Which custom tunes for me
 

I'm looking at finally ordering the custom tunes for my truck. I've got the gryphon with my 2005 F150. I've been wanting to order an 87 performance tune, but am wondering if I should go ahead and order a custom 87 towing tune too. What I'm trying to get is the best mileage out of my truck. I usually run the 87 canned tune.

I have the 5.4L 3v with a K&N FIPK, Flowmaster Catback, Efans, 35'' tires, and will probably get some underdrive pulleys to put on before my tunes arrive. Any help you guys might have would be appreciated.

I also have an 05 F-150, and I did both the 87 performance and 87 tow tunes. The only reason to get the tow is if there is a chance that you will be towing a lot. I havent used it yet, so I cant say anything about its gas mileage, but you should get better mileage with the performance tune unless you drive like I do... mine is the same before and after the tunes... lol

Unless you tow loads over 2500#, there's not much reason to get a tow tune.

- Jack

I object to this. I ordered a custom 87 performance tune and my mileage decreased by 3-4 mpg. That is 75 to 100 miles per tank. For me that is 3-4 round trip days to work. My driving habits did not change at all. Needless to say I have been running on the canned 87 tow tune. I was going to ask this in a new thread until I found this one: Is it possible to run the canned 93 performance tune with 87 octane and lowering the timing by 3.00 without causing any damage or having any trouble?

Bill has advised NOT to use low octane gas in a high octane tune. There are changes in the fueling strategy in addition to the timing changes. You DO risk some damage if you do that.

I'm VERY surprised at the "mileage decrease" you got. Is it possible your Tire Size (TS) or Gear Ratio (GR) is wrong in one of the tunes? Either one would strongly effect your perceived mileage (without actually changing the actual mileage much at all). Have you verified that your Gryphon speed matches an independent speed reading like a GPS? (Or that your odometer reading matches a measured distance?)

If you got a mileage drop like you say, I think you are the only one on the forum who did so. I know my mileage increased by about 0.5 mpg with custom tunes compared with canned, and canned was better than stock.

- Jack

So this is what I did. I reinstalled the custom tune. The gear ratio was correct. The tire size that was in the custom tune was different than the two numbers that I determined. I determined the tire size using two different methods: 1)by measuring one tire revolution and 2)by calculating using the tire diameter given by the manufacture website. So which one should I use? The actual measurment or the calculated?

First, please read through the discussion of using the Custom Options menu here: http://forum.gopowerhungry.com/faqs-...ions-menu.html

The way Tire Size (TS) and Gear Ratio (GR) are stored is VERY confusing. What you saw for TS may not have been the value that was used.

But, as far as determining a TS, I'm not a fan of measuring a tire revolution. There's too much potential error and, it does not account for the expansion of the tire at highway speeds (somewhere in the neighborhood of 700+RPM).

If you have P-metric tires, Bill has included a VERY accurate calculator with Pegasus. It is the Gear Ratio Calculator. Enter your "Old Tire Size" like this, using my 275/65r18 tires as an example: "275/65-18". If you don't have "low profile" tires (less than 60-series) use a 7% "squish factor" in the calculator. (The squish in the calculator is "rubber squish" - no squish in the rim). With a low profile tire I'd reduce the squish to 5%. You can then read the circumference in millimeters.

Another VERY GOOD way is to find the number of revolutions per mile for your tires from the tire manufacturer's website. Most post this figure and it accounts for squish. Then divide this number into 1609344 (the number of millimeters per mile).

If your tires are "inch" sized, multiply the diameter by pi and then 25.4 to get the inflated circumference. Then reduce that by 3% for "normal" tires or 2% for low-profile tires.

All these should give a very close starting point. Match a Gryphon speed readout with a stable speed reading on a GPS or match your dashboard odometer with a measured distance of at least 10 miles (more is better). The dash speedo will read about 2 mph fast at 70mph if you have everything right.

Hope this helps.

- Jack

Thank you Jack for the helpful information. I returned the truck to stock to start with. I then installed the 87 perf. custom tune. Then I went to "Power Programming", selected the custom tune, loaded previous settings, opened "tire size" and inputed the correct tire size and left all other things unchanged. I will post the results after I have gathered enough info.

Regear to 4.56 with those 35's it may not help the mpgs but your tranny will thank-you....