About every other day my speedo keeps going like 10 mph off and I have to go back in and reset it to my circum. The default setting is something like 2300 or something and my circum is 2779. Before the programmer my speedo was barely off 1mph according to some local speed traps. And now my speedo says I'm doing 70mph and you can feel that I'm only going around 55-60ish. I stop and redo the tune I'm on and cusomize it to my 285s and then it's fine for a day or so, then back to whats like 10 over. Any suggestions?

James

 

No real suggestions, because what you're saying doesn't seem possible (and don't take offense please - I'm not putting you down). Here's why I say that:

When you enter a tune, you program the PCM's EPROM with new data and instructions. Once that program is entered, it's "fixed" until you program it again. At this point, your Gryphon is just a "monitor", receiving data FROM the PCM, which it displays. It cannot and does not make further changes to the PCM until you tell it to through the Power Programming Menu.

So, there should be no way in hell for the speed to be correct for a few days and then suddenly be about 10 mph fast.

Are you using OEM tires and gears? If so, do me a favor and try programming the PCM to whatever level you normally use, but SKIP the Custom Options menu entirely! DO NOT even "open it up"! If you do it this way, the tune will be entered into the PCM using the Tire Size and Gear Ratio that are stored in the PCM's Vehicle ID (VID) section. It will essentially have "factory" information for those two parameters. If you can do this, let me know if you still have the speed errors after a couple of days, or if everything is fine.

Once I know the answer to this, we can proceed further.

- Jack

 

Yah, I don't know thats why I was asking. My wife was driving it the other day and the speedo said that she was doing 70 but people were still catching her on a speed limit 55. Earlier this week I would be doing 65 according to the speedo and by even watching objects that are stationary on the side of the road was going by at different speeds at different times driving. I don't know its weird. I mean I've been driving this truck a year and a half and I know how driving 55 feels. Today however it seemed fine.

I dont know, maybe I'll just leave it alone for a while. Every thing else runs excellent and I'm very happy with it, maybe with the truck performing differently (for the better) it is playing with my mind!

 

Well Jack, I did what you suggested to do and the speedo is dead nuts on, on the stock tire size. I had my wife and her completely stock trail blazer follow me during my testing to see what speeds I was actually going.

Before I reset the computer to the stock size she followed me to my "correct" and current tire size. Up to 60 mph my speedo was off just over 5 mph. Over 60 and it was off just under 10mph.

I then reset it on the side of the road to the "stock" tire size or the default setting just as you suggested by not even going into the custom settings and it id dead on now. All the way from 0 up to about 75mph it was identical to hers.

So even though the 285s Im running aren't the stock tire size, the speedo works now and I'm not even going to figure out what was happening.

 

Just a guess here, but it could be that the default gear setting is not what gears you actually have. So that in this case, two wrongs make it correct. Wrong gears offset wrong tire size to equal correct speed.

 

I don't think that's it, Jim. If he didn't use the custom options, the tire and gear information was taken from the VID section of the PCM, and they should be stock values. However, if the stock tires were 275/65R18s, the difference between those and the 285s is only 10 revs/mile. It may not be enough to make much of an error.

- Jack

 

Mine has always defaulted to the wrong gears. When it was Edge canned tunes, and then on one of Bill's custom tunes, he failed to change it. It defalts to 3.73 and I have 3.55, so I have to change it.

 

Stock was 275/65/18 correct? He has 285/65/18. Speed reads 1.6% slow. If speedo reads 60 you're actually doing 61.

Edit: My speedo was off too after putting in custom settings for tire size. I reprogrammed and left the tire size alone and all is fine now. Don't know why. I put in the correct size and allowed for squish. When you call up the tire size on the Edge/Gryphon I don't think it has any idea what the tire size is like it does for gears does it?

 

Guys, I just put this in another thread, but I'll add it here too. The ONLY way you're going to know what values the Edge/Gryphon is using is by opening the "Custom Options" menu! The second you do that, placeholder values are put into the TS and GR settings! These values have no real relationship to anything on your vehicle. Once you've opened this menu, you MUST correct those values either by "Reloading Previous Settings" (if you'd put correct values into a previous Custom tune) or by manually going to each and changing them.

Again, here's a link to a Q&A on this often misunderstood feature of the Edge/Gryphon: http://dygytalworld.ehost-services13...ead.php?t=1101

If you completely bypass Custom Options, the TS and GR are retrieved from the PCM's VID section and the values used are the ones the truck left the factory with.

Edit: 10 revs/mile is an error of about 1.5% - about 1 mph at 70. I doubt you would see any difference between two vehicles unless both had digital readouts.

- Jack

 

My default setting on the "canned" gryphon is 3.73s, and that is what I have on my truck.

 

That's fine! My "placeholder" value is also 3.73 and, that is what I have on my truck too! But, the placeholder value of Tire Size is some ridiculously low value.

Different people will get different readings for Tire Size (TS) and Gear Ratio (GR). Some might luck out and get correct readings for both. (It seems FORD DOES put a "popular" value for each of these into these placeholder positions.)

But YOU may find that one or both of these are wildly inaccurate. If you open the "Custom Options Menu", always check and correct if necessary, the TS and GR! Or, if you've entered correct values for a previous tune, just scroll immediately to "Load Previous Settings" when you open the Custom Options Menu and hit <Enter>.

- Jack

 

I used to notice that I'd set a TS in the Custom Options section, save that setting, then go back to double-check that setting, and it would be about 17 - 18 mm lower than what I just saved. However much it was, it never was enough to significantly impact the speedometer, though.

Like others have mentioned, I'd also be willing to bet that the OP is seeing the speedometer "right on" because the circumference difference between 285s and 275s (assuming the same aspect ratio) is very minimal.

 

The 17-18 mm difference is quite big! I can't explain that at all. Mine also changes, but it's only about 4 mm. I finally figured out that the programmer calculates the revs/mile and truncates the result - drops any decimal value to make the result a whole number. Then when you "Reload Custom Settings" to check your tire size, it converts the revs/mile figure back to circumference, but this time "rounds" the result to the nearest whole number. (The PCM actually wants a revs/mile figure.)

- Jack

 

That makes sense. Maybe it wasn't 17-18. All I know is that any time I've changed tires, I enter a number for tire size in the custom options menu, let the Edge load the tune, then drive a few miles, comparing the truck speedo, Edge speedo, and Garmin speedo. I keep adjusting the tire size in the custom options menu until the Edge speedo and the Garmin speedo match up.

 

I don't know. All I know is that I did what Jack told me to try to do without messing with the tire size and now it works, so I'm not even going to try to figure it out since it seems to be all good now.