Speedometer not accurate

[m|ng]

Hi Mates. Recently I found out my speedometer is not accurate. Its reading only at 90km/h even its actually at 110km/h. The Tachometer is working fine tho.

I have actually changed a meter last year. But same thing happened.
So Im actually thinking of installing a Speed Meter into my car (pivot Speed Meter).

But im worried if that the meter is actually faulty, or could there be another component (some sensor maybe) that is providing the wrong reading to the meter? Im just afraid that after fixing the the speed meter, the reading is the same as the dash speedometer.

Help?

 

[muzhaffar]

changing the radius of the tire also will affect the meter reading
if you change to the bigger diameter tire, your meter reading will be less than the actual

 

[r60262]

try change lor.. if same, i think speedo sensor got prob.... maybe la....

 

[Sonic Thunder]

i was using 13inch b4...nw im usin 16inch...
got difference ah bro?
u mean da reading is actually showing slower speed or higher speed?

 

[muzhaffar]

i was using 13inch b4...nw im usin 16inch...
got difference ah bro?
u mean da reading is actually showing slower speed or higher speed?

the speed sensor usually get its input from the gearbox. if you change the tire to bigger diameter, one rotation will move you further than the normal one.
but the speed should not differ that much
check your sensor first

 

[TRD.AE92]

the speed sensor usually get its input from the gearbox. if you change the tire to bigger diameter, one rotation will move you further than the normal one.
but the speed should not differ that much
check your sensor first

Mind to teach me how to check that sensor? Sorry for my newbie question. Wahahaha...

 

[muzhaffar]

Mind to teach me how to check that sensor? Sorry for my newbie question. Wahahaha...

u're the sifu..
for sure you know more than me..
i also not sure how to check
actually its depend on how the sensor works..
if it based on the pickup coil and the rotor or magnet, we may check by using osciloscope and observe its voltage generation
if there are not homogenous output, the sensor may couse of prob..
let say for 1 revolution it should produce 6 sine wave but in return its only produce 4 sine wave. so, it only send 2/3 signal and it like the tire rotating at 2/3 of its actual speed..thats why the speed reading is lower.

if it use reed switch, we need to supply the current to it before rotating it and observe its pulse of voltage output produce using the osciloscope..

if it use MRE type sensor, it should produce digital output. also need to use external power supply and osciloscope

it just my opinion..if i'm wrong, dont shoot me..hehehe

 

[ahaw]

http://www.carbibles.com/tyre_bible_pg2.html

make syre do lots of googleling...

 

[m|ng]

I just recently changed my tyre (still using 14"). I changed it back to the original spec. So that shouldnt be the problem.

Wow checking for a fault in the speed meter sounds very complicated. So most workshops would have these equipments to check right?

 

[futeball]

Aftermarket parts like Apexi RSM or Pivot Speed Meter reads the speed through the ECU. So, as said above speed sensor reads from the gearbox. My question, is it the same reading? Whether u change small/big wheels, i think if it reads from the ECU, the wheel changes doesn't effect the speed result from ECU.

Any idea?

 

[muzhaffar]

Aftermarket parts like Apexi RSM or Pivot Speed Meter reads the speed through the ECU. So, as said above speed sensor reads from the gearbox. My question, is it the same reading? Whether u change small/big wheels, i think if it reads from the ECU, the wheel changes doesn't effect the speed result from ECU.

Any idea?

if i'm not mistaken, this rsm or pivot speed meter can be calibrated to get the accurate speed.
because it is design to be used with any car and not all the car using the same type of sensor.
so, i think it can be adjusted to match with the actual speed..
hope someone using this things can give comments

 

[futeball]

Actually i'm using Apexi RSM on my seg. And it is conform that the speedometer is different. The RSM is less than the dashboard meter on speedo & RPM.

 

[Raymond_Hu]

I have this problem before ... most likely is problem from the meter. I change another meter get from chop shop and it solve all the problem.

 

[muzhaffar]

Actually i'm using Apexi RSM on my seg. And it is conform that the speedometer is different. The RSM is less than the dashboard meter on speedo & RPM.

adjust the tire correction value. than tou may get the accurate speed..
refer to the manual if you have one.
if dont, you can get it online


http://www.apexi-usa.com/content/pdf6138.pdf
hope this can help

---------- Post added at 03:21 PM ---------- 6 hour anti-bump limit - Previous post was at 03:07 PM ----------

if you use the old version one, this may help
Apexi Rsm Instruction

 

[cuscostrutbrace]

The stock speedo is calibrated to your stock wheel size,the speed signal is taken from the output shaft of your gearbox,there is a magnetic sensor or speedo cable attached to it (output shaft for rwd,final gear case for fwd).

When you change your rim size,the speedo will still read the same but the actual speed is your vehicle is not,(usually will be much faster than indicated),most electronic speed meter like RSM have tire size correction to get the accurate speed.

But however from the factory,the speedometer is always calibrated higher than actual speed,like 3-5kmh higher.The most accurate speedo is electronic speedo like most of cars nowadays using it.Cable speedo is not accurate especially at high speeds,because of the mechanism inside.

 

[shizilki]

got quite similiar problem also, but speed below 90 km/h only. it fluctuates badly. if above 90 km/h, the speed is constant. changed the speedometer from analog to digital. same problem. i doubt the speed sensor is the culprit.