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Engine basics => Engine set up tips => Topic started by: Mark Mc on June 04, 2019, 10:22:31 PM

Title: Which venturi for OS 40 LA-S?
Post by: Mark Mc on June 04, 2019, 10:22:31 PM

While at the Regionals in Roseburg, I got a Tower 40 aluminum backplate, an O.S. NVA, and an O.S. venturi cheap.  Today I figured I'd go ahead and convert an O.S. 40 LA to an LA-S with the parts.  I have an ARF Nobler that I plan to put together sometime in the not too distant future, and want to put the 40 LA-S in it.  I have a choice of three venturis that I can use, two O.S. parts and a delrin venturi.  I just used my digital calipers to measure the inner diameter of the three venturis.  Which of these three do you think I should throw in the 40?

0.265" Delrin
0.258" O.S.
0.282" O.S.

Mark

Title: Re: Which venturi for OS 40 LA-S?
Post by: Geoff Goodworth on June 04, 2019, 10:47:38 PM

So long as you are using the OS 3.5mm dia NVA, I would start with the 0.258" ID (6.55mm) venturi.

This is the factory venturi for the FP 20/25 and the LA 25. I have several FP40s that are fitted with that venturi. My favourite is very happy pulling a Cardinal ARF so it should be happy in your Nobler.

Title: Re: Which venturi for OS 40 LA-S?
Post by: RandySmith on June 05, 2019, 03:34:47 PM

Quote from: Mark Mc on June 04, 2019, 10:22:31 PM

While at the Regionals in Roseburg, I got a Tower 40 aluminum backplate, an O.S. NVA, and an O.S. venturi cheap.  Today I figured I'd go ahead and convert an O.S. 40 LA to an LA-S with the parts.  I have an ARF Nobler that I plan to put together sometime in the not too distant future, and want to put the 40 LA-S in it.  I have a choice of three venturis that I can use, two O.S. parts and a delrin venturi.  I just used my digital calipers to measure the inner diameter of the three venturis.  Which of these three do you think I should throw in the 40?

0.265" Delrin
0.258" O.S.
0.282" O.S.

Mark

Mark

What  needle assembly  will you use?  I use  a  .281  for  the  ST  or  PA  NVAs,  and  use  a  .255  for the  stock OS  20 Spraybar

The  ST and  enya  PA  are  .157  the  Stock OS  is  .135

Randy

Title: Re: Which venturi for OS 40 LA-S?
Post by: Mark Mc on June 07, 2019, 01:03:46 AM

Thanks for the replies guys.

Geoff, I put the 0.258" on the engine a little while ago.  Now to put it on the stand and check the run.

Randy, it is the standard O.S. NVA.  I'm just a sport flyer, so I tend to stick to stock items when possible.

Mark