V-8 Int. man. design

[Evert Rosseel]

> 	My plan is to make a manifold that utilizes two plenums, one per 
> bank of cylinders. Knowing that the V-8 fires as if it were 4 V-twins 
> stacked instead of two banks of four cylinder engines does this effect 
> the intake air flow to the individual cylinders? Do I need to design the 
> intake like a dual plane 180 degree carb manifold that plenums the two 
> outer cylinders of one bank with the inner two cylinders of the other 
> bank?

It does affect the air flow, and the design of the manifold should 
take that into consideration. If a number of cylinders are connected 
to a plenum, the firing intervals (of those cylinders) should be 
evenly spaced. Otherwise different amounts of air are sucked in each 
of the cylinders (the one sucking air in shortly after a predecessor 
did, gets less air as the pressure in the manifold has become lower).

There are several possibilities :
1 - as described above (I suggest you look at the carburated version 
and "copy" the dimensions)
2 - use individual pipes to each cylinder (all with the same length 
and cross section), without a plenum (complex : each cylinder 
has a seperate throttle and air filter)
3 - use 1 (large) plenum, with seperate pipes to each cylinder (again 
with the same length and cross section)

If you have a LOT of money, you can also :
4 - install a different crankshaft, so that it fires like two 4 in 
lines connected in V
Although this seems strange, it is done on some engines (Ferrari does 
for example) because the same effects of (unevenly) timed flow also come into 
play in the exhaust. An equal firing interval for each banks gives 
best performance because it allows the use of tuned exhausts. 
The disadvantage is that the engine balance is badly influenced (4 
cylinder like instead of V8).


> 	I feel that this being injected that it shouldn't make much 
> difference fuel wise, but would one cylinder rob the available air the 
> next cylinder is supposed to recieve?

Yes, the cylinders will definitely get different amounts of air if 
the wrong solution is adopted.
Also, the simpler solutions such as with a dual plane will still have 
this disadvantage to a certain extent (different lenghts between 
carburator and inlet valve). 


Dr. ir. Evert Rosseel
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*    Dr. ir. Evert Rosseel                                             *
*    Laboratory for Machines                                   *
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