Tachometer (RPM) over calibration ?

Rouxenator

Rouxenator

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Recently I had to go into the diagnostics display on my car because the battery is on the fritz so I keep an eye on the voltage. For the fun of it I switched to the speed/RPM read out to check how much the speedo is over calibrated and it's about 4% - 96 km/h when the needle shows 100 km/h.

What I did not expect was that the RPM is over calibrated. At 5000RPM the needle still shows 5000RPM but with the needle pointing to 6000RPM the actual value was 5720RPM. The engine cut outs before 6500RPM while the needle shows 7000RPM.

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Is this standard practice? I can't see why the tachometer is over calibrated.
 
interesting noticing that,

does it always? even when driving?

if you plug in a ELM 327 and get the readout on torque, what does it look like then?
as I find its many times the RPM on the dash wrong compared to torque.....
 
FiestaST said:
Offtopic but I didn't know the Corsa D had a gearshift indicator.
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It's a 2010 Essentia, after they canned the Enjoy they added some nifty features to the Essentia including the shift indicator.
eg2505 said:
if you plug in a ELM 327 and get the readout on torque, what does it look like then?
as I find its many times the RPM on the dash wrong compared to torque.....
Click to expand...
The values shown when in diagnostics mode is actual values on the CANBUS, I have checked and you get the exact same reading on Torque via ELM 327.
 
The tacho on my i30 is also a bit optimistic. At 120kph the tacho displays ~3800rpm in 5th when it's actually ~3500 according to Torque. The variation at idle is also off by about 100rpm.

Strange but your car isn't alone it seems
 
So the plot thickens then. :)

Do they do this to look more impressive? I can't really say that it is any more impressive to cut out at 7000RPM than at the actual 6500RPM.
 
Your best bet would be to find someone with an identical car to check.

I recall reading that certain electronic tachometers and speedometers can lose their calibration, as I know the Mitsubishi 4M40 based motors do it with their heat gauges sometimes!

Speaking of heat gauge, where is yours?
 
wabbit16 said:
Speaking of heat gauge, where is yours?
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One more reason I go use the diagnostics mode from time to time. As most Opel owners will tell you, a heat gauge is a crucial piece of instrumentation as your car gets older. But alas in their infinite wisdom they omitted the temperature gauge in the Astra H and Corsa D. Thankfully you can get the temperature if you go through the diagnostics readings.
 
Rouxenator said:
One more reason I go use the diagnostics mode from time to time. As most Opel owners will tell you, a heat gauge is a crucial piece of instrumentation as your car gets older. But alas in their infinite wisdom they omitted the temperature gauge in the Astra H and Corsa D. Thankfully you can get the temperature if you go through the diagnostics readings.
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on my car via the diagnostics its the only way to get a reading!
only a light, not even 3 like on the getz
 
Rouxenator said:
Did other manufacturers also do something as stupid as to get rid of the temperature gauge?
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Mine still has a gauge, although I am not sure how useful it really is. At ~40C temp as reported by OBD it starts moving up and at ~75C it more or less pegs at the 80C mark. It hasn't ever gone higher even though I have seen the coolant temp get to 95C on a hot day in bumper to bumper traffic. Even with the coolant temp over 90, it shows that it is below the 90C mark. Strange
 
Rouxenator said:
Did other manufacturers also do something as stupid as to get rid of the temperature gauge?
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Yip, extremely stupid,
Never understood the point of leaving it out,

If it overheats, you at least got a shot to do something before it cooks and seizes up....

Really bad move by Kia.....

Wonder if the new Picanto got a proper gauge?
 
Te Temp gauge are damped in modern cars. They have no meaning. Only when the car over heats does it move above the normal mark.

Hence removal(and cost saving)

Most RPM analog gauges are out in the up ranges, similar to speedo. The stepper motor is the issue.
 
If it was a stepper motor issue it would be gradually off from the start, like the speedo which is out by 4%. The RPM in this car is spot on all the way to 5000 RPM and then it starts to go out.
 
silver6933 said:
Te Temp gauge are damped in modern cars. They have no meaning. Only when the car over heats does it move above the normal mark.

Hence removal(and cost saving)

Most RPM analog gauges are out in the up ranges, similar to speedo. The stepper motor is the issue.
Click to expand...
+1

My polo temp gauge is anywhere between 0 and 90 on any type of day. I ignore it now. Only time it ever went over 90 is when my thermostat locked up and sent the needle to 120c. After a lot of steam and panic, got the thermostat replaced and it was back to not deciding where it wanted to be between 0 and 90.
 
Actually that would indicate that the thermostat is now either bypassed or it is stuck open. What that means is your car is never running at optimum temperature so you are using more fuel and the engine is getting more wear. My old Astra had that problem two times in the 235,000km I had it. It's always good to have the car running at normal operating temperature.

I see in both my new cars that normal is actually 100 degrees, so water won't cut it.
 
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A while back saw some tests on a UK website where they were measuring the RPM on new vehicles. It seems that the tachometer over-reporting is a common issue. This also included motorcycles.
 
Still pretty weird that they would do that. I see no value in doing that. Speedo I can understand, but not tacho.
 
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