Speedo Off?

[stkjock]

I'm figuring that since the gauge cluster is all electronic that the PCM is the source of the info for the speedo dial. I've notice that the indicated speed on the dial differs by 3-4 MPH @ 70 from the reading I get on my Aeroforce Scan gauge. ( Needle says 70 - Aeroforce says 66-67) The Aeroforce should be pulling the info from the same source.

So my question..... which is correct? My guess is the AeroForce and the needle is misaligned a bit.

All constructive and insightful comments welcome. Thanks.

 

[silverpoison]

get a friend next to you on ther car and see.......or go to a dyno..

 

[stkjock]

did that.... his speedo read diff than either of the readings I was getting

 

[MikeVistaBlue06]

Find a road that has mile markers spaced every 1 mile. Interstate highways have these. Cruise at 60mph. Start a stopwatch as you pass one, and then stop it as you pass another one. You should be exactly 60 seconds between mile markers at 60mph.

If the milemarker comes early, say 57 seconds, your speedo is slow. These are called ticket getters because your actual speed is (60/57)(60) = 63.16mph

If the milemarker comes late, say 63 seconds, your speedo is fast and your actual speed is (60/63)(60) = 57.14mph.

You should be able to correct this via an SCT tuner.

 

[Dread53]

Very well said, my good man!

 

[ChevyKiller]

Find a road that has mile markers spaced every 1 mile. Interstate highways have these. Cruise at 60mph. Start a stopwatch as you pass one, and then stop it as you pass another one. You should be exactly 60 seconds between mile markers at 60mph.

If the milemarker comes early, say 57 seconds, your speedo is slow. These are called ticket getters because your actual speed is (60/57)(60) = 63.16mph

If the milemarker comes late, say 63 seconds, your speedo is fast and your actual speed is (60/63)(60) = 57.14mph.

You should be able to correct this via an SCT tuner.

Best way IMO.

Or you could go my route -

My speedo has been off by about 10-15 mph for awhile now and I just tell myself I'm putting less miles on the motor...lol

+ it feels great when I can fly by a car doing 65.

 

[stkjock]

man...that's some good logic there!