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I wish...
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Discussion Starter · #1 ·
Is NOT possible

I asked jvitale (who has the service manual) to see if it can be done. Here's what he said:

jvitale wrote on 04-11-2002 06:48 PM:
According to the service manual, there is a sensor in the transmission that measures the vehicle speed and sends a signal to a computer chip in the speedometer. This chip sends another signal to a small electric motor that moves the speedometer needle. So there are no speedometer drive gears or speedo cables to play with. The manual does not say anything about being able to make adjustments. Looks to me like there is no way to alter the speedometer or odometer readings
It sounds like the computer system uses the current gear number (which corresponds to a hardcoded gear ratio), the engine RPM and a hardcoded wheel diameter to figure out what the current speed is. :(

The funny thing is that such a system should be very accurate, assuming the car is equipped with stock tires. Yet some people have reported that the speedometer can be quite inaccurate.

A.
 

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Future Z Driver
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I think it has the *potential* to be very accurate, but Nissan purposely makes it read a bit fast for our safety. Other car makers do this too; there was an article about it in C&D a few months ago. Interestingly, BMW had the least accurate speedometers in C&D's test.
 

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Afty said:
I think it has the *potential* to be very accurate, but Nissan purposely makes it read a bit fast for our safety. Other car makers do this too; there was an article about it in C&D a few months ago. Interestingly, BMW had the least accurate speedometers in C&D's test.
So let's say the speedo is off by 10%. I'm going at 60mph for an hour but only really travelled 54 miles. But my speedo say that I travelled 60. I just got rip off 6 miles. That means I have to service my car earlier than I really have to and my resale just sucked because of the extra mileage.
 

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I wish...
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235 Posts
Discussion Starter · #5 ·
Afty said:
I think it has the *potential* to be very accurate, but Nissan purposely makes it read a bit fast for our safety. Other car makers do this too; there was an article about it in C&D a few months ago. Interestingly, BMW had the least accurate speedometers in C&D's test.
Hmm, that gives me an idea. I could put on slightly larger tires (i was thinking 245/45-17, but I could do 245/50-17) which would get the speedo to work the way it should.:D
 

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Future Z Driver
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Xtrema said:
So let's say the speedo is off by 10%. I'm going at 60mph for an hour but only really travelled 54 miles. But my speedo say that I travelled 60. I just got rip off 6 miles. That means I have to service my car earlier than I really have to and my resale just sucked because of the extra mileage.
Not true, because the odo and speedo don't necessarily agree. Or at least that's what Car and Driver said. They found that on the whole odometers were very accurate (with Nissans being the most accurate of any car make tested), even though speedometers read too fast. I think the average Nissan's odometer was accurate to 1 mile for every 1000 miles travelled.

Check out the article here:
http://www.caranddriver.com/xp/Caranddriver/features/2002/april/200204_feature_speedometer.xml
 
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