0110 Posted March 5, 2021 Share Posted March 5, 2021 2008 Pair valve, snorkel, flapper delete K&N air filter Power commander with auto tune Delkevic cans Just installed Delkevic exhaust Bike ran good before exhaust install. Has money to burn so I bought full exhaust. Bike was absolutely louder but noticed drop in power throughout RPMs. Allowed auto tune to adjust trims no real change. Did I just waste my money and time on full exhaust? Trying to understand what happened to cause performance loss. Link to comment Share on other sites More sharing options...
Member Contributer BusyLittleShop Posted March 5, 2021 Member Contributer Share Posted March 5, 2021 What I learned tuning RC45s is that you can't just open up the back door (HRC exhaust) without a corresponding opening up of the front door (HRC airbox) and pump (HRC engine parts) and expect to enjoy the same wide stock power band... My experience with running the 38mm HRC is that the exhaust pipe diameter is critical on the stock engine... My HRC exhaust was 6 lb lighter but it was on for only a week because it effectively killed the meaty powerband... in fact the original 35mm stock pipes dents and all makes the best over all power because the tube diameter is small whereas HRC pipe diameter is large and only works best in concert with the HRC engine kit parts and HRC airbox... The goal of VFR aftermarket exhaust should be dropping weight not performance gains... Airbox advice... My RC45 flapper is still installed and working to tune the airbox so the engine doesn't hit any sour notes through the RPM range... HRC engineered it like a finely tuned instrument to optimize intake efficiency and after testing theory myself I don't advise any VFR owner to remove the flapper... Understanding your airbox by Kevin Cameron What Is The Secret Importance Of A Motorcycle Airbox? If you have ever had the gas tank off your late-model sportbike, you will notice that the front of the fuel tank doesn’t hold fuel; it holds an airbox. In the old days, when you bought a new bike, it had an air-filter case attached to feed the carburetors or the fuel-injection intakes. All the sharp, young guys would immediately rip off the filter case and replace it with four sock filters. Reduced airflow resistance. Much better performance. One day in the late 1980s, they began to rip off the airboxes of their new bikes and their engines fell on their faces. They lost a bunch of performance. “This can’t be happening! Putting on sock filters always worked before.” But it turns out the industry found a way to boost performance by making what is known as a resonant airbox. We have all in an idle moment blown across the mouth of a beer bottle and heard the "whoooo" of the bottle resonance. As air goes across the mouth of the bottle, it creates a low pressure, which causes air to flow up. That deflects the air away from the mouth of the bottle. Then the air goes back in, the airflow from your mouth goes back across, and the cycle repeats, rapidly fluttering and producing that deep tone. The compressible air in the bottle is acting as a spring, and the slug of air in the neck of the bottle is the mass that vibrates against that spring. This intake airbox from a Honda CBR600RR is just a glorified beer bottle. Instead of the engine blowing across the mouth of it, its four throttle bodies are sucking from the box, pulling its pressure down. Air rushes in through the ducts in the fairing to fill up that low pressure. The next cylinder sucks the bottle pressure down and more air rushes in and restores the pressure. If the volume of the box and the mass of the air in the intake pipes are correctly chosen, the box will hum like the beer bottle. The trick is to get your engine to draw air from the box when the pressure is up and then the box refills when the pressure is down. And that is why ripping the airboxes off and putting on old-time sock filters resulted in a reduction in performance. In a specific zone of rpm, a resonant airbox can boost your engine’s torque by 10 percent. That’s worth having! Link to comment Share on other sites More sharing options...
Member Contributer Cogswell Posted March 6, 2021 Member Contributer Share Posted March 6, 2021 4 hours ago, BusyLittleShop said: What I learned tuning RC45s is that you can't just open up the back door (HRC exhaust) without a corresponding opening up of the front door (HRC airbox) and pump (HRC engine parts) and expect to enjoy the same wide stock power band... My experience with running the 38mm HRC is that the exhaust pipe diameter is critical on the stock engine... My HRC exhaust was 6 lb lighter but it was on for only a week because it effectively killed the meaty powerband... in fact the original 35mm stock pipes dents and all makes the best over all power because the tube diameter is small whereas HRC pipe diameter is large and only works best in concert with the HRC engine kit parts and HRC airbox... The goal of VFR aftermarket exhaust should be dropping weight not performance gains... Airbox advice... My RC45 flapper is still installed and working to tune the airbox so the engine doesn't hit any sour notes through the RPM range... HRC engineered it like a finely tuned instrument to optimize intake efficiency and after testing theory myself I don't advise any VFR owner to remove the flapper... Understanding your airbox by Kevin Cameron What Is The Secret Importance Of A Motorcycle Airbox? If you have ever had the gas tank off your late-model sportbike, you will notice that the front of the fuel tank doesn’t hold fuel; it holds an airbox. In the old days, when you bought a new bike, it had an air-filter case attached to feed the carburetors or the fuel-injection intakes. All the sharp, young guys would immediately rip off the filter case and replace it with four sock filters. Reduced airflow resistance. Much better performance. One day in the late 1980s, they began to rip off the airboxes of their new bikes and their engines fell on their faces. They lost a bunch of performance. “This can’t be happening! Putting on sock filters always worked before.” But it turns out the industry found a way to boost performance by making what is known as a resonant airbox. We have all in an idle moment blown across the mouth of a beer bottle and heard the "whoooo" of the bottle resonance. As air goes across the mouth of the bottle, it creates a low pressure, which causes air to flow up. That deflects the air away from the mouth of the bottle. Then the air goes back in, the airflow from your mouth goes back across, and the cycle repeats, rapidly fluttering and producing that deep tone. The compressible air in the bottle is acting as a spring, and the slug of air in the neck of the bottle is the mass that vibrates against that spring. This intake airbox from a Honda CBR600RR is just a glorified beer bottle. Instead of the engine blowing across the mouth of it, its four throttle bodies are sucking from the box, pulling its pressure down. Air rushes in through the ducts in the fairing to fill up that low pressure. The next cylinder sucks the bottle pressure down and more air rushes in and restores the pressure. If the volume of the box and the mass of the air in the intake pipes are correctly chosen, the box will hum like the beer bottle. The trick is to get your engine to draw air from the box when the pressure is up and then the box refills when the pressure is down. And that is why ripping the airboxes off and putting on old-time sock filters resulted in a reduction in performance. In a specific zone of rpm, a resonant airbox can boost your engine’s torque by 10 percent. That’s worth having! That is a great explanation of the airbox's purpose and function. Thank you for posting it. I've never understood the fascination with the snorkel and flapper mods. It seems possibly related to a notion that "more air is better" - but that fails to take in to account the velocity of the flow, both intake and exhaust. Increase the tube diameter, and all else equal the velocity is slower. Removing the snorkel and disabling the flapper lowers intake velocity when the engine needs it most. By analogy, pursing one's lips can create a whistle by increasing the velocity of the air flow to a point where there is resonance at an audible frequency. Open the mouth and push the same amout of air out the lungs, and nothing - the flow is too slow. Same with the airbox - Honda tuned it to get the best flow / velocity at any given rpm / load. Garage mods to change that will only result in a lesser dregree of performance. As pointed out above - want max performance from the engine? Keep a clean filter in it and leave the airbox alone. Link to comment Share on other sites More sharing options...
Member Contributer Grum Posted March 6, 2021 Member Contributer Share Posted March 6, 2021 Excellent info there BLS and Cogswell. No doubt Honda have gone to great trouble designing their intake systems, the tuned airbox, different length intake funnels and the variable air intake control (flapper). I've keep both snorkel and flapper systems intact on all three of my 6gens. However, based on Honda removing the flapper on the 2017 8gen, I decided to do the same to my 8gen some 30,000k's ago, purely to free up extra space under the tank area. My seat of the pants dyno! has noticed No detrimental effect in performance or fuel economy. I've always believed that the air intake system is far greater effected by airflow through either a clean or dirty airfilter. YMMV. Link to comment Share on other sites More sharing options...
Member Contributer boOZZIE Posted March 6, 2021 Member Contributer Share Posted March 6, 2021 10 hours ago, 0110 said: 2008 Pair valve, snorkel, flapper delete K&N air filter Power commander with auto tune Delkevic cans Just installed Delkevic exhaust Bike ran good before exhaust install. Has money to burn so I bought full exhaust. Bike was absolutely louder but noticed drop in power throughout RPMs. Allowed auto tune to adjust trims no real change. Did I just waste my money and time on full exhaust? Trying to understand what happened to cause performance loss. Short answer, yes. Lol Should have jumped in on the WiLD Headers. The Delkevic merge connection is a thing of unspeakable horror. Just to try something, unplug the power commander and run stock o2 connections if possible. Link to comment Share on other sites More sharing options...
Member Contributer BusyLittleShop Posted March 6, 2021 Member Contributer Share Posted March 6, 2021 3 hours ago, Cogswell said: That is a great explanation of the airbox's purpose and function. Thank you for posting it. You're welcome... I've learned the hard way that bigger is not always better... 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 about modifying a stock box??? 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... Mr.RC45 fueling is not the problem... my air box will remain stock because our air box works like a finely tuned instrument... any wild ass guess mod disrupts this highly engineered resonant to where to you're producing nothing but sour notes... The airbox inlet tubes, or “horns”, are specifically designed to provide a resonance that can increase the total airflow by up to 10-15%. Second guessing these can cause the engine to loose power and increase the intake noise as in my case... Link to comment Share on other sites More sharing options...
Magneto Posted March 6, 2021 Share Posted March 6, 2021 Well explained topic, thanks. To add missing piece, location of the restrictions within the system is critical, mainly length from the valve. Imagine sax player shortening or extending his instrument to produce different tone. (Actually perfect exhaust would be motorized like that.😀) “By proper choice of the length of the intake and exhaust piping, the performance of internal combustion engines can be increased. Inlet and exhaust valve opening and closing creates a compressible flow process in which pressure waves flow back and forth through the inlet and exhaust system... “ Anyhow, the solution can be produced analytically and then improved by extensive testing/ adjusting. Properly engineered aftermarket exhaust should produce resonance to duplicate stock useful power band. I would go for at least not hurting useful power band, as there are also different considerations important to riders like esthetic, weight saving or produced sound. Link to comment Share on other sites More sharing options...
Member Contributer boOZZIE Posted March 6, 2021 Member Contributer Share Posted March 6, 2021 4 hours ago, BusyLittleShop said: You're welcome... I've learned the hard way that bigger is not always better... 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 about modifying a stock box??? 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... Mr.RC45 fueling is not the problem... my air box will remain stock because our air box works like a finely tuned instrument... any wild ass guess mod disrupts this highly engineered resonant to where to you're producing nothing but sour notes... The airbox inlet tubes, or “horns”, are specifically designed to provide a resonance that can increase the total airflow by up to 10-15%. Second guessing these can cause the engine to loose power and increase the intake noise as in my case... When you lost hp on the dyno what was you source for feeding air to the box, fans or just (edit - static) atmosphere? Also did you do a real world ,road test with the airbox? I ask coz as we know this (rc46) is not like sports bikes with intake runners, ie the air does not have a direct path to the intake. Link to comment Share on other sites More sharing options...
Member Contributer BusyLittleShop Posted March 6, 2021 Member Contributer Share Posted March 6, 2021 11 hours ago, boOZZIE said: When you lost hp on the dyno what was you source for feeding air to the box, fans or just (edit - static) atmosphere? Also did you do a real world ,road test with the airbox? I ask coz as we know this (rc46) is not like sports bikes with intake runners, ie the air does not have a direct path to the intake. RC45's stock intake horns are there for homologation purposes only and do not directly feed into the airbox only the HRC intakes feed ram air into the airbox... Link to comment Share on other sites More sharing options...
Member Contributer boOZZIE Posted March 6, 2021 Member Contributer Share Posted March 6, 2021 Just to clarify, you had the hrc intakes feeding ram air into the box with 47mm horns? Link to comment Share on other sites More sharing options...
Member Contributer BusyLittleShop Posted March 7, 2021 Member Contributer Share Posted March 7, 2021 5 hours ago, boOZZIE said: Just to clarify, you had the hrc intakes feeding ram air into the box with 47mm horns? Negative... I had stock fairing intakes feeding my home made 47mm horns... Link to comment Share on other sites More sharing options...
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