Second Venturi
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
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- Posts: 3485
- Joined: Sat May 06, 2006 6:05 pm
Re: Second Venturi
Thanks guys, I could not remember seeing a 4" long or a 8"dia venturi, makes sense now!
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
2023 Best Original 170A at Sault Ste. Marie
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
2023 Best Original 170A at Sault Ste. Marie
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
- GAHorn
- Posts: 21302
- Joined: Fri Apr 12, 2002 8:45 pm
Re: Second Venturi
....at 100 mph.Bruce Fenstermacher wrote:More specifically it is referring to the amount in inches a column of mercury would be raised by the vacuum over the level at atmospheric pressure.

'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.

- Bruce Fenstermacher
- Posts: 10425
- Joined: Tue Apr 23, 2002 11:24 am
Re: Second Venturi
It is a team effort to remember all the details.gahorn wrote:....at 100 mph.Bruce Fenstermacher wrote:More specifically it is referring to the amount in inches a column of mercury would be raised by the vacuum over the level at atmospheric pressure.

CAUTION - My forum posts may be worth what you paid for them!
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
- GAHorn
- Posts: 21302
- Joined: Fri Apr 12, 2002 8:45 pm
Re: Second Venturi
Yep. The group knowledge in this outfit is pretty impressive.Bruce Fenstermacher wrote:It is a team effort to remember all the details.gahorn wrote:....at 100 mph.Bruce Fenstermacher wrote:More specifically it is referring to the amount in inches a column of mercury would be raised by the vacuum over the level at atmospheric pressure.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.

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- Posts: 72
- Joined: Tue Jun 08, 2010 10:34 pm
Re: Second Venturi
I replaced my vacuum instruments with modern ones (Sigma-Tech DG & AI). The existing venturi's (old and of uncertain manufacture) would not generate the requisite 5" of Hg. Spoke to Spruce, their related manufacturing arm, and the engineers at Sigma-Tech. They confirmed what this thread says. My vacuum gage (which I had calibrated) showed that I needed a vac regulator. Bought one from Spruce (Rapco) and all is well now. As soon as the engine throttles up I have 5" vacuum through all phases of flight. 

The better is the enemy of the good.
1959 C-172
1959 C-172
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- Posts: 219
- Joined: Wed Sep 26, 2012 4:48 am
Re: Second Venturi
Alrighty then. That is what I shall do. Thanks for the infos. Once I am able I will upgrade to at least one 8" or 9"-er, add the vacuum regulator and install my Artificial Horizon.
N5448C -1950 170-A
Cessna® is a registered trademark of Textron Aviation, Inc. The International Cessna® 170 Association is an independent owners/operators association dedicated to C170 aircraft and early O-300-powered C172s. We are not affiliated with Cessna® or Textron Aviation, Inc. in any way.