Diablosport Forums

As you will all notice on the newest revision for U7151(9r08) there are a few new adjustable parameters in the Axle Ratio section. I will give you a breakdown of each here.

Enable Gear/Tire change - Anytime you need to adjust gears/tires or NOV you must set this parameter to enable. If not, the PCM will not use the values entered and refer to another area of the calibration. Anytime you enable gear/tire change you need to check the following three parameters listed to ensure they are correct. The default settings may not be the same as what is in the vehicle.


Axle Ratio - This is the gear ratio of your drive axle.


Tire Revs Per Mile - This is the number of revolutions your tire will make in one mile. This value can usually be found on the website of your tire manufacturer under the specifications for your particular tire. That is the best resource for this info as tires rarely meet the exact size that is on the sidewall. If you can't find the info anywhere then you will need to calculate the circumference of your tires based on the sidwall info and divide that number into a mile. There is a Tire diameter calculator stickied in this section, here's a link http://www.diablosport.com/index.php?na ... ic&t=15724

Once you have the diameter you need to calculate your circumference.

Circumference = Pi X Diameter where Pi = 3.1415926

Now that you have the circumference you can divide that into 63360 which is how many inches are in a mile. The outcome is your Tire Revs Per Mile.


NOV Adjust - This value represents eNgine speed Over Vehicle speed when the vehicle is in direct drive(OD off/3rd gear in a 04-08 F150) with the torque converter locked. The easy way to calculate this is using the following equation.

Tire Revs Per Mile x Axle Ratio divided by 60 = NOV

This parameter is used in some calibrations for transmission shift tables and is affected more with large changes in gears and tires.

Found a useful link for you guys to calculate your Tire Revs Per Mile....

http://www.net-comber.com/tirecalc.html

hello I have installed new wheels and tires on my 01 Bullitt the new tires are 245/40/18 what should I put in for the custom tune on my predator. Also I have installed the Kand N cold air for it is there a selection for this in the custom tune. thank you for your help

I did the math per the convertion and came up with 784.247 does this sound right and if so do i need to put in a 784 785 or the complete 784.247

When you say axle ratio, what are you entering in your equation? I have a 3.55 so would you input it as 3.55 or 3/55?

Why do you have to put in the gearing, tire size and NOV on the latest update? I just loaded the update last night and the one on there previously (I belive it was 9r04) only had axle and revs per mile. Seems a bit redundant to me.

That's a good point tomahawk -- I would have thought the tuner could calculate the NOV for you with the tire revs & axle ratio. Maybe they give you the option if the user doesn't know their axle ratio? I would think though, if you don't know your axle ratio, you probably shouldn't be messing with these settings to begin with. I agree, it seems redundant to me too to have that setting.

I have 305 55r 20 on my 150 wich is 607 revs per mile I entered that but my speedo was off didn't no I had to change nov ? My axle is 3.73 so I did the math came out with 37.7351667 basically 38. you no my nov was off, I changed it so lets see what happens

I have an 06 with the manual trans. with 3.73 Gears and 265/70/17 Tires.

Will the NOV effect the Speedometer and the Odometer?

Does NOV have the same effect with the manual as with the Automatic?

I noticed that when I tweeked the Revs so that My speed was at GPS, My Odometer was slightly behind the Mile Markers.

I had not adjusted the NOV since loading the 9r11. Recently I calculated the NOV and it was off by about 1.5.