I can't remember the reverse logic used for 3:73s.I know for 3:42s you set for 3:23s and change to 27" tire size.

Anyone remember?TIA

 

hehe.. I thought it had a direct setting for 3.73's? Or at least mine did <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

The 99 Hpp does not work correct on a gear change.

I think that they are still fixing the program for us 99s.Yeah,right.

 

29.5" for 3.73's John, this is our "fuzzy math" speedo calibration. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

Thanks Trevor.

"Fuzzy math",that is what it was called.

 

so I should not have mine set at 25.75?
I have a 99 T/A with 3.73's A4

 

OK, I'm confused. I just put 4.10s in my car. What's the correct formula for this?

 

I called Hypertech and they stated they're not aware of any issue. Can someone clarify this?

 

The HPP for 1999 cars would not set the speedo right.I don't know about other years but heard that 2000 and up was fixed.

Take your car out and pace someone with a good speedo or run a measured course to check how close you are.

 

BTW,Hpertech has been fixing the 99 HPP for I don't know how long.

Might be some later 99 Hpp's were fixed but mine does not work on a gear change.

 

Hypertech tells EVERYONE that they're not aware of this problem that's been going on since December 1998 with their HPP3! I was a beta tester for the POS. I swapped gears in my '98 T/A in June of '99, and when I reprogrammed for the correct gear (3.42:1) with the HPP3, it had a "quirk", of sorts, when going into OD. The trans would shift into 4th, the converter would lock, then unlock, then lock back up. I called Hypertech, and they told me to send them the unit. I paid to overnight it to them, they reflashed it, and I got it back only for it to do the same thing. Then they blamed it on my transmission, saying that a bad trans was causing the problem. I dropped my car off at a reputable trans place, and he verified after a lot of testing w/ his Tech II that the HPP3 was telling the PCM to do this. He ran the battery down once that I know of because he was programming so much. Besides all of this crap, I was also unhappy with the higher part-throttle shift points that Hypertech sets when you reprogram for a steeper gear. OH, let's not forget to mention that your speedo is actually off with the "correct" programming with the HPP3 because they got the tire height backwards in the unit. I was tired of the POS not working right, so I decided to program for the stock gear ratio and adjust the tire height accordingly. What I did was multiply my gear ratio by the tire height. (3.42 x 25.5"). Then you take this answer and divide by your stock gear ratio of 3.23:1. So, 3.42 x 25.5 = 87.21. Divide that by 3.23, and you end up with a corrected tire height of 27". Use this same method for 3.73's, and you come out with a tire height of 29.44". The HPP3 works in .25" increments, so you program for a 29.5" tall tire. The difference is so negligible that you won't notice it on your speedo. I used a radar gun and had another person pace me to verify that mine was right, and it was dead on. Just be sure that you re-adjust your shift points to get them back where they need to be. I came up with this when the "fuzzy math" was being discussed in politics, so I just carried it over. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

Thanks for the explanation. I'll try it out. I have an M6, so shift points are up to me <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Now it all comes back to me.I suffer from "fuzzy brain"sometimes.

Thanks again for the info Trevor,I added it to my HPP manual.

BTW,I think 98s shifted on mph,99s and up by rpms.

<small>[ April 01, 2002, 10:11 PM: Message edited by: jfm ]</small>