Plugged Exhaust Valves?

I have been following this for a while and can understand the advantage and disadvantage of doing this. My 06 600ho works very well at low alt. and just great at high alt. When using the proper clutching and gearing, it pulls really strong at any alt., and holds a good rpm on top end in deep powder or hardpack. I have no reason to try plugging the hoses. If I had a problem somewhere in my rpm range like some do, (stumble or hesitation, can't pull rpms with proper clutching and gearing) I sure would try this easy and quick test to verify the valve operation. I do have to say my 600ho runs a little warmer than I like at slow speed in the deep or conditions like thefullmonte was referring to. It isn't warm enough to warrant any changes. I think most 600ho run consistent like mine so it would be the 7s & 8s that could gain by plugging if having a valve related symptom.

Real world testing, continued

Ron,

As Monte pointed out and as I have previously stated, plugging the exhaust valves is such a simple NO cost mod, at the very minimum it's worth trying and let the consumer make their own decision for themselves, that's all.

Regarding effectiveness at altitude, back in 2002-2005 (the pre-solenoid days) I brought my flatlander sleds (2001 600 & 2002 800) to Yellowstone 3 seperate times to ride for 6-8 days at a time. Snowtech published a Tech Tip in their magazine suggesting using a lighter Yellow spring (which I did try in my sled) for use at altitude. Now why would they suggest there be any benefit to using a lighter spring to cause the valves to open sooner at altitude??

To discourage anyone from trying this simple no cost mod is just ridiculous. Reminds of 30+ years ago when Nitrous was rarely used and most guys were "afraid" of trying it because "it'll blow up your motor" lol

It ain't braggin' when you can back it up.

'Nuff said

Whats with the car...

Shouldnt' that car be in the swap meet section...can i trade an exhaust valve spring for the car...i've got some pink ones..

OK, guys I can see your personalities clashing a bit here. Keep the thread on track PLEASE. This is a good thread with a lot of useful info and I don't want to close it or start deleting more posts.

AirdrieTruckAcc said:

Shouldnt' that car be in the swap meet section...can i trade an exhaust valve spring for the car...i've got some pink ones..

Click to expand...

Only if the springs run 9.40's or faster in the 1/4 mile, and come to think of it, since that was a long time ago, we'd have to adjust for progress, so I'd say 8.90's today.

What color were those again?

kraven you have a 07 d7 that you ride in the U.P., i have a 08 D7 that i will be riding in cadillac gaylord and U.P. should i change the springs or is stock fine, i think you said earlier on here you switched to pink

Dragon 700 exhaust springs

purepolarisprox600 said:

kraven you have a 07 d7 that you ride in the U.P., i have a 08 D7 that i will be riding in cadillac gaylord and U.P. should i change the springs or is stock fine, i think you said earlier on here you switched to pink

Click to expand...

Pure Polaris,

Leave the stock springs in, they're fine.

I actually ran the YELLOW springs in my EDGE-X 800 (flatlander) when I trailered it to Yellowstone (6500+ Feet)

U.P. is only 1200' elevation

I think it was Monte?? that posted trying the Pink springs on the 800, not sure.??

I had the chance to do some testing with this yesterday, here's my findings:
06 900 rmk, 4000 - 6000', stock VES springs
My engine revs up quicker with the valves plugged for sure, I tried it in several situations back to back, and no matter where I was or what I was doing the RPM's built up noticeably quicker with the hoses plugged ( stud between the 2 hoses ) Additionally, when using 1/2 throttle and below, judging by the exhaust note, the valves seem to be fully capable of being truly variable.

I will be leaving my hoses plugged, and I see no reason to try any different springs. The valves work awesome now!

DiscoDan said:

I had the chance to do some testing with this yesterday, here's my findings:
06 900 rmk, 4000 - 6000', stock VES springs
My engine revs up quicker with the valves plugged for sure, I tried it in several situations back to back, and no matter where I was or what I was doing the RPM's built up noticeably quicker with the hoses plugged ( stud between the 2 hoses ) Additionally, when using 1/2 throttle and below, judging by the exhaust note, the valves seem to be fully capable of being truly variable.

I will be leaving my hoses plugged, and I see no reason to try any different springs. The valves work awesome now!

Click to expand...

Just curious-did you test against another sled, if so how much difference did it make plugging the line? Did you test in deep snow or on the trail?
It's probably a mistake to assume that the solenoid functions the same on all sleds. And it's possible that some solenoids aren't working properly.
It's been my experience that you can do a lot to make a sled faster on the trail-weights, springs,helix and gears included. But when we ride in the snow those setups don't work because the sled has to work harder and can't pull a drag race setup.
If your valves open too soon in deep snow then you will lose performance. Altitude and engine size likely affect how soon the sled will pull deep snow with the valves open.
It's likely that the fuel map attempts to sync RPM and Throttle Position to the point the valves open. When the valves open you need more fuel-is that when the high speed injectors open? What aboout ignition advance?
These systems aren't simple like they once were. There are cause and effect relationships made more complex since fuel maps are complicated. As far as I know there is no info published that spells out the interaction of all the sensors, TPS, and the advance curve. Then there's the issue of fuel...what happens when you get some bad gas. Hasn't Polaris had some dificulty getting this CFI system to work for the last two years.

The testing was done only on my sled.
I would get myself into a situation, say for example a deep snow climb... try a few runs with the stock setup. Then I quickly plugged the hoses, and make a few runs with the mod. During this testing I would pay close attention to rpm buildup, max rpm, the exhaust note, and seat of the pants feel.
I repeated this process in 6 different scenarios from packed trail with 4" of loose on top, and right up to 4 feet plus of dry champagne pow.

There was never any bog or power loss felt from exhaust valves opening too soon, in fact... in every situation I tested the mod in the engine sounded and felt like it flashed up to full operating rpm(7650) noticeably quicker. It felt like a peppier power all around.

Obviously there are some variables at play from machine to machine, and elevation etc. etc.. My 900 is fully clutched and has lower than stock gearing, so it's possible that these things play a factor on how the mod affected my machine as opposed to the next guys sled, although I doubt it.

Ron said:

Just curious-did you test against another sled, if so how much difference did it make plugging the line? Did you test in deep snow or on the trail?
It's probably a mistake to assume that the solenoid functions the same on all sleds. And it's possible that some solenoids aren't working properly.
It's been my experience that you can do a lot to make a sled faster on the trail-weights, springs,helix and gears included. But when we ride in the snow those setups don't work because the sled has to work harder and can't pull a drag race setup.
If your valves open too soon in deep snow then you will lose performance. Altitude and engine size likely affect how soon the sled will pull deep snow with the valves open.
It's likely that the fuel map attempts to sync RPM and Throttle Position to the point the valves open. When the valves open you need more fuel-is that when the high speed injectors open? What aboout ignition advance?
These systems aren't simple like they once were. There are cause and effect relationships made more complex since fuel maps are complicated. As far as I know there is no info published that spells out the interaction of all the sensors, TPS, and the advance curve. Then there's the issue of fuel...what happens when you get some bad gas. Hasn't Polaris had some dificulty getting this CFI system to work for the last two years.

Click to expand...

Ron,
Not picking on you buddy JMO on this. :beer;
I truly think the design of these valves was meant to be a variable system. The solenoid from my understanding was added for emissions reasons and prevents that. I can see that with enough pressure the valve may flutter at best until the solenoid closes.

It looks like a band aid to me. Again JMO. If they truly wanted it either open or closed, why wouldn't they ditch the rubber bellows and use a true solenoid operated system mounted on the motor? The more I look at it and study this system and take into consideration how other exhaust valve systems work they are all variable. Holding the guillotine closed until a set rpm doesn't necessarily make sense in my mind. As rpms increase so does exhaust flow and pressure.

The variable exhaust system was originally designed to create more low end response. This was to combat current pipe design. Manufactures were able to develop larger belly pipes that focused more on high rpm HP. With a variable exhaust system they could inherently change exhaust port height.
Which is the opinion I have and the point I'm trying to make. A constantly closed valve cannot adjust port height through different throttle openings.

By 6000 rpm you are easily at trail cruising speed. If those valves aren't opening you are going to create way too much heat in the valves and stifle proper exhaust flow. At least that is how I look at it as it sits on my work bench.

If you are an on/off throttle type of rider I doubt it would really matter either way. Full throttle in deep pow or climbing I doubt you would notice it. However, if you run partial throttle, or do slower tree crawling this could really benefit. I would think you would notice it in roll on throttle situations. And possibly on/off/on throttle when rpm is allowed to drop below the magic solenoid closing rpm.

I'm also taking into consideration how we changed springs on the old system to get them to open sooner and more completely at higher altitudes. It is just my thinking that they may be opening too late. For as easy as it is to test I still think it is at least worth trying.

Anyone care to take a test light and see what rpm the solenoid is triggered????:beer;

Sorry for my always lengthy reads. Hope it was at least informative to some. Please chime in with any conflicting thoughts as this thread has been great for getting the gears turning. :face-icon-small-hap
Cheers all and Happy Holidays.
:beer;

Real world results

DiscoDan said:

I had the chance to do some testing with this yesterday, here's my findings:
06 900 rmk, 4000 - 6000', stock VES springs
My engine revs up quicker with the valves plugged for sure, I tried it in several situations back to back, and no matter where I was or what I was doing the RPM's built up noticeably quicker with the hoses plugged ( stud between the 2 hoses ) Additionally, when using 1/2 throttle and below, judging by the exhaust note, the valves seem to be fully capable of being truly variable.

I will be leaving my hoses plugged, and I see no reason to try any different springs. The valves work awesome now!

Click to expand...

Another unsolicited testimonial.

Thanks for posting your real world positve experience and results.

thefullmonte said:

Ron,
Not picking on you buddy JMO on this. :beer;
I truly think the design of these valves was meant to be a variable system. The solenoid from my understanding was added for emissions reasons and prevents that. I can see that with enough pressure the valve may flutter at best until the solenoid closes.

It looks like a band aid to me. Again JMO. If they truly wanted it either open or closed, why wouldn't they ditch the rubber bellows and use a true solenoid operated system mounted on the motor? The more I look at it and study this system and take into consideration how other exhaust valve systems work they are all variable. Holding the guillotine closed until a set rpm doesn't necessarily make sense in my mind. As rpms increase so does exhaust flow and pressure.

The variable exhaust system was originally designed to create more low end response. This was to combat current pipe design. Manufactures were able to develop larger belly pipes that focused more on high rpm HP. With a variable exhaust system they could inherently change exhaust port height.
Which is the opinion I have and the point I'm trying to make. A constantly closed valve cannot adjust port height through different throttle openings.

By 6000 rpm you are easily at trail cruising speed. If those valves aren't opening you are going to create way too much heat in the valves and stifle proper exhaust flow. At least that is how I look at it as it sits on my work bench.

If you are an on/off throttle type of rider I doubt it would really matter either way. Full throttle in deep pow or climbing I doubt you would notice it. However, if you run partial throttle, or do slower tree crawling this could really benefit. I would think you would notice it in roll on throttle situations. And possibly on/off/on throttle when rpm is allowed to drop below the magic solenoid closing rpm.

I'm also taking into consideration how we changed springs on the old system to get them to open sooner and more completely at higher altitudes. It is just my thinking that they may be opening too late. For as easy as it is to test I still think it is at least worth trying.

Anyone care to take a test light and see what rpm the solenoid is triggered????:beer;

Sorry for my always lengthy reads. Hope it was at least informative to some. Please chime in with any conflicting thoughts as this thread has been great for getting the gears turning. :face-icon-small-hap
Cheers all and Happy Holidays.
:beer;

Click to expand...

I agree with thefullmonte on this variable valve system. Since I am from the flatland,as is Kraven and thefullmonte, the only drawback that I see is having to change springs when going from high alt. and back to low again. I have to change setups (clutching,jetting,needles and ev springs on my 04700). I leave the low gearing. On my 06 600 I also have to change clutching and jetting. This is why leaving my solenoid operational saves me one less thing to do when going back and forth. It would appear that thefullmonte should run the pink/yellow at low alt. and the green/yellow for Kraven's D7. I don't think Monte actually rides his D8 at low alt. very much since he has a ditch banger to ride at home. I might add that I tried the heavier green/yellow at 6500' on my 700 just to test. I could feel the power loss right away and switched to the lighter orange. You could feel the power boost before I even got out of the parking lot (big diff).

just a shoot in the dark here but could you put a valve in before the solenoid and run it that way or do you need to isolate the exhaust valves from each other?

Monte,

Not going to beat this to death but Polaris has always had EV's that are either open or closed. There is no in between, you might get fluttering if you have a hole in a bellows or a defective solenoid but the strength of the spring is always pushing the valves closed. Poo was not first to the party and had patents to contend with. I believe SkiDoo was first and used crank pressure to activate the EV's so Polaris picked Cylinder pressure. Yamaha had electronic controls (on 2 strokes), don't know about Cat but they all have to dance around each others patents.
SkiDoo came out with a 3 stage valve in 07 by adding a patented feature-the valve is fully closed until the engine fires (easier starting), goes to a 2nd point when started and full open based on crank pressure. Seems to me that in order to have an EV that opened in increments you would need a mechanical gear or a valve like SkiDoo's old rotary valve on the intake. You would also need multiple slices of the valve that could be incrementally opened one at a time. The shape & location of the exiting EV doesn't make for incremental opening-it's either closing the exhaust port or it isn't.
As far as testing when the EV's open-you can feel the surge in power simply running down the trail and gradually increasing RPM until they open-you will feel it. Or elevate the rear of the sled, open the hood and watch-the tips of the guillotine will protrude from the plastic cover when they open.
The EV springs control when the EV's open-the stiffer the spring the higher the R's to open.
Under hard acceleration we saw no difference with the solenoid plugged vs stock on the 08's. There have been several maps since then and none of us know the full parameters of the solenoid function since it's controlled by the ECU-a programmable function. If it opens sooner when "off throttle" that's a good thing since your fuel economy will be better cruising down the trail with the EV's closed. As I mentioned earlier the solenoid will let the EV's open sooner "off throttle" since latent cyclinder pressure holds them open when running with the hoses plugged ala Edge sleds. This (solenoid) is a good thing when boondocking, climbing over rough terrain because it gets your bottom end power back quickly. NO it's not a linear gradual change but still works pretty good for something simple and light weight.
If you want to test the value of the two stage exhaust (EV Function) that can be done easily. Remove the springs and push the valves out of the cap, then wrap some duct tape on the protruding tips to hold them open. Reinstall and try a short ride. Your sled will be a pig, they don't have enough power to pull the higher port timing.
So the EV springs control how much pressure it takes to open the EV's and the solenoid releases that cylinder pressure sooner when you let off the throttle. The only question in my mind is if in certain conditions, altitudes, fuel map, etc if the plugged valves allow any significant improvement in acceleration-in the snow. And then you should ask yourself the next question-if there is a slight gain do you want to lose the advantage offered by the solenoid in the other conditions mentioned above.
Edit: The solenoids only function is to close "plugging" the lines so that cylinder pressure can open the EV's. When it opens it releases pressure instantly letting the EV's close. The Polaris Service manual states that the solenoid is turned off based on RPM, Throttle position & Exhaust sensor on CFI sleds. A little insight comes from the function on carbed sleds. Quote; "The solenoid is turned off (closing) at 6700RPM when the throttle flipper is at least 3/4 throttle or at 7200 RPM when the throttle flipper is at least 1/2 throttle."

well i have a stock 08 d7 switchback that i have not moded yet or done and riding on yet, my dad also just bought a stock 08 d7 121" so i will be running them side by side and testing each mod individually, waiting for good snow but i will start with plugged valves and coolant shut off, then i will add my new PC-5 with mapping from JIM @ dynotech, then i will add my vents air horn and little stuff, and maybe slp single pipe and can w/ new mapping. I will post me results as soon as i can get out riding

WOW, now this is a THREAD! don't know how i missed this one, but i think i'm gonna try it. Took me 45 minutes to read the thread and 10 minutes to do the mod the way it looks. I can see both monte/kraven's point of view and also Rons. From what i understand, i should actually gain more from this being on the flatland.

metallicat said:

WOW, now this is a THREAD! don't know how i missed this one, but i think i'm gonna try it. Took me 45 minutes to read the thread and 10 minutes to do the mod the way it looks. I can see both monte/kraven's point of view and also Rons. From what i understand, i should actually gain more from this being on the flatland.

Click to expand...

It seems to work. Did it to an 09 800 and the mid range felt a lot more like an older edge VES motor. Not sure if I could feel a lot of gain really, but it was different for sure. This was at 1400-1500'

all pluged up

put a bolt in mine 07 600 /155 it rips

Did the mod and it works. Just think Polaris had a real midrange lean arear at around 6000 rpm and they are also holding the exhaust valves close there to. So you got a real hot burn and a small exhaust port not letting the heat out. That heat will come in contact with the side of the piston also when it is exposed overheating the piston and making it expand more. Sound familiar? The only way the engine will run when it is that lean is with the exhust valves down. Man talk about cooking your own goose. The reason in snowmobile that the vlaves do not have to have a controlled opening and can be open or closed is becuse becuase of the clutch system we never spend anytime at one rpm and demand power from the engine at that rpm. on a bike you can be in 3rd gear pulling a corner and you want power at 5000 rpm all the way until you need to swith to forth. On a sled whe you hit going around a corner your rpm goes up right away.