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What's my revs?


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3 replies to this topic

#1 jono

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Posted 19 September 2017 - 07:40 AM

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?

#2 DaveT

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Posted 19 September 2017 - 10:22 AM

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

#3 robm

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Posted 19 September 2017 - 11:30 AM

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. 



#4 jono

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Posted 19 September 2017 - 05:28 PM

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.




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