Apexi RSM inaccurate??

[kelvinthai]

Dont worry because speedo in small car actually show 1 - 3 km/h different than your actual speed. Any data obtain from your ecu are more accurate than the speedo. I know jazz, echo all have speed varies from actual speed because of their wheel size.

[JaCe]

Dont worry because speedo in small car actually show 1 - 3 km/h different than your actual speed. Any data obtain from your ecu are more accurate than the speedo. I know jazz, echo all have speed varies from actual speed because of their wheel size.

thanks.

[kelvinthai]

yes btw speedo always show 1 - 3 higher... my friend told me about it which i further confirm upon using my greedy informeter.

[JaCe]

^ i noticed that also from even my Tomtom GPS.. but i was more wondering if that's because the ECU outputs the inflated figure, or if the speedometer (in my case, the electronic speedo) was applying some kind of formula/calculation to inflate it.

[kelvinthai]

speedometer other than data obtain from ECU can silightly varies due to government legislation. Normally the difference is only a aspect ration of +-5 which makes around 1 or 2 km/h diff above 100. Car maker tend to set it to higher than actual reading.

The reason the speedometer will read differently is because of what is called roll-out. Roll-out is the distance the vehicle will travel for every complete revolution of the tires which is equal to the circumference of the tire. A speedometer is calibrated for a certain roll-out based on the tire size. Tires that are too big will cause you to be travelling faster than the speedometer reads because you will travel farther in the same amount of time. A smaller tire will be the opposite, you will travel less distance in the same amount of time. So if you do change the tyres or tyre wear, there is a difference.

Some question the reliability of GPS as a speedo as there is a time taken to transmit the data to and fro satellite while you are on the road. afterall you are a moving vehicle although GPS tend to have serveral satellite lock on.

I am not a expert on this tho

[noodleman27]

hmmm but my defi vsd speed shows the same as my speedo?? why is that?

[kelvinthai]

not too sure.. but your jazz is not normal thats for sure.

[noodleman27]

i had it in jazz and dc5....both had the same reading in both the defi and the speedo....i think they show the same speed for all cars

[Dreams]

just buy Greddy informeter. I still have mine for sale, brand new.

[hoey888]

just a question, would anybody happen to have a rms installed on a jazz? having trouble locating the rpm and speed signal wires to install it. have powered it up and found it working however the apexi instructions seem a bit off. anybody out there that can help me?