***** Secondary Butterflies ReVisited *****

tahoeacr also did it. You can find it by searching advrider. He removed the spindle and the stepper motors as well, so...error light.

Actually, I did it on my wife's Ninja 650. But, it's the same engine in the Versys, w/a bit of fiddling, so I figure it'll have about the same effect. It made a nice difference on the parallel twin. The low-end is a bit fuller, and notably smoother. Throttle response felt sharper, as well. It made a monster difference on the ZX14 and Concours 14. I hear it helps the litre bikes, but I didn't mess w/those when I had 'em. Also, FWIW, the Versys is the best balanaced street bike I've had (And that's a bunch of them.). It ain't cool, fast, slick, impressive, or anything else. It is incredibly well balanced, versatile, comfortable, and economical. It's just easy and fun!

I obviously did not dyno it, BTW, so I have no hard numbers. This bike is not worth that to me. If I can please my seat-of-the-pants dyno, that's all I need to do as a street rider. It's worth it on the little 650 twin. However, I did lose about 4-5 mpg w/the 'flies removed, PC/map, air filter, and a slip-on. YMMV, as always.

Removing the secondary butterflies has multiple effects. Understand that it all depends on the dynamics of the opening/closing of the 'flies. Removing them may increase throttle response at rpm/gear positions where the butterflies are mostly closed to reduce noise, mainly in the lower half of the rpm range (I'm making an assumption on the SD as I don't have any data logging to tell when and at what rate the secondaries open). The down side of removing the 'flies is that it will create a momentary lean condition at large throttle openings at low rpm due to slower intake velocity and if the FI map is not set to compensate by injecting extra fuel. Also, removal of the flies usually results in the loss of top end power due to turbulence in the intake stack. The butterflies help straighten and smooth the intake flow. We saw this most predominantly on the GenII Yamaha FZ1, where the secondaries were primarily closed until 6K rpm (as seen through real time data logging) and didn't open fully until 8K rpm. In short, the bike was flowing enough air to make any more power than a moped until 8k rpm, resulting in no power or torque until the top of the rev range - total EPA. Removing the secondaries resulted in the aforementioned lean conditions as well as a loss of 4 hp on the top end; the final solution was smaller diameter secondaries and a new map. This preserved the intake flow airspeed at low throttle openings but increased flow to give better response below 8K rpm, as well as preserved gains in top end power. This was a chief factor in taking that bike from a factory 127 rwhp to a modified 149 rwhp with a much fatter torque and power curve. I can personally attest to the effect: before the butterfly mods, my FZ1 would not pull a power wheelie in second gear; after the new butterflies and map, I damned near looped it just by whacking it WFO at 6K.

I've been pondering the butterflies, now that I've got the new Hooligan airbox on, I think it's time to start experimenting with smaller diameter plates. Until then, I'm keeping my secondaries in place until I know better how they're working on this particular bike.

I think there may be gains to be had here. I dont belive removing them all together is the best thing, the constant velosity feature has its upside. I think that idealy being able to alter the timing of the secondarys would be best but Im not sure thats posible with the tuning tools curently available. I think Zen's method of changing the shape of the 'flies may be a good place to start. I also think this is where the accelerator pump feature of the PCIII could come in very handy.

Thanks for the input. That's pretty much the gist of the original ZX14 discussion. It also seems to hold true for the other bikes. I took into account that I rarely whack the throttle open at lower rpm's (Or any rpm's, for that matter. Sacrilege, I know...). I am a street rider, and I don't hooligan/stunt. "Smooth" is my goal. I'll ride way too fast, and lean way too far, but I rarely rip the throttle. I figured that'd take care of any real concerns for the 'flies out/no PC lean issue.

I know it's not perfect, but I just can't see these things being that fragile. I've been riding a long time now, for a lot of miles, on a lot of bikes. I've just never seen these catastrophic failures everyone warns of. I know they can happen, but I think it's a rarity, and in very extreme situations. You, however, obviously have much more technical/mechanical knowledge than I (As does most everyone.). Do you disagree, under those circumstances? Or, more likely, do we just have to wait to see it on a dyno?

Chris

I think we're on the same page. Liking smooth and progressive riding, I think the issues are a bit unique for me (And others, I'm sure.).

Thanks much. Keep us posted. I'm always interested in the latest and greatest...

Zen - that was kinda like reading a novel then finding the last page missing!

Do you no what the outcome was of the tests and how much smaller the plates were?

S.

Let us knoe how you get on .

any news about the modification of the flies?
i had a 05 sd ,with bmc ,akra and akra map(dont know which one).
the bike also had the flies off.
the way the throtle responding was adorable!!!no jerkiness ,no coughing fronm the efi,very smooth all the way from 0 to max rpm...
the bike sold(due to a car crash),and im going to buy a standard 05 sd with no aftermarket installed(fillter,akras,etc).
should i start from the flies removal?or should i wait until the filter,akra+map improvement?
looking forward for an answer

Got the bike back and went for a brief ride. It is definitely smoother; revs quicker; and the power seems a bit fuller. The sound is also nice. I normally roll the throttle open to some partial throttle position. I rarely go WOT, and I almost never rip the throttle open. For these conditions, the bike runs well. If you get on the throttle hard and quick, a PC would definitely help. For now, I'll leave it like it is. I've been spending money, and time, like a madman lately. A PC is probably in the future. There's no fear of damaging anything, as it is, IMO, however.

For anyone interested.