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V-Boost Modification:  

More Links:

Schematic of a V-Boost Switch Schematic of a V-Boost switch with Diodes
DIY Adjustable V-Boost Timer

To Boost, early or not, that is the question.

Back a couple years ago, I developed a "State of the Art" V-Boost controller for my V-Max. The system entailed a microprocessor and a LCD screen and three button interface. 

Here is a Power Point Slide Show I put together

Although the prototype looked a little rough, it worked and worked exactly as planned. I had a little fun with the screen information (see the slide show). 

The unique feature of this unit was my ability to program any opening RPM and scale the opening to the next entered RPM. In other words, I could start to open the V-Boost at 1500 RPM and have the butterflies go wide open at 3000 RPM or have it go wide open at 6000 RPM. Any setting I wanted. This unit also had a shift light and rev limiter built into it.


I also used a Analog Devices linear accelerometer chip to record the G's pulled by the bike. The accelerometer recorded 2 axis up to 2 G's in .1 voltage increments. I never took the time to convert the voltage output of the accelerometer to actual HP readings. I just instructed the microprocessor to look at the voltage output of the accelerometer chip and record it in 50 RPM increments during each run. In my circuit, a higher recorded voltage corresponds to a higher G reading. I used this to determine if the V-Boost settings made a difference. 

After 6 months of testing this unit, the best setting I could find was to start opening the V-Boost at 5050 RPM and go wide open at 7.5k RPM. Only a slight difference from stock. The 3k to 4k settings (diode modification "T" input from adjacent coil) actually made my bike loose power from 3k RPM to 6.5k RPM verses stock settings. Something I must stress, I could only record this difference in a short shift or 5th gear roll on. Under normal race conditions, stock settings pass so fast in first gear the V-Boost almost does not have time to fully open by 8k RPM. When you shift into second gear, the servo keeps up with the engine quite well but you don't dip below the stock opening of 6k RPM when you shift from the bikes red line of 9500 RPM. I found that if you short shifted into the next gear or rolled on the throttle from cruising,  there was a pronounced loss in power recorded from 3000 RPM to 5000 RPM if the V-Boost was even slightly open at those RPM's. The bike felt about the same, but the recorder said differently. 

Here is a gear chart I fooled around with. It may or may not be right, it looked pretty close to what I saw happening on the bike but its not perfect.

My personal opinion of moving the settings from stock made the bike a pain in the ass to ride at times. Having the V-Boost open at anything prior to 4500 RPM didn't appeal to me, especially on a curve in the rain. Although this little kick is fun at times, it can be annoying when you don't need it.  With respect to other V-Boost modifications out there, if you like the modification and think its of some advantage, then enjoy. Hey, its your world. There may be an instance where opening the V-Boost early will help. The stock V-Boost system was well designed from the factory for the carbs to work in synchronization with volumetric efficiency and valve timing of the bike at any given RPM. Seems the major problem is the Mikuni Constant Velocity carbs may get a little out of whack when you have two feeding one cylinder at RPM's below 5k. Opening the V-Boost cuts the draw through one carb almost in half. Now you have changed the needle position with a CV carb. You do this at the wrong time, everything gets screwed up unless its engineered for it to function this way. My experience leads me to believe its a waste of time to even wire a Modification to a bike. It may help or hurt on a bike modified differently than mine, but I have my doubts. Stock carbs are stock carbs! After much testing, I found the very nice C2VB controller I made would be way too expensive for the benefit and dropped the project. I don't feel right selling something that is flashy, but really is no benefit to performance other than a shift light. I may dig out the unit and see how it works with a full blown Stage 7 and bored V-Boost tubes. For now, if your bike is stock, save your money and your time! Leave it alone!

If you want to venture out and try this one yourself, you could build your own V-Boost timing signal simulator with a few components from Radio Shack, click here.