Honing in the Speedo with my Tune after Rear Gear Change - Check Me

[1950StangJump$]

Okay, so just had a 2.97 Magnum XL and 4.10s installed (from the 3650 and 3.55). Now, my speedo says I am going considerably faster than I really am (+6-9 MPH)

Point me in the right direction here . . . to make it show slower, am I increasing or decreasing the revs-per-mile number on the SCT tuner?

 

[RocketcarX]

Start with selecting the new gear ratio

 

[1950StangJump$]

Again, I’m just adjusting the revs per mile .... found in the past that just setting the gear ratio on the SCT doesn’t result in much accuracy.

Just asking if anyone knows if the revs per mile has to go up or down to make the speedometer show slower

 

[Juice]

Speedo reads over, INCREASE revs/mile.

 

[1950StangJump$]

Perfect, thank you.

 

[stkjock]

have you asked your tuner if he can make adjustments in the tune for the new trans?

 

[1950StangJump$]

Nah, I would rather just hone it in myself. The 'revs per mile' is open for adjustment, and I can just compare the speeds against my phone's GPS for an exact number. Before the trans change, I had to adjust the tune a little to get it perfect with my tire setup, so no big deal.

I started this thread to ensure I was starting to make moves in the right direction. Juice saved me a little work.

 

[retfr8flyr]

If your tune is unlocked you can change the gear ratio to the 4.10's and set the revs per mile of the tire you are running. That should give you the most accurate reading.

 

[ixtlan]

You change your ratio and then revs per mile based on your tire size.

https://www.miata.net/garage/tirecalc.html

Then you should be dead on.

 

[1950StangJump$]

Yep, got it. For me, that’s 4.10 and 755 revs based on tire size. That’s gets me within 1 MPH of what my GPS says. Might play more next time I have a reason to load a new tune