'95 Del Sol Speedometer

I have a '95 Del Sol Si with about 138K miles. I have had the car for about
8,000 miles. I replaced the tires with "OEM size" and had the speedometer
checked with a GPS. The speedometer has about a 5 MPH error at 65 MPH
(actual speed 60 MPH when speedometer reads 65). How is the calibration
obtained; gear change or computer reprogramming?

Any input would be appreciated. Thanks in advance.

 

How about checking with another means than your GPS unit?

Chris

 

Unless you suspect his GPS receiver is faulty, what's going to be more
accurate than GPS (with many satellites in view)?

 

I have checked 4 different vehicles with my GPS and only my Del Sol shows
any discrepancy in readings!

 

The speedometer is a bipolar magnetic field motor. That field is generated by 2
coils. The coils get the power from from a chip. That chip counts pulses from
the speed sensor.

1. Insert a resistor in one of the coils to weaken the magnetic field. With a
proper resistor inserted in the right coil, you could dictate how much the
needle move with respect to the current output from the chip.

2. Make a custom gauge with the speed divisions moved to correct the errors.

3. Drive 5 mph faster to compensate for the error.

Both my Civics are off my 5 mph, according to the radar on the side of the
roads. The Odyssey's odometer is 5% off, according to markers on the I-5

 

The highways here have kilometer markers on them, so it is easy to
verify a speedometer reading of 120 kph: 30 sec/km. Running 4 km at
120 kph (2 minutes) reduces measurement error. You can do the same
thing at 60 mph (1 min/mile). A little algebra will show the speedo
error.
Dan

(This account is not used for email.)

 

Conceptually, sure, but how many people can maintain an exact speed of
any value?

 

Depending on the road, you can probably get pretty close to constant
speed using the cruise control. Then again, the reading varies as you
move your head, so there is a limit to how accurate you can read an
analog meter.

Here in California, the areas that have introduced Smog II mandate the
use of a dynamometer for smog testing. Perhaps if you are nice to the
technician he'll let you check the accuracy of your speedometer while
the car is on the dyno.

 

Wouldn't it just be easier to use a GPS receiver? I'm sure someone here
knows the margin of error for GPS.

 

I didn't see this thread earlier, but you are likely right. I also have
a '95 (my second one, first was an S and the current one a VTEC) and
they both had/have the same speedo error that you describe.

There was either a thread here or perhaps on the old Del Sol mail list
about this quite some time ago, and it seems that all the Sols were born
with the same problem.

I personally found it odd that a company with so much technology
apparently available couldn't make a stupid speedometer that reads
right...unless they meant for it to be wrong.