Topic: scoop data

[Don R]

   Recently there was a discussion on air scoops, and I thought of it while looking at our Racepak dragster data.
   I know it's not a motorcycle but thought it might be interesting to the scoop guys.  The mph was around 173, No big winds either way. I think the air over the top of the roll cage and windshield is somewhat disturbed but not a lot.
   The scoop is the big mouth K&N and it has a cone filter inside with a 567 cubic inch engine at 7,500 rpm sucking through it. It still makes about a half PSI of pressure in bottom of the scoop body.
   The green square line is the transmission brake, blue is engine RPM, yellow is driveshaft rpm, the converter has 3% slip at the top end. The pink line at the bottom is carb psi. formerly fuel pressure before I went to efi, if needs a new sending unit now.
   

[Old Scrambler]

Cool......Are you sure its positive air pressure, not engine vacuum?

That scoop shape is known to have a lot of internal drag. How big is the airbox on top of the carb/injector manifold? A large box provides quiet air to each intake runner.

[Don R]

  It's a pressure sensor so it would not read a vacuum. The airbox is the inside of the scoop. It sits flat over the injector body. I sealed the bottom of the pan. K&N said it makes no difference because the pressure inside it is cancelled out by drag. I chose to seal it anyway, they didn't convince me. 
  We race at sandy and rocky tracks, so it has a large cone shaped K&N air filter inside. It's now EFI and not a carb so the air flow doesn't mess with any air bleeds.

[Old Scrambler]

I agree with you about the bottom seal

You could extend the intake forward to provide stable air at the filter. Based on USAF; NASA; and NASCAR data, a rectangular shape has improved air-flow thus the size could be smaller. That same data indicates that the maximum benefit is a positive 1...........which is about double of what you now have

[Don R]

 One of our competitors at Cordova this weekend has the small mouth K&N scoop on two cars. I should have taken a pic. He said the difference between the old lower square scoop and the small mouth K&N was .02 in the quarter mile at approx. 170 mph in the traps at the finish line. They did A-B-A testing on both.
 I saw a cool Instagram video of Eddie Krawiec showing that the faux gas tank on his Suzuki is the plenum for the air box. Apparently they catch air under the faring and above the front wheel.