-----Original Message-----
From: TC <[EMAIL PROTECTED]>
To: V-MAX TECH LIST <[EMAIL PROTECTED]>
Date: Tuesday, March 07, 2000 2:41 PM
Subject: Drilling Slides and Reversing the Process.
>On the other hand ... take the "Y" off the Vmax and don't do anything else
and see where your low end response goes ... check the mid-range on the dyno
.... As you well know it is not uncommon for some of it to disappear but
often give you an additional horse on the top. <
TC has hit the nail on the head...the CV carb is great for the street
because it can be set up to deliver the right amount and of fuel and air
proportional to engine demand regardless how much the driver has twisted the
throttle plates open at any given rpm. But in order to reduce the effect of
the many different environments that the bike will be sold in, the
manufacturer generally relies on a large pressure differential between the
carb throat and the venturi to move the slide and to draw fuel. Small airbox
entries help to maximize this differential under heavy load conditions. In
fact it is not uncommon for a stock airbox under full load to be 25-30mb
BELOW standard air pressure (70 mb = 1 psi). However, for obvious reasons,
having an airbox with negative pressure is not conducive to getting air into
the engine. Opening up the box relieves the pressure but as TC pointed out,
it plays havoc with how the slide opens and how much fuel is drawn and often
ends up dropping the midrange. A balance can be found if you pay close
attention to each carb circuit and need to match fuel with air...yes,
Factory or Stage 1 or stage 7 jet kits can be made to work with the Max. I
always keep in mind that power is usually made with some form of compromise.
Nothing is free. The more you move away from stock the more finicky your
bike is going to be...
However, as an aside...some manufacturers are now relying on a great trick
that would be nice to mimic on the Max using the v-boost servo. At an rpm
less than a full carb slide opening, the airbox entry remains stock (small).
When you get on the throttle, the pressure diff created by the small box
opening helps to draw the slide up fast and still keep the fuel going. Just
as the box is starting to go into starvation mode though, an additional
airbox port opens to flow more air. The main circuit is set up for this
additional air and the bike gets a second wind... Low end grunt and top end
power both!!
cheers, Terry
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