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Discussion Starter #1
i started this thread because im tired of hearing all the :bs: . ive read and the discussions on here about chopping the divider out of the ram air tubes and swapping out the two tall stacks for shorter ones. I do dont understand what the argument is on how this will cause a power lose. in my mind if u chop the divider out of the ram air tubes your gonna flow more air, and if all the stacks are equal your gonna make more power, and its going to be consistant to all the cylinders. Its just that simple.

i mean ive been around high hp cars all my life and know a good bit about them. more air you can flow into an engine the more fuel you can inject and the more power you make its that simple, they dont have to worry about all this bs that gets discussed on here.

Isnt that the same for a bike the more air you can flow into the engine the more power you can make? ive had people argue that its about the smoothness of the air coming into the intake and not about the volume. This makes no sense to me. The more turbulent the air is flowing the better the fuel and air will mix, and this will create a better and more efficient burn thus making more power.

like to hear some feedback thanks.
 

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The volume is important. Also when you squeeze air in tighter places using a divider you get more speed, so more air faster right?
 

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Intake track length comes into place here too. Short tract=low end torque Long track=high end torque. I am more familar with cars myself. Have you ever noticed that stock intakes on old V8's tend to be low rise especially in trucks and heavy cars. They need to low end to tow and get rolling. The performance models (Z28, Corvette) come from the factory with "high rise" intakes. Chevy wanted them to pull more on the top end.
Take a look under the hood of shelby cobra.


or the drag cars of the 60's

HP=(peak tq x rpm)/ 5252. Shifting the torque higher in the rev range make more hp.
 

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Supercharged Mod
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It is often not a matter of "flowing more air". It is often a matter of how the pressure waves interact. Intake runner flow is highly unsteady and the effect of pressure waves is significant.

Regarding the divider in the (before-airbox) intake duct, I don't subscribe to the removal theory. When air has to go around a bend, it can help for the air to be guided around the bend. The inner part of the duct and the outer part of the duct, when looked at individually, each act like a longer-radius bend. The cross-sectional area available for flow isn't significantly affected. This part of the intake system is upstream of the part for which pulse-tuning is most effective.

Regarding the runner lengths, what happens is that the suction from the exhaust system and the motion of the piston starting to go down create a negative pressure wave going out the intake runner. At the end of the runner this gets reflected back as a positive pressure pulse towards the cylinder. At the cylinder it encounters an open volume (because the piston is now quite a bit down the stroke) and gets reflected back as another negative pulse, which gets reflected back to the cylinder *again* as a positive pulse. If that positive pulse ends up at the cylinder just as the intake valve is closing, it stuffs a little more air into the cylinder. The length combined with the speed of sound combined with the duration of the intake cam govern at what RPM this will be effective. If all four cylinders are tuned the same (which is the most common arrangement) this results in slight peaks and valleys in the torque curve. Having two cylinders tuned differently will tune those cylinders in at a different RPM - which means that although the peak might not be as high, it will get evened out some and give a broader, flatter torque curve as a whole, because at one speed the two inner cylinders are on their peak and the outers are off, then at another speed, the two outer cylinders are on their peak and the inners are off.
 

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Discussion Starter #6
The volume is important. Also when you squeeze air in tighter places using a divider you get more speed, so more air faster right?
THeoretically the smaller the tube is the more velocity there would be in a ram air type intake. But They say velocity and volume are complete opposites if you have more of one you have less of the other. So a bigger intake would equal more volume but with a slwoer velocity.. but really who knows which is best, im going to try it out and see how it runs..:eek:ccasion1
 

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Discussion Starter #7
It is often not a matter of "flowing more air". It is often a matter of how the pressure waves interact. Intake runner flow is highly unsteady and the effect of pressure waves is significant.

Regarding the divider in the (before-airbox) intake duct, I don't subscribe to the removal theory. When air has to go around a bend, it can help for the air to be guided around the bend. The inner part of the duct and the outer part of the duct, when looked at individually, each act like a longer-radius bend. The cross-sectional area available for flow isn't significantly affected. This part of the intake system is upstream of the part for which pulse-tuning is most effective.

Regarding the runner lengths, what happens is that the suction from the exhaust system and the motion of the piston starting to go down create a negative pressure wave going out the intake runner. At the end of the runner this gets reflected back as a positive pressure pulse towards the cylinder. At the cylinder it encounters an open volume (because the piston is now quite a bit down the stroke) and gets reflected back as another negative pulse, which gets reflected back to the cylinder *again* as a positive pulse. If that positive pulse ends up at the cylinder just as the intake valve is closing, it stuffs a little more air into the cylinder. The length combined with the speed of sound combined with the duration of the intake cam govern at what RPM this will be effective. If all four cylinders are tuned the same (which is the most common arrangement) this results in slight peaks and valleys in the torque curve. Having two cylinders tuned differently will tune those cylinders in at a different RPM - which means that although the peak might not be as high, it will get evened out some and give a broader, flatter torque curve as a whole, because at one speed the two inner cylinders are on their peak and the outers are off, then at another speed, the two outer cylinders are on their peak and the inners are off.
I can see what your argument is about removing the divider..its really prob not going to make a noticeable difference anyways so its not even worth the time of removal. Now

I plan on removing the two tall stacks and replacing them with the factory shorter ones (Velocity stacks are ridiculously overpriced). If i understand correctly i will gain a little at higher revs but lose a little down low in the rpm. But, Considering the fact that our bikes make hardly any power down low in the rpm anyways, it seems like it would be a good idea, especially if you race your bike to replace the tall ones for short ones so u make more power up high in the rpm.
 

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It is often not a matter of "flowing more air". It is often a matter of how the pressure waves interact. Intake runner flow is highly unsteady and the effect of pressure waves is significant.

Regarding the divider in the (before-airbox) intake duct, I don't subscribe to the removal theory. When air has to go around a bend, it can help for the air to be guided around the bend. The inner part of the duct and the outer part of the duct, when looked at individually, each act like a longer-radius bend. The cross-sectional area available for flow isn't significantly affected. This part of the intake system is upstream of the part for which pulse-tuning is most effective.

Regarding the runner lengths, what happens is that the suction from the exhaust system and the motion of the piston starting to go down create a negative pressure wave going out the intake runner. At the end of the runner this gets reflected back as a positive pressure pulse towards the cylinder. At the cylinder it encounters an open volume (because the piston is now quite a bit down the stroke) and gets reflected back as another negative pulse, which gets reflected back to the cylinder *again* as a positive pulse. If that positive pulse ends up at the cylinder just as the intake valve is closing, it stuffs a little more air into the cylinder. The length combined with the speed of sound combined with the duration of the intake cam govern at what RPM this will be effective. If all four cylinders are tuned the same (which is the most common arrangement) this results in slight peaks and valleys in the torque curve. Having two cylinders tuned differently will tune those cylinders in at a different RPM - which means that although the peak might not be as high, it will get evened out some and give a broader, flatter torque curve as a whole, because at one speed the two inner cylinders are on their peak and the outers are off, then at another speed, the two outer cylinders are on their peak and the inners are off.
Wow, way to break it down! I dont know if it means much to a mod but, Rep Sent! :eek:ccasion1
 

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Go research FLOW Bench Testing. This topic is far to in depth for a thread. Try this. Take your air-box and run the engine and give the throttle some good wacks. You will see the pressure wave hover over the intake mouths like a small cloud. Its kinda cool. Bottom line is I think the engineers know what they are doing and wanted.
 

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The flow bench is not the be-all and end-all, either. It's a tool, but it can be wrongly used.

Hog out intake ports bigger than what the engine wants for best "intake ramming" effect and you'll lose power.
 

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The flow bench is not the be-all and end-all, either. It's a tool, but it can be wrongly used.

Hog out intake ports bigger than what the engine wants for best "intake ramming" effect and you'll lose power.
 

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damn, i need a cheaper option for the two taller stacks...those factory pro stacks are a wallet bleeding 300bux +/- crazy shit for a lil piece of aluminum
 

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Bottom line is I think the engineers know what they are doing and wanted.
Yes.....BUT they are restricted by a number of things, not the least of which is noise. This simple thing will override everything else, as these 'road' bikes MUST get through stupid noise tests all around the world. There are other things too, but this is the hardest one to get around with decent performance....
 

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The stock rubber shorts or longs can be had for about $8 a piece thru kaw. I changed them on my old GenII and saw no difference from mixed to all short. Save ur $$
 

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It's about velocity also, ever see the intake runners on an LS series GM v8? They're shaped like a rectangle, good flow and high air speed. They make great power. There is always a compromise, ram air Trans Ams had those hoods that fed fresh air to the intake but had an indirect path to keep idiots who drove 100 mph in the rain from ingesting water in the engine.
 

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damn, i need a cheaper option for the two taller stacks...those factory pro stacks are a wallet bleeding 300bux +/- crazy shit for a lil piece of aluminum
http://www.superstreetbike.com/howtos/1102_sbkp_honda_cbr600rr_velocity_stack_mod/index.html


In the case of our 2008 CBR600RR, it came stock with short velocity stacks on the outer cylinders and two longer stacks on the inside holes. The "velocity stack mod" consists of using the shorter outer velocity stacks on all four cylinders. The claim is that this will offer several more HP at peak without costing anything in the middle.
 

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Discussion Starter #18
It's about velocity also, ever see the intake runners on an LS series GM v8? They're shaped like a rectangle, good flow and high air speed. They make great power. There is always a compromise, ram air Trans Ams had those hoods that fed fresh air to the intake but had an indirect path to keep idiots who drove 100 mph in the rain from ingesting water in the engine.
I actually know a lot of kids that dremel the hood out so they get straight through flow on their TAs lmao..

Really their are no other car manufacturers that makes the kinda power the LS series pushrod motors make for the money.
 

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i have actually done the mod of taking the divider out. personally on the butt dyno i felt like i had gained a little bit down low. (nothing crazy but, it is noticable). after reading what you wrote, it made me think twice about it, however; the way those dividers are put in doesn't create a higher pressure going into the air box. it seem as if they actually slow the air down. i used an air compressor to shoot air through both tubes to see which felt stronger. now honestly i don't have a machine that could graph exactly how hard the air was coming in but i used the back of my hand to feel the difference and there's most definitely a stronger air flow in the tube with out the divider. i know this isn't an exactly perfect experiment but it seems logical to me. i attached a picture to show the difference with and with out the the divider, comments?
 

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i just want to say that those tubes are exactly on the same angle and the camera is directly above both, i took this picture many time to make sure it was favoring to either side. so i know it may look like it favors but i promise it doesn't
 
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