Does the Gryphon Tuner also recalibrate/correct the truck's own odometer/spedometer readings, or is this calibration something that mechanic would have to do?

 

What year of truck? All after 1998, yes. However, the speedometer will always be 2-3 mph fast, Ford just builds them that way.

 

It is a 2007. That's pretty snazzy then. A new Ford with stock tires reads 2-3 fast and then you put a lift and 37" tires, recalibrate with the Gryphon, and voila, the Ford still reads 2-3 fast?

 

Yes, if you get the digital read out mph correct on the Gryphon, match it with a GPS, then the truck speedo will always show 2 or 3 mph faster. Probably Ford's way of not getting lawsuits on speeding tickets, or could be a way to run out the warranty quicker.

 

No - the speedo will read a bit high, but the odometer will be correct. I've verified that with my truck using GPS and highway mile markers. I lock my cruise at 75 indicated, GPS says 73, and over 100 miles the odo is within a couple tenths of a mile.

 

Ok, maybe I put my math brain on backwards today, but assuming what GLC says is correct, if I use my tuner and ajust for tire size ang get my speedo and GPS to agree on mph, right on the money, then would my odometer not read aprox 103 travelled miles, when in reality I have only travelled 100?

 

Given the math your miles should be off too. Figure if you're speedometer says you're going 75 mph, in 1&1/3 hours you'd driven 100 miles according to that. (75*1.33333). But if you're really only going 73, you really only made it 97.3 miles during that same time (73*1.3333333). Unless I messed that up, somewhere something is a little off.

 

I think you've got it backwards. If you make the dash speedo agree with the GPS, the truck "thinks" it's going slower than it really is. In other words, it would think it is covering less distance per unit of time and you might see 97 miles on the ODO when you really cover 100.

Edit: Silver T just beat me to the punch! But, we agree!

- Jack

 

I guess wednesdays are not my brightest huh?

 

Hey, welcome to the "stupid post club"! Another member, SSCULLY, (who mostly hangs out in the Electrical Forum) and I are competing for "leadership status" in this club. (I think I've got him beat for stupid posts, but he won't admit my superiority.)

- Jack

 

They should award 'Senior Moment' awards for some of us.....ME Included !!

 

The odometer doesnt work off the speedo, they are different extensions of the same output. the gauge just isnt that accurate, not sure why, gravity, karma, or gremlins. The odometer can be accurate if the speedo isnt. If the needle fell off the speedo the odometer wouldnt quit, right?
Without reprogramming for new tires/gears they would both be wrong but still different.

 

Jug - It's probably something like this: The Odometer is purely digital. It simply shows the "calculated" value from the PCM that is based on the number of revolutions a wheel makes and, its "understanding" of the radius/diameter/circumference of the tire. As such, the only error that's possible is the Tire Size (and/or Gear Ratio). A TS setting that's too low will make the PCM report a low value for miles driven, if it's too high, the miles shown will be too high too.

Now, it uses this same input: revolutions and TS in a unit of time to compute a speed. So far, so good. If the TS is correct, and if the revs are seen correctly, the speed will be computed properly. This value is sent to the dashboard speedo and is also seen in the OBDII port. An electronic device: Edge/Gryphon/Scangauge, that's plugged into the OBDII port will see and report this correct value without error. It doesn't have to "convert" what it receives.

But, the dash speedo has to take that electronic signal and convert it to a voltage that moves a mechanical needle, magnetically. This needle is subject to all kinds of errors: Friction, gravity, lag, electrical tolerances, etc. I suspect Ford biased the needle to the high side to avoid lawsuits over speeding for driving too fast. (I'd do that, if I knew there was a possibility of error in the reading.)

And, if I have this all wrong, I get more points in the "stupid post club"! Eat your heart out SSCULLY!

Edit: And Jug - your analysis is absolutely correct in my opinion, for whatever my opinion is worth. I just wanted to explain the speedo error in a bit more detail.

- Jack

 

Like I said Gremlins