[Diy_efi] Combustion chamber question

[Greg Hermann]

At 7:07 PM 5/11/02, Perry Harrington wrote:
>Here's a question for the gurus of the list.  I was under the impression that
>hemi heads are the best WRT detonation and power.  However a response countered
>that.
>
>So, here's the question:  How does Honda make 183HP per liter with 12:1 CR
>on the CBR600 engine?  I understand that RPM is more of an affect on the HP/l,
>but running 12:1 on pump gas without detonation is impressive.
>
>Perhaps someone could shed some light on this?
>
>--Perry
>
High rpm is also a huge detonation deterrent, for starters.

Not familiar with the CBR 600 engine or its chamber, but you can bet that,
one way or another, it has some squish area in it. This CAN be done with a
two valve hemi, I have done it with several Alfa motors. (Which are one of
the engine designs Honda copied pretty blatantly, back when !!) The shape
of the piston dome is the key.

The fact remains that there is NO squish area in a classic hemi chamber,
and they burn pretty atrociously.

A hemi chamber DOES give excellent breathing and minimal valve shrouding.
It is also very good thermally because it offers the minimum surface area
to volume ratio, thus minimizing heat rejection to the water jacket.

Just avoid confusing the advantages of the hemi chamber with the problems
it has !

Greg



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