hi compressions: wasDIY_EFI Digest V1 #258

[Daniel Ridge]

On Thu, 5 Sep 1996, Todd Knighton wrote:

> John Faubion wrote:
> > 
> > Actually the big reason for multivalve chambers is more area is exposed
> > around the valve to flow fuel. Two small valves have much more flow
> > capacity than 1 large valve but is more expensive that manufacture.
> 
> That's also what Yamaha though, they went to 5 valves to get even more
> flow.  They did pick up flow, but on the F1 motors the 4 valve engines
> made more power still.  
> Point is.  It's not all flow, but combustion chamber shape and flame
> propogation as well.

Well, I don't think anybody thought that multivalves flow better per unit
area of opening.... 

Todd's right about chamber shape and flame proopgation. Multivalves are a
hack around the hard limits that geometry places on things -- we're
constrained to have circular valves, it's tough to use real estate well
when you are nesting circles(valves) in circles(cylinder(head)s). The
multivalve people didn't want multivales -- they really wanted rectangular
valves :).

Two small valves have worse flow (per unit area) than one large valve, but
you can get better aggregate flow with multivalves with a larger total
area than would be possible with univalve configurations.

-Dan

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