LS2 Speedo calibration

[SRPerformance]

When we run up a car on the dyno we do a speedo check to verify any errors.

On LS1 powered cars: we adjust the tyre size to bring the speedo back in line with the actual speed, most cases we just increase the tyre size to slow down the speedo.

On a LS2, when we increased the tyre size, this did not work?

[Chris@HPTuners]

the PPM value is the one you need to change.

[SRPerformance]

the PPM value is the one you need to change.

Will retry, Thanks Chris.

[GHZ28]

Hi Chris,

I also have an LS2 which we just want to change the diff from 3.46 to 3.91, which is a 13% change.

Tried the tyre/ratio and auto scaling, which from SR's post we now know does not work.

To scale the auto shift points, how to do that given that changing just the PPM will correct the speedo error?

Will probably have the car back tomorrow or Thursday for another go, at least it is currently reading about 8% high, which is much better than the other way round.

Thanks,

Garry

[Chris@HPTuners]

you need to look at the stock file, in some cases the gear ratios are not all matching and in other cases the tire sizes are not all matching. I have no idea why GM makes this so hard but they do. In these cases the auto scaling will not work you need to manually scale each parameter according to the change you are making. Sometimes GM even just corrects the speedo to be right on the cluster itself and the shift points and PCM reported mph is wrong!

eg. if you are changing diff gears all you need to change is the gear ratio values and the PPM value, ie. for a 3.46 to 3.91 you change the gear values to 3.91 and scale the PPM up by 3.91/3.46. no need to mess with the tire revs/mile values.

you can then scale the shift points by using tha manual scale option adn enter the scaler, ie for a higher gear you want to lower the shift points so you multiply by 3.46/3.91

[GHZ28]

Thanks Chris,

will try again when I next see the car.

Garry

[GHZ28]

OK,

well got the LS2 vehicle back again, changed the PPM value only, to check whether the speedo would come into line, nothing. No change at all.

Even gross change to PPM made no difference, from 40xxx to 80xxx the speedo continued to read 9% high.

Tried several combinations of numbers, then finally gave up and took it to Holden and with Tech 2 they changed the PPK value by 13%, the actual gear ratio change, and all is well with the car. Speedo is now 2% high, OK, and gears shift normally before hitting the limiter.

Has anyone else tried to just change the PPM value on a 05 LS2 with the latest release of HPT?

I find it hard to believe that I am making a mistake after three years of doing this, but it is possible.

Cheers,


Garry

[SRPerformance]

eg. if you are changing diff gears all you need to change is the gear ratio values and the PPM value, ie. for a 3.46 to 3.91 you change the gear values to 3.91 and scale the PPM up by 3.91/3.46. no need to mess with the tire revs/mile values.

Chris, re-reading the above.

On a manual GTO we did 3.9 gears change, without adjusting the PPM value only the diff gear value, does this mean the speedo is out now? Joe

[GHZ28]

Well looks like interest in this thread died without a solution.

Did you get your speedo correct SR?

We had to resort to Tech 2 to get my one right, then just downloaded the program after Tech2 set it correctly and continued with other tuning.

Bit of a pain, lucky we have a Tech2 sitting in the US just waiting to be picked up.....and Aussie software for it too.

Might go shopping for a second Tech 2 on Ebay again....

Garry

[SRPerformance]

Hi Gary,

We wont see the car for a while, LS2 GTO 2006, so we will have to wait. We are also looking to get a tech 2....

Joe