I dont have any tuning software for my duramax, but i thought this would be the best place to ask my question.
I do however use a program called LT1edit to tune my camaro and one or more of the parameters uses the actual vehicle speed from the vss to help determine the fuel/timing /tranny/ etc

I aslo know that many cars do not use speed as a factor

Does the duramax vehicles speed get factored into the fueling/timing/tranny/whatever tables?

With bigger tires on my truck, I cant figure out weather to get a downloader type like the PPE etc witch can actually change the speed in the PCM, or a plug in type like the edge or banks witch does not.

My truck is near stock now and since i put much larger tires on it, the stock PCM seems to be having trouble performing correctly. the speedo is off by 24%. Its not performing like its broken, but like it thinks its really going 50 when im really doing almost 70mph


Thanks

You may want to look into getting EFI LIVE. If you have done some LT1 tuning the DURAMAX tuning is easier. EFI will alow you to make any changes you want from speedo correction to dif hp tunes plus its a great data logger.

You may want to look into getting EFI LIVE. If you have done some LT1 tuning the DURAMAX tuning is easier. EFI will alow you to make any changes you want from speedo correction to dif hp tunes plus its a great data logger.

EFI live sounds great, especially if your after monster power etc... but im not. I got a 10 second 640 hp sports car for that. I just want an easy, no thought mod just for a few extra ft/lbs.

Go to www.EFILive.com (http://www.EFILive.com) and download the software. It's free and there are stock Duramax tunes included. As an LT1 edit user you should have no trouble navigating the menus to see if it contains exactly what you would like to see.

The short answer is no, engine tuning is not based on speed. Rather rpm and a host of other factors.