I've had a few people ask me about this, so here are some pictures and info on how I'm controlling the boost on my s/c nytro.
Ive only put 100 miles on my sled since i installed it, but with the twist of a screw i was able to adjust the boost on the mountain. I was a little worried that it might not be able bleed boost without boost creeping on the top end, but it held 14 psi on couple long pulls, so boost creep doesn't seem to be an issue, (and I'm bleeding a lot of boost!) But more testing will be needed to know for sure. One thing I did notice is that it DOES have a limit on how much boost its capable of bleeding off. Near as I can tell, it will only bleed off 10 - 12 psi. I'm pullied for 23ish pounds of boost in my riding area, and the lowest I could get the boost was 10psi.
One thing to keep in mind when under driving the blower as much as I have or at all for that matter is that it also dramatically effects the midrange of the sled. Which will in turn effect fuel mileage. Being that my blower is pushing 23 psi at full throttle it makes 1/2 that psi at 1/2 throttle and so on. So I'm making 5 psi at clutch engagement and I'm usually cruising down the trail at 10 or so psi. Not good for fuel economy. BUT the responsiveness of my sled in the trees is unreal. I'll probably end up swapping the pullies to lower the boost a bit and call it a day.
But by far the best part about controlling boost on a s/c sled! Clutching setup. It is 100 times easier to get your clutching dialed in when every single change you make doesn't effect how much boost your making. Before I installed the boost limiter, I could get my boost where I wanted it or my rpm's where I wanted them but never both. Now I'm at 14 psi making 8,800 rpm's
As far as how it works. It's just a billet housing with ports around the sides, a ball and a spring. Turn the knob in, more spring pressure = more boost. Turn it out, less spring pressure = less boost.
Heres where I bought the boost limiter from.
http://www.928motorsports.com/parts/boostlimitervalve.php
Here are som pics of where I installed it.
Ive only put 100 miles on my sled since i installed it, but with the twist of a screw i was able to adjust the boost on the mountain. I was a little worried that it might not be able bleed boost without boost creeping on the top end, but it held 14 psi on couple long pulls, so boost creep doesn't seem to be an issue, (and I'm bleeding a lot of boost!) But more testing will be needed to know for sure. One thing I did notice is that it DOES have a limit on how much boost its capable of bleeding off. Near as I can tell, it will only bleed off 10 - 12 psi. I'm pullied for 23ish pounds of boost in my riding area, and the lowest I could get the boost was 10psi.
One thing to keep in mind when under driving the blower as much as I have or at all for that matter is that it also dramatically effects the midrange of the sled. Which will in turn effect fuel mileage. Being that my blower is pushing 23 psi at full throttle it makes 1/2 that psi at 1/2 throttle and so on. So I'm making 5 psi at clutch engagement and I'm usually cruising down the trail at 10 or so psi. Not good for fuel economy. BUT the responsiveness of my sled in the trees is unreal. I'll probably end up swapping the pullies to lower the boost a bit and call it a day.
But by far the best part about controlling boost on a s/c sled! Clutching setup. It is 100 times easier to get your clutching dialed in when every single change you make doesn't effect how much boost your making. Before I installed the boost limiter, I could get my boost where I wanted it or my rpm's where I wanted them but never both. Now I'm at 14 psi making 8,800 rpm's
As far as how it works. It's just a billet housing with ports around the sides, a ball and a spring. Turn the knob in, more spring pressure = more boost. Turn it out, less spring pressure = less boost.
Heres where I bought the boost limiter from.
http://www.928motorsports.com/parts/boostlimitervalve.php
Here are som pics of where I installed it.
