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For the great air mass demands of the three rotor 100mm
sounds OK to me. You are pulling approx 50% more air mass than the two
rotor.
One mitigating factor is the type of intake in back of the
TB. You want high velocity mixture flowing in our intake to use the
airmass inertia to stuff the combustion chamber fully. This generally
means smaller intake diameters (for our operating regime). Keep in mind we
are not talking about race engines but engines that have to develop enough
torque to pull the prop up into our operating rpm regime. Long, smaller
diameter intakes move the torque down the rpm range and large short diameter
intakes move it up. But, if you don't develop enough torque at 5000 rpm to
get through that point then having an engine designed for 8000 rpm won't do a
thing for you.
IF you have any intake runner length at all, then I
seriously doubt a large throttle body provides any clear benefit in our
usage. Clearly, you don't want one too small - like most things in our
hobby - finding the correct balance is the key factor.
But, on the other hand, I think experimenting to find out
if results meet our expectations is what this is all about. So let us know
what size you use, Buly and your impressions.
Ed
Ed
----- Original Message -----
Sent: Sunday, April 29, 2007 8:07
PM
Subject: [FlyRotary] Re: Throttle body
size
Buly,
I went with a 100mm Holly TB for my 20B. Its probably too
big, but that's better than it being too little. So far, it seems to be
working just fine.
Mark
On 4/29/07, Bulent
Aliev <atlasyts@bellsouth.net>
wrote:
I
originally planned and tried TA set up on my Cosmo 13B. Soon after
the
first few flights removed the turbo and vent NA. At the time did
not pay
much attention on the throttle body size, counting on the
turbo to make
up for any losses. Today I measured the inside opening
of the TB and was
surprised to find it was only 60mm. This is rather
small. Paul Lamar on
his visit also said I should get a bigger one. I
wander what size TB
other people are using, or any comments and
suggestions on the matter
will be
helpful.
Buly
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