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i have an 04 zx-10 and yesterday i unhooked the exhaust valve for the day, i think the midrange might be a little smoother but i can't tell if it's got more or less power. has anyone dyno'd their bike before and after this mod to see what the difference is
 

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i have an 04 zx-10 and yesterday i unhooked the exhaust valve for the day, i think the midrange might be a little smoother but i can't tell if it's got more or less power. has anyone dyno'd their bike before and after this mod to see what the difference is

In fact it does not boost power. If you remove/disable the power valve you will see a dip in the power curve low/mid.

If you move to a full system your tuning guy will work for about an hour on the dyno re mapping and smoothing that spot in the rev range.

FWIW- With a perfect map,you will see 1 hp gain between a full system and a slip-on with the stock headers-If I had to do it all over again I'd stick with the OEM header and a light can..The OEM header came matched from the factory pretty damn good on the stock exhaust porting..
 

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In fact it does not boost power. If you remove/disable the power valve you will see a dip in the power curve low/mid.

If you move to a full system your tuning guy will work for about an hour on the dyno re mapping and smoothing that spot in the rev range.

FWIW- With a perfect map,you will see 1 hp gain between a full system and a slip-on with the stock headers-If I had to do it all over again I'd stick with the OEM header and a light can..The OEM header came matched from the factory pretty damn good on the stock exhaust porting..

The "power valve" in the exhaust is nothing but a noise reduction device so the bikes can pass EPA noise emissions tests. There is no power to be lost or gained either way.

I know the bike makers are getting better and better with the exhaust systems they put on bikes but as far as only getting 1 extra hp from a full system over a slip-on I call BS. For one, you simply can't measure a loss or gain of 1 hp because of dyno variables. But even if it was possible to measure I'd still have to see a dyno sheet from a tuner showing that he got a slip-on equipped bike to put out the same power of a full system equipped bike.
 

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i completely agree with phastone:+1:
 

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The "power valve" in the exhaust is nothing but a noise reduction device so the bikes can pass EPA noise emissions tests. There is no power to be lost or gained either way.

I know the bike makers are getting better and better with the exhaust systems they put on bikes but as far as only getting 1 extra hp from a full system over a slip-on I call BS. For one, you simply can't measure a loss or gain of 1 hp because of dyno variables. But even if it was possible to measure I'd still have to see a dyno sheet from a tuner showing that he got a slip-on equipped bike to put out the same power of a full system equipped bike.
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It's purpose is,and I quote Kawasaki-

"Butterfly valve in the collector is controlled by rpm, throttle position and gear position to improve low-end response and help smooth overall power. Optimum exhaust tuning is attained at all engine speeds to prevent blowback that can occur with high overlapping valve timing."

If you look at your Dyno sheet you will see a dip in the power curve right at 6000 RPM to about 7600 with the power valve removed/disabled without the re map.

AND
Yes I do have all my dyno sheets available.
All my pulls where done on DynoJet 200i

Bone stock OEM- 142RWHP

PCIII/stock header Yoshimura TRS Exhaust can,custom smoothing map 150.3RWHP

PCIII/Hamaguchi full Ti exhaust,Custom smoothing,pump gas 151.6 RWHP

Everyone who knows Dynometers will tell you that the Dyno jet one is the "stingy" one with pretty close to real world numbers.

All pulls done at sea level with NO ram air or vacuum assisted exhaust.
 

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^^^

Do you believe everything you read or are told?

AND
while I don't have any sheets from a stock bike, I have plenty of them from after doing mods or having engine work done and the professional(AMA engine builder/tuner/crew chief) that does my work would have told me by now if aftermarket headers were such a waste of time/money. And he probably wouldn't put them on the bikes he builds for racers, either.

And I've never heard a dynojet called stingy in my whole life whether measuring bike or car power. Factory Pro dynos are the ones that typically give lower and supposedly more realistic numbers.
 

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^^^

Do you believe everything you read or are told?

AND
while I don't have any sheets from a stock bike, I have plenty of them from after doing mods or having engine work done and the professional(AMA engine builder/tuner/crew chief) that does my work would have told me by now if aftermarket headers were such a waste of time/money. And he probably wouldn't put them on the bikes he builds for racers, either.

And I've never heard a dynojet called stingy in my whole life whether measuring bike or car power. Factory Pro dynos are the ones that typically give lower and supposedly more realistic numbers.
In my opinion for this specific application (2004 ZX-10R) If we are comparing apples to apples (that being a completely stock motor with only a programed CDI) than yes,I stick by my opinion that the OEM header is flow matched to within 1 to 2 hp of any aftermarket header offered by any vendor on the market.To utilize the extra flow a larger diameter header usually is intended for-a "race motor" is built for providing the heat(power) that will utilize the larger capacity.

If your shifting the discussion to "my race tuner says this..."
Than your moving the exchange here to a place where every advantage is trying to be exploited by a builder to produce maximum power. In which case a larger diameter exhaust port needs to be complimented by a larger diameter exhaust pipe manifold,along with a host of other modifications that will work in concert with the desired results in mind.
 

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In my opinion for this specific application (2004 ZX-10R) If we are comparing apples to apples (that being a completely stock motor with only a programed CDI) than yes,I stick by my opinion that the OEM header is flow matched to within 1 to 2 hp of any aftermarket header offered by any vendor on the market.To utilize the extra flow a larger diameter header usually is intended for-a "race motor" is built for providing the heat(power) that will utilize the larger capacity.

If your shifting the discussion to "my race tuner says this..."
Than your moving the exchange here to a place where every advantage is trying to be exploited by a builder to produce maximum power. In which case a larger diameter exhaust port needs to be complimented by a larger diameter exhaust pipe manifold,along with a host of other modifications that will work in concert with the desired results in mind.
I'm not talking about a built "race engine". I was just stating that the guy/shop that does my work also builds/tunes engines for racers and the owner is a part-time AMA crew chief so I think he might know a little bit about what he's talking about. And I'm pretty sure a member here named Ivan who is a well known tuner/shop owner/parts maker shares the same opinion.

Like I said before, I agree that the bike makers are putting more R&D into the stock exhausts and you don't get the 15 hp from a full system like 10 years ago. But on the other hand, either your tuner sucks or the hamaguchi exhaust isn't as good as it's supposed to be.

I'm not trying to be a jerk or anything. It's just that I've seen too many dyno runs from numerous tuners showing what a slip-on does and then what a full system does. And while none of them showed a huge difference, none of them only showed a 1 hp difference between the two. And like I said, a 1 hp difference on a dyno isn't even considered a difference because of the fact that there are rarely two runs that come out the same even when it's the same bike/car/whatever with nothing changed between the two runs.
 

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I'm not talking about a built "race engine". I was just stating that the guy/shop that does my work also builds/tunes engines for racers and the owner is a part-time AMA crew chief so I think he might know a little bit about what he's talking about. And I'm pretty sure a member here named Ivan who is a well known tuner/shop owner/parts maker shares the same opinion.

Like I said before, I agree that the bike makers are putting more R&D into the stock exhausts and you don't get the 15 hp from a full system like 10 years ago. But on the other hand, either your tuner sucks or the hamaguchi exhaust isn't as good as it's supposed to be.

I'm not trying to be a jerk or anything. It's just that I've seen too many dyno runs from numerous tuners showing what a slip-on does and then what a full system does. And while none of them showed a huge difference, none of them only showed a 1 hp difference between the two. And like I said, a 1 hp difference on a dyno isn't even considered a difference because of the fact that there are rarely two runs that come out the same even when it's the same bike/car/whatever with nothing changed between the two runs.
All I'm saying is that for me and my experience with the Power valve and the full system for the 04 ZX-10R was that I gained 8hp with a can and a good map-and 9hp with a good map and a full Hamaguchi system.The power curve is perfect and linear with no dips and the air/fuel is virtually a straight line at 13:1. I don't think you can ask for much more from a tuner?
 
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