EcoModder Forum 2010 Honda Insight Intake: Ram air or just coincidence?

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 04-17-2009, 01:14 AM #11 (permalink) DieselMiser     Join Date: Jun 2008 Location: Richland,WA Posts: 967 Das Schlepper Frog - '85 Mercedes Benz 300SD 90 day: 23.23 mpg (US) Gentoo320 - '04 Mercedes C320 4Matic 90 day: 22.44 mpg (US) Thanks: 46 Thanked 227 Times in 156 Posts I was referring ti the insight. Sticking a funnel on the front to act like a diffuser is going to be like breathing through a straw for a car. You can't just throw together an effective diffuser. Ideally you have to match the airflow through the engine with the effective increase in pressure to the flow entering the diffuser at the speed the diffuser is moving through the air. In practice you want it slightly larger than this. I went through all the calculations for this on my car and found that my intake was almost the exact same size I calculated. __________________
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Quote:
 Originally Posted by ConnClark I was referring ti the insight. Sticking a funnel on the front to act like a diffuser is going to be like breathing through a straw for a car. You can't just throw together an effective diffuser. Ideally you have to match the airflow through the engine with the effective increase in pressure to the flow entering the diffuser at the speed the diffuser is moving through the air. In practice you want it slightly larger than this. I went through all the calculations for this on my car and found that my intake was almost the exact same size I calculated.
Not really. The air intake will ONLY be suffering from extra pumping when the car is stationary. Between 10-20 mph(depending on the size of the cone) the diffuser is going to be converting the airspeed into pressure in the manifold. Also in that range its matching the flow speed so its not having to substantially accelerate the air.

At 3000 rpm my car flows 245 cfm and if I am in second its going to be creating nominal pressure inside the intake, opposed to vacuum.

A trick that decreases the effectiveness of the scoop but avoids pumping losses is to seat the scoop along the air intake tubing so it can still pull air in from the sides of the intake opposed to only being able to pull it from directly ahead. Usually when this setup can be used people vary it until its just right(as measuring and calculating the flow rate at various points as well as the flow and compression rate of the diffuser at various speeds is not as easy as getting in and driving it.)