Speedo, always 4km/h too high (regardless of speed) - can anything other than techstream fix this?

[cnd]

My speedo jumps from 5km to 9km as I accelerate, then stays 4km above my real speed always (24=20, 64=60, 104=100, etc).

I gather this can be fixed in techstream (which I'm afraid to try - virus nightmare). I've got other ODB-II adapters though... does anyone know any other software that can sort this out?

The speed I don't care so much about, but the range and fuel consumption is always wrong now, and since it's a constant 4km/h and not a ratio of my speed, there's no way to work out what the real numbers should be (if I drove 104 for a whole tank, it would be 4% over, but if I drove 54, it would be 8%, so you can't even average it properly.).

 

[kcjaz]

My speedo jumps from 5km to 9km as I accelerate, then stays 4km above my real speed always (24=20, 64=60, 104=100, etc).

I gather this can be fixed in techstream (which I'm afraid to try - virus nightmare). I've got other ODB-II adapters though... does anyone know any other software that can sort this out?

The speed I don't care so much about, but the range and fuel consumption is always wrong now, and since it's a constant 4km/h and not a ratio of my speed, there's no way to work out what the real numbers should be (if I drove 104 for a whole tank, it would be 4% over, but if I drove 54, it would be 8%, so you can't even average it properly.).

My understanding of this is that for JDM vehicles (made in Japan) The speedo is factory set to be 4 to 5% high. I do not think this can be changed even in text stream, but I’m not sure about that. This has to do with some Japanese law. While the speed is off, the odometer is correct as these are two different inputs. It’s not a ratio of speed, or I should say it is a wheel speed calculation, but the offset in displayed speed on the dash is corrected somewhere in the vehicle computer. I confirm this by tracking speed and distance in GPS and also physically timing mile markers. The funny thing is that going to 33 inch tires fixes the speedometer reading but messes up the odometer.

FWIW, I think you can make some techstream adjustment to correct miles per gallon. I say this because I was able to make a wheel diameter correction by entering a factor into my OBD two reader (OBD Fusion). After doing that, I’ve noticed that the dash displayed MPG is reasonably correct even though I run 34 inch tires. The OBD correction factor did not change the vehicles speedometer.

 

[cnd]

Thanks @kcjaz - that's extremely useful to know.

I did spend all day setting up techstream safely inside a VM and hooking it up; there's no setting anyplace I could find relating to the speedo, so I guess I'll just have to ignore that. At least being wrong by 4 at all times makes it easy to go the correct speed, no matter what zone I'm in... probably what the Japanese software engineers were thinking when they encoded "if speed>5: speed += 4 " into their software

Like I said - super handy to know that the ODO is not affected (I'll double-check myself, to be sure, but I expect I'll just confirm what you already checked yourself)

 

[skrypj]

Thanks @kcjaz - that's extremely useful to know.

I did spend all day setting up techstream safely inside a VM and hooking it up; there's no setting anyplace I could find relating to the speedo, so I guess I'll just have to ignore that. At least being wrong by 4 at all times makes it easy to go the correct speed, no matter what zone I'm in... probably what the Japanese software engineers were thinking when they encoded "if speed>5: speed += 4 " into their software

Like I said - super handy to know that the ODO is not affected (I'll double-check myself, to be sure, but I expect I'll just confirm what you already checked yourself)

There is a setting for tire size in the ECU tuning in VFTuner. I am still waiting for my new WiFlash device to come in so I can flash my truck and experiment with it to see if it actually affects the speedometer.

That wouldnt really fix your 4km/h offset issue though. It would just make it less severe at certain speeds.

 

[DallasTide]

I corrected this by upgrading to bigger tires

 

[rscoleman]

Every vehicle we own is like this 2mph over actual speed. All of all vehicles are from Japan made in Japan and shipped to US. Including the one no longer listed as we are selling it. 2009 Infiniti G37S Coupe

 

[DallasTide]

BMWs are all 2 mph over actual speed as well in my experience.