In a message dated 8/17/2007 9:31:07 P.M. Eastern Daylight Time,=20 lendich@optusnet.com.au writes:

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I have asked Revmaster for air flow and v= elocity=20 figures, but these may be derived from piston engine type=20 figures.

If you or Lynn could comment on this it w= ould be=20 greatly appreciated.

Also my research indicates that flow air/= =20 fuel mix richens at higher RPM and altitude. I can't remember why at=20 higher RPM - mind block, however for altitude it is because fuel flow= =20 is driven by air flow and even though the density of the air is lower= (=20 at altitude) the flow remains the same - therefore richer mixture. Revmast= er=20 says their needle design is self leaning ( to a degree) because of design.= =20 I assume because the air density directly affects the suction to the=20= rear=20 side of the flat ground needle, ( this provides the low pressure area rath= er=20 than the venturi) therefore with reduced density you have reduced suc= tion=20 and reduced fuel and leaner mixture. However I will clarify that when= =20 next we talk.

I find this all very interesting!<= /DIV>

George ( down=20 under)

I have missed the question.

Carbs get leaner near the top of their RPM ranges and use a number of=20 tricks to maintain a reasonable F/A at high RPM. Even Webers with a hug= e=20 number of emulsion tubes and jets for any imagined situation. If you actuall= y=20 remove the venturi (called the choke) from a carburetor it no longer will=20 develop any differential pressure, and no fuel will flow through it.

None is way too lean.

More like the Bendix dribble fuel injection that is based on a positive= =20 displacement pump geared to the engine. It just pees fuel all of the time. C= rude=20 but effective.

In many cases of a slide and needle type of carb, the edges of the slid= e=20 hole and the flat shelf the slide seals against, is more than enough turbule= nce=20 to form the choke. Like Posa, Stromberg, SU and any motorcycle carb. They al= l=20 have chokes even though it is not obvious.

A 12A dyno sheet shows 139.6 foot pounds of torque at 6,500 RPM.=20= and=20 173.3 HP. This is an engine designed for 9,600 RPM shifting. This has a Webe= r=20 carb has two 36MM chokes. Two 40MM chokes would be real nice. Longer runners= =20 would be better, so cruise RPM is also the peak torque or a bit above peak.=20

Lynn E. Hanover

Get a sneak peek of the all-new AOL.com= .

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