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Re: wide or close ratio?--

To: Dave Dahlgren <ddahlgren@snet.net>
Subject: Re: wide or close ratio?--
From: William T Smith <WmTSmith@landracing.com>
Date: Wed, 20 Jun 2001 06:20:23 -0600 (MDT)
Aaaahhh as a glimmer goes on in the almost empty head 
cavity..
 A Shift Chart--- we do those all the time when spec. 
trucks to graph what you said about staying on the high 
side of peak touque-- as you fall back up the torque 
curve we call that Torque Rise.

This is very helpful because this determines a 
vechicles ability to acclerate in that gear or to 
maintain speed on a hill. wmts 



Quoting Dave Dahlgren <ddahlgren@snet.net>:

> Well in the copy you sent back in your reply the 
letters after 8500 seem to
> be
> goofy. They did have the new rpm if you made the 
shift at 8500 rpm. The
> torque
> will come out close to what you have as the rpm goes 
down the torque goes
> up. It
> is all full throttle stuff. I use Ft/lbs at the rear 
wheel to do the gear
> splits.. HP is a calculated # torque is what the 
parts really see.
> Dave
>
> William T Smith wrote:
> >
> > Dave,
> > I don't understand Point 2
> > How can the wheel power be close to the same as you 
go
> > up the gear shifts when your mechanical advantage 
drops
> > so much with each shift. Is it because you dont 
have to
> > use full throtle to get the RPMs?
> > Also what were you giving an example of when your 
put
> > the trans ratios. what were the .625 .7 .785 was 
this
> > the percentage of total torque reflect by the part
> > throttle?
> >
> > Quoting Dave Dahlgren <ddahlgren@snet.net>:
> >
> > > Wide or close ratio has a lot to due with the 
power
> > curve of your engine.
> > > there
> > > have to be a bunch of e-mails about this in the 
past
> > too as i remember the
> > > discussion well. i was the guy with no clue about
> > what really works(at
> > > least the
> > > was the opinion of the old salts as i remember it
> > anyway).  When i work on
> > > gear
> > > splits what i try to do is this.
> > > Launch the car as quickly as possible so as to not
> > waste any track length
> > > at the
> > > start.
> > > each gear change should result in 3 things 
happening
> > if possible and less
> > > important in the lower gears.
> > > The first and most important is that the new gear
> > selected is still above
> > > the
> > > torque peak of the engine. This is so if you have
> > trouble making the gear
> > > change
> > > or have to peddle the car and lose some RPM you 
are
> > falling back into the
> > > peak
> > > and not away from it. This will insure that you 
will
> > hopefully have the
> > > power to
> > > pull the next gear if there is a problem.
> > >
> > > The second is to have the new gear selected to 
have
> > the same amount of
> > > ft/lbs on
> > > the rear tires as the previous one. You can do 
this
> > if you have a dyno
> > > sheet for
> > > the engine. This will ensure 2 things happening.
> > first you will not have
> > > any
> > > problem pulling the next gear up as the power at 
the
> > wheels is the same as
> > > it
> > > was. second you will not shock the tires and lose
> > traction.
> > >
> > > To do this right depends on the torque curve of 
the
> > engine and whether it
> > > has
> > > nitrous or not and when you turn the nitrous on 
if it
> > has it.
> > >
> > > For a typical N/A car with 300 inches i would 
shoot
> > for 5 or 6 gears.
> > > something like
> > > assuming peak power at 8000 rpm
> > > 1   3.2
> > > 2   2.0  .625 X 8500S13
> > > 3   1.4  .7   X 8500Y50
> > > 4   1.1  .785 X 8500f73
> > > 5   1.0  .91  X 8500w35
> > > with this you should be in 5 'th about 1/4 mile
> > before the mile of interest
> > > and exit that mile at 8500 to 8800 rpm..
> > >
> > > My opinion and your mileage may vary.
> > >
> > >
> > > Bill & Dee Bennett wrote:
> > > >
> > > > Ok somebody explain to me why with having a 
longer
> > distance to run at
> > > > Bonneville using a close ratio transmission is
> > better.  I realize that
> > > you
> > > > might  experience to low a drop in rpm in the 
gear
> > changes using a wide
> > > > ratio. Is this the reason why or is it something
> > else. I would have
> > > thought
> > > > the 6 speed would be a good choice for the salt
> > given the ability to
> > > space
> > > > the ratios over 5 speeds and using 6th for
> > overdrive. If close ratios are
> > > > what are needed why not the something similar to
> > the old style Doug Nash
> > > > tranny with 5th being 1:1 and no overdrive. If
> > horsepower lose is the
> > > deal,
> > > > I don't think that matters to a few as already
> > stated over the past few
> > > > weeks. It seems to be no problem building the 
power
> > it is getting the
> > > > traction to use it.
> > > >
> > > > Bill

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