Another airbox adventure - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 38 (permalink) Old 12-07-2016, 02:53 AM Thread Starter
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Another airbox adventure

Having purchased a second hand airbox from ebay, I have decided to try and get a little more from the stock unit as opposed to purchasing and aftermarket example. After reviewing the standard set up it really has you wondering about exactly what arrangement they had in Edward's bike. The vents in the frame are top notch whilst the snorkel and airbox are compromised. It would appear that they didn't have a filter after the frame. The frame makes wonderful use of the Coanda effect which would be lost if the air was filtered afterwards. The stock box ruins this. The tapered and assymetrical nature of the box also lends itself to filling the rear cylinder if the filters and baffle weren't there. The forward cylinder is shrouded. I am also surprised at the lack of heat shielding on the box as well as no mat between the engine and airbox. I have already begun machining up new velocity stacks out of acetal that will allow me to test the compatability of varying lengths. I will fabricate a new snorkel out of aluminium sheet that will improve flow and provide room for a filter and air laminiser prior to flowing through the frame. I know many ideas have been tried before.....hopefully a set of fresh eyes may be of some benefit.
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post #2 of 38 (permalink) Old 12-07-2016, 06:57 AM
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Works air box & TB's

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post #3 of 38 (permalink) Old 12-07-2016, 07:26 AM Thread Starter
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Nice velocity stacks.
I am surprised the heat shielding is on the inside of the lid of the box.
One thing that is interesting with all three of the stock boxes I have is that there is oil on all of the internal sensors. Obviously the crankcase breather is the culprit here and will be messing with the data. Re-routing the breather through its own catch tank and then to atmosphere will benefit. Alternatively, Routing the crankcase breather through the pair system and out the exhaust is usually good for a couple of HP as well.
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post #4 of 38 (permalink) Old 12-10-2016, 02:43 AM Thread Starter
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A couple of quick photos.
The air box has been opened up. New velocity stacks made which are a little taller but with scope to reduce them to find the optimum. Testing soon.
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post #5 of 38 (permalink) Old 12-10-2016, 02:54 AM Thread Starter
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With front cover attached
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post #6 of 38 (permalink) Old 12-10-2016, 03:10 AM Thread Starter
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The frame has been really well designed to account for pressure fill inside the box. Clearly the performance will be improved by having the filter before the air passes through the frame.
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post #7 of 38 (permalink) Old 12-10-2016, 06:48 AM
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That looks like nice work on the velocity stacks, I'd like a pair.
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post #8 of 38 (permalink) Old 12-10-2016, 02:58 PM
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Quote:
Originally Posted by JB's_SP3 View Post
Works air box & TB's

It would be nice if this airbox could be replicated without the need for thermostat removal (and ETI fuel tank compatible).
Plus a replaceable commonly used filter element easily accessable inside the airbox.
This is what I've been waiting for for years.
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post #9 of 38 (permalink) Old 12-10-2016, 06:03 PM Thread Starter
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I hear what you are saying about the air filter. I would like to incorporate a "slide in" filter cartridge within the snorkel. It would simply be a case of reaching up below the snorkel and releasing a couple of thumb screws to service the filter. No tools required. The box on my first bike has BMC filters in it. There is plenty of material in just one of those to unfurl and create the heart of the cartridge.
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post #10 of 38 (permalink) Old 12-10-2016, 06:31 PM Thread Starter
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JB
I have made a second pair of velocity stacks for the other bike. Given that the other bike has extremely low miles I would be inclined to use it sparingly and perhaps keep it original. Once I have settled on the right heights for the stacks I will make them the same and you are most welcome to the other set. I am guessing the stock heights will work best. No doubt Honda have done their homework here.
The ones in the pictures are fresh off the mill and still need a little tidying up. They will be a lot nicer once finished as well as lighter. I will start on the snorkel next week. After checking my stocks I only have 1/8" sheet aluminium. Needs to be 1/16".
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