My mph #'s on my scanmaster

[Turbo6Smackdown]

When accelerating, my mph's don't seem right. They are a lot slower than the mph on the factory faceplate. Although there's a 149mph faceplate on there, and it could be off, I still think my scanmaster's giving me inaccurate readings. Is this possible at all?

 

[bosted86]

If Its Only When Accelerating And Not At Cruise You Are Ok. Scanmaster Has A Slow Update.

 

[Turbo6Smackdown]

I see. I heard something about chips having an effect on this. Is that true, that a chip can speed up the 'updates'?

 

[turbojd]

Do you have a speedometer reducer on your speedo cable? if you do then thats why your 145 speedometer and scanmaster read different. The scanmaster readings is what the car is reporting to the VSS sensor, this can also affect torque converter lockup.(the reducer)

 

[Turbo6Smackdown]

What would be a reason to install a speedo reducer? I don't know much about this area of cars. And what would it do to the converter lockup. Make it sooner or later.

 

[NVRL8]

I see. I heard something about chips having an effect on this. Is that true, that a chip can speed up the 'updates'?

Yes. I run a TT chip that has the fast update rate for the scanmaster. The o2's etc. are updated faster as well. I have run chips without the fast update and it is a huge difference in how fast you see the data.

 

[Turbo6Smackdown]

Ok, got it all sorted out. The reducer will screw with my scanmaster readings, making them slower than actual. All I see, is this faceplate mod screwing with what I need to get done. It came with the car, and I gotta get it back to stock.

And I'm guessing, that the reducer, would quicken up the tcc lock huh. Did I guess right?

 

[turbojd]

Ok, got it all sorted out. The reducer will screw with my scanmaster readings, making them slower than actual. All I see, is this faceplate mod screwing with what I need to get done. It came with the car, and I gotta get it back to stock.

And I'm guessing, that the reducer, would quicken up the tcc lock huh. Did I guess right?

If you still have your stock faceplate(85mph) underneath the 145 mph overlay,simply remove the 145 overlay and remove the reducer and your speedometer and scanmaster should be reading the same then. Or you could simply leave the 145 overlay on and send the speedometer head out and have it calibrated. If the scanmaster is reading alot less mph then your 145 speedo is reading that would delay the torque converter lockup to a higher mph reading on your 145 overlay.

 

[Turbo6Smackdown]

So it would delay the tc lockup eh? That would make sense, as the lockup would be based off of what the ecm's puttin' out (what the scanmaster sees) and that is actually 40, when the scanmaster thinks I'm doin' 30. WTF I was thinkin' is beyond me lol. This all makes perfect sense, as to what my car's doin'. I now know the direction I have to go. My car has alway ran fine, but with tiny little glitches here and there.
Looks like I don't have that much to sort out after all. I have nice O2's, and zero knock, all the way thru the powerband, with perfect oil pressure at idle, and at speed. (which is completely amazing to me.. I thought I had a lot of issues goin' on.) Thanks guys.