Speedo calibration

[badass_2002_z28]

going from 26" tire and 4.10's to 28" tire and 4.10's? how do I properly set it up?

I set the tire and ratio and clicked save changes and scaled the transmission tables and loaded the tune, but my speedo is still off...here's what it's set at now

Engine PPM: 36786
Trans scalar: 47.1699
Speed input PPM: 4000

I noticed that if you keep clicking on save changes it keeps changing the values until a window pops up and says "Maximum engine PPM reached, tire size adjusted" so when do I know when the table is right?

Does anyone have the proper values?

[badass_2002_z28]

anyone ???

[FDLS6]

I'd be curious to know the breakdown as well... if you adjust your trans scalar or engine ppm (i assume there is a multiplior or divisor association between the two) to get the speedo showing correct on the scanner, then you know the mph references for fuel cut, top speed, etc are ok. Then you could adjust your speed input ppm to make your speedo match the scanner(only needed if you have a non stock speedo like me(rx7 rotary 8208ppm), or an inaccurate one). I think i understand the relationshipe... just curious about the trans scalar and engine ppm... not sure of the correlation

[Keith@HPTuners]

Here is what I show for a stock 2002 A4 F-body

3.23 gear 25.9 Tire
Engine PPM: 26781
Trans Scalar: 43.5898

Enter in your old tire height of 25.9
Enter in a new tire height of 28
Enter in a new gear of 4.1

Save Chagnes

Engine PPM: 36786
Trans Scalar: 59.8740

[FDLS6]

ok.. i think i've got a feel for it. The ppm and the trans scalar are proportional... if the scalar and ppm are confusing, compare the speedo to how fast you know you're going.. (pace car?).. if your speedo shows 10% too fast, multiply both your engine ppm and trans scalar by 110% (1.1) and enter those manually... from my understanding that should do the trick
Bryan

[Chris@HPTuners]

We are working to enhance this in future versions, so its a bit more intuitive and easy to use. It seems GM made this a lot harder to understand than it should be IMHO.

[badass_2002_z28]

thanks for the input, I think I got it figured out

[badass_2002_z28]

ok after furter testing my speedo is STILL off...does anyone here have this done properly on their car?

[Chris@HPTuners]

was you speedo accurate when you started with the 4.10's and 26' tire?

[badass_2002_z28]

it was off by a few MPH. Now it's like 10-15mph off

[Keith@HPTuners]

what scalars are you using now?

Give us your engine PPM and trans scalar, and the gear/tire height you are currently using.

[badass_2002_z28]

right now it's at

engine PPM: 39672
trans scalar: 50.8701
speed input PPM: 4000

28" tire and 4.10 gears

[Keith@HPTuners]

Did you try these values like I suggested?

Engine PPM: 36786
Trans Scalar: 59.8740

[Keith@HPTuners]

any luck yet?

[badass_2002_z28]

it's been raining here the last few days so i haven't had a chance to drive the car around

[Keith@HPTuners]

Those scalars I posted SHOULD work.. Just enter them into the fields at the bottom and hit save changes. It will pop up an invalid tire height error message but the changes will take place, save the file, then write the PCM and give it a go.

[badass_2002_z28]

I just got back from lots of back and forth testing and finally have my speedo calibrated correctly.

I tried the PPM and trans scalar u posted as well as many others and they didn't work. I've read that with software like LS1edit you have to "trick" the pcm to get the speedo working correctly. So after lots of highway testing this is the best setting for running 28" tall tires and 4.10 gears:

Engine PPM: 28491
Trans scalar: 36.5332

[Dom]

Did you do anything with the 'scale the transmission tables function' thing?

[Keith@HPTuners]

The scale trans tables is just a utility function for convenience. If you put in a shorter gear, you may want to quicken all of your shift points and lock up tables. Instead of doing each manually, you can use the scale all tables function to get it done in 1 sweep. Just be careful with your factor.

[badass_2002_z28]

Did you do anything with the 'scale the transmission tables function' thing?

I scaled them manually to my liking