Does anybody know how Yamaha's new throttle bodies work?

[Petrovich]

Thanks for the link! This should help me out with wiring. I got the fuel pump yesterday, so hopefully I'll begin tuning this weekend, if I sort my ignition issues by then.
As for yamaha bits... Suzuki throttle bodies are almost double the price, for some reason...
Plus, those weird slide thingies are starting to grow on me

[nobbi1977]

The Suzi bodies are better spaced to fit on a DOCE manifold so the car guys love them, hence the price.

[smurph]

Those slides keep air velocity high. A variable venturi, so to speak. Look at the bottom of the black slides and you will see a air bleed hole there. As the air flow through the thottle body increases, a siphon effect is applied to the air bleed. This creates a pressure drop inside the pot that overcomes the spring pressure and raises the slide. The external tubes should not be connected to any vacuume source. Instead, they are connected to a filtered atmoshperic pressure air source (air box) and are there merely to keep pressure off the back side of the diaphram. The correct orientation of the throttle bodies is diaphram up, bleed hole down. In other words, the slide should raise, not lower.

The R6 injector is a nice unit. The slides should allow for the throttle bodies to be used on smaller displacement engines or engines that are not capable of the air flow that the R6 engine is. And it should make for easier tuning.

Also, spacing is not so much of an issue as each throttle body is it's own seperate unit. You and easily space them apart with bushings. I have made up a set of R6 throttle bodies that are properly spaced for an RZ350 here.

Steve

[FIntruder]

The R6 throttle bodies are CV, constant velocity. When you open the butterfly it gives the diaphram vacumn and the diaphram is what opens the slide. It only opens as much as the engine needs and is more accurate in the carburator world than direct pull or flatslides. This is the only bike I've seen with a CV throttle body set up. I'd like to know Yamaha's reason for doing this.

[ptegler]

All you need to do is read up on SU (Skinner Union)  and ZS (Zentih Stromberg) carbs to under stand this point. The reason I mention these two CV carbs specifically is you'll easily find 100's of pages on the net on how and why they work the way they do. They were all used extensively on MANY British and European cars.
Heck...for the SU carbs... you can even start on one of my own web pages about SU carbs
http://www.teglerizer.com/sucarbs/index.html
 
In short... a cv carb is more consistent than other carbs in regards to retaining atomized fuel in suspension. You don't get sudden air velocity (pressure) changes which can lead to momentary lean conditions and fuel puddling in the intake tract do to sudden opening or closing of the butterfly. 
 
Paul Tegler
ptegler@cablespeed.com (ptegler@cablespeed.com)
www.teglerizer.com

----- Original Message -----
From: FIntruder (beebispem@yahoo.com)
To: megasquirt-oem@msefi.com (megasquirt-oem@msefi.com)
Sent: Thursday, July 13, 2006 5:55 PM
Subject: Does anybody know how Yamaha's new throttle bodies work?



The R6 throttle bodies are CV, constant velocity. When you open the butterfly it gives the diaphram vacumn and the diaphram is what opens the slide. It only opens as much as the engine needs and is more accurate in the carburator world than direct pull or flatslides. This is the only bike I've seen with a CV throttle body set up. I'd like to know Yamaha's reason for doing this.



This post is at: http://www.msefi.com/viewtopic.php?p=130478#130478

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[FIntruder]

I guess what I meant by what Yamaha's reason for doing this was why on the R6 but not R1 or not by any other manufacturer. Does EFI react quickly enough so that a bog is avoided when the throttle is quickly whacked open?

[reelrazor]

It's all about keeping intake velocity high for inertial ramming at high revs.

That's a 16k rpm engine they came from. The R1 doesn't rev that high and so isn't benefitted(as much-yet).