What does a power valve do again?
- Thread starter MADMAT
- Start date
- Location
- sunbury ,ohio
YPVS Yamaha engines, Yamaha Power Valve System: Yamaha engineers realized that by altering the height of the exhaust port they could effectively change the engine power delivery thereby having optimal power and torque across the entire rev range, so it was that the YPVS was born. The valve is of a cylindrical design running across the top of the exhaust port, it is turned by a servo motor controlled from a control box taking information from the CDI (and other locations). The valve is a slightly ovular shape. This changes the height and size of the exhaust port at different engine speeds, maximizing the available power at all rev ranges.
yup. what he said.
they look badazz too.
they look badazz too.
Idok
F1pro
- Location
- Nations oldest muthaF+++kin city
think of it as variable timing...
as RPMS build, the exhaust port opens in proportion....its what makes the motor feel like its pulling and pulling and pulling...
rather than just one big GRUNT then it falls flat
as RPMS build, the exhaust port opens in proportion....its what makes the motor feel like its pulling and pulling and pulling...
rather than just one big GRUNT then it falls flat
masterblaster
X-H2
ts and dasa pv are controlled by a much more simple vacuum at a set rpm,but the larger ? in my mind is how they effect the power curve down low at larger bores?
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
On DASA and Rotax engines it controls the widening and narrowing of the exhaust port,on Yamahas it destroys engines.
vacuum or pressure?
GIL
Power In The Hands Of Few
- Location
- Cullman AL
My opinion on powervalves, if u have a builder worth a dam he can create a setup that does not need p/v's to create linear power. Next I think carbs have alot of influence on the overall powercurve. If you are one of those that have to have powervalves because the other kids in the sandbox have powervalves and you don't-then the TS powervalves look practical unlike the traditional p/v's that require butchering your headpipe and manifold. One of our board members offered to add p/v's to my Lamey REALLY cheap and I do NOT have p/v's as per reccomendation of my engine guy.
Matt-I swear-if you do NOT quit starting new posts about what is what and what works and what don't-U WILL GO NUTS!!! Call a builder and do what he says to do! I promise the advice I am giving is SOLID. Let the engine builder help you!!! You will be MUCH happier in the long run! I'm not bustin yer ballz, just trying to help you help yourself.
Matt-I swear-if you do NOT quit starting new posts about what is what and what works and what don't-U WILL GO NUTS!!! Call a builder and do what he says to do! I promise the advice I am giving is SOLID. Let the engine builder help you!!! You will be MUCH happier in the long run! I'm not bustin yer ballz, just trying to help you help yourself.
suva
57
- Location
- Just south of the Citadel, Idaho
If a power valve is stuck closed it will kill your top end, and if it's stuck open you will lose bottom end power.
Think of it as having a race port and frestyle port all in one and the PV switches between the two.
infamy
Westside Freeride
jetkid
Paul Lambers
- Location
- Grand Rapids MI
i love this thread. I have learned a lot and i am not going to call a builder and waist his time because i am not ready to buy anything yet.
Boris
The Good Old Days
- Location
- The surf-less coast
SJBrit
Extraordinary Alien
- Location
- Bradenton, FL
Gil, grab one of your hormone pills and settle down old chap :cool2: Matt knows he has to talk to a builder but, like me, he likes to be smart enough when he does that to be able to ask sensible questions and understand the answers. There are two ways to talk to a builder: here's what I want to achieve, tell me how much; and: here's what I want to achieve, let's discuss options so I can understand the differences and make a the right decision.
Besides, as Infamy says, what do the rest of us learn if this kind of conversation goes on in private? It's is one of the main purposes of forums like this to share experiences and ideas so we can all learn from each other.
Keep it up Matt - I'm learning lots at a time when I'm making similar decisions. 'Tis the season....
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
Power valve setups or should I say good powervalve setups have only one moving part,the powervalve itself.The only maintaince is removal ,disassembly and cleaning at regular intervals.This only takes a few minutes per power valve unless we are talking about factory Yami setups,then its several hours,lots of cussing and a couple of thrown wrenches.If you use a good oil that dosen't gum everything up the powervalves go a long time without needing to be cleaned.There are really no drawbacks to a power valve setup,it gives you the small exhaust port for bottom end and then gradually opens the port as rpms increase to give you nice top end power.The power valve allows you to make big reliable power with a smaller engine ,of course the bigger the bore and the stroke the more power you are going to see out of one of these setups.
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wsuwrhr
Purveyor of the Biggest Brapp
- Location
- Alta Loma, working in Upland
#1. Exactly
#2. In a nutshell yes.
PV's aren't necessary in an engine, but they certainly help things and even if they aren't exactly needed, they certainly don't hurt to have them either.
The GP Yamaha absolutely needs them. The factory exhaust port size is too big for the smaller bores to run well without one. Because of this reason, in the Yamaha, as the piston gets larger proportionately to the exhaust, the PV becomes less and less important, but still usable.
Brian
#2. In a nutshell yes.
PV's aren't necessary in an engine, but they certainly help things and even if they aren't exactly needed, they certainly don't hurt to have them either.
The GP Yamaha absolutely needs them. The factory exhaust port size is too big for the smaller bores to run well without one. Because of this reason, in the Yamaha, as the piston gets larger proportionately to the exhaust, the PV becomes less and less important, but still usable.
Brian
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