R6 - velocity stacks for my 2007 VFR 800 ?

Anyone know what year R6 velocity stacks I need for my 2007 VFR? also I looked and I seen some kits where they were all the same length I'm sure that's not right . anyone have a link that I can go to ? Also Do they really make a difference ?

 

These look like the ones I am using:

http://www.ebay.com/itm/B257-36720-...Parts_Accessories&hash=item1e8615bc99&vxp=mtr

You will have to remove a considerable amount of material from the air box entries and throttle body entries above the butterflies by port matching the throttle bodies to the bigger r6 velocity stacks though.

 

Do they really make a difference ?

 

no i did it for looks

 

veeerry subtle candy.... veeeerry sutble :disturbed:

 

Lol don't expect to just slap on some big velocity stacks and really make a difference. All modifications should be thought of as a complete package. I already had a full exhaust and open air box and Pipercross air filter, so the small velocity stacks and throttle body openings and casting marks were a bit of a bottle neck.

But if you are planing on doing this to an otherwise stock Vfr, there's not much point.


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I have my old velocity stacks from my old 2002 R6 would they just screw in? I have a 2 bos carbon slip on and plan on adding a pipercross for 30% more air

 

No they don't screw on. You need to remove the factory ones. Then epoxy the r6 stacks on, as best fit as you can. Then port match everything together. So it's all 100% smooth.


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Do you have any pics of this mod? I am pretty sure I have the stacks in my closet. However I like power down low, so the only mod I think would help is a simple air Higher Flowing filter. When I changed out my air filter oem for another I did notice more air getting in and it was running better. I don't want to get too much in the power game-I am a balance rider who is a bit imbalanced:boozer: My Mr. Beer kit from sears has produced results.

 

Yeah I did a write up on it already. If you want more low end you want to invest in a one down sprocket kit, ignition advance and dropping weight.


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the only weight reduction I could come up with is a shoie battery-2.2 pounds-the one with 270 cc power

 

Ballistics Evo 8 is 7 pounds lighter than stock.

Remove the pair valves, evap/charcoal canister, flapper and snorkel you're looking at at least another 10 pounds.

Passenger pegs and grab rails are a little more than ten pounds.

A nice carbon slip on will save another 20 pounds or so.

An aftermarket catless header will get you maybe 10 pounds.

A 520 conversion sprocket kit will save you 2 pounds of rotational weight.

Now you start getting to the fun stuff.
A brake delink will get you 10 pounds.
A custom subframe could save you about 20 pounds.
Forged wheels and a Ducati rear axle conversion could save you 5-10 pounds of rotational weight.
Then you have the heavy Vfr headlights and fairing stay etc......

You can get this bike down to competitive weight levels fairly easily.
I have managed to get mine to 460 pounds with a gallon in the fuel tank. That's about a 50 pound drop. Mind you this was done on a starving college kids budget with out a daily driver, so I don't want to hear any excuses.




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:horn:out:well I did do the big one carbon 2 bos carbon can-took off 19.5 pounds, carbon canister 3 pounds, added scotts damper and sliders gained back maybe 5 pounds, but I am adding hard bags and hard ware. The hard ware is about 5 pounds, I would balance that with a shoie battery. This bike is a fat pig-I don't want to take off passenger pegs or grab rails. I am leaving on the flapper stuff for now and pair valve because it seems to help warming up the engine fast. I never fill up the gas tank

 

Ever been shot at with an "air gun" (without ammo!)? That teeny bit of air, moving really fast - does have energy and the "mass" of the air has "inertia" and can demonstrate power, for instance, by stunning pesky unsuspecting flies, for instance. Basically - that demonstrates that air, moving fast, can pile up against something and build up high pressure. and knock flies out, for instance.

In an engine, we have a much larger amount of air, in a "tube" (intake tract) moving a bit slower, like 220 -275 feet per second - (for scale, I believe that 250 feet per second is just a tad over 170 mph) but it definitely wants to keep moving in the direction that it was going! And there's a lot more air moving through than my 1000 feet per second (681 mph at the muzzle?) pellet gun.
So - there's a fair amount of air mass in an engine at 170 mph to work with.

Sorry to muddle the waters, but that 220 -275 air speed is not really correct, as I think about it - That's what "somebody proclaimed" and is rarely questioned and is really 220-274 fps at "some" flowbench pressure (12"?). Most people generally forget to qualify velocity number with pressure numbers when bantering.
In actuality, the real flow rate in an engine's intake port, at any point in time, varies from slightly backwards, to not moving much at all to REALLY fast during the intake stroke.
But the point is - it's like going, you know, a "million miles an hour" when it's going into the engine, through the intake tract.

So - Engine's running -

Have to start somewhere, so... we jump in here......

Air's going into the combustion chamber, though the intake tract assembly (port, throttle body / carb and "velocity stack").

All that air in the intake port and stack is running real fast, like a "million miles an hour", towards the combustion chamber when the valve was open.


The piston was helping by going down, sucking, so to speak.
It gets to BDC and starts coming back up. It stops "sucking" at BDC.
Air's still a runnin' in. Because of that million mile an hour column of air in the intake tract......

At some degree of crank rotation (degrees) the air molecules in the front are stopped against the piston but the ones in the back kept running in and crashed all into the guys in the front. Pretty soon, there's the a big 'ole compressed pile of air molecules in the port and the combustion chamber and intake tract. What a high pressure mess.
At low rpm, the guys in the back of the pile have enough time to shake their heads and say "Woah! What the heck as that?" "I dunno, but, lets get the heck back outta this high pressure port and go back into the lower pressure airbox - there's too many of us in here. Can't stand the pressure!"

So - out they start going..... back out the port and throttle body / carb and the velocity stack and the pressure in the intake tract is lessened as the guys in the back get the heck back out and the guys in front turn around and follow the bum's rush back out to the airbox. The intake valve is still open.

Then the intake valve closes - trapping whatever air and fuel is still in the combustion chamber.
If it's a bit below the rpm that the intake tract is tuned for (length and diameter), you'll end up with a bit more trapped air (dynamic compression) than what it would be if the air was just getting sucked into the engine with no "complimentary" intake tract length and diameter, but not as many air molecules as you could have trapped.....

That's if it was just below the "tuned range" of the intake tract.

If it's a lot of rpm below the "tuned length" of the intake tract, you would see fuel actually get pumped back out of the velocity stack.
A tuner would call that "reversion" and power would probably not be very good at those rpms.

Under what we call reversion conditions, trapped compression would probably be a ratio that is related to "even less than atmospheric" - as the air rushing back out drags the first air molecules back out with it.
You'd have to lean that out a bunch, as the air that got punted back out the stack was already fueled up - but it goes out, then eventually back though the intake tract and get "fueled" again.... yuck.

"Reversion" basically, "sucks". (small joke!)

MAJOR POINT!
Whatever air is still in the combustion chamber when the intake valve is closed is what gets burned and makes pressure to push down on the piston. More air molecules is better (and if you have the same combustion chamber volume and more air molecules there, then you have more pressure, aka "dynamic compression").

The trapped air pressure (dynamic compression) changes based on rpm. Actually, it changes based on anything that changes flow rates, velocity, intake tract length or..... the intake valve's closing timing.....

Air goes in as long as it can before the pressure inside the combustion chamber, with the intake valve open, is greater than the pressure in the intake tract. Then it wants to turn around and go back out......

So - now we know what's inside the combustion chamber and the engine will use the trapped air to make power on this next power stroke.

That's what happens at low rpm, below where the intake tract wants to work......

How about at higher rpm, or "the rpm that the intake tract was tuned" for? (stack length, inner diameter, airbox volume)

Piston's going down on the intake stroke, with the intake valve open. The column of air, running a million miles an hour, follows the piston and after BDC, keeps trying to cram itself in, but eventually it reaches high enough pressure in the combustion chamber, that even though the backdoor guys are still trying to ram themselves in, they can't. Before they turn around, you slam the intake valve closed. Ahah! TRAPPED air!

So - if you are at the right rpm range, and the intake tract is just the right length and diameter for that rpm, and the intake valve closing event is timed EXACTLY at the right time - (right before the air starts back out) - you'll catch a bunch more air molecules at higher than outside air pressure in the combustion chamber -
Magic! Power!

If you time everything just right, you pick up free power due to the higher "dynamic compression".

Depending on the original intake tract, changing velocity stacks can be good for as much as 2% to 5% power across about a 3000 to 3500 ish rpm range without hurting power anywhere on 2000ish vintage engines.

That part of the story on intake tracts.
There's the other 2/3rds.

The 2nd part:
That pressure wave -
Add that the air "pressure wave" column of air that gets bounced out into the airbox when that intake valve is closed and then makes a low pressure in the port (when the intake valve is still closed - then, there is lower pressure in the port and higher in the airbox. Dang! Wouldn't it be cool if we could do something with that?

The molecular dude-airs say "Whoa!! It's high pressure out here in the airbox and low back in the port! This way guys! Back into the port! Charge!!!"

So they all start zooming back into the intake tract "tube" and they keep runnin' in, in a column of air, through that intake tract "tube" until they start that crashing up against the closed intake valve again. "Whoa baby! It's high pressure in here and we......" Whammo! The intake valve opens up!!!! and ZOOM! You have "higher than standard air pressure" in the port when the intake valve opens. Neat trick!!

And the engine had thought that it had to lamely "suck" that new intake charge in. Fooled it! The air was high pressure when it opened the intake valve! If you time that in/out just right - you'll get "supercharging for free".

Like I said, a well developed intake tract configuration usually works strongly over a 3000 to 3500 rpm spread.

If you don't like the rpm that this boost occurs, you have to change the length and or diameter of the intake tract (each length change changes the frequency / time of the confused air molecules in / out routine) , change the fill rate of the cylinder (porting or TB/carb size change), change the intake cam timing.

You have to change something that changes the overall resistance to flow or the frequency.


Think I'd tell you everything?
Buy an EC997 dyno like #1 Vesrah Racing, #1 Robert Jensen, 4&6 Cycle and F-USA nd learn the rest or you can pay $2000 to a different dyno company for a week long school in AZ and get a diploma saying you are an "Authorized" tuner....... and call them and ask them how this stuff works......

.........................................

Dynamic compression?
It's the air pressure trapped by the intake valve closing in a running engine.
Cranking compression?
You already know what that is.

One day I took a spark plug out of a 4 cylinder bike.
Put a compression tester in the one spark plug hole and started the engine.

At low rpm in neutral, I got a stable reading.
As I raised the rpm in neutral and the engine got more towards the powerband, the compression rose.
I would guess that the highest "dynamic compression" value would be at the torque peak.
Since I was using a compression tester, I could only see pressure rising. To see lower at higher, past the power peak, I'd have to release the pressure from the gauge holding the throttle and I don't have 4 arms.... (or 3 eyes or legs, either

Marc

The term "velocity stack" generally refers to the cylindrical tube with a radiused air inlet that part of the inlet tract that is generally "attached" to the "fuel delivery device" - a fuel injection throttle body, a carburetor, or in the case of he fuel being "direct injected" the combustion chamber, directly to the intake port.

Confusion with airbox "intake snorkel"

If it's part of or attached to the plenum or "airbox", it's more of a "flow resistance decreasing, radius device" and technically, not an intake runner "velocity stack" and usually doesn't increase air "velocity", though it may increase airflow by decreasing flow resistance.

The lower flow resistance results in potentially more air volume delivered to the engine, but at a lower velocity. However, generally replacing a restrictive intake inlet, that was designed to reduce intake sound levels will commonly result in improved air delivery and improved performance.

Definition and purpose

The term "velocity stack" refers to an IR (individual runner) intake arrangement, where each cylinder has it's own inlet port. A velocity stack may be used with or without an "airbox" or plenum and the length and shape of the device determines several items, including.

1. Average dynamic air flow rates into the engine under the chaotic intake airflow and pressure conditions of a running engine.

2. Pressure wave propagation and recovery rates as a factor of the inlet radius and inlet side profile.

3. Average dynamic air velocity across the inner diameter.

Used with or without an "airbox". They are designed to:

1. Allow smooth and even entry of air into the intake duct with the flow stream's boundary layer adhering to the pipe walls.

2. Allow choosing of the effective rpm range of dynamic compression (cylinder fill rate).

3. Allow choosing of the overall dynamic compression by choosing inlet profile.

Image:Velocity stack.GIF

Highly modified engines

Highly modified race engines sometimes have the original air box and associated ducting removed and velocity stacks are installed and profiles, lengths and inner diameters are modified to improve performance.

Generally stock engines

Generally, OEM (original equipment) "velocity stacks" are designed with more than just power output in mind. For example, intake noise. Stock inlet stack profiles, in the original airbox, commonly have velocity stack configurations that tend to decrease sound levels, rather than optimizing power output.

An optimally designed intake runner "velocity stack" will improve power over a range of 3000 to 3500 rpm range in current reciprocating IC engines.

Modern fuel injection systems with a single air inlet typically incorporate some sort of radiused air entrance, and if that initial airbox or plenum airflow restriction is retained while modifying the "downstream" velocity stacks, power across a range is still evident, reinforcing the concept that a properly designed inlet stack improves power, predominantly by increasing "dynamic compression" rather than improving bulk airflow.

Testing of replacement "velocity stacks"

Detailed dynamometer testing and design work commonly results in different length velocity stacks on different cylinders.

The "optimal for power" velocity stack configuration is affected by many factors

1. Desired RPM range

2. Changes in intake and exhaust cam timing or cam profiles

3 Exhaust system changes.

4. Port flow changes.

5. Airbox or plenum volume changes

5. Anything that affects dynamic air flow and pressure wave timing.

A velocity stack configuration that works as required for s "stock" unmodified engine may be distressingly non-optimal for a ported and re-cammed engine.

When replacing an original equipment current (2008) motorcycle velocity stack profile, the power improvements are usually in the range of 2% to 3% power in the stack's effective rpm range, with some applications at some rpms points occasionally gaining as much 5%. There are a few motorcycle applications that have optimal velocity stacks as delivered.

Engine testing vs. mathematically calculated "intake tract" (velocity stack) length

There are multiple formulas to calculate "intake tract length" and it is easy to calculate a number. It has been shown over many 100's of dynamometer engine tests, that a "calculated" intake tract length is only a rough guide to within +/- 25mm of what is optimal for a running engine. Some formulas are obviously too simple (an intake isn't simply a closed cylinder) and some more realistic formulas and most computer programs attempt to take more factors into account, but still can't take every one into account, as it's simply not realistically possible to measure and provide every applicable input into the calculation. Optimal intake track length is almost always derived through dynamometer testing, using calculated intake tract length as an initial starting point.


Engine testing vs. flow bench "intake tract" velocity stack profiles

An engine's dynamically flowing and pressure pulsing intake tract is only somewhat related to a common steady state flow bench. "Optimal" steady state flow rates are only a small portion of the complex factors involved in optimizing an intake ports inlet profile. It's common to compare flow bench developed "better air flow" velocity stacks vs. an "engine designed" optimally radiused stacks with an optimal inner diameter and find a 4% to 5% power improvements over "flow bench developed" inlet profile. (2008)


Fuel "Standoff"

Sometimes an intake tract of a particular configuration produces air/fuel mist "standoff" at some rpm, most often, full throttle at low rpm. The term: "standoff" is actually the port's dynamic air "backflow", the result of the intake cam closing too late or retarded for the intake tract length. The air "overfills" the cylinder above atmospheric pressure and then the intake air (with the previously metered fuel) is blown back out the intake port, before the intake valve closes (which would trap the higher the atmospheric pressure" air in the cylinder. The fuel is then "re-metered" again, producing an overrich air/fuel mixture that degrades power, in addition to losing power from the lowered potential dynamic compression.



(Source - Factory Pro website)

There is a lot more to it than just changing the stacks and you might (probably will) end up doing more harm than good if you don't go about it the right way.

 

Good stuff


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If any of you guys are interested in more power or in the market for a power commander / bazzaz etc...

Check this out:

Here you go:



http://www.vfrdiscussion.com/forum/index.php?/topic/78467-Official-Rapid-Bike-Race-Group-Buy!






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I am interested in this computer mod, but how much does all this fancy stuff cost. The 06 vfr computer is detuned to run on 86 gas, so advancing the timing to run on available pump gas 91 would be a Big jump in power as added a high flow air filter and exhaust. I have the piper cross air filter coming next week and the single slip-on 2 bos installed, so the engine is now going to be getting more air in and out. the computer is now holding back the engine a bit or maybe not. The stock FI computer should adj for this change. But for now I don't really want to run 91 because its more expensive. Once I change the air filter-I am going to run 89 just to be safe for the adding cooling power of more octane. I can run 87 shell right now because of the stock air filter. This bike handles as well as my R6 does and I all most have gotten my chicken lips gone. I am at #6 on the M5 tires-not too bad. I would like to hit elephant, but I doubt I will.:madgrin::smokin:

 

It's all there on the thread. $175 for the harness and the computer is $530.

If you want cheap power with out all the fancy auto tuning and multiple maps, I'll be selling my rapid bike 2 after I have the rapid bike race installed.


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Here is the cumulation of all of our hard work and efforts. We did it!


http://rapidbike.us/products/2002-2009-vfr800-special-project


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The exact length of the stacks is a factor in tuning and needs to be adjusted in accordance with scientifik formulae, varying with rpms for any real benefit. Often factory-set length is tuned to boost a flat spot on torque or hp curve on some bikes.

Drag racers in the 50's were tunin with stacks.