Tire Size

svt2205 · #1 Thu, October 15th, 2009, 06:36 PM

How the heck do you know what the tire size setting is that is programmed into a custom tune?

My speedo has been off since day one with my custom tunes. It's not really an problem as I think I've been able to adjust the size to one that works. But when I recently decided to swap to my custom tow tune (I'd never tried it), I couldn't remember what the size needed to be.

My tires are 275/70-18 and the unit always shows 2669 in either of my 2 custom tunes (tow and performance). I set the size to 2566, which is what is the number I get when I use the calculation in the Gryphon manual (yes I actually use it). After the PCM has been programmed and I go into the custom tune mode, it still shows the 2669.

Maybe this is normal, but it seems odd I can't verify my setting.

Any suggestions?

Thanks

***Jackpine*** · #2 Thu, October 15th, 2009, 07:58 PM

Yes - Henry, this is a super confusing issue. Please read through the FAQs at the top of this section on using the Custom Options menu. Unless you are "Reloading Previous Settings" every time you open that menu, you are going to get simple "placeholder" values which are probably wrong.

And, if you bypass the Custom Options menu, you will get the values that were included in your tune - but, there's no way to "check" them!

- Jack

***Power Hungry*** · #3 Thu, October 15th, 2009, 11:50 PM

Quote:

Originally Posted by svt2205

My speedo has been off since day one with my custom tunes...

My tires are 275/70-18...

Henry,

The reason your tire size is off is because on your custom order form you entered 275/75-18 instead of 275/70-18.

This accounts for just over an inch in tire diameter (33.42" vs. 32.39") and will cause the speedo to be off quite a bit.

The current values in the calibration (as you've no doubt noticed) is 2669mm. The correct values should be 2584mm @ 5% squish and 2570mm @ 6% squish.

The files have been corrected and reloaded on the server. You can download then whenever it's convenient.

Take care.

svt2205 · #4 Fri, October 16th, 2009, 03:54 AM

Jack

I read the FAQ but that point didn't click. Thanks for repeating that again.

Bill

That would explain it. Now what's the practical temperature limit for tuning? We've had the first real cold snap here in NH. Heck it's all of 35 right now and I don't think it got out of the 30's yesterday. Ugh, too soon for winter. (yes we've seen our first snow already)

As soon as it's warm enough, I'll return to stock and load the adjusted files.

Thanks for catching my mistake and better yet, FIXING it...

Henry

***88Racing*** · #5 Fri, October 16th, 2009, 06:37 AM

Practical tuning temp?
You should be ok in the 30's.
Usually any temps in the teens and below you would want to run the truck first for 5 minutes.
Lars

***Power Hungry*** · #6 Fri, October 16th, 2009, 06:04 PM

As Lars indicated, just run the engine a few minutes first. Since the PCM is located right above the engine, it'll warm up pretty quick. Ford specs say don't program below 30 degrees, but that relating to core PCM temps. If the engine has been run for a while, it's fine.

Glad we could get the other fixed easily.

Take care.

***Jackpine*** · #7 Fri, October 16th, 2009, 06:36 PM

Quote:

Originally Posted by Power Hungry

As Lars indicated, just run the engine a few minutes first. Since the PCM is located right above the engine, it'll warm up pretty quick. Ford specs say don't program below 30 degrees, but that relating to core PCM temps. If the engine has been run for a while, it's fine.

Glad we could get the other fixed easily.

Take care.

I'd also have the Gryphon in the house, before your programming session, so it's nice and warm too.

Glad things are squared away!

- Jack

svt2205 · #8 Fri, October 16th, 2009, 07:27 PM

Great support from all of you for helping with what was my mistake from the get go.

Good to know all the details regarding cold temp tuning. I ruled out being able to adjust things during our 6 months of COLD. Now I've got a work around, if I need to swap tunes.

A big thanks to each of you.

Have a good one
Henry

***Jackpine*** · #9 Fri, October 16th, 2009, 08:51 PM

Quote:

Originally Posted by svt2205

Great support from all of you for helping with what was my mistake from the get go.

Good to know all the details regarding cold temp tuning. I ruled out being able to adjust things during our 6 months of COLD. Now I've got a work around, if I need to swap tunes.

A big thanks to each of you.

Have a good one
Henry

Henry, this was posted in an earlier thread and "approved" by Bill too. If it's cold, it doesn't hurt to have a low Amp charger (about 2 Amps) on the battery anytime you want to change the tunes. It will keep the voltage at the level needed for a proper update to the PCM. Low temperature tends to reduce the voltage output of even a fully charged battery, and this is a "work-around".

- Jack