Gears?

[Justin]

K...I'm confused. The build sticker on my truck says I have 3.55's, but if i go in to change the gear setting it said I had 3.31. Which one do I trust?

[twintips_17]

Originally Posted by Justin

K...I'm confused. The build sticker on my truck says I have 3.55's, but if i go in to change the gear setting it said I had 3.31. Which one do I trust?

The sticker on the truck. I belive that all of them start out at 3.31 when you adjust them.

[Jackpine]

Originally Posted by Justin

K...I'm confused. The build sticker on my truck says I have 3.55's, but if i go in to change the gear setting it said I had 3.31. Which one do I trust?

Justin - Twintips was ALMOST right. You DO want to use the Gear Ratio that is shown on the truck's sticker.

The confusing part is, each and every time you open the Custom Options menu, the software in the Gryphon ignores what's in your tunes or in the Vehicle ID section of your PCM and it loads simple "placeholder" values for Gear Ratio AND Tire Size. This means you HAVE to make sure they are BOTH correct if you go into Custom Options. My GR DOES always happen to be correct - at 3.73, but my TS is not. So, during a tuning session, set your GR and TS to the correct values and then program the PCM.

Now, the NEXT time you decide to program the PCM and use Custom Options, scroll to "Load Previous Settings" immediately! This will retrieve and load the previous values for GR and TS, as well as any other options you changed from default values. It's a quick way to get back to where you were the last time you programmed the PCM. Once you've done that, you can go to any individual option and make further changes. Any changes you make will be part of the Previous Settings file the next time you Reload Previous Settings.

Hope this makes a bit of sense.

- Jack

[twintips_17]

Thanks for finishing my thoughts Jack.

Thats some great info. I will have to go check that on mine.

[Justin]

Thanks for the help.

[Jackpine]

You're both very welcome! This "feature" of the Gryphon has caused me grief for longer than I care to mention. I think I FINALLY understand it though, enough at least to "put into words".

- Jack

[88Racing]

Originally Posted by JackandJanet

You're both very welcome! This "feature" of the Gryphon has caused me grief for longer than I care to mention. I think I FINALLY understand it though, enough at least to "put into words".

- Jack

Glad you beat me to it!
That's odd my place holder for GR is always 3.73.

[Jackpine]

Originally Posted by 88Racing

Glad you beat me to it!
That's odd my place holder for GR is always 3.73.

Same here, and it happens to be correct in my case. However, the TS value is an itty, bitty number that might be correct for my Honda Accord. Bill says both these values come from the Calibration area of the PCM, and it happens to be the area that is changed (I think) when we tune the thing. You'd think the values retrieved would be the ones we've put in there during that last programming session, wouldn't you? However, this does not seem to be the case.

What's even more confusing (at least to me) is that the TS value I want to use is 2481 mm, and that's what I enter. Anytime I Load Previous Settings, I find it has been changed to 2484 mm. Now I know that 3 mm is pretty small (about one-tenth of an inch), but why is it changed at all? I recall Bill once saying that it was caused by some "rounding" of values by the software, but since 2481 is a whole number, it doesn't need to be rounded.

The engineer/programmer in me wants to know what REALLY happens!

- Jack

[88Racing]

That's approximately the place holder for the TS on my gryphon also. And yes that "rounding up 3mm is weird also but maybe its upping it to an inch scale value that we don't get to see?

[Jackpine]

Originally Posted by 88Racing

That's approximately the place holder for the TS on my gryphon also. And yes that "rounding up 3mm is weird also but maybe its upping it to an inch scale value that we don't get to see?

I thought maybe that was the case too, but since there are EXACTLY 25.4 mm in an inch, I checked both values. 2481 is 97.677... inches and 2484 is 97.795... inches. Neither one is a simple whole number.

But, here's a thought: 2481 works out to 648.667 revs/mile. 2484 is 647.884 revs. Now, if the figure actually needed for the PCM was revs/mile, it MAY be using 648, which works out to a TS of 2483.555.... (which "rounds" to 2484). So, I think the software in the Gryphon is calculating revs/mile from the TS and then "truncating" it (dropping the decimal result) and using 648. In reloading previous settings, it calculates TS as 2483.5556, which it "rounds" to 2484.

And here's where it gets interesting: If you leave 2484 in for TS, the next rev/mile result is 647.88, which truncates to 647. Reloading again, the TS becomes 2487.394 which rounds to 2487 (another increase of 3 mm). And, I remember this happening, way back when I left the 2484 value in. From now on though, nothing should change, because the new revs/mile is 647.103 which truncates to 647 again.

In my case, the accumulated error is only 0.2% (12.8 feet/mile), or almost 1 mile every 400 miles. Obviously not enough to worry about. Different TS values might take longer to "stabilize" though and there could be a larger accumulative error. If I'm right about "truncating" and "rounding", it would be better to "truncate" all the time, I think. (I would stabilize at 2483 in that case).

I know this has bored most everyone to death, so I apologize. But knowing these things helps me put out meaningful advice to the "new" people. And, I know other programmers ask for revs/mile, not tire circumference. Wonder why the Gryphon/Edge chose circumference?

- Jack