odometer reading

[johnvtls1]

hey guys ive got 3.9's in my vs and the speedo is still out. Now my odometer after this week has read 380kms now im pretty sure the actual distance travled is less then this but im not sure by how much. can anyone help me out with this? cheers

[HoldenManDan]

do you have anything installed to correct the speedo at all? Changing to a higher diff ratio will make your speedo and everything related to it (trip meter, odo) turn over faster unless you've got something to correct it installed. A little more info about what you've got will help buddy

edit: you can find out the % difference by dividing the stock diff ratio by the new one:

3.08/3.9 X100= nearly 79%. So your odo is ticking over 21% faster than it should be.

[johnvtls1]

nah i havent installed anything yet mate. i thought the same thing as u did with the 21% but is that right? cos the speedo is not off by the same amount at every speed if that makes sence

[TheForgotten]

it wouldn't be always 15km over (for example) but it'll always be 21% over whatever speed you're doing

at 60 your speedo shows 72
70 shows 85
80 shows 97
90 shows 109
100 shows 121

the difference you see is proportionate to your actual speed, and your odo/trip etc work on the same sensors as your speedo, so they will be out by the same amount

[johnvtls1]

oh really that kinda sucks things only getting like 300 kms out of a tank then.

[TheForgotten]

it is quite possible that since getting the new diff gears you're harder on the loud pedal than you used to be. changing diff gears has a positive effect on economy, but if you drve it like a racecar then economy will suffer. if you haven't changed your driving style, then either you had poor economy pre-diff change, or you should wait to judge it till you fix the odo

[HoldenManDan]

yeah exactly what TheForgotten said, only just having changed diff gears in my vs you do seem to be a little more on the loud pedal until you get used to it lol.

Get a hold of the jaycar speedo corrector kit and install it in the speedo circuit before the signal goes into the ecu. The one you splice the corrector into is a violet wire with a white trace. And for power hook it up to an ignition switched 12v and ground.

You can adjust in 1% increments so you can get it very accurate. Mine's set to 15% with my 3.50:1 gears. Just get it calibrated with a GPS that you know shows an accurate km/h (as apparently some arent all that accurate).

If you wanted to double check you can also calibrate it against your digital speedo in the trip computer. I did this for mine but found the digital and analogue werent always in sync.

Hope this helps.

oh as a side note how are your shift points? They may get better after installing the speedo corrector, failing that you may need a memcal rewrite.

[johnvtls1]

yeh ive got a jay car kit sitting right here just javent got around to putting it in. But i dont really give the car that much of a hard time ive had the diff gears in for a while so i am used to em. i used to run the car on gas since i bought it but after i had it tuned its just been run on petrol. and the gas use was probably less then petrol

[HoldenManDan]

could also have something to do with the cam you've got in it mate, and the overall condition of the fuel system... next time you go for a long trip just drive it like a granny and see how many k's you get out of a tank then. Let us know what you find when ya get the speedo corrector in.

cheers