Re: Could be simple question on gear ratios..

["Brian Wagner" <scirocco_88_16v@hotmail.com>]

Question on why VW choose the .91 gear, at the time the speed limit in the 
US was 55. Cruising at 55 the rpm is around 3000, not bad in my opinion. The 
engineers designed the transmission and car for maximum output through the 
speedlimit of the day. Now that the speed limit has been raised to 70 
3800rpm is just to much, if the car was being produced today I'm sure the 
R&P and gear range would more closely relate to the speed limits and turn a 
much lower rpm.

my .02

Brian

87 16v
86 8v (parts car)
85 Wolfsburg (white coming to a garage near me soon)



>From: 16V Jason <jason@scirocco.org>
>To: scirocco-l@scirocco.org
>CC: Cory Langford <cory.langford@icbc.com>
>Subject: Re: Could be simple question on gear ratios..
>Date: Wed, 31 Oct 2001 12:04:41 -0500
>
>At 11:35 AM 10/31/2001, you wrote:
>>--- Cory Langford <cory.langford@icbc.com> wrote:
>> >
>> > I have been looking at the chart for gear ratios on the Org site and
>> > I
>> > am now completely confused :)
>> >
>> > So someone want to explain all the basics to me..
>> >
>> > 5th gear ranges from 1.26 to .71 <- what is this ratio to?  Is this a
>> > percentage of travel or something (ie: one turn on the fly wheel =
>> > .71
>> > turns on the dif flange?)  Simple question: Is bigger better in this
>> > ratio or is smaller better?
>
>Hey Cory,
>         Cheapass gave you a correct explaination, but I'll say it again in
>different terms.
>
>The 5th gear ratio of 0.71 means that the output of the transmission to the
>differential (essentially) will turn 0.71 times for each 1 turn that comes
>in.  A 0.91 gear ratio would make the output turn faster.
>
>The final drive ratio (or ring and pinion as it's sometimes called)
>multiplies this again.  So with a final drive of 3.94, the input turns 3.94
>faster than the output.
>
>To calculate the overall drive ratio, you multiply the final drive and the
>gear ratio.  So with a 0.91 5th gear and a 3.94 final drive:
>
>         3.94 x 0.91 = 3.5854.
>
>This means that your engine turns 3.854 times for each time your wheels 
>turn.
>
>When you're looking at gear ratios and trying to pick one that's best for
>you (there is no "better" gear ratios, it all depends on what you're
>looking for) you don't have to worry about the final drive because it's a
>constant.
>
>Essentially, the choices you have for 5th gears are listed below, and I
>wrote in a few benefits of each.
>
>0.71:  The lowest gear, meaning the lowest revs at highway speeds.  You
>will almost definitely lose top speed vs. the other gears at the expense of
>quiet cruising, reduced engine temperature and wear, and marginally better
>fuel economy.
>
>0.75:  The second lowest.  Your top speed will be higher than the 0.71, and
>elasticity will be better (top gear passing power).  Revs will be slightly
>higher than with the 0.71, and likely so will noise. Fuel economy will
>probably be the same since any benefit the 0.71 would have is reduced by
>forcing you to downshift into 4th more often.
>
>0.80:  I call this the top speed gear.  For most 16V Volkswagens, this gear
>will give you the highest top speed of any of the 5th gears; but that
>depends on your engine's torque curve.  Revs are again higher than the
>0.75, so 5th gear passing will be quicker, but fuel economy will be ever so
>slightly worse.  This gear is usually the best compromise.
>
>0.91:  The stock 16V 5th gear.  This gear is unnecessarily short, I will
>never understand why VW used it.  Top speed is not as high as with the 0.80
>(stock 16V motor), but passing power is considerably better.  This gear
>will give you the most noise, the most engine wear, and the worst fuel 
>economy.
>
>You need to pick a gear based on what is important to you -- top
>speed?  elasticity?  economy/quietness?  Once you decide what's important,
>use a torque curve to decide which one meets your needs the best.  If you
>need help with that, don't hesitate to ask.
>
>Jason
>
>
>
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