Hello Don,
How are thing going?
Here is some of the info I have collated due to my carb research.
The Stock Harley is about 80 hp, so if the stock Harley is needing  185 CFM
my guess is that equals about 80 hp.

Advise to me ( Carb salesman) is that if you need in excess of 120hp you
need the Mikuni HSR 48 ( 42mm Venturi).

I would suggest that a HSR 42 ( 36mm Venturi) would get you to about 100hp
and a HSR 45 ( 39mm Venturi) would get you to 120HP.

Now we need between 140 CFM ( 6,000 rpm) to 175CFM ( 7,500 rpm)  each rotor
( 100 VE only), this equates to needing a 44mm dia carb ( no Venturi) each
rotor - my calculations. The Venturi does speed up inlet velocity but can
also act as a restrictor - so where the benefits start and stop is anyone's
guess.

My own guess is that I need a 44mm ( no Venturi) for my single development -
44mm will give me about 120mph inlet velocity. Advice to me is that between
200 and 300 mph is optimum for best VE. This seems to gel with the HSR48 (
42mm Venturi) for anything over 120 hp. I'm targeting a Max of 125 hp for
the single P-port. The max venturi I would look at is actually 42mm so the
HSR is indeed what I would look at.

So I don't see how you could be getting the stated 120 hp on a 40mm carb
with unknown venturi. My feeling is your not getting the advertised HP even
though your getting better than you did before. Given the velocity might be
higher (higher VE), 146 mph ( half as fast again to PL's 48mm dia) there is
also the skin wall friction drag Paul speaks of, to consider. I haven't
worked on that aspect of the calculations yet.

So I'm a little confused myself. I guess as long as it's doing the job is
the main argument. If your Revmaster 40mm has no Venturi (no restriction)
and the Velocity is right up there, getting max VE, you might just be on the
cusp of 120hp or a little below that. However your no where near the magical
200 to 300 mph for max VE, as suggested to me.

Please advise of any Venturi restriction and I will work out the inlet
speed.

George (down under)


Hi Gorge,
I would suggest that you do a lot more research and maybe fly a little
more. As I stated the figures are actual in two aircraft one a 6 jab
and and 8 jab with two carbs. These figures are not made up and I have
flown many hours with data collection. There are 5 Jabirus flying on
Revmaster 40 mm Carbs and achieving better performance where \
I have assisted the owners to get through all
the problems. I am only on here to give people some of my
experiences and I only post actual things I have achieved or what I
have experienced. I do not talk about what I think will work. I go and
do it and them tell the results. In the face of all the info I posted
you question the result. Up to you what you believe?
Don