3 questions

[webbug]

Okay today I tried to fix the accuracy of the speedo, I followed one this method:

I clocked 25.5 km on the odemeter and 24.6 km on my GPS.

25.5/24 * 2661 = 2758

I have 05' F-150 using 33x12.5x20 Toyo Open Country MT's.

okay now the problem of putting this number in. I have selected the custom tune and custom settings, put the above number and selected done. After the turn off and one process, I'm not sure if the number was stored there. Because when I choose the custom options again I see the old number 2634 not the new one 2758 plus there is no difference in the speedo adjustment

Test in KM
Gryphon / Speedometer / GPS
36/40/34
55/60/53
75/80/72
113/120/109

I really need to get this working, I had 4 tickets because of this issue and cost me the price of gryphon!!

[ticopowell]

Thanks for the clarification on my info , and to help more the speedo is always going to be a bit faster than the grypon, so those numbers look close to what I see on my 05 f-150. What happens is that if you dont first go to the "load previous settings" or whatever it is called, and load the last customizations you set, then it will show the original settings you had there. the gryphon SHOULD save them that way, and after the previous settings are saved you should be able to look and verify that they are in there correct, but you shouldnt need to worry about it. if you still want to fine tune the speedometer to show more accurately, you could adjust the tire size again to make it more accurate, or adjust the GR in the gryphon to make it more accurate, but IMHO you are getting fairly accurate results from the gryphon, so you really shouldnt need too much to make them better... and If you are getting speeding tickets at 120mph then you probably dont need a gryphon after all... jk lol , like I said though, that looks pretty accurate, so you maybe need to drop the tire size by 1% or so, or add 1%, i dont remember which, and it should make it a lot more accurate.

[Longshot270]

And to add, the GPS mph isn't always accurate for moment by moment due to elevation changes and slight miscalculations. The misscalculations are very common for standard GPSs that are accurate up to 7 or so feet at the most and on average to 20 ft. Also my gps says my max speed is 371 mph...I wish.

But one thing I'm not seeing is what your intial tire size was. If you have the 2758 programmed in, drive another 20 and redo the calculation. It usually takes a few tries because of rounding errors in the programmer. But if your getting speeding tickets for the speedo being 2 off of the GPS then you are just going a bit too fast.

[Jackpine]

AND, I think you corrected the wrong way? You said you recorded 25.5 km on the dash, but the GPS said 24.6? This tells me your "entered" Tire Size (TS) is too large. The PCM "thinks" you've traveled farther than you really have, because your entered circumference is larger than it should be. Notice your Gryphon and your dash are saying you are traveling FASTER than your GPS is saying, which also correlates to using a TS that is too large.

But, now I have a bit of a problem. Your tires are 33x12.5x20 ones. These work out to 33 x 25.4 x pi = 2633.3 mm without reducing for "squish", which is even smaller than the number you were apparently using before (2661).

If I apply the correction to 2661 properly, I get: 24.6/25.5 x 2661 = 2567mm, which is the number I think you should enter to make your Gryphon and GPS agree - the truck's speedo will still read about 3% FASTER - about 82.5km/hr (indicated) at 80km/hr (actual). And, the 2567 corresponds to a "squish" of about 2.5% which sounds right for your low-profile tires.

And here's the rub - In ALL cases, your speedometer was telling you you were going faster than you really were, yet you got tickets for speeding! Were you "indicating" 100km/hr in an 80km/hr zone? Do the police have you on their "hit list"?

Things don't quite add up. However, to get your speedo where it should be, try 2567mm.

- Jack