Disclaimer: this isn't an RV, but my questions apply to all lycoming powered airplanes, especially fast ones and this forum really considers the math and science.
Recently I noticed this picture over on another site:
Now, that is very very very very fast for an airplane with 31" tires, a belly pod, and cub style cabane V. Obviously the secret sauce is the 23.7 MAP at 10,500. The builder says he gets ram air into his EFII throttle body and lycoming/barrett cold air sump. The intake is a front facing inlet like an RV-10, but probably 4 times the size.
What I can't get my head around is the fact that he is getting 3" of manifold pressure over a standard day at 10,500 when my dynamic pressure calculations suggest that there is only 1" of ram air available at those speeds and altitudes.
Here are my questions:
1. How is this possible without a turbo charger?
2. How much does the EFII have to do with it. It doesn't have the big venturi in the middle of it's throat like an AFP or Bendix fuel servo, how much does that matter?
3. How much performance can one expect going to the Barrett cold air sump? Rhonda at Barrett told me that they see 18hp and a few inches at sea level going from a stock io-540 to their cold air sump and an FM-300 servo.
Surely some RV peeps have searched the deep well of cold air sumps and moving from the small stock lycoming updraft sump with an FM-150 and converting to the much larger horizonal setup and the far larger FM-300.
Recently I noticed this picture over on another site:
Now, that is very very very very fast for an airplane with 31" tires, a belly pod, and cub style cabane V. Obviously the secret sauce is the 23.7 MAP at 10,500. The builder says he gets ram air into his EFII throttle body and lycoming/barrett cold air sump. The intake is a front facing inlet like an RV-10, but probably 4 times the size.
What I can't get my head around is the fact that he is getting 3" of manifold pressure over a standard day at 10,500 when my dynamic pressure calculations suggest that there is only 1" of ram air available at those speeds and altitudes.
Here are my questions:
1. How is this possible without a turbo charger?
2. How much does the EFII have to do with it. It doesn't have the big venturi in the middle of it's throat like an AFP or Bendix fuel servo, how much does that matter?
3. How much performance can one expect going to the Barrett cold air sump? Rhonda at Barrett told me that they see 18hp and a few inches at sea level going from a stock io-540 to their cold air sump and an FM-300 servo.
Surely some RV peeps have searched the deep well of cold air sumps and moving from the small stock lycoming updraft sump with an FM-150 and converting to the much larger horizonal setup and the far larger FM-300.
