What about final drive/diff ratio?Internet suggests Mk 5 Golf FSI ratios are:
1st gear: 3.46:1
2nd gear: 1.96:1
3rd gear: 1.28:1
4th gear: 0.98:1
5th gear: 0.81:1
6th gear: 0.71:1
Mac.
What about final drive/diff ratio?
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One reason for having a closer ratio 6 speed box is that the engine is mapped with a narrow power band. (I believe this is the primary reason for the proliferation of 6,7,8 etc speed boxes, not so much to lower revs at cruising speed). Maybe the FSI engine in the heavier Mk5 Golf is mapped differently to the lighter A2.Let's assume that the gear ratios posted by Mac above are indeed correct.
Mk5 Golf FSI -
1st gear: 3.46:1
2nd gear: 1.96:1
3rd gear: 1.28:1
4th gear: 0.98:1
5th gear: 0.81:1
6th gear: 0.71:1
Final transmission: 4,53:1
A2 FSI -
1st gear: 3.45:1
2nd gear: 2.10:1
3rd gear: 1.39:1
4th gear: 1.03:1
5th gear: 0.81:1
final transmission: 3.93:1
When doing RPM vs. speed calculations, we need to remember that both gearboxes will be using the A2's wheel/tyre size. For this purpose, I have assumed that we're using the standard SE alloys with 185/50/R16 tyres. This means...
Standard A2 FSI gearbox in 5th: 3216rpm at 70mph
Mk5 Golf gearbox in 6th: 3249rpm at 70mph
So, the Mk5 6-speed box seemingly compresses 6 gears into the range of the existing 5. It actually increases revs by 33rpm at 70mph.
Again, this assumes that the gear ratios listed above are correct. If we knew the gearbox code, that would definitely help to verify the accuracy of our data. I have an accurate record of the FSI's gear ratios, but they're not immediately to hand.
Cheers,
Tom
The gear ratios aren't especially close when used in its intended vehicle. On average, the Mk5 Golf uses tyres that have a 7.3% larger rolling circumference than those used by the A2. This means that, in a Mk5 Golf, the 6-speed gearbox achieves approximately what we're looking for: 5 gears of similar length to those we know and love, plus a 6th gear for reduced-rev motorway cruising. Unfortunately, when combined with the A2's smaller wheels, the ratios aren't long enough. Tyre size is effectively part of the final drive ratio, after all.One reason for having a closer ratio 6 speed box...
How feasible would it be to fit an alternative ratio diff, to give longer gearing?
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How feasible would it be to fit an alternative ratio diff, to give longer gearing?
Steep hill starts could be a problem though...
This is another good point. I'd only been looking at the top gears, but the short gears are also less than ideal. It does mean, theoretically at least, that the final drive could be lengthened without creating hill-start problems.Comparing the first gear ratios...