06-07-2011, 12:03 PM #1
Increasing the airflow at the intake airbox
Ok, so it's time for some more tweaking! On turbo r and F models. Some of the honda riders here have seen some gains from shortening the the plastic stacks in the throttle body intake plenum. Yes I'm aware of those who have cut them down, and seen the shorter aftermarket stacks that are available. I could do either, but am curious of this other option to add to the mix.
I have however heard, from a learned wrench, that there is also available, a spacer, that just bumps the sub air box out. Thus allowing the the air to flow more freely, without cutting the stacks down. Anyone who has had the sub air box open is aware of the minuscule amount of airspace between the stacks, and the cover.
Those that have modded their turbo ski's with extra boost, lager turbo's, ect.. where more air is being pushed into the sub air box know what I'm talking about.
If anyone has seen this available, or want's to make one, and has thoughts, please chime on in.
06-08-2011, 11:25 AM #2
Ramon has three kits, The air box cover spacer, the shorter stacks and a huge airbox with huge inlet. They must work well because all of his stuff will put a smile on your face...or he would not sell it.
06-08-2011, 03:59 PM #3
My advice is to keep them the stock length. Feel free to experiment though.
06-09-2011, 06:39 PM #4
To add a little more technical input on this subject…
If you cut and remove the “horn entrance area” (this is know as the K factor for intake flow calculations.) If you change that you will alter the flow characteristics of the engine induction tract. This will influence the power band. If you don’t have a flow bench and/or other type of instrumentation to see your modifications, you are simply guessing or more blindly hurting your air flow.
Bottom line is you always need a K factors that promotes any turning of the air flow to be positive and not to hinder air flow changes in any direction. This is why you will see Velocity stacks with a curved intake opening (optimum K Factor)
If you modify you must always follow the correct physics of air flow. Keep this in mind. Just chopping and or changing the length needs to be controlled and data collected as to where you need to be to reach your engine characteristics goals.
Hope that helps you.
06-10-2011, 07:46 AM #5
Most of my questions on the intake tract had to do with the tight dimension in front of the intake horn due to the air box cover. It appeared there was very little room for air to make the turn into the horn, especially at low boost to raise the manifold pressure inside the throttle body assembly. Since I cut mine, I get a much quicker holeshot with it hitting the soft/sometimes hard limiter coming out of the hole. It never hit the limiter before the modification. The mod could have been a shot-in-the-dark but the additional room for air to make it into the horn did seem to help. I have not seen any flat spots in the power band except the one before the mod between 4.5 and 5K RPM that seems to be realated to the MacBoost Modules on all my Hondas.
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