Secondary Butterfly Questions

I was spending some quality time with the Rocket III service manual and came across the description for the second throttle stepper motor. In that description it states "The second butterfly optimises engine torque by maintaining intake air flow speed. It does not act as a choke for cold start purposes."

So I started to google search the topic and found that Suzuki uses the same for its bikes to increase torque and smooth throttle response.

Quoted from http://www.media.suzuki.com/svlaunch/fuel.htm

The engine incorporates the exclusive Suzuki Dual Throttle Valve (SDTV) digital fuel-injection system. The SDTV system uses a secondary butterfly valve in each 39mm throttle body to control intake area and maintain intake velocity, thereby smoothing power delivery, especially during the off/on throttle transitions encountered exiting a corner.
When the rider turns the twist grip, a cable opens the primary butterfly valve and moves the throttle position sensor.
The secondary butterfly valve is opened and closed by a new type of compact, lightweight DC motor controlled by a 16-bit electronic control module (ECM). The primary butterfly valve determines optimum throttle opening; the ECM reads throttle position and engine rpm then progressively opens the secondary butterfly valve to optimize intake velocity. The results are more seamless and more linear throttle response and increased low-rpm and mid-rpm torque

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Upon further reading from other sites much of the same reasons are given however I found on the 2005 GSXR-1000, Suzuki has added a second set of injectors just below the secondaries that spray at higher rpms.

Also found that the Triumph Daytona 600 has secondaries. Jamie I wonder if your 675 does.

The Caviga Raptor 650 also: "It now has a dual throttle valve fuel-injection system with secondary 39mm butterfly valves housed in each throttle body throat to control air intake and maintain air-flow velocity to match power output."

The logical arguement to these claims would be that if they don't limit power then why do they stay open in third, fourth and fifth gears? Well a potential retort is that torque isn't as big of a factor once your rolling at a higher speed, that is where hp matters. Right? So is it possible that the secondaries are in place to deliver more torque in the first couple of gears?

Does Triumph's use of the term "optimize" to mean smooth delivery or highest potential?

I know Tom can attest to the fact he felt more power off the line once they were removed. Anyone dynoed before and after? Are the secondaries just to smooth throttle response at lower RPMs and the other claims just propaganda? Do the secondaries increase velocity and help with fuel atomization? What was the origin of the 7% power limit?

I know Tom can attest to the fact he felt more power off the line once they were removed

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Speaking with Wayne from Tuneboy... He reckons it is a mistake to remove the secondaries. They are there for a number of reasons, NOT just to slow the bike down! Even when they are removed the mapping system thinks they are still there and delivers fuel etc as if they are in place! The fuel mix is different in first and second. I think you are on the right track here Pigman!

I know I'm exhuming an ancient thread here, but since everyone here seemed to agree that eliminating the secondaries (by removing them physically or via the ECU with Tuneboy/Tuneecu) is a no-brainer performance mod, it was one of the first things I did when I got my '06 Classic a year and a half ago. The bike had D&Ds on it and, once I installed a suitable tune (I believe it was 20050), the bike had the awesome power you guys all know about, easily lifting the front end (a time or two unintentionally with the wife on the back-she wasn't too thrilled) and smoking the 240 at will. This was all with just an underseat K&N (ductwork on bottom of seat removed) for the intake. It was, however, way too loud for me so I opted to sell the D&Ds and reinstall the stock mufflers along with a cat-bypass and proper tune. This was also much more suited to the RV campgrounds we stayed at throughout this past summer. Using TuneECU I've switched a time or two between enabling and disabling the secondaries, and what I've found is that (and this is only a seat of the pants observation) with the secondaries enabled, the beast seems to have more torque in the first 3 gears at the lower rpms I usually ride in (2 to 3.5k, especially when 2-up). Is this actually true? I plan on keeping the current set up, not going with triple K&Ns or high performance (and noise) pipes, and aren't looking for best quarter mile times. Oh, and I also like the additional engine braking with the secondaries enabled. Any input is, as always, appreciated.
Vin

Interesting discussion.

I planned to reinstall my secondaries for another reason. Without the secondaries I get a chirping noise during the excellartion. It's a nontypical sound for a motorcycle and I dont like it at all.

think if I will correct the secondaries I have still the possiblitie with TunECU.

But to learn that is eventually consuming power - well thats different to all what I read before.

I will keep a eye to this particular thread.

Secondaries removal DIY

I noticed absolutely no real change in power with my secondarys removed"seat of the pants observation" it just seemed to have a smoother throttle response is all.
The GIpro/atre on the other hand woke her up down low because of the ignition timing being changed to that of the higher gears "from what i understand anyway"
and its those first three gears that wher restricted 7% because of this .
not because of the secondarys . removing them adds no extra power i think those that report more power from removal just have a vivid imagination lol

Very interesting. I removed them at the same time as installing a GiPro and commented at the time that I wasn't able to tell which mod did what. But the bike did have more power in 1-3 and most definitiely had smoother throttle response. By smoother I mean more direct; it did exactly what I said, when I said it. I'd probably rather not mess with putting them back in as I'd hate one of the screws to come loose - having been out and put back - but would be very interested to see what Rayvin and Hardy find out.

Evil Mitch said:

The GIpro/atre on the other hand woke her up down low because of the ignition timing being changed to that of the higher gears "from what i understand anyway"
and its those first three gears that wher restricted 7% because of this .
not because of the secondarys .

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Now that makes more sense (seat of the pants sense) to me, Mitch. Is the GIPro the easiest way to change the timing in gears 1-3 (other than getting a PC5), or can I do it with TuneECU?

And yes, what Mitch said. The GiPro unlocks the 7% by 'fixing' the timing. Neither mod actually produces more power and until now I hadn't heard that removing (or eliminating) secondaries could have a negative effect.

Let's not forget that this thread originated in 2006. Not sure if that makes Wayne's comments to SteveRed in post #2 (regarding the mapping) moot since we now have TuneBoy/ECU, etc. to modify the fuel mapping. No?

Rayvin said:

Let's not forget that this thread originated in 2006. Not sure if that makes Wayne's comments to SteveRed in post #2 (regarding the mapping) moot since we now have TuneBoy/ECU, etc. to modify the fuel mapping. No?

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Exactly! simply removing the secondaries does not change the fuelling. If the ECU thinks that the throttles are opened 60% then it will supply the appropriate mixture for that. Using TuneBoy or Tune ECU then the proper mixture can be supplied . Having said that I know there were quite a few that removed them and reported power gains with no ill effects.