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  #1  
Old 10-25-2022, 10:55 AM
Teal Teal is offline
 
Join Date: Jun 2022
Location: buckeye
Posts: 37
Default Cowl modification

Hello, I am considering cutting off the round inlet/snorkel on the bottom of my cowl and reducing my exit air size at the back of my cowl as I am running a alternative engine and dont need the carb inlet below and have more than sufficient cooling. Does anyone know what speed gains are made with this airframe and a removed carb snorkel?
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  #2  
Old 10-25-2022, 11:55 AM
andoman andoman is offline
 
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Default

You may get a specific response, but I’m betting there are few data points on speed gains that would account for just the drag reduction.
I doubt the speed gain would be measurable.
I believe your justification for the work involved will end up being aesthetics.
-The unused intake is blocked off, yes?
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  #3  
Old 10-28-2022, 07:21 PM
dlomheim dlomheim is offline
 
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Location: (2OK2) OK City, OK
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Default Alt Engine

Quote:
Originally Posted by Teal View Post
... I am running a alternative engine...
Which alternative engine are you running with?

Doug

RV-9A Mazda 13B/ FWF
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  #4  
Old 11-19-2022, 03:32 PM
Teal Teal is offline
 
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Yamaha sidewinder
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  #5  
Old 11-19-2022, 03:32 PM
Teal Teal is offline
 
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The inlet is not covered. currently it is feeding oil cooler
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  #6  
Old 11-19-2022, 03:34 PM
Teal Teal is offline
 
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I read somewhere that significant speed gains were made by using the injected engine and removing the snorkel.
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  #7  
Old 11-19-2022, 03:50 PM
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koupster koupster is offline
 
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Quote:
Originally Posted by Teal View Post
I read somewhere that significant speed gains were made by using the injected engine and removing the snorkel.

Feeding your injection/carb intake from the round inlet on the bottom of the cowl can increase power and speed by increasing available manifold pressure because of the ram rise in pressure provided by that forward facing inlet.

My understanding of the term snorkel as applied to RV's is taking air from the front of one of the two upper air intakes and feeding it down to the injection/carb intake.
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  #8  
Old 11-19-2022, 09:17 PM
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RVbySDI RVbySDI is offline
 
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Location: Tuttle, Oklahoma
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Quote:
Originally Posted by koupster View Post
Feeding your injection/carb intake from the round inlet on the bottom of the cowl can increase power and speed by increasing available manifold pressure because of the ram rise in pressure provided by that forward facing inlet.

My understanding of the term snorkel as applied to RV's is taking air from the front of one of the two upper air intakes and feeding it down to the injection/carb intake.
This is a “snorkel”:
https://store.vansaircraft.com/va-13...-va-132-2.html

This protrusion on the bottom of the cowl, below the prop, in this picture of an RV7 is a “snout”:
https://www.vansaircraft.com/rv-7/#image-gallery-4
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  #9  
Old 11-19-2022, 10:38 PM
Teal Teal is offline
 
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My engine pulls air from one of the main air inlets. Then the turbo charger compresses and sends to the intercooler
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  #10  
Old 11-20-2022, 07:30 AM
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Toobuilder Toobuilder is offline
 
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after the first few posts I was going to chime in and tell you that removing the pitot style scoop on the bottom of the cowl in favor of the snorkle in the the cooling inlet will actually cost you speed due to the loss of MAP. I just did this mod to my Rocket in the hopes that the loss of MAP would be offset by lower airframe drag. It was not to be. Looks like the pitot is going back on.

That said, your MAP is not dependant on a ram rise because of the turbo so the pitot scoop is not contibuting anything but drag (but it isnt much). I would not expect to see much, if any, gains in speed with the removal of the scoop. Airflow management and cooling exit size, sure.
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