Date:         Sat, 18 Jan 2003 16:47:37 -0800
Reply-To:     David Marshall <vanagon@VOLKSWAGEN.ORG>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Marshall <vanagon@VOLKSWAGEN.ORG>
Subject:      Can someone double check my Engine / Tire / R+P math?
In-Reply-To:  <Pine.SUN.3.96.1030118152053.14880B-100000@grex.cyberspace.org>
Content-Type: text/plain; charset="us-ascii"

I am still hashing over which transmission / tire combo that I should
install into my Syncro Double Cab in the next few weeks.  I want to know if
my math is correct.

Constants:      Wasserboxer is 117ft/lbs torque
                TDI         is 149ft/lbs torque

So it can be said that the TDI has 27% more torque than a boxer motor.

                Original tire size (185/80-14) is 25.6" tall
                Desired tire size (215/85-16) is 30.3" tall

The difference between the two tires is 19%

So... what I am trying to get at is if I install these tires and install the
TDI motor and keep the transmission and the weight of the vehicle the same
it will 'feel' about 8% faster (not counting torque vs RPM differences).

Assuming this is correct, how would you mathematically show the difference
between a 4.86:1 and a 5.43:1 final drive?  The percentage difference of
these two final drives is 12%.  Would it be correct to assume that if you
keep the motor and weight the same and install 12% larger tires and change
the 4.86:1 final drive to a 5.43:1 final drive it would feel like there is
no change?

If I did the motor swap (to a TDI) and the tire swap (to 30.3" tall) and the
R+P swap (to a 5.43:1) would the end result be a 12% + 8% = 16% increase in
performance?

Thanks in advance!

David Marshall

Fast Forward Automotive Inc.
4356 Quesnel-Hixon Road
Quesnel BC Canada  V2J 6Z3

http://www.fastforward.ca    mailto:sales@fastforward.ca
Phone: (250) 992 7775        FAX: (250) 992 1160

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