Jump to content
Ultimate Subaru Message Board
jono

What's my revs?

Recommended Posts

If in my five speed part time 4wd box from ea82 I don't know gear ratios figure all the same for3.7:1 diff ratio.

 

If I reach 80 kph in second gear on 175.70.13 tyres nearly new tread....am I really doing the near 8000 rpm my tacho tells me?

Share this post


Link to post
Share on other sites

Something wrong here. Ea82 red line is at 6000? Mine won't go faster than that anyway, they just stop increasing rpm.

Share this post


Link to post
Share on other sites

According to Wikipedia, second gear is 1.95:1.  At 3.7: 1 final drive, total ratio from the engine to wheels is 7.215:1

 

175/70-R13 tires are supposed to be about 1807 mm around.

 

80 km/h is 1333.3 m/minute

 

So I get 1333.3/1.807*7.215 = 5324 RPM.  Not 8000.

 

If it is a 3.9:1 final drive, then the RPM is 5612 RPM.  That is a bit closer to a redline marked at 6000 RPM.  Could the tach read 7% high?  If so, this may be what you are seeing. 

Share this post


Link to post
Share on other sites

Thanks for the smart work. It is suspected tacho is way out and useless. Something to take up with the company. I do have somewhere my ea82 tacho in a box I should hook up and compare. If I find tachi is out it is just a waste of space time and money.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×