Intreractive exhaust valve question

[1001yos]

What is the logic behind the position of the stock exhaust valve loading? Is it throttle position, timing, vacuum, ect... What dictates the percent opening of this valve, and can it be reprogrammed differently with ECM spy or other tuning software? I was thinking of creating a exhaust and incorperating this valve in the design. (purely to reduce sound to an appropriate neibhourhood level)

 

[nativeXb12Rbuell]

the stock xb12 muffler; the purpose of the exhaust valve on the xb12 muffler is to give the engine optimal back pressure during different rpms and differnent throttle positions for the what the ECM is programed for .by letting the gases flow through it faster or longer time building up presssure depending on if the vavle is open or closed...I.E stock is basicly for epa regulations(amount of sound) and best MPG,& and best HP &torque , also why the ECM is a Learning ECM(to a certain amount).the D&D and SpecOps only have a exhaust valve if built from xb12 muffler and of course the ones built from the xb9 muffler dont have an exhaust valve.

this is what the BUELL service manual says about the Exhaust vavle on the xb 12 muffler, and how it works...
the ECM monitors engine speed & Throttle postion while alternating flow paths between the chambers to adjust BackPressure optimizing TORQUE & HORSEPOWER for the riding condition.
For Example:
1. at low RPM with a wide open throttle, the valve is opened to reduce back pressure so the engine can gain RPM quickly. The exhaust enters the muffler & flows through the open valve into the chamber C( the front chamber) then exits.(through the exit pipe).(see Yellow arrow flow path)
2. in the mid-range, the valve is closed to increase acceleration Torque. The exhaust flows through pipe to chamber A(the rear chamber), around to the pipe going through chamber B(the middle chamber with the pipes)and then through Chamber C and exits (through exit pipe).).(see RED arrow flow path)

3. At HIGH RPM, the valve opens again to maximize HORSEPOWER. The exhaust enters the muffler & flows through the OPEN valve into chamber C and then exits (through exit pipe).).(see Yellow arrow flow path)


the D&D and/or SpecOps basicly only have one or two chambers & an exit pipe (see some of the pics in other posts of the inside of those mufflers )if they retained the valve if built from a xb12 muffler.

if you disconnect the valve to stay closed on a stock XB12 with Stock muffler you will not recieve the benifits of it building RPM faster at LOW or HIGH RPM like in examples 1 & 3 above, WHEN IT REALY NEEDS IT THE MOST . you will lose that TORQUE & HORSEPOWER at low & high RPM .like when at higher speeds and when coming out of a corner or off the line from a stop or from a slowing down going into a speed up fast.

-exhaust-valve-on-stock-XB12-exaust

and yes with ecm spy you can turn off the exhaust valve but I DO N0T Reccommend it with a stock exhaust (you would lose your torque when you need it most).

or any custom that i can think of (most any custom /aftermartket exhaust that stills has the valve in it usually doesnt use the valve and has it turned off because they're gutted or have baffles installed or re piped inside for performance.)



is your neighorhood picky/bitchy or what because in my opinion the stock exhaust isn't loud, unless wide open throttle.

 

[1001yos]

Very informative.

The logic for this valve is probably a little complicated, probably has an X and Y axis maybe? Is it possible to re-program this valve, or incorperate it into a semi-race tune?

I am a shift worker and leave the house at 0430. Not cool with the neibhours. I have to walk it down the road to start up. (Sucks!)

Right now, I have a GB exhaust and it is a little loud. I was thinking of riging up a valve for one of the outlets to control the sound a little. I don't want to give up the exhaust because... well... it's a GB exhaust.

I can afford to sacrifice a little power for a little ettiquette.

2010 XBR

 

[nativeXb12Rbuell]

Buells are RUTHLESS FOR A REASON,

A BUELL MAKE WON'T YOU ANY FRIENDS

here read this again
BOOK OF BUELL


f*** Ettiquette , if it is not above the decibels set by the local laws for noise pollution they can't do anything except bitch & complain, then just find something they do you dont like or against the laws, to bitch back about to them , & i bet they stop bitching. (most state & local laws are on state/local city/county websites if you need to find some)

BOOK OF BUELL

 

[nativeXb12Rbuell]

for the 2010 buells read theoctopus threads for remapping Flashing-a-Race-Map-to-ALL-Buells-08-too talk to him about 08+ years for remapping info he seems to be the man on that.