HUD speed off compared to speed gauge

[Left Lane]

I'm driving 40 MPH according to my needle speed gauge and my HUD will read 42 or 43. It seems that there is always a two or three MPH difference between the two displays. Is this common? I know there must be some sort of tolerence between the two systems, but I'm just anal and it bothers me that they don't display the same speed. Quit being the engineer that I am and accept it?

Car is 2002.

 

[vettepilot]

Mine is about 1/2 - 1 MPH difference, I am willing to bet the HUD is the more accurate display because the needle accuracy is dependent upon the needle installation at the time of the speedo assembly. The HUD display being a digital, receives it's signal from the same source, but it displays exactly what it receives. I'm sure there is a build tolorance specified when the assembly is manufactured, but what that might be, I have no clue. Maybe C4C5specialist can help on this one.
vettepilot

 

[Left Lane]

Humm, thanks for the reply, vettepilot; which reminded me of a second question that I had originally forgot to ask. If both speed indicators are showing different values, which one is correct? I've been going with the faster of the two, the HUD, since I'd rather be radar clocked at 62MPH when I'm thinking I'm traveling at 65MPH. Guess I should just do the old stopwatch and mile marker and figure it out.

 

[c4c5specialist]

Hi there,
Yes, you may see a difference in the mph, from DIC to HUD, this is classified as a normal condition, if it is only 1 to 3 mph.
You see, the information is sent from the IPC to the HUD, so the IPC is the accurate part of the equation.
Allthebest, c4c5

 

[Left Lane]

Thanks for you help.

 

[danl72]

I have about a one mile difference as well, but I figured that it was normal so I didn't worry about it. I just go by the HUD speed.

 

[c4vette92]

my hud is within 1 to 2 mph difference. its normal