Powervalve Vs. NON PV

[woodsracer144]

so what do you gain with a PV? i rode on a ESR 265 PV and the stock motor felt caster then that thing...

there was a guy on ebay with a CT full motor for sale, and he said
"CT Pro-X 350 Big Bore "powervalve" kit installed with cases machined and 4mm stroker crank installed. This is not the standard 350 head, it is the Powervalve head which produces more power throughout the power curve on the dyno. Good for 55-60 rear wheel horsepower."

i thought the PV smoothed out the curve on the power ban? i didnt think it GAINED you Hp... if anything i thought it would take your peak Hp away...


what is it? :ermm:

[Honda 250r 001]

i dont think you gain much more hp total but what it does is allow you to raise the exhaust port up to drag pport specs sort of. but when the powervalve is closed at lower rpm's its more like a low end port job because it closes down the exhaust port.

[gandgracing]

The powervalve is in the front part of the cylinder not the head. It smooths out the power delivery. I tried blocking my powervalve off and liked the snap of the powerband.

[8686]

Go with a non-pv. They're cheaper, have less moving parts, and are more fun to ride.

[woodsracer144]

what factory?

[machwon]

The powervalve makes for better port timing than a traditional cylinder when bought from the big name companies. The valve is closed at lower rpm and this gives lower exhuast port duration for bottom end and mid range power. As the rpm picks up the valve opens for longer ex. duration which makes better power at top end.

The powervavle cylinders basically are enhanced porting giving better power at low, mid and topend. Cylinders without powervalves typically hit only 2 of the 3 areas with strong power. If you're looking for good dune power or all out power, buy the cheaper non pv and just make sure it gets a good port job.

[Honda 250r 001]

i would just a new esr 310 kit. pv is great for racing. but if your not racing. dont waist your money.

[albertp86]

so what are the disadvantage's of the pv other then cost? I am asuming that if money is not a problem then you would go with a p/v? I am trying to figure it out myself because I am a few weeks from making a purchase of a 310 or 310 pv

[woodsracer144]

I'm racing the d23 hairscrambles this year. The motor I have now I'm kinda blind with I don't know the bore. It once has a stroker from duncan and I would like to make it a full race quad I have a buddy with a CT 310 Cylnder and I think I could get a good deal on it by I wasn't sure what route to go with that ct is a non of aswell

[Honda 250r 001]

well you will loose that powerband hit. it will be a softer hit. and if they wear out or arent maitained they can fall on top of the piston and ruin your cylinder.

[Witz]

If you're racing XC/hare scrambles, and have the ability to afford the extra cost, I definitely recommend a powervalve cylinder. The valve does nothing to add horsepower. It allows the engine builder to cut the cylinder so that it has strong low end as well as a strong top end pull. It works very well to smooth out the power delivery. Smoother power is easier to ride and will wear you out less.

As far as having extra moving parts and fears of it failing, that's ridiculous. The Rotax RAVE style and the CT style valve have 1 moving part - the valve itself. The only maintenance that they ever require is a periodic cleaning. And if they're not cleaned, the only repercussion will be that it won't operate properly.

[woodsracer144]

i would like a PC2000 but thats way too much any one know where theres a good used CT or PC for a good price?

[dtek01]

I may have a PC200 kit on my bike I may sell. I am looking just to go back to an unmolested stock 88 setup.

Pm me and we can talk.

[troybilt]

I posted this some time ago but here is a comparison of an LRD power valve vs. non powervalve:

NON-PV

[troybilt]

PV

[Honda 250r 001]

which one is the powervalve?

[troybilt]

The second one. I edited the post to label them.

You can see the smoother power band in the knee of the curve and the decreased slope in the overall HP curve. But relative HP numbers and torque are virtually the same.

[machwon]

Here's a couple more runs for viewing. The red graph was a 350pv with mx porting to emphasize low end power, lrd pipe, 39 carb and other parts I forgot. The green graph is from a non pv 350 on race fuel, fully ported, drag pipe, 40.5 carb, cr ignition, cr rad valve.

[woodsracer144]

Originally posted by machwon
Here's a couple more runs for viewing. The red graph was a 350pv with mx porting to emphasize low end power, lrd pipe, 39 carb and other parts I forgot. The green graph is from a non pv 350 on race fuel, fully ported, drag pipe, 40.5 carb, cr ignition, cr rad valve.
that last one the curve for the non PV is way higher i know its a drag one but i dont see how a PV would help me that much? i thought that it would take the peak HP away and smooth the power out but there isnt much of a change to me... or am i missing something?

[jas250r]

i sort of had the same problem. stock bore had great power and a great snap. went the route of a ct 350 pv. glade i did, a lot smoother power delivery, easier to control, more usable power put to the ground. non pv for dunes and wide open trials would be good. just my 2 cents

[voodoochassis]

i have the esr 350pv cylinder and for some reason it hits hard as crap just about right off throttle..pulls to much for me considering i race mx..just my two cents..would trade for a 265-295pv if someone has one

[Michael88R]

Voodoo, what pipe and porting are you running? That hit might be the ESR valve opening. They open too quickly. A CT or rotax valve might solve your problem.

[woodsracer144]

are teh 295's the 310's or do they make a true 310?

[machwon]

Originally posted by woodsracer144
that last one the curve for the non PV is way higher i know its a drag one but i dont see how a PV would help me that much? i thought that it would take the peak HP away and smooth the power out but there isnt much of a change to me... or am i missing something?

Lots of people look at the HP numbers but torque is really more important. On the runs I posted, the pv motors kick in at 5500 rpm while the non pv's kick in at 6500 rpm. The pv's could be tuned much better and yes I've given several guys the ski-doo powervalve spring charts to help improve the pv's power spread.

Even a nice stock cylinder 270cc motor can have 30-32 ft-lbs of torque from 6500-8000 rpms.

In my opinion, most guys don't ride at 5500 or 6500 rpms, in fact its very difficult to keep the rpms that low by shifting all the time, especially with the adrenaline from any race. Most guys pin it in a certain gear and hold it if they need to. "drag porting" gets too much of a bad rap. There's nothing wrong with having the torque pull like a freight train, unless it just too much power.

[woodsracer144]

is that drag port doing that much?

to me im still seeing the 350 Non PV with more...

[dtek01]

machwon:

Could I get one of those powervalve charts?

I would love to see if I can tune this 275 beast. Hits real hard in the low/mid but I would like it to rev a litttle more. I am light weight and it gets hard to hold sometimes and alot of wheelspin.

I think the PC2000 setup uses those powervalves.

[woodsracer144]

am I on crack? I still don't see a differance in the pv. And non pv what is the max rpm a 250r hit? Do the aftermarket
Cdi boxxes do Much to gain hp I'm just gettn lost. Is 295 a 310 or is there true 310? Thanks

[matt250r21]

You get four bores with a 310 "kit". Your first bore is around 295 and your fourth and last bore is around 310.

[machwon]

Originally posted by woodsracer144
am I on crack? I still don't see a differance in the pv. And non pv what is the max rpm a 250r hit? Do the aftermarket
Cdi boxxes do Much to gain hp I'm just gettn lost. Is 295 a 310 or is there true 310? Thanks

I don't think you find any difference. I didn't do the port work on the pv cylinder, but I'm sure it can be done way better. I did do the work on the non pv version. Either cylinder can be made better with porting. Stock cdi's or cr ignitions will work just fine.

dtek01, I'll look for that spring chart.

[Witz]

If you don't mind, make that 2 of us that would like the spring chart :)

[morse250r]

i own that 350 non power valve and it rocks alot of torq and pull it does have v force reeds in it i wouldnt go with a powervalve if i did it again id stick with the set up i have now

[machwon]

I thought this chart was better, but its the best I could find.

[machwon]

Hope this one works better.

[woodsracer144]

What is that?

[machwon]

I should have explained it better, here goes. Its a spring chart from Ski-Doo showing the year of snowmobile the part comes from, the engine type (almost equals the size), the Part Numbers P/N, and the dimensions of each spring in length and diameter.

These spring choices would offer those with the Ski-Doo RAVE type PV cylinders to get some optional springs to affect the power valve hitting earlier or later.