Does anyone no if u can add a 1/4 mile recorder to the 09 hhr ss screen or do I need a new aftermarket gauge

 

You mean the RPD?

 

I highly doubt you can add to the factory software but I could be wrong
if you have an android phone you could buy an obd2 bluetooth adapter and then you can monitor just about everything that your computer is looking at.
Unfortunatly I have found that the 0-60 1/8 mile and 1/4 mile parts of this program to be off,
I am working with the developer of the software to see if it is something on my end but one of the answers I received was ,well a half a second is not that far off.
I explained that that was a huge difference in the 1/4 mile.

I stick with my Gtech for time runs I have an older one and it is withing a tenth of a second every pass. It will however show the actual mph at the end of the 1/4 mile unlike the race track where they average your speed in the last 100 feet.
another words my gtech will show say 135mph and the track may show 132
either way GTECH or vbox would be my advice on which way to go
just do a google search on them

Here is a very good comparison of the G-tech vs an actual track.

It does appear that with the newer gtechs even the mph is on
great investment for anyone doing any tuning.
The dyno can show all it wants but what really matters as everyone should know is what the car will actually do