plenum volume

[Eric Schumacher]

HI
In the Bosch CIS/CIS-E (note continuous/non-timed injection) manual they
state that the optimum volume for the runner between valve and plenum should
be equal in Volume to 1.5 times the cc of the cylinder it feeds. Their idea
is that the backwave when the valve slams will not push the air/fuel charge
back into the plenum and disturb the cylinder to cylinder a/f ratio.  This
is kinda hard to do on a V8 as anyone who looked under the hood of a Porsche
928 can observe. Big ole tarantula sitting in the valley.

At 11:52 PM 2/19/98 PST, you wrote:
>ref Paul Tholey:
>   IMHO, for a SBC runners should be thought of more in
>this manner.
>   Large cross sectional area runners are for better cylinder filling at 
>       high rpm.
>   Shorter runners enable a motor to rev quicker.
>   Long runners help to minimize reversion.  Reversion
>   can truely hinder MAF readings.
>(needless to stay the inverse apply)
>So a vehicle with a wide ratio gear box, and lower
>   (numerically) gears would need to min reversion
>   (long runners), and would not need to change rpm
>   quickly.
>Part of the reasoning for this is the Can-Am big blocks 
>of the mid/late 60's, really long IR with huge cross-
>sectional areas.  
>  It sorta follows the flow, of what most people do/think
>but I like my tweaks.
>  Bruce
>Any others with other thoughts?.   
>
Lotsa Luck Eric
85 GTI with VR6 power