Hello everybody,
I just like to mingle in into the discussion about variable air stacks or velocity stacks.
Also in answer to some remarks that are made on this topic.
With these few typed down words and lines I like to explain, and hopefully enlighten, the public a bit about this matter.
And hopefully it clarifies some questions about them, why should you install them and how they work.
First the question, is there a real need for variable air-inlet stacks, or velocity stacks.
No. (period, point, the end, etc.).
Variable velocity stacks are just a way of making an already fine engine breath and therefore perform even better, should you want to.
You see sir? Should YOU want to!
If you are happy with how things are now, then leave it there and be happily on your way.
For those who are ready for more power and want to get more of that out of their trusted, but in fact somewhat tamed steed, read on.
I was reading the following remark:
Does Yamaha leave things out when they don’t install variable stacks right from the factory?
I think not. This is a personal thing, as all modifications, farkles and/or improvement attempts are.
Yes, Yamaha installed these stacks on the R1 and R6 models, but that are motorcycles build with a race track in mind. Simply said they are build for one purpose only.
The CP03 engine obviously is not designed with 1 purpose in mind, but a variety of them.
This engine is designed to perform well from slightly above low, through mid and halfway under high RPM.
With the possibility to tweak that a bit so it will serve a wide array of purposes and therewith attract a wide array of customers.
By this way the manufacturer can make a competitive motorcycle, at a competitive price range.
If they would install a system like the one on the R6, then you also need a minimal 8 or more (mostly) non-sensible “mode settings” on top of the 5 ones that (usually) are already there.
Witch will make the bike (at least) €1000 to €2500,- more expensive then the competition.
All because of a system that the main public does not understand or does not actually need.
I think if you where a bike builder, because of that reason you would leave it out too.
And leave it to a few enthousiast who like to get things a bit further, at their own expenses.
Now for a couple of details, because that is what we are looking at in this matter, details.
Number one is the detail in “perform well”. That means they do not “perform at their best”.
Why is that? Because of the fixed air intake lengths.
1 long, so 1 cylinder performs well at low RPM.
1 middle length, so 1 cilinder performs well at middle RPM
1 short stack, so 1 cylinder performs well at high RPM.
You can visualize it as a cart pulled along by three horses.
1 is a sturdy pulling workhorse, the second is a race horse, and the third is a pony.
For all three RPM ranges there is a horse (or horselike animal) available.
Sounds good, don’t you think?
Well…. What it really means is that no matter at which speed the cart is going, or witch horse is doing the work, it is always just 1 horse that is actually pulling the cart.
The other 2 are either drinking fuel or just farting along.
When you make the air intake variable, you can create an environment where all 3 cilinders perform together at the same time, and (with some tuning) possibly perform at there best, for at least 2 of the RPM ranges
So by this way, 2 of the 3 horses are transformed into strong pulling horses (1 was already there)
And therefore use the strength of the three horses, to pull at the same time.
That is why you see a greater effect in torque than in actual HP.
Variable stacks have to be told when to act, so there is another detail.
At which point in time do you want the stacks to do there magic? Well, that is up to you.
You like to go out and have fun on a race track (or imagine you are on one)?
Then maybe you need them to open at the RPM point where you like to shoot yourself out of a turn or corner, into the next straight.
Or if you are a touring person with some occasionally wild idea’s, maybe opening them on a somewhat lower RPM level will do the trick for you.
In other words, it needs some tuning and testing to fit your personal needs.
Another detail is in the air/fuel mixture. After many tests it is becoming clear that with these stacks in long position, the mixture has to be slightly more rich than stock or standard setting.
When the stacks open up, they need a little bit less fuel than the stock or standard setting
That means that if you use the CP03 engine for commuting only, combined with variable stacks witch are tuned to open above a certain RPM at, let’s say, 100 kph. With some distance of highway traveling, it wil cost you a little less fuel.
(NOTE: A little means a little. It does not mean you will save enough money on fuel in 1 year to pay back for a variable stack system…)
So you see, there are more options than you might have first thought.
There are more details you need to look at in order to get a properly working variable stack system, but sorry, those are designer secrets…
So, in short:
Does it work? oooohhh YES!
When does it work? anytime YOU want it to.
For now, That’s all folks….
Greetings from the designer of these variable velocity stacks,
My name is Danker.
