Airbox resonance
04-10-2009, 11:45 AM
#1
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Airbox resonance
Anyone ever do any testing with airbox resonance?
What about testing with deflecting the wave that reverberates out of the velocity stacks back into the carb throat?
What about testing with deflecting the wave that reverberates out of the velocity stacks back into the carb throat?
04-15-2009, 09:59 AM
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This is from Roger
Dear Martin,
Thank you for your enquiry.
Due to the VTR being classed as a "Sports Tourer" there was never such sophisticated development done by the factory on the standard machine. There was virtually no development done by HRC only by Mamoru Moriwaki and myself who were paid by HRC to develop and race the bikes.
We both did extensive testing on the standard airbox and found that it was totally inadequate if you were to upgrade the engine to racing spec. Therefore Moriwaki designed and developed the "ram air system" which solved all the issues. As I could not improve upon the design I used the Moriwaki system on my race bikes (see attachment). The only people to race these bikes at World level was Mamoru Moriwaki, myself and Bob Hyashida in the States. The VTR was quickly superceded by the SP range and again we were paid by HRC to continue development on that machine so all VTR development stopped. On my ST3 bikes power was raised from the standard UK spec of 102bhp @ R/Wheel to 152bhp. The largest percentage increase I have ever squeezed out of any bike!!!
Sorry but all this does not really answer the question. The short answer is NO as regard to the airbox. However, this pulsing issue is considerably addressed by the re-designing of the camshafts, cylinder head tracts and exhaust system in conjunction with the valve timing where the variance of overlap length is purely done to harness the exhaust pulsing to efficiently scour the cylinders. The added effect is for the pulsing to pass through to carbs and draw addition fuel into a fully emptied cylinder. On a low revving twin engine I can see no measurable benefit to be gained over and above the current gains by impulse cones.
I do not know if this helps or not!!!. One thing is certain there is no point in spending time with the standard airbox - we all been there and done it !!!
Regards
Roger
Dear Martin,
Thank you for your enquiry.
Due to the VTR being classed as a "Sports Tourer" there was never such sophisticated development done by the factory on the standard machine. There was virtually no development done by HRC only by Mamoru Moriwaki and myself who were paid by HRC to develop and race the bikes.
We both did extensive testing on the standard airbox and found that it was totally inadequate if you were to upgrade the engine to racing spec. Therefore Moriwaki designed and developed the "ram air system" which solved all the issues. As I could not improve upon the design I used the Moriwaki system on my race bikes (see attachment). The only people to race these bikes at World level was Mamoru Moriwaki, myself and Bob Hyashida in the States. The VTR was quickly superceded by the SP range and again we were paid by HRC to continue development on that machine so all VTR development stopped. On my ST3 bikes power was raised from the standard UK spec of 102bhp @ R/Wheel to 152bhp. The largest percentage increase I have ever squeezed out of any bike!!!
Sorry but all this does not really answer the question. The short answer is NO as regard to the airbox. However, this pulsing issue is considerably addressed by the re-designing of the camshafts, cylinder head tracts and exhaust system in conjunction with the valve timing where the variance of overlap length is purely done to harness the exhaust pulsing to efficiently scour the cylinders. The added effect is for the pulsing to pass through to carbs and draw addition fuel into a fully emptied cylinder. On a low revving twin engine I can see no measurable benefit to be gained over and above the current gains by impulse cones.
I do not know if this helps or not!!!. One thing is certain there is no point in spending time with the standard airbox - we all been there and done it !!!
Regards
Roger
04-15-2009, 10:59 AM
#6
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Very cool!
Good stuff. Bob Hayashida told me that he saw no increase in HP with an aftermarket airbox, until he got to Stage 2 engine development on an RC51. Below that, the stock airbox was adequate.
I talked with him about airbox mods on a VTR with the engine I was building. He basically told me not to mess with it. He tested filters and various modifications with a Stage 1 engine. I believe he ran the stock airbox (with some modification) and different velocity stacks on his Stage 2 VTR. I know he had (has) a Moriwaki airbox and snorkel on his RC51, but that is a very serious, full-race Superbike engine.
Good stuff. Bob Hayashida told me that he saw no increase in HP with an aftermarket airbox, until he got to Stage 2 engine development on an RC51. Below that, the stock airbox was adequate.
I talked with him about airbox mods on a VTR with the engine I was building. He basically told me not to mess with it. He tested filters and various modifications with a Stage 1 engine. I believe he ran the stock airbox (with some modification) and different velocity stacks on his Stage 2 VTR. I know he had (has) a Moriwaki airbox and snorkel on his RC51, but that is a very serious, full-race Superbike engine.
04-15-2009, 11:27 AM
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Very cool!
Good stuff. Bob Hayashida told me that he saw no increase in HP with an aftermarket airbox, until he got to Stage 2 engine development on an RC51. Below that, the stock airbox was adequate.
I talked with him about airbox mods on a VTR with the engine I was building. He basically told me not to mess with it. He tested filters and various modifications with a Stage 1 engine. I believe he ran the stock airbox (with some modification) and different velocity stacks on his Stage 2 VTR. I know he had (has) a Moriwaki airbox and snorkel on his RC51, but that is a very serious, full-race Superbike engine.
Good stuff. Bob Hayashida told me that he saw no increase in HP with an aftermarket airbox, until he got to Stage 2 engine development on an RC51. Below that, the stock airbox was adequate.
I talked with him about airbox mods on a VTR with the engine I was building. He basically told me not to mess with it. He tested filters and various modifications with a Stage 1 engine. I believe he ran the stock airbox (with some modification) and different velocity stacks on his Stage 2 VTR. I know he had (has) a Moriwaki airbox and snorkel on his RC51, but that is a very serious, full-race Superbike engine.
04-15-2009, 12:35 PM
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04-15-2009, 12:46 PM
#12
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Also...
I don't believe that Honda just stuck any old airbox on the VTR. It was designed and tuned to work with the engine, carbs and exhaust system.
Any significant modifications are likely to require extensive tuning to produce a good torque profile over a wide RPM range.
I don't believe that Honda just stuck any old airbox on the VTR. It was designed and tuned to work with the engine, carbs and exhaust system.
Any significant modifications are likely to require extensive tuning to produce a good torque profile over a wide RPM range.
04-16-2009, 04:49 AM
#13
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Also...
I don't believe that Honda just stuck any old airbox on the VTR. It was designed and tuned to work with the engine, carbs and exhaust system.
Any significant modifications are likely to require extensive tuning to produce a good torque profile over a wide RPM range.
I don't believe that Honda just stuck any old airbox on the VTR. It was designed and tuned to work with the engine, carbs and exhaust system.
Any significant modifications are likely to require extensive tuning to produce a good torque profile over a wide RPM range.
Yep, that is what I found. If you are gunna mess with it, get some flat slides first. I could never get the CV's right, so had to go back to a more normal intake. It will have to stay that way until I get rid of those carbs.
04-16-2009, 06:07 AM
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04-16-2009, 06:15 AM
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LOL!, I know that was comming, but I'm way ahead of you
Mark is looking at what he needs from me and what they will cost us and once we get that hammered out I may try to set up a group buy so we can get them as cheap as possible...
Mark is looking at what he needs from me and what they will cost us and once we get that hammered out I may try to set up a group buy so we can get them as cheap as possible...
04-16-2009, 06:26 AM
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no problem. I think it`s great that you`re even helping, you could have told me to screw off... Besides, the sun still rises every morning (and the VTR runs great, although perhaps not as great as it could, lol) 
Did you get an ETA on "our" pistons yet? lol
Did you get an ETA on "our" pistons yet? lol
04-16-2009, 07:55 AM
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150 HP is another story. Can't get there. But to get to 150 HP, if the engine is making 65 ft-lb of torque you have to have over 12k RPM. and cams to match. Maybe you can make a bit more torque at drop the revs a bit. At 70 ft-lb, the revs drop to 11,250, which I think is more like what the race engines did. But in any case, the engine is higly stressed.
We're building street engines here.
Last edited by RCVTR; 04-16-2009 at 07:58 AM.
04-16-2009, 09:44 AM
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Sorry that was my last post of the day. I don't have any pics and the bike is together. I can tell you it has the vent tubes hooked up the snorkle on and filter hasn't been modded. I think the pair tubes are blocked off, that's about it.
04-16-2009, 10:07 AM
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The vent hoses being fed into the snorkel makes sense as it means the fuel bowls "feel" the same pressure as that in the airbox, keeping the jetting consistant regardless of speed or crosswinds (many snowmobiles vent the carbs in the airbox also for the same basic reasons).
04-16-2009, 10:10 AM
#28
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I would say the airbox might be the most stock part on the bike, besides the foot pegs.
04-16-2009, 10:14 AM
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The vent hoses being fed into the snorkel makes sense as it means the fuel bowls "feel" the same pressure as that in the airbox, keeping the jetting consistant regardless of speed or crosswinds (many snowmobiles vent the carbs in the airbox also for the same basic reasons).
04-16-2009, 10:25 AM
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Mick, The float vents sit between the carb bodies. I'm pretty sure there is too much pressure fluctuation inside the airbox, to make a good float signal. It needs to see steady, ambient pressure.
Here is a message I sent in response to a question from Mikstr this morning, with some more thoughts
and discussions I have had in the past:
I have spoken with Bob about this. The airbox is not the problem. Tuning for airbox modifications is the problem. With carbs, you need to be able to tune the needle profile to produce a reasonably flat torque curve, with the airflow curve you get with the mods.
Bob tested air filters and ran the stock filter in his race bike, because the K&N filter produced a hole in the midrange torque that he couldn't get rid of. A couple HP on the top end was not worth the loss of drive off corners. I am guessing that what Rick is feeling is more top-end rush as it climbs out of the torque hole.
I've had all of these discussions in the past. I go with what the guy who has dyno'd everything tells me. And that's what he told me.
I was doing the same thing with the RC51 airbox. They are all the rage over on Speedzilla, but only one person has produced any dyno results. Admittedly they look good, but require significant remapping. The good thing is, a fuel injection system allows you to produce whatever fuel mapping you need to match the airflow characteristics. I decided not to try and deal with the headache right now, because it's time to ride. I'll do it eventually. The stock RC51 airbox and stock cams are good to 140 HP, with a stock redline. The primary benefit of changing the airbox, is a significant weight reduction up high on the motorcycle.
The stock RC51 air filters have a plastic tube that fits inside one of the filter elements. I suggested to Bob that I was going to remove it, because it looks like a major flow restrictor. He said, "you don't want to take that out". I asked "Why? What does it do?" He said, "I don't know. It works with the airbox." "But you can remove the paper filter element and replace it with foam, and remove the outer screen. That works"
Here is a message I sent in response to a question from Mikstr this morning, with some more thoughts
and discussions I have had in the past:
I have spoken with Bob about this. The airbox is not the problem. Tuning for airbox modifications is the problem. With carbs, you need to be able to tune the needle profile to produce a reasonably flat torque curve, with the airflow curve you get with the mods.
Bob tested air filters and ran the stock filter in his race bike, because the K&N filter produced a hole in the midrange torque that he couldn't get rid of. A couple HP on the top end was not worth the loss of drive off corners. I am guessing that what Rick is feeling is more top-end rush as it climbs out of the torque hole.
I've had all of these discussions in the past. I go with what the guy who has dyno'd everything tells me. And that's what he told me.
I was doing the same thing with the RC51 airbox. They are all the rage over on Speedzilla, but only one person has produced any dyno results. Admittedly they look good, but require significant remapping. The good thing is, a fuel injection system allows you to produce whatever fuel mapping you need to match the airflow characteristics. I decided not to try and deal with the headache right now, because it's time to ride. I'll do it eventually. The stock RC51 airbox and stock cams are good to 140 HP, with a stock redline. The primary benefit of changing the airbox, is a significant weight reduction up high on the motorcycle.
The stock RC51 air filters have a plastic tube that fits inside one of the filter elements. I suggested to Bob that I was going to remove it, because it looks like a major flow restrictor. He said, "you don't want to take that out". I asked "Why? What does it do?" He said, "I don't know. It works with the airbox." "But you can remove the paper filter element and replace it with foam, and remove the outer screen. That works"
