Member Contributer BusyLittleShop Posted May 15, 2023 Member Contributer Share Posted May 15, 2023 I learned the hard way that bigger is not always better when it comes to our air boxes... My friend Stephen called long distance from England because he just installed a $900.00 HRC air box on his RC45 and saw 120HP on the dyno... mmmmm... together we wondered if the stock box be modified??? We found that stock RC45 throttle bodies are 46mm but the air box was restricted to 40mm... no problem... I'll bore the air box out to 47mm on the milling machine... I drew up plans for 47mm bell mouth based on the stock 40mm bell mouths and purchased a block of black Delrin... I'm not happy doing repetitious work but I labored long hours to machine 4 each bell mouths with my best accuracy... Don't you love when a plan comes together especially if it turns out perfect??? Now I had an unrestricted air box with my own 47mm bell mouths... it was the best I could do to replicate HRC $900.00 air box... not to mention I wanted to keep my home made K&N filter... Time to put the Mod to the test... this is Dave at Chandelle Motorsports... No joy... I lost 1.8HP on the dyno... so bigger is not better in this case... a whole week worth of work shot down in flames... it seems Honda got the intake velocity right for a stock pipe after all... air boxes are like tuned instruments... alter the holes and the tune suffers... 2 Quote Link to comment Share on other sites More sharing options...
Member Contributer Resina Posted May 17, 2023 Member Contributer Share Posted May 17, 2023 thanks for sharing 😃 Quote Link to comment Share on other sites More sharing options...
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