Speedo not accurate

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Craigh

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So I have a 2008 D22 2.5ltr Nav that my son and I have fixed up and got on the road for his first car, we have noticed the speedo is out quite a bit, the car is stock standers. When the speedo says 60km we are doing 53km and this is a gps speed and dash cam speed, when we are doing 70km on the speedo we are only cruising at 60km. Is there a fix for this ?
 
Don’t know about a fix but mine does exactly the same . It’s apparently pretty common with the d22s . There’s a few threads on here about it. Tyre size and different diff are pretty much your only option if I remember correctly. I just go ten kms over.
 
Seems like a common problem with the later models. Think they're allowed to be under by something like 10% but less leeway the other direction. Hence most modern cars read under.

All the old zd30 models I have been in have been pretty accurate. When the speedo says 100kph in mine it's actually doing 101/2kph according to the gps. Once the tyres wear a bit it would probably be spot on.

Wonder if it's the electronics or the sensor? If the sensor you might be able to find one off an older one at a wreckers (assuming they fit)?
 
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It's pretty typical.

The legal requirement under Australian Design Rules is that the speedo is NEVER allowed to indicate a speed lower than you're actually travelling (this is important), but it is allowed to indicate up to "10% + 4km/h above" the speed you're actually travelling at. Compliance with this rule is all the manufacturer requires.

That means that when travelling at an actual 100km/h, your speedo is allowed to indicate +10% +4km/h = 114km/h shown on the speedo.

It is NEVER allowed to indicate 98km/h when you are in fact doing 100. This renders the car unroadworthy and may result in consequences for insurance if the assessors notice larger tyres, for instance, when inspecting a post-crash vehicle (see note below). Even if you're not at fault, being in a roadworthy vehicle is a requirement and can impact on your situation.

My personal solution: use a GPS. Most are accurate to about 1% which is similar to detection equipment.

A note on changing tyre size to "fix" this: you'll also change the deliverable torque, the cruise RPM point, the fuel economy and put insurance at risk. That's not to say you can't change tyre sizes - but it IS to say that using a GPS for vehicle speed is a superior solution even if you change tyres.

Note: knowing the tyre size for a vehicle allows an assessor to calculate whether or not a speedo may have been indicating correct speeds. They can calculate that, at any given speed on standard tyres, your speedo should have been indicating within a specific range. They can then extrapolate what the actual road speed would have been with the different tyres, simply by plugging in the expected engine RPM and drive train ratios.
 
My STX550 shows 43 (using cruise control) dash cam (GPS) shows 40, at 60k and above there is a difference of 4kmh. I had this confirmed by a very kind motorbike policeman with a speed camera who was having a bad day, no speeding cars! He said basically the same as Old Tony above.
My 2000 VT Commodore is spot on 60 - 60 etc.
 
OK, this may not help but if anyone knows it may help me. I have a 2010 Pathfinder 550 TI. It has the (at the time) up market nav display. NOW, if you have the ignition on, the radio OFF, you depress & "HOLD" the panel button marked "SELECT" then at the same time, rotate the radio volume knob up & down, the nav display will come up with a built in test. Many tests!
Can't recall the sequence but a speedo adjustment page can be brought up, adding or subtracting "X % amount of change.
My problem, any change does not seem to effect the speedo reading.
Anyone aware of this test sequence & what it achieves
 
Chances are that "speedo adjustment" is only for the navigation display itself.

The instrument cluster's speedo is fed a voltage from the ECU which works out the vehicle speed based on the ABS inputs. The instrument cluster does not do anything more than deflect the needle based on the voltage sent. This means that even the Jaycar unit (which plugs into the gearbox) won't help to adjust the vehicle's speedo reading.
 
Seems like a common problem with the later models. Think they're allowed to be under by something like 10% but less leeway the other direction. Hence most modern cars read under.

All the old zd30 models I have been in have been pretty accurate. When the speedo says 100kph in mine it's actually doing 101/2kph according to the gps. Once the tyres wear a bit it would probably be spot on.

Wonder if it's the electronics or the sensor? If the sensor you might be able to find one off an older one at a wreckers (assuming they fit)?
when I 've attached a scanner to the ECU/BCM its says the car is doing spot on the GPS speed BUT the speedo on mine is exactly 10% indicating faster...hence its a scaling factor either as an output of the BCM or internal to the speedo..either way its intentional....the other issue is the oddmeter reads 10% fast too....so when your 10000km service comes up--the car has ONLY actually travelled 9000km :(

food for thought gents
 
The odometer is actually quite accurate, the error is in the amount of deflection of the speedo's needle. The odometer information that you see is stored in the instrument cluster and is given to the instrument cluster by the ECU (again, gathered from the ABS sensors in the D40).

Easy enough to test: either on one of those odometer test areas comparing it to the trip meter (which measures in increments of 100m, so there's a chance of 1/50 error) or on a long journey using a GPS mapping tool (which has a chance of up to 10m of error in position at start and finish, so it could be out by 20m total).

Using the ABS rings for speed/odometer information is a good idea. You can't guarantee that the vehicle is moving if it's lifted a rear wheel, so there's value in using the aggregate value from all 4 wheels (probably a "best 3 of the 4" reckoning in the ECU). The number of rotations of the wheel are sent to the instrument cluster (odometer) and the number of rotations per unit time are sent as a voltage (speedo).

This is also used for traction control and for deciding whether or not 4WD can be used (which is why your 4WD light comes on when a wheel bearing starts to let go and the ABS ring fills with debris). It's basically a good system that - most of the time - provides accurate information about the car's movement. Drifting, sliding on ice or moving through surfaces like sand/mud/gravel are exceptions that this system can't really be 100% accurate on, but for general use it's pretty good.
 
The odometer is actually quite accurate, the error is in the amount of deflection of the speedo's needle. The odometer information that you see is stored in the instrument cluster and is given to the instrument cluster by the ECU (again, gathered from the ABS sensors in the D40).

Easy enough to test: either on one of those odometer test areas comparing it to the trip meter (which measures in increments of 100m, so there's a chance of 1/50 error) or on a long journey using a GPS mapping tool (which has a chance of up to 10m of error in position at start and finish, so it could be out by 20m total).

Using the ABS rings for speed/odometer information is a good idea. You can't guarantee that the vehicle is moving if it's lifted a rear wheel, so there's value in using the aggregate value from all 4 wheels (probably a "best 3 of the 4" reckoning in the ECU). The number of rotations of the wheel are sent to the instrument cluster (odometer) and the number of rotations per unit time are sent as a voltage (speedo).

This is also used for traction control and for deciding whether or not 4WD can be used (which is why your 4WD light comes on when a wheel bearing starts to let go and the ABS ring fills with debris). It's basically a good system that - most of the time - provides accurate information about the car's movement. Drifting, sliding on ice or moving through surfaces like sand/mud/gravel are exceptions that this system can't really be 100% accurate on, but for general use it's pretty good.

Tony are you referring to the D22 now or side tracked over to the D40 ?..
 
Tony are you referring to the D22 now or side tracked over to the D40 ?..

Talking specifics for the D40, true, mostly in response to discussion about the 550 (which uses the same method of determining speed, distance and wheel motion as my D40). I believe the D22 from 2008 may actually use the gearbox output shaft for speed + distance calcs, but won't have traction control. It may have ABS but I don't think they linked that in the D22 until about 2010.
 
I get frustrated following people that sit just below the posted speed limit, because I've known for years that their actual speed is up to 10% lower than they think it is (assuming they're not aware of the speedometer ADR's).
I always cruise a couple of km/h over the posted limit for this reason.
(don't get me started on Australia's ridiculous speed limits :mad:)
 
I have a 550 Nav and from WA and find that people sit on 92 to 95 on the freeway trying to be safe just under the speed limit 100. To be doing 100kms/h speedo reads 107.Have checked it on google maps, Garman sat nav and also plugged in my scan tool which must read straight off the computer and 100km/h
is 100kms/h. So to me they must have adjusted something in the head unit to make it read fast.I don't think its just Nissan that do this, maybe all manufactures
I find it annoying.
 
The Nissan is not an exception but its not the case always. My 100 series landcruiser is so spot on thru out the speed range its not funny. Years ago on Lake Gardner at Speed week I took it for a run and it topped out at 160kmhr indicated ( its speed limited ) and 2 GPS's in the car were at 160 and 161 kms per hr...I held that speed for a measured mile. My road registered Hayabusa's all read 8% fast and its not linear..but for arguments sake thats what it is at 100kmhr.
 
My D22 (which definitely does not have ABS, speed is determined by a gearbox sensor afaik) is perfectly on-spot. 100 on the speedo is 100 on the GPS.
106 on the speedo past the WA police's unmarked white D-Max is a $100 less for new toys a few weeks later..

Measuring long-distance speed with the GPS is tricky: it can be 10m off to the left one time, and 10m off to the right next time, 100m down the route, measuring a meandering path much longer than you've actually driven.
But it can also cut corners, shortening the path you've driven.

I've seen on average that the GPS tracing measures a few % more distance travelled than the odometer. (on the Perth-Exmouth route, which hasn't too much corners..)
 
GPS speed depends on the sample rate, number of satellite locked on and how it calculates stuff. Modern GPS sample often and gets lots of satellites to compare so they are pretty accurate, normally only a second or two before the speed is bang on.
 
Might have already been mentioned, the D40 isn't much better when it comes to accuracy. It's the worst of all the cars I've had.
 
Just from an article I found that refers to the relevant ADR, "Australian Design Rule that requires that the speedo must not indicate a speed less than the vehicle’s true speed or a speed greater than the vehicle’s true speed by an amount of more than 10 per cent plus 4km/h.

That is, with the speedo displaying 100km/h the vehicle must be travelling between 87.3km/h and 100km/h. This gives the perception that drivers are travelling faster than what they really are - or exactly at the limit"
 

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