[SOLVED] Two final drive ratios

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snowfree52
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[SOLVED] Two final drive ratios

Post by snowfree52 » Mon Nov 14, 2011 10:39 pm

One of my cars is a golf and it seems there are two differents drive ratios by gearbox :

one for 1, 2, 3 and 4th gear
a second for 5 et 6th

I wonder how is that possible and if there is a way to implement that in the laptimer ?

Thanks
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Harry
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Re: Two final drive ratios

Post by Harry » Mon Nov 14, 2011 11:25 pm

Hi,

Frequent question. To map this, simply calculate the full ratio (drive + gear) for each gear and enter these value for the gear ratio. In addition, set the drive ratio to 1.

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Re: Two final drive ratios

Post by snowfree52 » Tue Nov 15, 2011 4:52 pm

Thank you very much

Since I found the "how to" by myself :

formula is: (final drive ratio * gear ratio) /2

and put 2 as the final drive (because the app doesn't accept more than 10 as gear ratio ;)

edit : I have a problem :

since I have a car with the max power at low RPM, the app gives me max speeds that are way too slow (for 6th speed there is a 45kmh difference) :(
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Re: Two final drive ratios

Post by fluppie00 » Thu Nov 17, 2011 9:07 pm

I've driven a Audi S3 for a week, this car has also 2 drive ratios, I recalculated the drive ratios like this:

I've multiplied all the gear ratios with the final drive ratio and then the results from 5th and 6th I divided by 4.24.
Like this I calculated the 5th and 6th for a 4.24 final drive ( The 'real' final drive in 5th and 6th is 3.27 ). Should work fine !

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Re: Two final drive ratios

Post by Harry » Thu Nov 17, 2011 9:50 pm

snowfree52 wrote:edit : I have a problem :

since I have a car with the max power at low RPM, the app gives me max speeds that are way too slow (for 6th speed there is a 45kmh difference) :(
HI again,

max is calculated for the rpm max power is developed. You need to read is exactly like this. With the data given, it is not possible to calculate max speeds for every configuration available in the market. To achieve this, I'd need to add a sketch pad to draw any picture :-)

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Re: Two final drive ratios

Post by snowfree52 » Thu Nov 17, 2011 10:36 pm

@fluppie00 : thank you.

@harry : should I put the max power at max RPM then ? does it affect the way the app records laptimes of anything else ?
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Re: Two final drive ratios

Post by Harry » Thu Nov 17, 2011 10:48 pm

Please check the documentation for more information on these settings: http://www.gps-laptimer.de/User_Interface.html (search for 'OBD Information'). It is mainly used to calculate the current gear from speed and rpms.

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