Speed and RPM ratio

[ssoleas]

Hi,

I have a 2003 BMW Z4, and I wanted to ask what should the RPMs be at 80MPH? I think it's revving a bit high because at 80MPH my RPMs are over 3500. Any insight into this would be extremely helpful. Thanks!

 

[nicko]

I don't know if the ratios are different for different engine sizes
What size tyres are you running?

for my 3.0si with 255/35R18 on the rear, in 6th would be at 3160rpm for 80mph
6th ratio 0.85
diff ratio 3.46

 

[nicko]

if you have a 5-speed 2.5 with 225/45R17 then 80mph could be 3920rpm

Have a look at these pages and you can work it out for yourself
http://www.bokchoys.com/differential/GearRatios.htm
http://www.bokchoys.com/differential/e46_gear_ratio_calculator.htm