MOOK3456

Well, the way you two did it leaves alot of room for human error as well and are really relying on his word that he was doing the exact same speed. You're also relying on the fact that the Toyota cruize control works exactly the same as yours.

Even a tiny bit over what you're at and he would pull away... Also why are you so certain that it's your speedo thats off and not his? Does he have the factory size tires?

These little things add up for a test like that.

JasperGT

You should know right off the bat that you had new gears installed. I went from 3.31s to 4.10s and I knew immediately just in seat of the pants feel. My speedo was not correct because I didn't know and I didn't have a tuner. I was driving much slower than my indicated speed.

Check out this excel file that this guy made, and you should be able to tell easily if you're gears have changed.

https://mustangforums.com/forum/2005...ear-chart.html

With the tune, you should be able to adjust the options from "default" to "4.10" gears and you should also be able to adjust your tire revs/min which you can find here.

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

bilbob2

Here's a pic of my speedo.

70mph in 5th gear

gman73

RPMs are low, but the are you really doing 70? Your revs per mile should be about 778 to 780.

bilbob2

I'm horrible at this stuff.
I really need some help.

According to this... my stock tires are 235/50/18. I had 3.55 gears stock.
I now have 275/40/18's and 4.10's

So given my tire change and the 4.10's... can someone help me at what
RPM's I should be at in 5th gear at 70 MPH?

gman73

Read post #13

Never2mucHP

Ok, go on iTunes and download MotionX GPS lite. It's free. There is a screen that shows a huge compass in the middle among other data. In the top right corner it will display MPH.

Get in your car and drive. Start the app, get to what your car says is 70. See what the phone says. If they match, you're good. If they don't then your speedo is probably off.


+1 that you should be able to tell if they put they replaced your stock gears with 4.10s. Just get on it, the acceleration should be dramaticly different.


(Oh, and I've never used the app above; I just did a quick search. You may be able to find something different.)

bilbob2

PROBLEM SOLVED.
It was the revs per mile.

I adjusted it on the SCT and reloaded the tune.
Now in 5th gear at 70mph it is RIGHT ON 2450

Thanks everyone!

bilbob2

If my RPMs are at 2450 at 70 in 5th gear like it's supposed to be with 4.10's.
Then they HAVE to be installed correct?

bilbob2

Anyone on that last question??????