5.0 Quick Questions

[Dr Wu]

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-

 

[stkjock]

huh?

the SCT doesnt shift the transmission does. the trans is controlled by the PCM and the tune in it. the tune will shift at what ever rpm has been programmed.

will changing tire size alter what MPH the shift occurs - if the tire is much different then stock, sure will.


TPM should not have any effect

 

[Full_Tilt]

lol whut

 

[Dr Wu]

lol whut

Two SCT dealers gave me opposite info on the first question imagine that.
lol whut to you...

 

[fdjizm]

The MPH may be different with the tire size but rpm is rpm, so it should shift where it's set.

 

[GeorgeInNePa]

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.

 

[fdjizm]

So in the tuner you have to set rpm and mph as two seperate values? damn automatics.

 

[Dr Wu]

The shift points are set by RPM & MPH.

Bet a $1 on this one-

 

[SlowA$$5.0]

I'm confused.

 

[Ducky]

Why wouldn't you adjust the tire size? That's an end user parameter on the handhelds.

 

[uncle phil]

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.

 

[Dr Wu]

Why wouldn't you adjust the tire size? That's an end user parameter on the handhelds.

That's what I will do.

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.

Yes, I know tuners will raise the shift points higher than the SCT tune.


Thanks everyone-

 

[VTXFrank]

Don't forget that you can also set "Revs Per Mile" in the SCT yourself. This will correct your speedo in the car.

If you don't know your Revs Per Mile for your tire, look on Tirerack or call the manufacturer and they can tell you.

If you use Tirerack to look up your Revs Per Mile, check out this page. That's the page for my tires. Look at the tabs on the bottom and one will say "Specs". Click on that tab and the next page will give you all the specs for the tire, to include Revs Per Mile in the column second furthest to your right. This works no matter the diameter tire you're running. Just match up the tire size in the first column, then get the RPM for the tire. When you go to load a tune, chose the one to change saved options. Under the options list in the SCT, it will show you where to enter the number for Revs Per Mile.

Just in case ya didn't know.

 

[Full_Tilt]

lol whut

 

[BSell]

Help 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?

 

[Ducky]

Help 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?

Your logic is correct. But this post

The shift points are set by RPM & MPH.

Leads me to believe speed does in fact matter. These cars are so computerized today, that it wouldn't surprise me at all if speed was part of the calculation.

 

[DarkTrak]

lol whut

LMAO thats 2....

 

[Full_Tilt]

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.

 

[KJGT]

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.

Actually all part throttle upshifts and downshifts, and TCC lock/unlock is mph based.

WOT upshift is RPM based.

If you get too far off on the mph at higher throttle openings it can affect the rpm it shifts at. Same if you spin the tires.

Naturally if you change the gear or tires and dont correct for it everything will be off. Theoretically the RPM based WOT upshifts shouldnt change but after a few weeks of fooling with the shift points on mine there is some interaction between rpm and mph on wot upshifts.