For those who think they're smarter than a team of dedicated powertrain engineers, the secondary flies are there for a legitimate reason, or manufacturers wouldn't have spent the money and R&D to incorporate them.
What's going on here is some folks want to alter the nature of a sport-touring bike by making it a sport one. Nothing wrong with that, but every such change has consequences, even if they don't know which ones
I don't think any of us are claiming to be smarter than the engineers who designed in the secondary butterflies. The engineers had to play by rules, and those rules are not "give the bike maximum performance", they are more like: "make the bike 'safe', comply with noise, emissions, and power regulations, and be reliable". And am I sure they met those goals admirably, and those are certainly legitimate reasons (and they can't sell a bike that doesn't meet most of those, anyway).
But OUR goals as end-users are often a little different. Perhaps something like "without making the bike too unreliable and without going overboard, how do we reclaim power that was sacrificed for those other goals?" And we know for a fact that power and response was lost. Is anyone actually arguing against that?
<snip>
It strikes me that some are arguing against exactly that, somehow linking secondary butterflies being present and to some degree (no pun intended) restricting the intakes and actually making more power. And I am not arguing, in fact I am not actually responding to anyone in particular [...]
I understand what you are saying, Brian. To a point. If the entire area of the intake tract is not needed to carry the volume of air required by the engine, reducing the area while flowing the same volume of air will cause the air to flow faster. It's why automobiles use dual plane intake manifolds. At lower rpms the smaller ports create a higher velocity. When the rpms increase, the larger tracts come into play to be able to provide the necessary air flow. A single plane intake will absolutely produce more power at higher rpms but at the cost of lower rpm torque and drivability. Think of your engine needing X number of gallons per minute at any given rpm. Call rpms Y . As Y increases, so does X. As Y decreases, so does X. The volume needed is not constant, but you do want the pressure (velocity) to be constant. The size of pipe required to provide 1 gallon per minute at 30 psi is far smaller than one needing to provide 10 gallons per minute at 30 psi. At 3k rpms, an engine requires far less air than at 10k rpms. At any given rpm, higher velocity is preferred, as long as volume requirements are being met.
I have no idea if this makes sense to anyone but those of us that have put too large of a carburetor on a vehicle only to experience a loss of performance. I've been there, done that.
...or you could just ask me. I HAVE Chet's old bike (Silverdammit!), along with a less-modified C14.While higher velocity will reduce volume, the lower volume only matters if the volume is insufficient to meet the requirements of the engine. The same volume isn't required across the rpm spectrum.
Silverdammit! has more power EVERYWHERE, right from idle. Period. SO MUCH more midrange. And then there is the mad rush that starts about 5500rpm.
We wonder how I keep my license...40,000 miles last year between the two C14s.
The need to keep air velocity high through the carburetor venturi is not needed with FI, so carb tuning tricks are irrelevant here. With carbs, you are tuning a resonant cavity to keep velocity high. FI is a lot more like diesel, which has no throttle at all (using the word carefully, a restriction in the intake tract) . Wide open all the time, with fuel being metered by the ECU according to demand, engine speed, etc.
Welcome to the present!
...or you could just ask me. I HAVE Chet's old bike (Silverdammit!), along with a less-modified C14.
Silverdammit! has more power EVERYWHERE, right from idle. Period. SO MUCH more midrange. And then there is the mad rush that starts about 5500rpm.
We wonder how I keep my license...40,000 miles last year between the two C14s.
The need to keep air velocity high through the carburetor venturi is not needed with FI, so carb tuning tricks are irrelevant here. With carbs, you are tuning a resonant cavity to keep velocity high. FI is a lot more like diesel, which has no throttle at all (using the word carefully, a restriction in the intake tract) . Wide open all the time, with fuel being metered by the ECU according to demand, engine speed, etc.
Welcome to the present!
While higher velocity will reduce volume, the lower volume only matters if the volume is insufficient to meet the requirements of the engine. The same volume isn't required across the rpm spectrum.
And velocity absolutely matters. The higher the velocity, the better the atomization of the fuel and the better to fill the cylinders. X amount of air will flow through an intake tract, add a supercharger and that flow is increased. Why? Because the velocity increased. The intake tract got no larger, yet the volume going into the cylinder increased. The vacuum of a naturally aspirated engine drops drastically when the throttle is snapped open then increases as the rpms increase due to the sudden decrease in the velocity of the air, not due to lack of volume.
Masochist?
<snip>
And I really, really want to know what the secondary flies role is in all this, other than neuter this wonderful 1400 cc beast to make it (perhaps?) more drivable, tree-huggers compliant, etc. But performance? Torque? HP? I still don't see it, and since I don't understand much of it, I keep reading what you guys write.