Variance between Gryphon and actual milage

[Savagetwelve]

Thanks Lars! That was short n sweet....

[Jackpine]

Yea, Lars does have a tendency to reduce it all to "essentials" *boring*.

His value is a good starting point, but I think mine is better!

DO use a GPS if you have one. It will give you an accurate readout of your speed. Get the Gryphon to agree with it by changing your TS as needed. Your dash speedo will then read about 2 mph faster, because Ford set it that way.

I suspect LT tires may have less squish, so the circumference value could be larger. The user manual calculation assumes zero squish. If you enter that value, your TS will be too big.

- Jack

[p40whk]

I checked mine with GPS this morning and the Gryphon is much more accurate than the Speedo.

At lunch today I went out to check the custom settings of my TS and GR and they were not set to what they should be. So, I reset them using the custom option. I'm using the 87 canned Tow tune until my performance tunes come in (have a CAI) but I got to thinking (since I don't have the manual handy) Do I need to revert to stock before I make custom changes or change the tune level? I couldn't find this in the Q&A's but thought I read somewhere that you should go back to the stock tune before changing to a Gryphon Tune.

I didn't do that in this case (haven't driven the truck yet) an am wondering if I need to reset it to stock then load the 87 Tow with the custom settings.

[Jackpine]

No, you DO NOT have to return to stock before opening the Custom Options menu. But, you're not really going to be able to "check" things in that menu either unless the first thing you did was "Reload Previous Settings". Even then, your TS will probably be slightly different.

Do look again at the Q & A that I wrote for the Gryphon Custom Options menu. I think it will answer all your questions.

(I probably need to add the part about not having to return to stock though - thanks!)

- Jack

[p40whk]

Thanks Jack,

I did read the Q&A's and understand that those fields are not populated by the PCM as values to be checked and that they are user entered values. I guess I should have clarified that in my post above and probably worded it differently. When I went into the custom menu for TS and GR there were numbers already in the fields that did not correspond to my setup. I think this is where a lot of people get confused thinking they can "Check" theirs.

Biggest problem with the written word is the interpretation. I've written aircraft maintenance manuals for over 20 years and no matter how hard I try to be clear, someone always reads my instructions differently than I intended.

[Savagetwelve]

Ok I was able to try out your sugesstions today with a GPS.
I set the TS to 2500 (+/-10) to see how it compared to GPS.
I noticed on constant acceleration and cruise speed the GR was reading about 1 mph vs. GPS.
When I punched it I nitice that the GR was 5-10mph more that the GPS until I reached a constant speed where the GPS then caught up
Why would this happen? Is the GPS just that slow to pick up the change in speed?

[Jackpine]

Originally Posted by Savagetwelve

Ok I was able to try out your sugesstions today with a GPS.
I set the TS to 2500 (+/-10) to see how it compared to GPS.
I noticed on constant acceleration and cruise speed the GR was reading about 1 mph vs. GPS.
When I punched it I nitice that the GR was 5-10mph more that the GPS until I reached a constant speed where the GPS then caught up
Why would this happen? Is the GPS just that slow to pick up the change in speed?

I think you just nailed it! The GPS updates it's information at regular intervals, and I imagine it's not the same for different models. Then, the processor inside the GPS has to perform some calculations to display your speed, and that takes time too. I would not expect it to react to abrupt changes instantly.

I think my Garmin hiking GPS updates on one-second intervals, and it's far more precise than my Ford Magellan GPS because the map scale it works with is more exact.

- Jack

[Jackpine]

Originally Posted by p40whk

Thanks Jack,

I did read the Q&A's and understand that those fields are not populated by the PCM as values to be checked and that they are user entered values. I guess I should have clarified that in my post above and probably worded it differently. When I went into the custom menu for TS and GR there were numbers already in the fields that did not correspond to my setup. I think this is where a lot of people get confused thinking they can "Check" theirs.

Biggest problem with the written word is the interpretation. I've written aircraft maintenance manuals for over 20 years and no matter how hard I try to be clear, someone always reads my instructions differently than I intended.

Yup! Those are "placeholder" values. And, since you've opened the Custom Options menu, those placeholder values are what will be loaded into your tune unless you change them manually or, "Load Previous Settings" (assuming you've manually entered correct values before).

If you've never used the Custom Options menu, there IS NO "Previous Settings" file to "Load"! A tune by itself does not create one.

I KNOW it's confusing! It took me at least six months to finally put all the pieces together.

I like your avatar! The P-40 was always one of my favorite WWII aircraft.

- Jack