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Gear ratios-what do they mean in fact.

778 views 1 reply 2 participants last post by  BradCMSP 
#1 ·
Hi guys,I'm thinking eventually to upgrade to new Maptun/Quaife 6 speed gearbox.
Regarding that I have few questions.:eek: Here are few popular cars gear ratios:

Present 9-5
1-3.38
2-1.76
3-1.18
4-0.89
5-0.66
Maptun
1-3.00
2-1.933
3-1.368
4-1.045
5-0833
6-0.701
Porsche 911Turbo
1-3.82
2-2.05
3-1.41
4-1.12
5-0.92
6-0.75
BMW 530
1-4.35
2-2.50
3-1.66
4-1.23
5-1.00
6-0.85
BMW 335turbo
1-4.06
2-2.40
3-1.58
4-1.19
5-1.00
6-0.87
What does this numbers mean?Are turbo cars with shorter gears generally?Will the new kit make car to accelerate faster on equal gears?Are the new gears longer or shorter or we can't compare 5 with 6 speed gearbox?
Looking to gear ratios of other turbo cars-BMW335 and 911,the Porsches ratios are closer to this of new kit.
At short -will be there noticeable effect on the road holding at all?
 
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#2 ·
DoctorPhill said:
What does this numbers mean?Are turbo cars with shorter gears generally?Will the new kit make car to accelerate faster on equal gears?Are the new gears longer or shorter or we can't compare 5 with 6 speed gearbox?
Looking to gear ratios of other turbo cars-BMW335 and 911,the Porsches ratios are closer to this of new kit.
At short -will be there noticeable effect on the road holding at all?
Turbo cars generally want taller (numerically lower, empirically higher) gears vs. a similar motor w/no turbo.

A high-tuned N/A inline-4 will generally want short ratios that are close together to keep the motor spinning where it makes power.

With a turbo car you get a much broader torque curve, allowing for taller gears to be used.

A better comparo to your listed ratios is to look at a N/A 911 vs. 911T. See how the N/A motor has shorter gears?

911 Turbo

6 Speed Manual
Final Drive - 3.44:1
1st Gear Ratio - 3.82:1
2nd Gear Ratio - 2.05:1
3rd Gear Ratio - 1.41:1
4th Gear Ratio - 1.12:1
5th Gear Ratio - 0.92:1
6th Gear Ratio - 0.75:1


911 GT3


6 Speed Manual
Final Drive - 3.44:1
1st Gear Ratio - 3.82:1
2nd Gear Ratio - 2.26:1
3rd Gear Ratio - 1.64:1
4th Gear Ratio - 1.29:1
5th Gear Ratio - 1.06:1
6th Gear Ratio - 0.92:1
 
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