW F650CS) is quite a bit different: she seems to be too modest about distance (the speedo is still over, of course), last time I checked (on a Czech motorway) the error was ~2.5%. I usually correct by +2%, to be on the safe side (I don't want to exaggerate my mileage ) - and add the distance I coast with the key off...

When I bought new (Michelin Pilot Road 2) tires I hoped they'll be more accurate than the previous Heidenau K73s (I used +1% correction back then), but the difference just became larger. At least I got a tiny bit taller gears which I couldn't otherwise

This difference should get smaller as the tires wear, but now, ~1mm down from new I still can't measure the effect.


Last edited by alvaro84; 08-06-2013 at 08:02 PM..
  Reply With Quote
Reply  Post New Thread


Thread Tools




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