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Re: gear ratios

To: land-speed@autox.team.net
Subject: Re: gear ratios
From: ARDUNDOUG@aol.com
Date: Mon, 2 Jul 2001 09:51:47 EDT
In a message dated 7/2/2001 6:41:08 AM Pacific Daylight Time, 
scowle@mentorcollege.edu writes:


> 
>   List, I know this subject has been hashed over but I need to get this
> right. Does the gear ratio affect how much torque the rear wheels see or
> does it merely change at what speed the torque is usable at? In other words
> are the gears acting as a torque multiplier. Do gear changes affect the
> readings that would come from a chassis dyno? I need to know this so I make
> the right changes to my differential so I can help my big block run over
> 6000rpm at Maxton and then at Bonneville (hopefully next year).
> Scott
> 

Scott,
       This may be an over-simplification, but when I pick a gear ratio I try 
to estimate what maximum continuous RPM my engine will be happy with and at 
what MPH speed I'd like my car to run at. My chart or "dream-wheel" will give 
me the ratio I want once I factor in the tire diameter.
       If I get to that RPM before the timing trap I need more gear. If I 
can't reach that RPM by the traps I either need less gear or more horsepower.
       The way you stated the question provides some food for thought. To me 
the differential is indeed a torque multiplier. When I ran my car on a 
chassis dyno I used the ratio I'd just run at Muroc or El Mirage. The dyno 
factors in torque and RPM to determine horsepower.
       Maybe someone else with more/better experience can shed some light.
                                                       Ardun Doug King

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