Dr Wu
Faraway
Quick questions, does the SCT shift at the RPM set by ANY tuner at WOT regardless of tire size or must you adjust to tire size? Will performance be hurt by not having TPM on the rear wheels? Thanks-
lol whut
The MPH may be different with the tire size but rpm is rpm, so it should shift where it's set.
The shift points are set by RPM & MPH.
Why wouldn't you adjust the tire size? That's an end user parameter on the handhelds.
If your asking if the shift points are set lower with the tunes that come with an out of box sct tuner than custom tunes installed by Jon Lund ,Livermois etc. the answer is yes. With the sct tunes on my car it shifts at 6500-6600 rpms. I think the custom tunes are around 7000 depending what you tell the tuner.
Your logic is correct. But this postHelp me out here...
Tire size shouldn't affect the shift points when related to engine and drive shaft speeds. In other words, the engine and transmission don't care how fast you are going down the road, it only cares about how fast the things on either end of it are spinning in relation to each other (and of course load on engine at less than WOT, but who cares about that? ).
Your speed down the road will be different from OEM given smaller or larger tires when driven at the same drive shaft speed as OEM.
This means the mph displayed in your GPS unit when the tranny shifts will be different from stock with smaller or larger tires, but your drive shaft speed at the shift point will be identical as nothing changed between the engine/transmission.
Do I have this right or am I out in left field chasing grasshoppers?
GeorgeInNePa said:The shift points are set by RPM & MPH.
I can see how maybe the software would have some provisions for helping you figure out at what speed you will shift, given the RPM, but it makes very little sense to use the VSS as the input for shift points.
The car is going to want to have the shift point at one place in the RPM range. Speed is a byproduct of that, not the source.