[EXLNavi]

Anyone have an accurate measure of the RPM's I should be expecting on my car with a given speed in 5th gear (5AT)?

Something like a table.

Specifically what RPM's I should be getting at 70MPH.

 

[Inspector1]

Check this out for the ratios....

I1

I will see if I can find a ratio conversion chart for you

 

[04EXNavi]

Aha, I can use some of my useless info!

If you know the gear ratios and tire circumference, you can use this formula:
RPM=MPH*gear ratio*336/tire diameter in inches

the gear ratio figure is the product of the gear * final drive ratio

so, for the I4 5 spd auto, in 5th gear at 70mph:

rpm=70*(.566*4.438)*336/25.685

rpm=2300

(this is approximate; a lot of cars use a transfer gear ratio that can be hard to find; it can also throw this off by a couple percent. But it's a close measure)
I've had this formula memorized for ages, don't ask me why.

And I'll see if mine does 2300 rpm @ 70mph on the way home.

 

[anysia]

hmmm. wonder if i can see if mine does 2300 at 70mph on my way home??? :lmao: fastest speed limit in my path is 35!

 

[04EXNavi]

Well, I had to cut off a couple people to do it, but it's pretty accurate. I only hit the highway for about a mile on my drive, but I managed to reach 65 before my exit, and it was right about there.

So, plugging in the numbers for 5th gear:

46mph = 1500 rpm
61 mph = 2000 rpm
76 mph = 2500 rpm
91 mph = 3000 rpm

To get mph if you know the rpm:
mph=(rpm*tire diameter)/(gear ratio*final drive*336)

Hope this helps, or confuses. Making a spreadsheet for it makes it a lot easier.

Anysia, just tell the officers that you were conducting an experiment, I'm sure they would understand.

 

[VTECaddict]

i think theyre off a little (or are they for the V6?).

i know the manual's gears are shorter than the auto, and when i'm at 1500 rpm in 5th, it's doing about 35mph for me. 2500 is about 65. 3000 is right about 75. (give or take a couple mph)

 

[BenjiBoy650]

Wow they really shortened the gears on the manual compared to the 6th gen. I'm running a 205/65 tire (vs. 195/65 stock) but I don't think it's that big a different. I'm getting 3000RPM @ 82MPH or so.