Exhaust valve disconnect - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
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post #1 of 9 Old 06-13-2014, 06:06 PM Thread Starter
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Exhaust valve disconnect

Has anybody disconnected the exhaust backpressure valve yet?

I would think it would increase performance a little, and increase the noise a little.

Jim
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post #2 of 9 Old 06-13-2014, 07:46 PM
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You will get a check engine light and one or more of the following Diagnostic Trouble Codes:

P1657-L EXCVA position sensor low voltage
C46 EXCVA position sensor circuit malfunction

JohnB

2015 BMW F650GS
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post #3 of 9 Old 06-13-2014, 09:35 PM
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Quote:
Originally Posted by Jim McFaden View Post
Has anybody disconnected the exhaust backpressure valve yet?

I would think it would increase performance a little, and increase the noise a little.

Jim
It may increase gas flow at high rpms, but you may find low rpm performance adversely affected. The valve is similar to the one fitted some years to the Gen I FZ1 and it wasn't there just for noise suppression.
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post #4 of 9 Old 06-13-2014, 10:18 PM
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Can someone please explain what the exhaust valve does?

pmk
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post #5 of 9 Old 06-14-2014, 12:32 AM
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Quote:
Originally Posted by pmk View Post
Can someone please explain what the exhaust valve does?

pmk
It acts as an exhaust system tuning device by altering the back pressure. You'll find a lot about it, but a lot of that is misinformed forum posts regarding noise and emissions, often based on stories from dealers who want to sell after-market full exhaust systems

The system was first used by Yamaha in the pre-R1 days and also used by Honda later. This Wiki link is the best description of what it *really* does that I can find:

Four-stroke power valve system - Wikipedia, the free encyclopedia

If you were prepping a bike for the track where low end is of little value and improved top end is the target, then removing the restriction would be logical. However, for a bike where low and mid range is a positive benefit, such as the Vstrom, it makes no real sense.

Last edited by Santah; 06-14-2014 at 12:37 AM.
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post #6 of 9 Old 06-14-2014, 10:16 AM
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One of the probs with switching to an aftermarket has always been that low end. Ie; you will get a lot of slow down burping and also missing when idling thru town. Carbs was fiddling with the right idle jets combined with main jets. And that could take a lot of fiddling for the back yard mechanic. Injection involves an electronic control unit flash and, sometimes, Power Commander. If this is the easy fix for all that, mine will be staying in.
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post #7 of 9 Old 06-14-2014, 01:43 PM
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We need someone with a well placed GoPro to video the valve opening. I know it's shut for low end torque, but it would just be interesting to know when and see it open under ECU control.


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post #8 of 9 Old 06-14-2014, 06:46 PM
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Very interesting technology. Here's more explanation of what's happening in general in an exhaust system, an one can visualize how this exhaust tuning valve can change the characteristics of the exhaust system for optimizing the scavenging at different rpms, and it is not about back pressure per se--

"...there are two main phenomenon occurring in the exhaust, gas particle flow and pressure wave propagation. The objective of the exhaust is to remove as many gas particles as possible during the exhaust stroke. The proper handling of the pressure waves in the exhaust can help us to this end, and even help us “supercharge” the engine.

"As the exhaust pressure wave arrives at the end of the exhaust pipe, part of the wave is reflected back towards the cylinder as a negative pressure (or vacuum) wave. This negative wave, if timed properly to arrive at the cylinder during the overlap period can help scavenge the residual exhaust gases in the cylinder and also can initiate the flow of intake charge into the cylinder. Since the pressure waves travel at near the speed of sound, the timing of the negative wave can be controlled by the primary pipe length for a particular rpm.

"The strength of the wave reflection is based on the area change compared to the area of the originating pipe. A large area change such as the end of a pipe will produce a strong reflection, whereas a smaller area change, as occurs in a collector, will produce a less-strong wave. A 2-1 collector will have a smaller area change than a 4-1 collector producing a weaker pressure wave. Also, a merge collector will have a smaller area change than a standard formed collector producing a weaker wave.

"So, the trick to proper exhaust tuning is to tune an exhaust system is produce a negative wave of the proper strength timed to occur at cylinder overlap."

Theory

"Older people who are reasonable, good-tempered, and gracious will bear aging well. Those who are mean-spirited and irritable will be unhappy at every period of their lives.

"Let each of use properly whatever strengths he has and strive to use them well. If he does this, he will never find himself lacking."

Marcus Tullius Cicero
44 B.C.
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post #9 of 9 Old 06-16-2014, 11:46 AM
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Does the 1000 come with the PAIR system like the SV?

2012 Suzuki DL650AL2, over 45k miles already!
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