Discussion in 'Non Technical' started by Gunwarm, May 4, 2018.
50 kmh = 1500 rpm 80 kmh = 2000 rpm 100 kmh = 2500 rpm
How does yours match up ?
Cheers Peter RTE38
You neglected to mention the diameter of the rear tyres, which will have an effect on speed vs RPM.
Beware of speed cameras with your current setup Gunwarm
A TT auto should do 46kmhr/1000rpm (assuming the same rolling circumference as oem tyres) so something is 'amiss' with your current setup .......... yours doesn't even make sense mathematically (50kmhr=1500rpm but 100kmhr is only 2500rpm ????)
Been past speed cameras over 2 years all good clean slate.
You have 275 30R20's on the rear.
In comparison to the OEM 245 45R16's that are fitted to the 8.5" Twin Turbo rims.
You have increased the diameter by 6.8% & decreased the revolutions per mile by 35.
There is no way your speedo is reading accurately.
I stated mile as the distance it should be kilometre.
It's also a diameter increase of 7.3%.
Your speedo would indicate 110, but you would be doing 118.
Your Z will also accelerate SLOWER.
Thank you for feed back but the speedo cant be out as I have not been booked and trust me they stay on my tail for some time.(Police)
Check your speedo against a GPS unit.
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i assumed you had been using a gps in the 1st post. 1st thing i do to a car. my standard VW with original tyres sizes, but admittedly in a different brand, indicates 110klm/hr and is only doing 104klms . life is too short to be driving at 104.
No I was not using a GPS just eye sight lol. and its 20+20 vision with extra wide fields that are very rare.
Can't trust your speedo to be *that* accurate. Get a GPS app on your phone, thats what I do with my old antique as it's in MPH and more of a guide
My phone is a I Mate Jass Jam don't know if app work on it Cost $1800 back in 2006 Ill just buy a nice gps and then ill know whats close or not close. Thanks any way.
This is all I need http://www.supercheapauto.com.au/Product/SCA-GPS-Head-Up-Display/525173
if you don't mind having a sticker on your windscreen.
"20+20 vision with extra wide fields " - like Sid from the ice age movie?
Wont use the stickers ,just the gauge place it some where neat as it wont be viewed only just check the above.
Ithink you will need to project it onto something it will be back to front if looking straight at the display. i imagine it has to put out a mirrored image to appear correct in reflection. i could be wrong there may be other devices better suited if you just want to look straight at a readout. You could just borrow a gps and work out whats what and then you don't really need it anymore. i have a cheap gps $120 and it doubles as a confuser when i travel to the city. Kills two stones with one bird.
HUD's are great for monitoring your speed past speed cameras.
Downside is you can't see the numbers if you wear polarised sunglasses.
A normal GPS is OK to gauge speedo accuracy, however they only update around once per second.
If you require better accuracy then a GPS unit that updates at 10 times per second is required.
Something like this:
There is also this one that logs the drift angles:
Then there is this one that updates at 20 times a second:
When you use one of the above units you will notice the speedos are not very accurate.
As an example, if you are running stock JDM Nissan 7.5" rims on the rear wheels the tyre size is 225 50ZR16.
This tyre rotates
Hit the wrong button!
The 225 50ZR16 rotates 504.13 times over a mile.
Euro & US spec TT Z32's were factory fitted with 8.5" wide rear rims & 225 45ZR16 tyres.
These rotate 522.17 times over a mile.
JDM, Euro & US Z32's run the same transmissions, diffs & speed sensors, therefore there are speedo errors from the factory.
Changing to aftermarket wheels & tyres compounds the problem, as do tyre pressures.
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