Thought I would share the joy's of running a 9" Vs a quick change....
I have been waiting on a dyno sheet to start selecting the right gear for
speedweek..... keep in mind I have the axle's out and the Driveshaft out so
it's an easy time to swap them out.
The motor makes it Peak power at 8300rpm ( correction from previous post )
So we are looking to spin it around 8600rpm or so....
we have 3.25 gears as well as 3.07's..... and three sets of tires ranging
from 26" .... 27".... and 28"
There are Two ways to play this game mathmatically... both of which are
accurate and can cross check each other.....
1. Finding MPH
Rpm X tire height in Inches divided by 336... divided by the gear...
for example.... 8500rpm X 26" = 221000 divided by 336 = 657.73 divided by
3.25 = 202mph then we could pitch the Overdrive into the fray by dividing
that 202mph by the .91 OD which would give us an output speed of 222.393
mph...... this just happens to be 3mph faster then the current record in the
class.
2. Finding Rpm
MPH X Gear ratio X 336 divided by tire hieght in inches
for example.... 225mph X 3.25 X 336 = 245700 divided by 26" tire = 9450 rpm
Obviously a bit much till we X it by the OD of .91 which is 9450 X .91 =
8599.5 rpm
So that gets you through the Gas record..... we want to consider the Fuel
record as well.... as that is where are best chances are with a Motor
designed to run on Nitrous Oxide. the record is 230mph in that class...
Here is the challange ... come up with the best combinations and the
reason's why..... I think I have already decided how we are going to do it
and Beleive it or not the example I just gave isn't the best combination in
my Humble opinion..... thou it's not a bad choice.... it just might not be
the BEST choice as there are other things to consider .... such as Drag
associated with running in OD and the Tire size/ wheel bearing speed.
I'll Give fella that comes up with the best choice a So-Al T-shirt...
Keith
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