How Accurate Is The Ralliart Colt Speedo?

[Rdster]

I had the use of a GPS for a few days last week, so I decided to check out the accuracy of the speedo. I was quite shocked! A speedo indicated 100km/h was actually 92 km/h, and an indicated 110km/h was actually 98 km/h. Yes, I have standard wheels and tyres.

Does anybody else have a GPS unit, that could check the accuracy of the Ralliart Colt speedo as well?

[lovecolt]

I'm actually not surprised of that. You will find most of the cars nowadays do that. But then again, how accurate is your GPS system??

To me, i don't understand how a GPS system can accurately calculate your speed. Ok, to my understanding, it uses the satelite to pinpoint your car at 1 instant of the time from above and how quick its move to the next point. But IMO, since there's different slope angles, the distance travelled can only be calculated vectically and not horizontally as used by satelite.

Not sure if you understand what i mean.....nor if my concept correct... :p

[Rdster]

How GPS Works.

Click Here http://www.itc.nl/gpsi/popups/gps.pdf

[Raymond6]

About 4 weeks ago I got pulled over by the local police the laser speed gun showed 76kmph however I looked at my speedo and it indicated 83kmph and my speed had been steady at the time the police officer jumped out with lolly pop. Lucky for me he only gave me a warning as I was 6kms over the limit.

It sounds to me that their could be a problem with the speed indicated by our speedo's

[lovecolt]

How GPS Works.

Click Here http://www.itc.nl/gpsi/popups/gps.pdf

Thanks for the link. So, GPS system uses varies satellites at different location to achieve a synchronized result.

Oh well, its actually good for us to have speedo reading a higher speed than actual. At least that gets us away from speeding tickets ;)

[|2colt]

When i drove to melb i was using gps as well and the speed was out by approximatley 10 kph. I think if the cars speedo is out by more than 10% it should be fixed as. Not sure but i thought adr permitts australian speedos to be out by a maximum 10%?

[Noel]

The majority of speedometers obtain the reading from the rotation sensors mounted on the wheels/axles which also updates the milegage counter. It's a calculated percentage that is then fed into the ECU which produces the number. It's an estimation of your speed, not your true representation and often the number displayed is a lot higher vs. actual speed.

There are products on the market to calibrate it to make it even closer with less error, generally used by people who upgrade to larger wheels and don't want the added nonsense mileage for wrong service/maintenance intervals and of course, to reduce hurting the resale value overall.

[Steve-B]

Hey Noel,
got any names or numbers of such equipment ? would be interested to look into them further.

[lovecolt]

Oh yes.......if that's the case, it means that our mileage will also be higher by 10% than actual....hmm.....this looks like its something we can look into.

[Noel]

The famous Yellow Box Speedometer Calibrator (http://www.yellr.com/yb_home.htm). Just about everyone I know who has one loves it.

[Steve-B]

many thanks noel

[Macca]

Speed sensor should be in the gearbox, it is for most cars, not sure on teh colt but the gear box is german isnt it. (they think strange like french people)

The GPS will be the one at error, they work on clocks, i bet the cheep timers on the GPS unit chips arent all that accurate.

Check you dyno speeds they will be more accurate.

[Steve-B]

macca mate, the speed sensors are actually on all 4 wheels. i have the workshop manual. weird setup but thats how they run it.

[Macca]

that is strange, everyother car, my mirage, pulsars, and most others its in the gearbox.

More mitsubishi techo stuff, part of the abs systems too i would beleve.

How much was the manual, and has it got all the wiring diagrams?
I would love to get my hands on a copy.

[Steve-B]

they are 160 from the dealer. the part number is on the forums somewhere, covers everything and i mean everything except part number catalogue which is missing surprise surprise..lol

[Macca]

do they even have discription and operations like the gregories manuals?

And i also read they are a CD copy, what file format, im a MAC user ;)

[Steve-B]

all pdf's brother, and all of us cool people that own colts are mac users....well should be. Works a treat on my macbook pro. and yeah its on a cd.

[Rdster]

The GPS will be the one at error, they work on clocks, i bet the cheep timers on the GPS unit chips arent all that accurate.

Actually, the GPS is more accurate than a speedometer. Professional surveyors, road planners,city planners, and the military, use nothing less...

[Macca]

Yes very true, but i can guarentee there are big differences in quality.

Commercial jets dont use them much yet, we are only just getting gps nav onto our jumbos, and sydney airport is developing GPS landing systems.

The only downside to all GPS is that AMERICA is in compete control of it!

[DamoMcTitz]

Drove back from the farm tonight, had the blackberry GPS (Garmin software) fired up to do a few speed readings.

I had the needle dead on the 120km/hr mark, and the gps was steady at 112km/hr.

Is this normal? My other car which is an ES Lancer 07 only shows 120km/hr on the GPS when i hit about 135km/hr on the speedo. The higher the speed, the further out the speed reading.

[danny darco]

yeah i just got a gps n its doing the same - its alway 5-6 k's lower on the gps , dosnt suprise me . i just got booked (yay) cop got me for 62kph ,but my dial was sayin somthing alot closer to 70 . . . .

[DamoMcTitz]

You reckon its some Australian standard to have a "leighway" built into the speedo for the sake of "the benefit of the doubt" to the motorist?

My TH magna was the same / similar - 120 km/hr on the dial = 114km/hr on the gps. But on highway cruises often you'll find a bunch of cars all within 1 km/hr speed difference all around that 120 - 117 km/hr mark. its like all models and makes behave similarly?

On the TH also, if you set the cruise control to 120km/hr, and then reset the computer, average speed sticks dead on 114 km/hr. go figure.

[Rcolt_Fantasia]

i have a kenwood DDX-7039 deck in my car and it has garmin software loaded onto it, when im going 100km it shows 99km, so thats pretty accurate, i dunno maybe its just the software or maybe its were the gps is placed, who knows??

[lovecolt]

After i got my GPS at the beginning of this year, the speed reading is mostly spot on with my speedometer.....or maybe because i'm on 17inch :)

[Turbo_Tim]

You will find most cars read a little low with the standard wheel/tyre package.

Pick up an issue on wheels/motor, when they do a full review they do (or used to) but an 'speed at indicated 100km/h'. Almost all cars are 96-98km/h or so.

[why_bother]

my gps is pretty well spot on once a speed is reached, accellerating is laggy on the gps but what would you expect.

[Payload]

You will find most cars read a little low with the standard wheel/tyre package.

Pick up an issue on wheels/motor, when they do a full review they do (or used to) but an 'speed at indicated 100km/h'. Almost all cars are 96-98km/h or so.

I'd say that's most likely cause they don't want you getting speeding fines when your needle is on the mark. If you hook up a scanguage it shows the speed as about 5% lower than what the guage on the dash shows.

[Macca]

With my 17's scanguage shows a lil slower by about 5 and gps copilot shows about 10 slower.

I wouldnt worry, but i wouldnt reply on gps for speed, always go by your cars speedo.

[fauxpas]

...always go by your cars speedo.

I agree for safety's sake, but not bragging rites... If you time your 0-100 off the speedo you won't be able to back it up in reality...

Most guys with 17" rims will be running 10k slower than their speedos which is laughable... The GPS, even a cheap one, will be more accurate than your speedo or scangauge... Every GPS I've used in the colt (TomToms, Navmans, Handhelds) all indicate the same 5-6k inaccuracy of our speedo...

Speedos are always optimistic for safety's sake, but if it becomes even more inaccurate due to mods then I'd certainly prefer to take my speed off the TomTom :D

[bchliu]

Of the 5 different GPS's and 8 programs I use.. (dont ask).. The RColt does come in about -8% difference in the speed to the speedo. I remember the 97 Prelude being about -5% difference and my 02 Suzuki XL-7 is actually 2-3km/h over (all stock wheels/tyres).

I took it back to Lander and asked them about the speedo variance and they basically told me that GPS is never accurate. This is true to a certain extent (the method is accurate, but the hardware and software can lag behind by a second or two).

I remember researching on the tolerance levels in speeding offences after I received one when I was driving a hire car in Victoria. I've always thought it was meant to be 10% variance, but that seems to only apply to NSW. Victoria's draconian rules states a 3% variance saying that all cars are strictly within that range..

[filofaith]

yeh pretty sure cars speedo's are shown lower to make sure they dont read off with different size rims... its better to be under the speedo then over...