Altering the back axle ratio for economy
Discussion
When i was young my dad had a Ford Consul 375 with a 3 speed gear box, then we had various cars with 4 gears, then the norm became 5 gears, now you can get cars with 6 or 7 gears where is it all going to end.
My 520i does 1400 rpm at 30mph in 5th, 1800rpm in 4th and 2200 in 3rd but will quite easily poddle along in top at 25mph.
So if i could alter the back axle ratio from what ever it is now, lets say 3.8 to maybe 4.3 I could just do 30mph in 4th at 1400rpm and then in theory do maybe 70mph in top more economically.
I know a ton comes up at 4800rpm so do you think i could get enough BHP or torque at about 4200rpm to move the car along at 100mph.
I think it is geared for four people and a bit of luggage but normally its just me and the wife so surely the gearing could be altered a litte bit.
Has anybody out there tried it?.
>> Edited by bmw114 on Monday 14th November 15:20
My 520i does 1400 rpm at 30mph in 5th, 1800rpm in 4th and 2200 in 3rd but will quite easily poddle along in top at 25mph.
So if i could alter the back axle ratio from what ever it is now, lets say 3.8 to maybe 4.3 I could just do 30mph in 4th at 1400rpm and then in theory do maybe 70mph in top more economically.
I know a ton comes up at 4800rpm so do you think i could get enough BHP or torque at about 4200rpm to move the car along at 100mph.
I think it is geared for four people and a bit of luggage but normally its just me and the wife so surely the gearing could be altered a litte bit.
Has anybody out there tried it?.
>> Edited by bmw114 on Monday 14th November 15:20
Sorry about the back axle ratio but you know what i meant.
I have a Mitsubishi Pistachio and it was made for economy, it weighs 700kg, developes 74bhp and the back axle is 3.778 and the 5th gear is 0.697.
Unfortunatly it has`nt got a rev counter but you don`t us top gear below 55kph, On a trip over the Troudos mountains we covered 388k and i put in 16.6 ltrs of petrol so thats 65mpg which is`nt bad.
The M5 from 1992 onwards had a back axle change from 3.91;1 to 3.71;1 for better fuel economy, but i still don`t know what my axle ratio is.
Any help?
>> Edited by bmw114 on Monday 14th November 17:40
I have a Mitsubishi Pistachio and it was made for economy, it weighs 700kg, developes 74bhp and the back axle is 3.778 and the 5th gear is 0.697.
Unfortunatly it has`nt got a rev counter but you don`t us top gear below 55kph, On a trip over the Troudos mountains we covered 388k and i put in 16.6 ltrs of petrol so thats 65mpg which is`nt bad.
The M5 from 1992 onwards had a back axle change from 3.91;1 to 3.71;1 for better fuel economy, but i still don`t know what my axle ratio is.
Any help?
>> Edited by bmw114 on Monday 14th November 17:40
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