Secondary Butterflies

[Steve in Sunny Fla]

any part of this discussion that deals with maximum power over 5000 rpm is pointless.  We are not talking about building peak power, we're dealing with lower rpm rideability, and maximimizing power in that range.

 Anyone who is posting to this thread and is pointing out peak horsepower gains at peak rpm is simply not in step with the discussion, and is conflating the terms for some unknown purpose.

  And yes, factory design is always the best. What was I thinking... apparently i'm     steve

[maxtog]

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.

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?

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

It is not just the nature of a sports-touring bike, it is the nature of most all bikes now.  I had similar problems with my old carburated ZRX-11.   A new jet kit instantly recovered considerable power that was sacrificed by the engineers to meet regulations (and whatever other goals they had).   My solution to the same problem on the C14 was a reflash...  and it exceed my expectations.  For others it is a flies removal + PC.   Both have different advantages and a little different outcomes.  And some people don't care at all and are perfectly happy with the way the bike is, stock.  That is fine too, and is certainly the easiest and cheapest option.  It is nice to have options/solutions.

[Deziner]

  Max! How is anyone supposed to argue with that?  What were you thinking?

[B.D.F.]

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 have no horse in this race and am not selling any of the products or methods available, my only goal is to provide information that may be useful to some reading through these threads.

We seem to love our urban legends regardless of the fact that they are often wrong, and that they actually make no sense from a casual observation, such as 'hot water freezes faster than cold water', 'higher octane fuel makes more power than low octane fuel' and so forth. More power by restricting the intakes falls into the same category. My only interest here is to point out  a bit of logic and science, not cast an opinion on anything anyone wants to do to his / her motorcycle. Absolutely nothing wrong with re-flashing the ECU as far as I know, and a lot of people seem quite happy after having that done to a C-14 but twisting reality until closing the secondary throttle plates ('flies') will produce more power than directly compared to having them wide open or removed is moving into fantasy land.

Brian

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>

[VirginiaJim]

Many years ago a 'plumber' attached an ice maker for my in-laws.  What made it strange for me was that he attached it to a hot water line...  I even mentioned that this just didn't seem logical to me but they trusted their 'plumber'.

[MAN OF BLUES]

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 [...]

[xxx]I ve been above 150 mph so many times on this bike, I can truly say, the induction system, I.e. ram air, in combination with the VVT is actually what Kawasaki attempted to do right.. Come up to ohio [xxx] and I'll run my stone stock 08 on ya.... better practice your launch

[Deziner]

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.

[Deziner]

Before some of you rebuke some of what I said, I skipped over the whole part of valve timing and overlap and how it relates to the airflow requirements. None of the high performance vehicles I was involved with had VVT. Ah the variables......

[B.D.F.]

Higher velocity results in lower fluid flow. There is no way around that one, and velocity is not the goal, fluid flow is.

The problem with too large a carburetor is that the flow through the carburetor becomes too low to draw adequate fuel and the mixture goes lean, resulting in what feels like bogging and definite power loss. This is why carburators include an acceleration pump, to compensate for a sudden increase in throttle resulting in a lean mixture. None of that applies to fuel injected I.C. engines though as the correct amount of fuel is simply injected, under pressure, on each full cycle of the engine (w/in two rotations the mixture is corrected) into the airstream regardless of flow, velocity or pressure drop. The venturi effect is simply not needed in fuel injection, which is why throttle bodies can be bored larger without any performance loss or hesitation.

Again, track down Son of Pappy's (his name is Chet) posts on this very forum about changing the throttle bodies on a C-14 to ZX 14 T.B.'s; the result was a power increase across the entire range of the engine's power-band without any detrimental effects that he could detect, all due to the far superior behavior of F.I. over carburetion.

Brian

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.

[datsaxman@hotmail.com]

...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!

[Deziner]

...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.

[Deziner]

And unless we are talking about direct injection, which the C14 does not have, diesel is entirely different. There is no fuel in the intake tract of a diesel, only air. The gasoline on a C14 is sprayed into the incoming air charge, not directly into the combustion chamber. Welcome back to the stone age 

[Steve in Sunny Fla]

and of course, total lack of comprehension about cam timing issues, just bigger is better. WOOHOO pull the throttle bodies off and run the fuel pump right into the ports, that ought to get us some better low end torque!

 

Steve

[Steve in Sunny Fla]

Let me take another stab at this.

 assume we can develop 1" vacuum at wot on the primary plates at a given rpm, in this case lets say 4000rpm with the flies opened as much as possible, but no more . Brian continues to argue that the secondaries, if causing a restriction would lower the power, so let's use a real number, 3" vacuum. So 1" vacuum will make more power than 3" vacuum. I'm contending that opening the secondaries just enough to get the 1" vacuum achieved by the primary throttles but no more open than that could actually pay off in power gains, depending on back flow issues due to the cam timing. in fact I think there may be points where the secondaries can help trap reversion and actually slighlty pressurize the intake port.

 This has been my point all along. somehow we cycled back to the "more is better" theory of tuning without considering any other issues going on in the engine. Steve

[B.D.F.]

Yeah, in the end, F.I. gasoline engines do behave more like diesels in behavior if not actual mechanics. Diesels differ in that the flame front propagation is limited by the fuel and therefore cannot be too lean but in practice, adding the proper amount of fuel to the actual airflow through a gasoline engine does have a similar effect.

Of course even a thin fluid such as aid does have inertia and this leads is the reason to limit the venturi area of the intakes. But for the purposes of this discussion (secondary butterflies partially closed produce more power) this can be dismissed, especially regarding street vehicles. The ram air effect is dubious in a lot of racing vehicles too, and those engines producing great power are always artificially induced anyway, not normally aspirated.

It really is too bad Kawasaki neutered the bike though as it is superb IMO as a stock, 1,400 cc engine without the artificial muting provided by the secondaries.

Brian

...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!

[martin_14]

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.

I can't follow these statements. How would higher velocity reduce volume? Did I miss a class on Bernoulli's?

And why does velocity matter for the atomization of the fuel? That is critical for carburators, but as far as I understand, the fuel is atomised by the injector, whereas the charge is more homogeneous with the proper design of the intake tract and the combustion chamber/piston shape, which induce swirl and tumble. Velocity helps the distribution and homogenisation of the charge, not its atomisation. And a perfectly homogeneous charge is not always desired, as the flame front starting around the spark is not as fast as people think.

All in all, I read here how speed is important, volume, pressure, etc, but the only important thing you need to put into the cylinder is mass. Molecules of air, which are the ones that are going to combust. How you get it there is the discussion, and for that we make use of compressors, turbos and whatnot.

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.

[VirginiaJim]

Masochist?

[Rembrant]

Masochist?

Haha...every time I hear that word I think of Lapchink? from the Gumball Rally (1976-ish?).
He was riding the old Kawi 400 triple "2-smoke" and kept crashing...
The two old guys in the Benz said "I do believe that man Lapchink suffers from a severe case of masochism".
LOL.

[VirginiaJim]

Of everything in that movie he is the one I remember the most and can still see his expression before he runs off the road into a tree.  Thanks for that.

[B.D.F.]

Well, what if you sold something that altered the behavior of the 'flies.... would it not then be beneficial to state that your modification was better in some way? Perhaps you are using too much science and fact when a little shilling would explain everything? 

A while back, the people who wanted better low- to- mid range performance from a C-14 pulled the 'flies and added a Power Commander. Along comes a gentleman who can put new software in the ECU to open the 'flies sooner but he could not open them all the way, all the time (simulating actual removal) because that would engage the fast idle cam on the secondary throttle rod linkage. So he makes a compromise and opens them sooner but of course not all the way until the engine is turning very fast and under heavy load, just like a stock bike. Initially people found this to be a significant improvement, somewhere between the behavior of the bike stock and having the 'flies removed.

Now after a while, the folks selling the re-flash want to sell more of them and they have a shill walk through the town, ringing a bell and stating that leaving the 'flies in and restricting the airflow is actually BETTER than removing them. Why? To increase sales of the re-flash of course.

Now there are new folks looking to enter the C-14 'farkle' market and are trying to find something to sell. Looks like that may be some type of secondary 'flie "twiddle". The end result is that we have another shill stating that closing the 'flies is 'better' than removing them..... and of course he will be happy to sell everyone some of this better method.

Some of you guys are trying to understand what is happening here by using Bernoulli, Boyle, physics, logic and facts while the true explanation lies with Elmer Wheeler.

Brian

<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.