Team-BHP - Odo Difference For Different Cars?

Hai,

In the last few years, I have noticed the difference in different cars on the odo reading for the distance from my residance to my office, one way. The route is exactly the same:

1. Santro : 5.6 Kms
2. Fusion : 5.7 Kms
2. Scorpio: 5.8 Kms

I wonder if this difference is acceptable? An error range of 20%? Does this happen in other cars? I thought the Odo's are standardized?

Is is because of the different profiles of the tyres or the calibration of the ODDs? The Santro has analogue Odo, Fusion and Scorpio has the digital displays.

Your thoughts please......

--Ramky
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ramkya1,
with all due respect, its not 20% error, its 3.5%
Assuming Santro is correct, ((5.8-5.6)/5.6) *100 = 3.5%

Actually its just 200 mts over 5.6 kms.

I could have attirbuted this difference to driving straignt vs driving waving around, but i guess you did your normal drivings.
So I guess there is difference in odo's of different cars.

Just to add to this, I once was driving neck to neck with a guy with digital speedo(Pulsar 200), and his speed read 55kmph, where as my analog speedo was exactly at 50kmph mark.
If speedometers can have that much error, i guess odometers can too..

Regards,

Quote:

Originally Posted by ramkya1 (Post 568968)

1. Santro : 5.6 Kms
2. Fusion : 5.7 Kms
2. Scorpio: 5.8 Kms

I wonder if this difference is acceptable? An error range of 20%? Does this happen in other cars?

hey!! good observation, lucky u have all the 3 cars to compare.

but 4 of our office chaps too noticed this one on our individual cars a few times. 2 OHCs did the same though!! the other 2 cars have stock tyres and both the OHCs are on 185/65 R14

P.S.: you are one of those who are lucky to have an office at 5.~ kms!!

Even the extent of tread wear will make a difference of 1-2% in the odo reading. With stock tubetype S322 tyres, my Santro recorded ~94 kms across the Expressway. When I shifted to tubeless S322 tyres (stock-size) the distance initially read 93 kms on the odo. After about 24000 kms on these tubeless tyres, the odo now records the distance as 93.7 kms.

Quote:

Originally Posted by anandpadhye (Post 569051)

How did you arrive at the 20% mark?
(5.8-5.6)/5.6 = 3.57%

I read somewhere that Indian laws allow an error of +-4%.

Sorry ppl, I guess I need to re-look at my maths basics:Shockked: .

Yes, the difference is around 3.5 % as two of you pointed out, thanks.

Is the +-4% acceptable? I would discount thread wear and differences driving straight / turns etc. as the road is relatively straight and santro and fusion were used for 24 months.

--Ramky

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The manufacturers are allowed +-4% error in odo by ARAI.
Don't know the rationale behind but read in Auto India sometime back that when Palio took a beating due to it's poor FE (when it was launched), Fiat (among other things) realized that Palio in Europ was running on bigger tyres but was launched in India with smaller ones and they forgot to recalibrate the odo! They were running -4% so when they launched Palio 1.2 nv, they calibrated to +4%. This, apart from the real detuning of the engine, brought the palio FE to some reasonale level....

Note: As read in Auto India, don't know if this really happened, but it must have. If ARAI has a range of 8%, manufacturers will play within it...

I too had the same variation between my 800 and WagonR---for every 22 kms on the 800, the WagonR was showing 21. I comforted myself thinking that the WagonR was actually traveling more, and hence giving more mileage :).
My Fiesta's figures are again slightly more than the WagonR--they more or less match with the 800, but I don't own the 800 anymore.

Its quiet natural that these tolerances are present. When a odometer is designed and later calibrated, the wheel diameter and in turn circumference is one parameter that is used to calculate the distance traveled by the car in a single revolution. So obviously if the wheel wears than you will get a variation in distance.

Also its natural that different cars give readings that don't match, this again boils down to the calibration, there will be some difference creeping in, unless car manufacturers want to spend good amounts of money to make their odometers more accurate, which may not justify the ROI.

But this lights a bulb in my head, do we need to recalibrate the odo if we change the tires to bigger size, I see lot of guys doing the upgrade, has somebody checked this aspect.

IMO, the oldest car or the car which has run the most will give the highest Odo reading. The tyres of this car would be worn out most , resulting in less overall dia of the wheel. The circumfrance of the wheel is directly proportional to the distance it covers, which in turn is related to the odo reading.

Hence a worn out tyre would give an odo and speed error of 4-5%, which is quiet understandable!:)

Quote:

Originally Posted by deepaktpatil (Post 569298)

But this lights a bulb in my head, do we need to recalibrate the odo if we change the tires to bigger size, I see lot of guys doing the upgrade, has somebody checked this aspect.

Yes. That's why all tyre upsize calculators you see on the net tell you the odo error that the upsize will cause. The upsize is not the right one for your car if the odo error is going to be more than +-2% (generally).

Hai,

I wonder how we find out the error factor in our Odo'S? Which is the bench mark for measuring 1 KM.

May be I can roll from a typical mile stone on the highway to the next indicating one KM and chek the error on my odo and calculate the deviation would work? That wold depend on the accuracy of the mile stones on the highway? Is there some other way to reliably measure a KM?

Happy Driving,

--Ramky
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