wrote:=20 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=20 wander what size TB other people are using, or any comments and suggestions on the matter will be helpful. Buly -- Homepage: http://www.flyrotary.com/=20 Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_003D_01C78A9D.C9D58260 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

For the great air mass demands of the three = rotor 100mm=20 sounds OK to me. You are pulling approx 50% more air mass than the = two=20 rotor.

One mitigating factor is the type of intake in = back of the=20 TB. You want high velocity mixture flowing in our intake to use = the=20 airmass inertia to stuff the combustion chamber fully. This = generally=20 means smaller intake diameters (for our operating regime). Keep in = mind we=20 are not talking about race engines but engines that have to develop = enough=20 torque to pull the prop up into our operating rpm regime. Long, = smaller=20 diameter intakes move the torque down the rpm range and large short = diameter=20 intakes move it up. But, if you don't develop enough torque at = 5000 rpm to=20 get through that point then having an engine designed for 8000 rpm won't = do a=20 thing for you.

IF you have any intake runner length at all, = then I=20 seriously doubt a large throttle body provides any clear benefit in our=20 usage. Clearly, you don't want one too small - like most things in = our=20 hobby - finding the correct balance is the key factor.

But, on the other hand, I think experimenting to = find out=20 if results meet our expectations is what this is all about. So let = us know=20 what size you use, Buly and your impressions.

----- Original Message -----

From:=20 Mark = Steitle=20

To: Rotary motors in = aircraft

Sent: Sunday, April 29, 2007 = 8:07=20 PM

Subject: [FlyRotary] Re: = Throttle body=20 size

Buly,

I went with a 100mm Holly TB for my 20B. Its = probably too=20 big, but that's better than it being too little. So far, it = seems to be=20 working just fine.

Mark

On 4/29/07, Bulent=20 Aliev <atlasyts@bellsouth.net>=20 wrote:=20

I=20 originally planned and tried TA set up on my Cosmo 13B. Soon = after
the=20 first few flights removed the turbo and vent NA. At the time did =
not pay=20 much attention on the throttle body size, counting on the
turbo = to make=20 up for any losses. Today I measured the inside opening
of the TB = and was=20 surprised to find it was only 60mm. This is rather
small. Paul = Lamar on=20 his visit also said I should get a bigger one. I
wander what = size TB=20 other people are using, or any comments and
suggestions on the = matter=20 will be=20 = helpful.

Buly

--
Homepage: http://www.flyrotary.com/ =
Archive=20 and UnSub: http:= //mail.lancaironline.net:81/lists/flyrotary/List.html

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