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Discussion Starter · #1 ·
2010-2012 z1000/or ninja;slip-ons or full exhaust,when you install an aftermarket exhaust your also removing exhaust valve:confused:,my question, is the valve more for passing noise emmissions,or is it for changing volume of mufflers,i.e.as to change the torque curve of the motor:confused:....and also is it tied into the ECM through the secondaries/throttle position,or is it a stand alone system,for noise only:dontknow:...any Tech,please chime in on this:D
 

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If im not mistaken, the valves are there for backpressure. When the rpms are low, you need more back pressure to still have decent power. More rpms and there is less back pressure needed due to the flow of more exhaust:2cents:
 

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Discussion Starter · #4 ·
If im not mistaken, the valves are there for backpressure. When the rpms are low, you need more back pressure to still have decent power. More rpms and there is less back pressure needed due to the flow of more exhaust:2cents:
THX,but I need more specific info,if everyone is putting slip-ons,or full exhaust on these bikes that have an exhaust valve,and spending $500 to $1000+,just to find that they possibly Killed the low-end,mid-range grunt ,hopefully there is a "Tech Guru" on this forum that can explain the workings of this valve,and the pro's and con's of removing it.
 

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Think of the exhaust system as a tuned port in a speaker box. Different size speaker boxes have different resonant frequencies. An internal combustion engine is nothing more than the musical equivalent of a speaker that moves air. All air has a frequency and an amplitude (a waveform). An engine is capable of producing a wide range of frequencies and amplitudes (rpms and load). The exhaust valve is nothing more than a variable port in that speaker box. It can alter how the waveform travels up and down the exhaust pipe.

If you can time the negative waveform to hit the combustion chamber during valve overlap, you can suck in more air quicker (increasing volumetric efficiency) and increase your power. Since the engine changes rpms, the exhaust valve tries to change this timing so that the waveform will hit the combustion chamber across the rpm range. This increases power across a wider powerband.

Removing the exhaust valve prevents you from having the ability to alter the timing for more power everywhere. This is fine on a narrow powerband race bike, not so fine on a street bike that needs to be more versatile.

Basically, you will lose power somewhere when you remove it. Where depends on the camshaft profile and ignition map.

Removing it actually gains you nothing. If you THINK you feel more power when you remove it, it is because you lost power somewhere and by comparision it feels like you gained a HIT. You really, really did not. The dyno has never lied on this subject.

There's a whole lot of interaction between multiple components in the power equation. Slapping on an exhaust and hoping the ECM or PC will compensate is usually just pissing in the wind without taking the intake, heads and cam timing into consideration as well.
 

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Discussion Starter · #6 ·
X1Glider,I understand and agree with what you said,too bad no one on this forum has done a dyno pull,showing results "Before & after",either with slip-ons or full exhaust:dontknow:
 

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well said glider, its almost as if your adjusting the manifold pressure towards the rpm level, always trying to find the best mixture of fuel and air that will deliver a positive pressure towards the rotar blades which give you thrust. just some airplane talk
 

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Motorcyclist put on some Akropovic slipons and they should be reporting dyno results before and after. Most all high end Aftermarket exhaust manufacturers have "tuned" their exhausts as you say, and post the charts. I say buy a good one like Yoshimura, Akropovic, Leo Vince and maybe even Two Brothers, they are almost all track tested technology boosting performance up to 7% accross the range - horsepower and torque - some even with silencers installed!

I'm getting the Leo Vince EVO-II 8496 for my Ninja 1000 (SX). maybe [email protected]#$#%
or the Akrapovic GP Dual Megaphone - really cool looking too
or the Vance Hines CS1 Black, really affordable, no dyno tuning info.

I'll be her more after this week . . . My Kwak will be ready then!:)
 

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Let it be noted, an exhaust system on it's own does very little. You really need a new ECU map to take full advantage of the better flow.

Slip on's really only serve the purpose of more noise and in the Zed's case, doesn't do that all that well because of the giant collector underneath.
 

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I've removed them from both my second and third generation and have noticed no significant power loss or gain. I just like the sound the slip ons provide over the stock exhaust.
 

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Most mods only mention peek power gains. Few tell you that the bike lost power down low, caught up with stock in the mid range and gained a few hp at red line. That does not sell parts.

Thats pretty much exactly what you get. Yoshimura and a few others will actually show a dyno sheet on their website. Usually you get a significant weight loss though.
 

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You just bridge it out so the ECU thinks it's open all the time.
Isn't there some sort of cam that you can replace the hex-shaped gear that's on the servo that opens up the valve? When I had my M109R the new exhaust came with this cam so I could keep the servo motor installed and not have to jump any connectors to trick the ECU. If this cam doesn't exist, what is necessary to jump the connector?
 
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