Grinding power valves on XP ?
- Thread starter doox
- Start date
Must be top secret
Stronger midrange
Be nice if someone would make some aftermarket power valves that we can just slip in . . . Hint, Hint!!
R
RideGuy
Well-known member
No doubt hey.....
as for grinding them I'd either enlarge the opening or change the angle so that it opens easier under less pressure.....
I'm guessing just hogging them out is easier so that you have more flow at lower RPM.....??
Al at Boulder Mountain Sled Shed in revy does them. Just got mine back so i don't know how they work yet. Al says it doesn't make them open sooner it just bring the exhaust opening back out to where it was on the 06 motors.
I proposed building a tachometer circuit with an adjustable output relay that the rider can dial in the rpm where the valves opens. We actually built a proto that works but did not install on the sled. The reason I did not procede was that I read the xp manual and it states that if you punch the throttle on the xp, the ecm will actualy pick a map that by-passes the half open position and goes to full open. This said Turboal still thinks midrange power is lost as the first valve lift is done at 6200 rpm and he likes how the 06 did it near approx 5300 rpm. This he says would make the sled more responsive. The worry for me is that from experience I know that 2 strokes develop more torque with more back pressure at lower rpms. If you decrease the back pressure too much you may actually develop a bog and less bottom end torque. I see it like going to twin pipes at high altitude.
This is just my opinion and I would like to try one of his with cut valves but like Winterbrew (I think) said has anybody tried adding some extra thick gaskets under these valves to lift up 12 thousands of an inch?
This is just my opinion and I would like to try one of his with cut valves but like Winterbrew (I think) said has anybody tried adding some extra thick gaskets under these valves to lift up 12 thousands of an inch?
T
TLKDPROD
Well-known member
If Al machines them down .200" and you want to achieve the same result with offsetting the position of the Rave valve itself, you'd proably need a spacer, similar to the reed spacer, instead of a stack of gasket.
Personnally, I think it would be a great idea if someone made a .050" or .100" thick spacer, so you can try different stacks of these spacers one at a time and see what they really doo. Don't know if you may end up with problems doing that though, I'm not a Rave Valve guru !
how would that be any different than cutting the valve itself???
i'd like someone to clarify this for us. If you are cutting the valve, i'm assuming its cut even across the face of the valve on exhaust stream face. IF that is the case, you are basically increasing the port size at low rpms (and depending on where the valve sits at full open, you are also increasing the port size and full open, or as noted above - recessing the valve at full open? SO - can someone confirm for me this is indeed the case?
T
TLKDPROD
Well-known member
I have my motor opened up as I write this (waiting on a set of pistons) and I just checked, Fully opened, the Rave valve ends up flush with the top part of the exhaust port opening. So if you cut the valve or add a spacer, the valve will recess further into its slot, further than the exhaust port for sure. Has to be. That's on my 800HO by the way, I would think the same logic will apply for an 800R motor.
And Basically, what you're doing when doing that is increasing exhaust port size everywhere on the powerband, low, mid & hi RPM. You just offset higher the tip of the valve by .200" if you cut them by .200".
I know that a smaller port size will help create horses at low RPM and I don't know how you end up loosing, fact is we don't use the powerband in that low RPM anyway... (?) The gains must be great if Al does it. He knows his stuff.
Question for ya'all (or more specifically for you turboal if you read this) : Does an MPEM or ECU reprogramming can achieve these results without cutting the valves ?
H
HPJUNKIE
Active member
You can double check with Al, but I was under the impression that the cut on the valves that control the main exhaust port was only on the portion of the valve which is the first to open. When the second half of the main valve opens, it is flush with the top of the ex port.
Since the valves are pressure activated, couldn't we put a controler in the vacuum lines much like a boost controler that would allow us to fine tune how much pressure it gets?
Rt
Al wouldn't be doing this mod for everyone if it wasn't worth his time. Many people do so many things to their sled that make no sense, but Al only suggests simple things that really make a difference, so I trust his research. I got my RAVES done by him, but have not had a ride with them done. I will post as soon as we get some snow.
The way I read the manual, the middle position is the resting position. to go to low position, the valve moves against one spring and for high position it moves the other way, compressing the other spring. I suppose putting 1 longer spring in and 1 shorter spring would make the middle position open more at rest. This might have a sililar effect. To play with the pressure might be just a little harder to calibrate and control especially since your dealing with pulses of pressure and pulses of vacuum with the ecm controlling 2 solenoid valves to choose between pressure side, vacuum side or neither to hit the middle position.
Farther more:
How about another way of simulating what Al is doing without doing the cutting. Al has the valves .200" open more than the low position, at middle position he has the valves .200" open more and fully open is fully open. The valves so far, are still controlled the same way so they move at the same RPM points. So why not make a mechanical limit stop to set them open .200" more at minimum, lengthen one spring by .200" and shorten the other by .200" to move up the middle position by .200" and fully open is still fully open.
Even one spring shim may accomplish all of this if there is clearance?
Anybody have these apart to know if I'm on the right track?
How about another way of simulating what Al is doing without doing the cutting. Al has the valves .200" open more than the low position, at middle position he has the valves .200" open more and fully open is fully open. The valves so far, are still controlled the same way so they move at the same RPM points. So why not make a mechanical limit stop to set them open .200" more at minimum, lengthen one spring by .200" and shorten the other by .200" to move up the middle position by .200" and fully open is still fully open.
Even one spring shim may accomplish all of this if there is clearance?
Anybody have these apart to know if I'm on the right track?
If you were running cut valves. I would be curious to know if the timing should be changed for the rpm range that the valves are closed.
D
doowhite
New member
Hey Teth Air
I was looking at power valve part numbers from the 07,08,09 and I think there were 3 parts that were different from the 07's to present. Just wondering if anyone knows why. Have heard the 08 and 09's don't make as much power as the 07's did.Wonder if the power valves have any effect on that.
I was looking at power valve part numbers from the 07,08,09 and I think there were 3 parts that were different from the 07's to present. Just wondering if anyone knows why. Have heard the 08 and 09's don't make as much power as the 07's did.Wonder if the power valves have any effect on that.
