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Chubby Chaser
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Out of everything that was said here I would pay close attention to what Tim Radley said (as you should with whatever Tim says in regards to anything with a motor in it). Ram-air's purpose is not simply to try and achieve some sort of positive pressure in the air box (which as mentioned doesn't start happening until you are well into triple digit speeds on most sport bikes) but it is a mechanism full allowing the air box to pull clean cool air from the front of the bike, as opposed to hotter/dirtier air from behind the middle of it.
 

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The Dreaded Midnight Taint Slapper
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Which is exactly why Suzuki didn't invest millions in it's design and development over the last 20 years...... oh wait... they did! I guess Suzuki's engineers are smarter than your tuner.

Ram air does 2 things. It reduces intake temps by allowing the bike to breathe clean air. It also helps to reduce the resistance of the air filter.

If Suzuki was the only company doing ram air, then it would be questionable. But take a look at every single bike, and most performance cars, and it's pretty clear there's benefit to ram air. Forget "boost". It not the only thing that matters.
Correct. Once upon a time we made some sound supression devices ( basically a bucket lined with sound absorbing foam) to go around the k & n air filters on our two stroke racing kart engines due to a decibel limit regulation at a track in Jacksonville. Once installed, the kart picked up about 2mph on the long strait and I could feel the difference in power. The dyno confirmed what we experienced, showing almost a 2hp gain over the entire range on a 45hp engine. I was shocked. There is more to making power than the obvious stuff everyone thinks of. While at the track, I thought the gain was due to the air being calmer around the filter at speed, but it even worked on the dyno with no air moving. I'm guessing it was suppressing the sonic pulses coming from the intake, but I'm not sure. :dunno
 

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Chubby Chaser
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What Suzuki does get wrong is their placement of the intakes. Its been demonstrated time and again that the central design of the R6 or RC51 is the optimal placement of the intake.
 

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Premium Member
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117,182 Posts
What Suzuki does get wrong is their placement of the intakes. Its been demonstrated time and again that the central design of the R6 or RC51 is the optimal placement of the intake.
They've actually done a lot of work on that too. Like the r1, they both seem to think the volume of having two is beneficial. The nostril design is always changing though and on big race bike teams they have adjustable plates to catch the air better often. The big issue they face is catching air that "spills" over the outer edges
 

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Dreaming of buttsecks for years...
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What Suzuki does get wrong is their placement of the intakes. Its been demonstrated time and again that the central design of the R6 or RC51 is the optimal placement of the intake.
There's still debate about that. I remember reading somewhere that the 2 offset intakes benefited from not only catching the direct air, but the air deflected from center as well. It accounted for why the intake design over the last few years as gotten taller and the outer edge moved forward. Makes me think of wings on a snowplow.
 

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Chubby Chaser
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But MotoGP where they can design it anyway they like without worrying about copyright/design infringement.........







Not exactly center but close








Moto2





 

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Dreaming of buttsecks for years...
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How much of that placement do you think is attributed to design factors other than optimal placement? I think aerodynamic function is only one factor in that placement. Overall aerodynamics, frame design, and general space availability will all play a part.

I'm not saying that central placement doesn't yield maximum benefit, because I have absolutely no clue. Just for the sake of discussion, what if.....

If the dual outer placement actually yielded more benefit and produced more power, but also increased the aerodynamic drag significantly? Race teams would sacrifice the horsepower numbers to gain top speed and place it centrally. Manufacturers would sacrifice top speed so they could publish bigger horsepower numbers in their marketing to sell more bikes.

All of which is just conjecture. It's quite possible that central positioning is beneficial in both respects. Suzuki may have just designed it this way and continue to do so because the trickle down design changes required are too costly.
 

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SPL170db,

The cool air theory posted by The Geek is 100% correct. For every 10 degree increase in inlet temperature, there is a corresponding 2% decrease in horsepower - so drawing from the hot area under the gas tank on a modern day machine is certainly not a good idea.

As far as the 'Ram Air Effect', for all street and most race (excluding land speed) applications, it's best to not worry about 'positive' pressure as much as think about 'less negative'. Positive pressure occurs at high speeds (typically over 150 MPH), is minimal (less than .5 psig) and has a marginal effect on acceleration (you are already going too fast to pick up much more acceleration). BUT every little bit helps, especially in normally aspirated applications, so we love it! When a bikes engine draws from an air box, it creates a negative pressure situation that can use as much fresh air VOLUME replenishment as possible. The ram air inlet(s) do a fantastic job of this at a relatively low speed. Want to test this theory? Stick your cupped hand out of your car window at 55 MPH and feel the ‘push’. Most sportbikes today can attain that speed in the top of 1st gear, so ‘less negative’ basically contributes to harder acceleration (progressively) from the time you begin twisting the gas until 150 MPH and beyond. It’s difficult to find a modern sportbike without a well-designed air box these days, and for good reason – the benefits are tangible and measurable.

At my company, we embraced the benefits of the air box years ago and began designing our oversize exhaust systems to compensate for the extra intake/exhaust flow required to properly utilize them. We did this engineering work as a result of incremental performance measurements obtained in the field (drag strip, land speed, data logging street bikes etc.) – instead just designing our exhausts using horsepower numbers from our dyno… as they only told a fraction of the story.

If you Google land speed ‘naked’ bikes. You will notice that they will remove the bodywork, but they all keep the ram air scoops… performance will seriously suffer otherwise.

I hope this helps with your dilemma.

Brock Davidson
www.BrocksPerformance.com
 

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Chubby Chaser
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57,820 Posts
SPL170db,

The cool air theory posted by The Geek is 100% correct. For every 10 degree increase in inlet temperature, there is a corresponding 2% decrease in horsepower - so drawing from the hot area under the gas tank on a modern day machine is certainly not a good idea.

As far as the 'Ram Air Effect', for all street and most race (excluding land speed) applications, it's best to not worry about 'positive' pressure as much as think about 'less negative'. Positive pressure occurs at high speeds (typically over 150 MPH), is minimal (less than .5 psig) and has a marginal effect on acceleration (you are already going too fast to pick up much more acceleration). BUT every little bit helps, especially in normally aspirated applications, so we love it! When a bikes engine draws from an air box, it creates a negative pressure situation that can use as much fresh air VOLUME replenishment as possible. The ram air inlet(s) do a fantastic job of this at a relatively low speed. Want to test this theory? Stick your cupped hand out of your car window at 55 MPH and feel the ‘push’. Most sportbikes today can attain that speed in the top of 1st gear, so ‘less negative’ basically contributes to harder acceleration (progressively) from the time you begin twisting the gas until 150 MPH and beyond. It’s difficult to find a modern sportbike without a well-designed air box these days, and for good reason – the benefits are tangible and measurable.

At my company, we embraced the benefits of the air box years ago and began designing our oversize exhaust systems to compensate for the extra intake/exhaust flow required to properly utilize them. We did this engineering work as a result of incremental performance measurements obtained in the field (drag strip, land speed, data logging street bikes etc.) – instead just designing our exhausts using horsepower numbers from our dyno… as they only told a fraction of the story.

If you Google land speed ‘naked’ bikes. You will notice that they will remove the bodywork, but they all keep the ram air scoops… performance will seriously suffer otherwise.

I hope this helps with your dilemma.

Brock Davidson
www.BrocksPerformance.com

I think you might have missed what I already typed earlier in the thread ;)


Out of everything that was said here I would pay close attention to what Tim Radley said (as you should with whatever Tim says in regards to anything with a motor in it). Ram-air's purpose is not simply to try and achieve some sort of positive pressure in the air box (which as mentioned doesn't start happening until you are well into triple digit speeds on most sport bikes) but it is a mechanism full allowing the air box to pull clean cool air from the front of the bike, as opposed to hotter/dirtier air from behind the middle of it.
 

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Taught Goatsee everything he "knows"
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There's still debate about that. I remember reading somewhere that the 2 offset intakes benefited from not only catching the direct air, but the air deflected from center as well. It accounted for why the intake design over the last few years as gotten taller and the outer edge moved forward. Makes me think of wings on a snowplow.

I could see that.

The HP ratings we see listed for our bikes, is that with or without ram air effect?
 

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And then there is the 'tuning the air box' for air pulse from the engine itself. V twins being more susceptible of course ...
DT
 

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Great reads. There was one particular line that caught my eye though in regards to what SPL said earlier about central placement design...

What Suzuki does get wrong is their placement of the intakes. Its been demonstrated time and again that the central design of the R6 or RC51 is the optimal placement of the intake.
From the first article:
"As air is jammed into the opening, the high-pressure area that is created builds outward, effectively stopping more air from entering."

This may be getting way into the physics aspect of it and I could be wrong about what the article was trying to say, but if this is true, then shouldn't a central placement result in more air entering the intake at a lower speed thus resulting in the stopping effect occurring at a lower speed than it would if the intake(s) were placed away from the nose where the air pressure is at it's maximum?

It seems to me that it would be similar to when a jet breaks the sound barrier. The faster you go, the more pressure is built up at the very front resulting in a push back effect.
 

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Dreaming of buttsecks for years...
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In theory, I think you would be right. I didn't go back and look at the graphs, but did you see a steeper slope in the graph on bikes that had central placement?
 
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