What does a power valve do again?

[wsuwrhr]

Good answer

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.

 

[BruceSki]

matt if you have ridden 2 smoker dirtbikes before you know the hit when the powervalve opens up top. It is a big hit and helps make more linear power from the bottom to the top for sure.

Like WFO said it just need periodic cleaning to keep them from gumming up with sludge/carbon from premix. On my mx bike it would clean powervalves and do a top end once a season.

 

[MADMAT]

Great stuff in these threads guys and thanks most all of you for your input.

Yea I have ridden the hell out of dirtbikes and that along with all the rest of these posts has helped make total sense out of all this.

 

[sflsurfrider]

im glad that gil was able to help.


:haha:

 

[kevbo]

Great stuff in these threads guys and thanks most all of you for your input.

Yea I have ridden the hell out of dirtbikes and that along with all the rest of these posts has helped make total sense out of all this.

Exhaust valves make a huge difference on anything that is tied to the ground, except a snowmobile. They help heavy overproped sitdowns get out of the hole better. A freestyle ski is one application where they have the least bennefit, unless its overproped. Linear power? not with giant carbs and a short prop, its pretty much on or off. How many jetskiers are slow and smooth with the throttle, none that Ive ever seen.

 

[WFO Speedracer]

im glad that gil was able to help.


:haha:

Yeah we were holding out till you chimed in but we just couldn't wait any longer Charlie, maybe next time.

 

[masterblaster]

kevbo..interesting points,Ive found that carbs deff play a huge roll in a linear power curve as well.One of the most non linear ive ever used was a 50 mil mech fuel inj.
I can see much more use for a pv motor for guys like flash and his crew that do high speed reed runs,but for your average ocean freeride guy? we only can go so fast.do we need it?The main diff is they cost alot more! Will the right shape and duration exh port give us the linear curve we are after with out the pv?

with the dirtbike pv and tranny its alot diff,but you mostly feel the powerband when the motor gets on the pipe.

 

[egbrig]

A pv will smooth out the torque curve. In laymen terms, will give low end and let you have a higher duration ex port timing for that upper end power. Best of both worlds. It also saves fuel and helps emissions.

 

[masterblaster]

i wouldnt have guessed the fuel savings

 

[Flash-FX]

i wouldnt have guessed the fuel savings

Funny you mention fuel savings.....The FX guys went for a "creek" ride last weekend and, at first I was a little concerned with the new SS865 W/PV's and fuel consumption. About 2/3 thru the ride, we stopped on the marsh to take a break, and I checked my fuel. About the same as every one else....all 4 boats. Back at the trucks, I actually had more fuel left than the sport ported, 701's w/ single 46's...imagine that.

 

[wsuwrhr]

Funny you mention fuel savings.....The FX guys went for a "creek" ride last weekend and, at first I was a little concerned with the new SS865 W/PV's and fuel consumption. About 2/3 thru the ride, we stopped on the marsh to take a break, and I checked my fuel. About the same as every one else....all 4 boats. Back at the trucks, I actually had more fuel left than the sport ported, 701's w/ single 46's...imagine that.

As you should.....

Goes along with what I have posted several times, at part throttle opening, the more power an engine makes, the less fuel it has the potential to consume.

This is due to a couple reasons, making enough power that the engine doesn't have to spend as much time with the blades open as far and not having them open as long comparitively to a smaller or less powerful engine.

You are hard pressed to get many people to believe it until they see it for themselves.

In my opinion, single carbs are the worst thing for a twin for this very reason.

Brian

 

[masterblaster]

ive seen it also,a single can burn alot of fuel and makes less power

 

[cookerq62]

The solenoid got stuck on in my couch so to finish out the day with some slalom skiing and hauling stuff back we just disconnected the battery. The PV's won't work without the battery. Off idle nothing changes. Out of the hole it just didn't spin the prop so no real diff. While towing and trying to maintain one speed or power through a corner smoothly it was impossible. The pipe comes on so much harder with out the valves and never the same way twice. Then the power just falls off. A motor like this in a stand up would be about useless. It was comparable to my buddies big bore 6m6 (81mm) on 61x cases that was ported by Tim Judge for sport class. The thing had gobs of power but it wasn't good for much in his squarenose other than getting an arm workout.

 

[kevbo]

Part throttle fuel economy will be good if the engine stays in a clean two-cycle below the pipe, like stock carbs are set. High popoff pressure will usually do it but will reduce throttle response at some point. The best response setting almost always require the engine to be four-cycling below the pipe. This can really consume a lot of fuel at low speeds. I can tell exactly who will run out of gas first by the sound of their exhaust.

 

[Flash-FX]

Part throttle fuel economy will be good if the engine stays in a clean two-cycle below the pipe, like stock carbs are set. High popoff pressure will usually do it but will reduce throttle response at some point. The best response setting almost always require the engine to be four-cycling below the pipe. This can really consume a lot of fuel at low speeds. I can tell exactly who will run out of gas first by the sound of their exhaust.

You're right about that! It's something a simple low speed jet change won't fix....It's a fine tune "metering" adjustment,that works with the whole package. Cylinder design,pipe,carbs,load...ect. Every motor is different.

Has anyone here ever "adjusted" your low speed circuit metering?

 

[nickwad]

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.

Keep asking Matt. thats what the forum is all about ........We are all learning loads!!

 

[FyrHazard]

Keep asking Matt. thats what the forum is all about ........We are all learning loads!!

Ditto, kinda nice to rehash some of this stuff once in a while. Or just hash it if you haven't seen it before.

 

[yamaslut]

On DASA and Rotax engines it controls the widening and narrowing of the exhaust port,on Yamahas it destroys engines.

yes it does... bastards

 

[masterblaster]

You're right about that! It's something a simple low speed jet change won't fix....It's a fine tune "metering" adjustment,that works with the whole package. Cylinder design,pipe,carbs,load...ect. Every motor is different.

Has anyone here ever "adjusted" your low speed circuit metering?

thats the heart surgury to a carb,I doubt many here have the know how,maybe you could get a little help from tim at novi

 

[Dustin Mustangs]

Ditto, kinda nice to rehash some of this stuff once in a while. Or just hash it if you haven't seen it before.

And who doesn't like hash?

:439: