Anyone having difficulty calibrating their spedo with the X3?

Running Toyo 33's and adjusted my custom tune with the correct rev's per mile and also the gear ratio to 3.55, however I'm still out considerably according to my GPS.

Any info would be appreciated!

 

Did you take squish into account?

 

Ok...I'll bite!

"Squish"? Sorry man, not familiar with that one! Hehehe

 

Flattening of the tire at the contact point. It effectively reduces the tire's circumference. Depending on the sidewall, air pressure, tire construction, etc., it gain reduce the circumference by 3-5% or increase the revs/mile by the same percentage.

The best way to modify the circumference or revs/mile is to drive a known distance (at least 10 miles and longer is better - use a GPS or Google maps to confirm the distance), then use the following formula:

 

If you're using the rev per mile data from the manufacturer, it will already factor a load into the equation. If you're tuner didn't change the value for the minimum tire revs that might be your problem. For my 2008, the stock minimum value is 644 revs per mile. If I'm not mistaken a 33" tire would be in the 630 revs per mile range.

 

32.984" (unloaded) circumference =

Revs/Mile
611 No squish
630 3%
636 4%
642 5%

 

Ahhh! Got you now Gunns! lol

Ok, and yes Windsor, 630 is the correct ratio for my Toyo's from their site.

It's almost like the tuner is ignoring the values I'm inputting since it did not change a thing. I'm going to try over-correcting just to see if things change, if not, it may be my tuner not accepting my changes.

Sent an e-mail to Justin to get his input also, but any info you guy's can offer is always welcome.

 

Just be glad its easy to calibrate with the tuner, if you had a 98 or older truck then you gotta crawl under the truck and change the VSS gear on the tranny. Not hard just a pita.

 

Justin just replied to my e-mail (Gotta love the response time from this guy!)

He says it sound like a firmware problem in my tuner, so i gave him the info he wanted and is working on it.

I'll keep you posted on the progress.....

 

I reprogrammed my PCM to show MPH instead of KM/Hr. My speedo now goes up to 160 mph...... I have 305/70 R 16 BFG ATs and 3.55: gears. I programmed 4.10: gears and 900 revs per mile into the PCM. My speedo is fast by 1 MPH at 70 MPH.

.

 

Checked my e-mail, and Justin sent me a new 91 Perf tune! Man, i can't be happier with the service from that man.

Anyhow, going to try out the new tune tomorrow if I can remember how to load the darn thing in the X3 again.