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Discussion Starter #1
A question for those people who have fitted full exhaust systems which involve removal of the HTEV valve:

What has been the effect on low down power? I would like to fit a full system but not if it only adds power at the top end at the expense of low down power. In all honesty, I normally use only the first 5000rpm riding around town and rarely get a chance to get above 7000rpm (those people who do mustn't live in the city or must have an "arrangement" with the local police). Thus I'd prefer a powerband that, as one forum user with an Arata system said, "pulls like a Rhino at any revs". Is this truly possible without the HTEV valve?
 

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The Arata or Hindle are probably the way to go. My arata sacrifices very little down low, and that is mostly below 3000rpm. There is mor emidrange and top end - mid range being what most riders would get the most out of. I personally think the HTEV is more an emitions thing than anything else. Z...
 

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Discussion Starter #3
The Arata or Hindle are probably the way to go. My arata sacrifices very little down low, and that is mostly below 3000rpm. There is mor emidrange and top end - mid range being what most riders would get the most out of. I personally think the HTEV is more an emitions thing than anything else. Z...
I wouldn't mind losing a little below 3000 especially if the power built smoothly from low revs. At the moment the bike has a distinct surge as it gets to 3000 (when the HTEV valve opens to its mid-way point). In fact, I wonder if there is a way to stop the HTEV valve from ever closing fully? I'll bet that the bike would actually be stronger below 3000 if it never fully closed. As you say, the HTEV valve at low rpm is probably only good for keeping emissions low.
 

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HTEV has nothing to do w/ emissions.... it's for back pressure.

When you decrease back pressure w/ a free flow exhaust, you lose responsiveness at low rpm.

The valve is to correct this low rpm loss, and still have the high flow at the top end.
 

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Discussion Starter #5
hoagie said:
HTEV has nothing to do w/ emissions.... it's for back pressure.

When you decrease back pressure w/ a free flow exhaust, you lose responsiveness at low rpm.

The valve is to correct this low rpm loss, and still have the high flow at the top end.
Hmm. OK. Makes sense. However there must be something wrong in the execution of the concept as the bike goes from nothing below 3000 to a surge of power at 3000rpm when the HTEV opens to its mid-position. From 3000 onward the bike is very strong and then has another kick at high rpm when the HTEV fully opens. This makes me think that maybe the most closed position of the HTEV is not necessary. If not emissions, could it be needed to pass noise laws?
 

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ndj said:
Hmm. OK. Makes sense. However there must be something wrong in the execution of the concept as the bike goes from nothing below 3000 to a surge of power at 3000rpm when the HTEV opens to its mid-position. From 3000 onward the bike is very strong and then has another kick at high rpm when the HTEV fully opens. This makes me think that maybe the most closed position of the HTEV is not necessary. If not emissions, could it be needed to pass noise laws?
Nah... the can does all the noise cancellation.

Gettin back to my muscle car days... whenever you go to a higher flowing header/exhaust, you sacrifice throttle response (around town driveability) for full throttle top end pulling performance.

It's far from perfect. But I know when I took my entire exhaust off and test rode the bike(just for kicks :devil:, when I'd sharply WOT from around idle, there would be a distinct stumble... almost as if the bike was going to stall... then it would pick up and rev up normally.

IMHO... meeza tinks HTEV works as intended, and for street riding it does increase power useability. BUT if I had a track bike it would definetly be off the bike!!
 

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On the 929, I removed the HTEV valve, and the Hindle full system made more power without it in every possible RPM in the rev range, I lost 0 and gained power at just about every RPM. Luckily we had Dr. Abtech at that time, you have to examine the exhaust system of choice, think about the type of riding you do, and decide if losing power in certain places is worth it. Unless your bike is designated 'track only' choose the exhaust system with the best midrange gains.
 

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I have a full Arata and PCIII with a custom map on my 929. I don't feel as though I lost anything at the lower rpms. It pulls great. I do a lot of street riding and trackdays with it. I don't miss the HTEV or the heavy stock exhaust!
 

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its not like the valve is ever fully closed for any significant amount of time. Its actually explained in the book Sport Bike Performance Handbook. While there weren't exhaust valves then it still tells about the backpressures and such. In exhausts there are negative and positive waves. A negative wave (back pressure) is when the wave goes back up the pipe to the cylinder. It helps to pull more air/fuel charge into the cylinders at low rpm. Get the book, (or read that little section in the store if you prefer) and you'll understand it better than I can explain it.
 

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Discussion Starter #10 (Edited)
hoagie wrote:
HTEV has nothing to do w/ emissions.... it's for back pressure.
I can't say for sure about Honda's HTEV but this is from Suzuki's press info about the GSXR1000's "SET" valve:

"This system uses a butterfly valve in the exhaust pipe to suit running conditions....engine torque at low rpm with full throttle has been significantly improved, by about 6% at 3000rpm, with hydrocarbon emissions reduced by about 17%."
 

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I agree with others that have mentioned that the HTEV is not used for emissions. When considering exhaust you should also consider the airbox, and fuel injection as well. Honda engineered the HTEV valve as part of a whole with the fuel injection, airbox flapper, timing, etc. Sure some steps have been taken to meet the US emission and noise standards but again it has all been engineered together. I see that Yamaha and Suzuki put the exhaust valves in their bikes as well. The valves must provide some needed function so I wonder why the rush to get rid of them? Slap on a bolt on can, get a PCIII and have fun. :)
 

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I'd be willing to bet that the reduced emissions figure was just a by-product of that valve and a little icing on the cake for the epa and PR in general.
 

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Discussion Starter #13
jaim said:
Slap on a bolt on can, get a PCIII and have fun. :)
No doubt this would be the cheaper option and it would be a shame to remove the standard titanium headers and have just sitting in my shed collecting dust.

What bolt-on cans do you guys recommend? I would like a metal can as I am a bit bored with carbon cans. So long as it doesn't hurt performance or cost too much, I'd like the best possible looks and exhaust note.
 

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If you think these valves on bikes are put on there for performance, I'd like to get some of what you're smoking. And whomever said "it was engineered with everything else" :rotfl:
 

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Discussion Starter #15
deez said:
If you think these valves on bikes are put on there for performance, I'd like to get some of what you're smoking. And whomever said "it was engineered with everything else" :rotfl:
I think its important to realise that Honda designs these bikes as ROAD bikes. Of course performance is going to be compromised to ensure good driveablity, that it can run on low octane pump fuel, and that it meets noise and emission requirements. To say that a team of professional engineers would add features that do nothing, or fail to coordinate various components in order to achieve optimum overall performance, is incorrect and wrong.
 

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ndj said:
To say that a team of professional engineers would add features that do nothing, or fail to coordinate various components in order to achieve optimum overall performance, is incorrect and wrong.
:rotfl: Dude you don't know me. I know full well why it's on there, in fact you stated it.

and that it meets noise and emission requirements.
That is the only reason it's there. The "Honda engineers designed it that way and that's the way it needs to be" philosophy is utter bullshit. Any bike I've modded, runs heaps better after adding an exhaust and mapping the FI.

Furthermore, you should talk to them boys at HRC. They failed to coordinate various components correctly, on the front end of my CBR1000, it sucks. The forks have Suzukish internals, and the tubes are too short. ;)
 

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jaim said:
I agree with others that have mentioned that the HTEV is not used for emissions. When considering exhaust you should also consider the airbox, and fuel injection as well. Honda engineered the HTEV valve as part of a whole with the fuel injection, airbox flapper, timing, etc. Sure some steps have been taken to meet the US emission and noise standards but again it has all been engineered together. I see that Yamaha and Suzuki put the exhaust valves in their bikes as well. The valves must provide some needed function so I wonder why the rush to get rid of them? Slap on a bolt on can, get a PCIII and have fun. :)
Ask Dan Kyle about the improved performanxw and higher HP numbers from differant exhausts with out the use of the HTEV valve.
 

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CBR Riding Fool said:
Ask Dan Kyle about the improved performanxw and higher HP numbers from differant exhausts with out the use of the HTEV valve.
Just give us the short version.

I am not saying the HTEV is there for racing. But if you remove it and replace it with a new exhaust system you should also mod up the airbox, fuel injection and probably valves and pistons as well to get the bike to run to its fullest potential.

I would like to know what emission standards are satisfied by having the HTEV valve there? The flapper in the airbox I can understand for noise abatement but not sure what the HTEV would do other than provide back pressure.
 

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jaim said:
Just give us the short version.

I am not saying the HTEV is there for racing. But if you remove it and replace it with a new exhaust system you should also mod up the airbox, fuel injection and probably valves and pistons as well to get the bike to run to its fullest potential.
:rotfl:

Wrong. All you need to do is map the bike.
 
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