Ryan, I dont mind you "counting" PCMs as a whole... but please note the programming sequence as a whole to everyone…

12209624 was the original provided PCM and was programmed twice before I decided it was time to switch to the 09380717 which has only been programmed twice to this point. So yes, this is 5 total, but if we had started with 09380717 first, this all would have never happen in the negative sense. Lets just try to be positive and move on pass this negative issue part. I had no idea you even had a PowrTuner until you posted that mess about your license issue with DHP. You can start your learning curve with OBDII programming now and see the “ups” and “downs”…

As far as that speedo calibration. I have to use HP Tuners right now to program the PCMs. My PowrTuner is only for 2000 and upcoming 2004 models. Let me show you what it looks like in HP tuners. It is completely different in Powrtuner if you have that loaded and running on a computer.

Now, see the light gray numbers in the boxes to the left center section. What would be current tire size and Calculated gear…. Well in the boxes label NEW, is the only boxes I can manually change, so the HPT program can auto calculate the shift parameters that are very associated with this type of change. You will notice in Powrtuner software that you make a gear ratio change, or a pulses per mile change, you have to manually go back to the shift tables and change those MPH per TPS vs RPM (or ever how those are labeled) yourself. DHP has excel spreadsheets with formulas to do some of this for point of entry starting place, but again, just a starting place. What works for one, does not work for everyone.

Thanks to you also Ryan for your new patience in this matter.

Loyde

I wrote down 5% error on the plus side according to Pete tonight.

Now, we have to correct the 25.82 only, because the trans ratio stays 3.29. When I hit the calculate new values button, it does all the updates to the shift tables automaticly...

Thanks for your input..

Trust me, if I knew the 09380717 PCM would have been easier for you to work with without any major issues right off the bat, I am sure we (Pete and I) could have traded the 2002 PCM off to someone or a junkyard in exchange for the 09380717 unit instead; and this whole situation probably would not have happened.

Look, I will admit that I was quick to get upset about this PCM matter because it was very frustrating. It also didn't help that this project suffered a couple of other setbacks that were out of my control and I guess this was just the straw that broke the proverbial camel's back. As I am sure you understand, being the only one in a one-bay shop it is quite difficult to stick to deadlines and tight schedules when the setbacks start to pile up. Needless to say I have a new found respect for the employees of OCC on American Chopper and what those guys go thru to get projects done on time and as scheduled.

OK...heres my thought's on this...

Tire size is currently 25.82 inches with 5% error. The transmission is at 3.29 calculated gear ratio. Thats all the numbers I can work with because I am not going into the shift tables and changing all those values manually. You can do it with the same percentage you come up with here, but the tables are suppose to update automaticly if you have that check box "auto scale transmission tables" clicked.

Now, if we go to the trusty tire rack tire converter http://www.s-series.org/htm/calc/tiresizeconv.htm

Example: LT235/75R16 = 30"
LT(225)/R(50)=Diameter'' 24.9
Section Width:'' 8.9 Section Height:'' 4.5

Well, 25.82 is stock for the GTP car. Had I put the 24.9 Pete's error would be greater. Back some time ago when you sent that email about the 5% speedo error, we were still working on the shifting problem. Since shifting needs recalculated when you change this speed cal area, I had omited that at the time to not change this in order to not be changing to many parameters at one time. Then I flat forgot to change it in this last PCM I sent, but makes no difference, the P0446 has decided to come up and now that the shifting on the car is 100%, its time to kill this last code (hopefully) and resolve the speedo cal.

In the picture there's the bigger tire. Now if we note how tire size reacts in the real world of experience I believe if you put a bigger tire on a car, it would make the speedo read slower. Takes a further distance to make one revolution, so today in 25.82 inches, we see .......... well I dont know what we see... This is were I hate math...

I know you have a 30 tooth reluctor ring on the diff that the VSS picks up the pulses at. It turns more than one revolution in 25.82 inches, but I dont have a clue how much.

I am out on this math thing... I will add 5% of tire size to this 25.82 to get 27.11 (rounded off)..

Now we have this

Anyone else have a better explanation of how I should approach this?

Loyde

I don't usually work with tire diameters because there is an easier way. What I do is go to tire rack, as you do, and find the tire rev's per mile and use that for my calculations, it is MUCH easier. A problem is the static tire diameter measurement does not take into account rolling circumference diameter so your numbers could always be off (vehicle weight on the tire causes the sidewall to crush slightly which makes the rolling diameter of the tire smaller). What I usually do is just go to the Tire Manufacturer's website (for whatever tire I am working with) and look up their specs for rev's per mile. It looks like your HP Tuners has attempted to calculate this value using diameter but, like I just mentioned, it may not take into account loaded tire rolling diameter.

I just emailed Pete and he said (as best he could remember from memory) that he is running this tire: Falken ZE-512 ZIEX, 225/50-16. I just looked up the specs on the Falken Tire website for Pete's tires. They say the Falken ZE-512 ZIEX, 225/50-16 tire has a diameter of 24.9" but does not give a rev's per mile spec (I wish they did like most every other mfgr, it is more accurate). Anyway since this is all we have to go on we will have to use it. This diameter of 24.9" is smaller than the previous diameter that was previously entered in HP Tuners of 25.82" by approx 3.6%. But like I said the Falken website does not give us REV PER MILE specs on these tires, just a static diameter so it is reasonable to assume there could be a 1.4% error allowed for the speedo cal due to tire loading. We know for sure at present the speedo is 5% too fast so we need the following changes to be made to the PCM programming:

Original Settings:

Tire Dia: 25.82"
VSS Pulses/Mile: 23430
Trans Revs/Mile: 2568.3980

I would suggest these settings be changed to the following to fix the speedo cal:

Tire Dia: 24.53" (which should automatically make the following changes)
VSS Pulses/Mile: 24602
Trans Revs/Mile: 2696.8179

Glad to see you guys working things out,

Dan