Check out Powderbuggies comprehensive review of Silber’s plug-and-play turbo solution. Is this truly a riders dream or a tuners nightmare? How rideable was the sled? How reliable? What problems did we experience? Was it a cheat code to the video game that is snowmobiling? Find out…
Polaris Axys Silber External Wastegate Turbo Review
Unless you’ve been living under the proverbial rock, Silber Turbos is likely a company you are aware of if you are into mountain snowmobile riding. As one of the pioneers of the “tunerless turbo”, Silber offers the promise of less tuning, more riding, better reliability and quicker installs when compared to most of the other guys’ products. Oh and they offer their kit at a price hundreds below that of the competition.
Lets get the specs out the way first, we’ll dive into what they mean thereafter.
- kPA ceramic ball bearing water cooled turbo
- Recirculating blow off valve
- External wastegate housing setup with 7psi spring stock (we changed to 5)
- Stainless steel exhaust
- Silicone charge tubes
- ECU Reflash – ECU must be sent back to Silber to be flashed with their turbo map. There is no tuner box with this setup.
- Oil Protection – Silber turns up the Axys oil pump to satisfy the demands of a turbo sled at altitude. This is something proprietary to Silber.
- Clutching to match
Sled – Stock 163 Axys RMK
Silber has taken a lot of time to create a nice, tight, clean package. When considering how little room there is under the hood (or side panels) of the Polaris Axys-RMK, its a bit of an engineering feat just to cram all that technology into the space. Silber has found a way to do so eloquently, without anything binding, getting in the way, or generally causing problems.
Installation of the Silber setup is incredibly easy. No, its not as easy as putting on a pipe or a can, but if you are at all mechanically inclined and understand how a snowmobile works, you’ll likely have little problem installing the kit. Check this video below to watch the Silber boys themself install a kit in the back of a trailer in under an hour. Clutching wasn’t done up in this video, but clutching is something we all know is pretty simple to do. Worth noting, there is no cutting or permanent alteration of the sled when installing a Silber kit.
How it Works
Lets start at the basic level of how-a-turbo-works for those that are unaware. A turbo, most simply, is a compressor driven by exhaust gasses that pressurizes air before going into the intake. The more air a motor can cycle, the more power it can put out (think of a motor as one big air pump). With respect to a snowmobile, most manufactures have relied on a secondary ECU to control the fueling via a secondary set of injectors. This is why most turbo setups prior to the “Silber ECU reflash” relied on a stand alone ECU box where the user had to program in fueling requirements based of boost levels, temperature, elevation and even clutching. For obvious reasons, this can be a bit overwhelming to your weekend warrior.
Silber solved this problem by utilizing the sleds tmap sensor, the sensor that detects intake pressure. This sensor is utilized by the stock sled ECU to accurately fuel via the injection system based off elevation and temperature (which is why nobody has to “jet” a fuel injected sled).
Silber has developed a dynamic map based off this sensor that not far removed from the sleds stock map. Like the stock map, it can dynamically respond to elevation, temperature, boost levels etc and fuel accordingly. Obviously, Silber is using this sensor beyond what it was intended. Does it work? Just keep scrolling down…
Fueling & Power
Hi. I’m Jeff. I’m not Chris Burandt or Keith Curtis and I know it. Hence, I don’t need a 240 horse sled. Being I ride in the Wyoming/Idaho area where elevations can touch 10,000 feet, the initial goal with this kit was to bring the sled back to slightly-better-than stock performance at elevation (bring sea level performance to the mountains). And sure, if I can get a little more, that’s great but I wanted a sled I could run on pump gas and not create engine or driveline issues along the way. I wasn’t looking for a chute climbing monster or similar. I wanted something that’d keep me from getting stuck (as much anyway), give me more options in tight, technical trees and let me venture off the beaten path on those **really** deep days where most stockers are track-poaching
The Author enjoying some boost. Day one on the setup. This is with sub-par clutching.
So how much boost to run to achieve slightly-better-than-sea-level performance in the mountains?
Anyone who has gone from sea level to the mountains of Colorado or Wyoming can attest to the “elevation headache”. Simply, the air is thinner and the body has to work a lot harder to garner the same amount of performance at higher elveations. Same rings true for snowmobiles. A motor is effectively one big air pump. More air equals more power. If there is less air at elevation (which there is), one can use the turbo charger to add the “lost air” back into the motor and get back those precious horses lost in the mountains
Some quick math reveals atmospheric pressure is 4.1(ish) psi less at “Jeff’s riding elevation” than it is at sea level knocking the sled’s performance nearly 30%. This means, if I’m running 5psi through the turbo, I’m gaining about 1 psi, or 10 horse power, over a stock sea level sled at elevation.
All things considered, I felt 5psi is a great way to keep motor output “reasonable” (probably around 160-175 horse at elevation) while still noting a major improvement in sled performance. Worth mentioning, we did not run a boost gauge, all boost pressure settings were governed by the wastegate spring (more on that below).
At 5psi, I should be fine on 91 non ethanol pump gas, but being we often start riding at 6,000 feet, I felt the assurance of a few gallons of AV gas to be well worth it. To add, much of my riding can be lower than 10,000, somewhere around 8,000. Though it’s 99% certain I’d be fine on pump gas in my riding environment/boost levels/compression ratio, I found it cheap insurance to have too much octane than not enough, even if some people do comment on over-octane to create poorer performance (they’d be right, but with a gallon or two of 100AV, they’d also be splitting hairs).
The problem with running a less-powerful setup than the out-of-the-box Silber kit (which comes ready to run at 7psi) is my clutching would be too heavy for the sled. After trying the stock Silber setup with less weight, I went back to the drawing board, settling on a steeper helix, softer spring primary spring and lower weight. For those that are wondering here are my settings…
- 160-320 Primary Spring with delrin washers (2)
- 10-70 weights
- 46 deg Helix
- Orange secondary spring
This is an area of contention for us here at PowderBuggies. So many people spend a ton of money and time on their turbo setup and clutching but completely ignore suspension, most notably rear skid setup. As rad as #wheeliewednesday may be, if you are lifting your skis excessively, you likely aren’t able to effectively control the sled and much of the energy is going into that sweet, sweet trench you just laid, (not propelling you up the mountain).
The ability to couple a skid as well as increasing compression and spring rate of your rear suspension all should be considered when installing a turbo kit. Otherwise, ridability will suffer. No, you don’t need to go buy a new set of Fox Evols, but you should at minimum bring your stockers to a good shop for a rebuild, revalve, and considering going up one spring weight on the rear skid shock. Adding a KISS coupler is also an excellent idea (and gives you “wheelie” mode as an option.)
For us, we ended up going to a set of clickers (running the rear track shock nearly closed with respect to compression), going up one spring weight and re-valving for slightly slower rebound (compression stack unchanged). This resulted in an incredibly balanced sled that was still “light” on the front end. (I was still able to keep a fair amount of preload on the front track shock)
As implied above, Here is the million dollar question – “Does the Silber kit work?” Yes. Hell yes. Its like being touched by the hand of God. Did I have tuning or reliability problems? Not with the kit – but I did have to tinker, more on that below.
Throttle response was crisp, especially while actually riding. I honestly noticed no difference in ride-ability from a stock sled. Compared to a year-prior Pro RMK, the turbo spooled more quickly and more precisely, likely due to the lightened crank and new exhaust valves of the 800HO motor, a welcome surprise.
I often ride in tighter, more technical terrain where aggressive blipping of the throttle is paramount. This is where I was most concerned the ECU reflash would not be able to keep up with the throttle demands, but my concerns were quickly put to rest on my first day in the trees. It was no different than riding a stock sled, I just had a more power on tap if I needed it. Oh, and lag was certainly there, but considering the RPM we operate a 2-stroke sled at, it wasn’t that noticeable with a very usable “top of the” bottom end. The turbo really started to come on around 5,500 RPM (though not at full boost). If I had to describe power delivery in one word it would be “smooth”. In two words “Smooth” “Unleashing All Hell”…oh wait, that’s 4 words. But I digress.
The only problem with the setup is a slight amount of hesitation down low prior to clutch engagement. This was more prevalent on my sled than other Silber setups leading me to believe the TPS was not adjusted properly (or some other problem such as a heavy fuel pump at idle). Either way, I grew accustomed to clearing out the sled after letting it idle for a period of time. When riding, I never noticed the issue as it was never prevalent when RPMs were north of clutch engagement. In the end it was far more of an annoyance than it was a real problem, something I generally forgot about until I went to start my sled up after lunch and had let it idle for a few minutes.
The only other time I had the sled “miss” was due to fouled plugs and a slipping belt. The turbo needs load to develop boost. If this load is inconsistent or sporadic, the ECU gets confused and the sled will fall on its face. Once I dialed my clutching in and made sure my plugs were not fouled, the sled never missed a beat.
As I implied above, clutching took me entirely too long to really work out. Remember, I knowingly went into no-mans land, new chassis, redesigned motor, new turbo setup and a low-boost setup. Certain setups had me missing RPM, others were slow to get there, some were blowing belts. I ended up *really* progressing my knowledge of clutching as a result of my experimenting but in the end, I found a setup (and belt) that worked awesome, and I couldn’t have been more happy.
One side note, after arriving at the correct clutch setup, the kit really took on a life of its own, so much so, I questioned if I was *really* running 5psi as the waste-gate. After poising this question to the Silber boys, they noted we may be seeing a little north of the PSI the waste gate spring is built to putout. This is due to their waste gate plumbing. So, users take note – and fuel accordingly. This year, I’ll plumb in a boost gauge to be certain of where I’m at. That said, external waste gates are notorious for limiting boost spikes and smooth power delivery, both of which I found to be true, anecdotally, while riding the setup.
Do you need to be a pro?
People often scoff when they hear I have a turbo on the sled. Though I come from a fairly athletic background and am a “professional” in various other mountain sports, I do have a limited amount of time on a sled. Still, I enjoyed it and found it to make mountain riding easier as it gave me more line options in heavily treed/steep terrain. While not appropriate for an absolute begginner, if you are comfortable sidehilling, riding wrong foot forward and can generally place your sled where you like, you likely are a good enough rider to enjoy a turbo kit such as this.
Two things worth mentioning that do not have to do with performance. First, the kit is not quiet. I rode in earplugs and suggest you do too. Silber is working on a fix for this, as they too would like a quieter kit, but they also know anything to limit sound could also limit performance. They value performance first and foremost (which we like). Second, the kit drinks oil. We love this. Silber is the only turbo company that learned Polaris is limiting oil usage at higher elevation. The thought by Polaris was, at higher elevation the sled is putting out less power so it needs less oil. Obviously, this is far from the truth with a turbo sled. Through Silber’s reflash, you are actually getting the correct amount of oil through the top/bottom end, something that should vastly improve reliability.
Vs the Other Guys
Really, there is only one other turbo on the market that competes with Silber’s kit, the Sidekick from Boondocker, and it’d be unfair for me to make a full comparison as I don’t have nearly enough time on the Sidekick to comment. Maybe we’ll get to do a direct comparison later this season. Having ridden a number of Boondocker products we can say their stuff too works excellent, but the overall ease, price point and performance of the Silber kit is pretty hard to argue with. That said, until we have both in our hands, we’ll leave the direct comparison to another time…
Dollar for dollar, Silber is offering top shelf performance and entry level turbo pricing. Anyone looking to add real horsepower to their sled really out to look no further than a turbo kit, and the Silber kit is one of the cleanest, easiest going products on the market. The only real downside to the kit is its a bit like crossing into a new dimension of the snowmobile world, simply – there is life before boost and life after boost. And like Pandora’s Box – once opened, it can be next to impossible to ‘go back’. Use at your own discretion…