Boost Clutching- lower elevations
- Thread starter kidder17
- Start date
I wonder if they are clutched to rev high to cure the strange running issues from last year? I would bet.....
I wouldn't spend much time worrying about what their dyno shows. I've found it doesn't usually translate to reality
Also I've run my NA 850s at 83 to 8400 and turbos 8400+ and thst motor seems to LOVE rpm and never fade. Vs if u only do 8200 or so it pulls down a lot more often. Paper says it shouldnt run thst well up high but reality dictates otherwise.
Could be the tac reading high a couple of hundred rpms.
These heavy weights are now up. Not sure if they can be ordered or not, but might be worth looking into
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onetwothreego
Member
Something I ran across.
I have an assault boost with p22 stock & p85 as ill probably be using this more
I got a trs bar which I like cuz of no lead in. I had my p85 on with 0.030" gap from front of secondary with trs bar. Toke my p85 off & put my p22 back on. Checked the clutch alignment again with trs bar & seen the p22 sits 0.100" further back then p85 when torqued in. The total was 0.130" Anybody else notice this?
I have an assault boost with p22 stock & p85 as ill probably be using this more
I got a trs bar which I like cuz of no lead in. I had my p85 on with 0.030" gap from front of secondary with trs bar. Toke my p85 off & put my p22 back on. Checked the clutch alignment again with trs bar & seen the p22 sits 0.100" further back then p85 when torqued in. The total was 0.130" Anybody else notice this?
With the smart boost get your clutch dialed and you should be good at any elevation up to 12000 ft. The power you lose it makes up for with more boost it's like efi for altitude.
These turbo sleds should only need one clutch set-up for any altitude but before boost is built (engagement rpms) they will lag at higher altitude more than lower altitude because of air pressure. I would change springs before weights though as heavier weights will make the pre-boost performance worse than if a guy was to put in a lighter primary spring. Springs are cheaper too.
So my thoughts on this after almost 2 winters on a boost riding from 1500 to 10k feet is as follows.
Peak power is almost the same high to low. There does seem to be a little bit of variance in polaris' altitude correction tables. Seems like they target an absolute pressure only and not an air density. Higher elevations mean more boost less atmospheric so inherently higher intake air Temps = less actual oxygen in combustion chamber. Regardless the change is fairly small amd does not warrant clutching changes unless your very picky.
The much bigger issue when making large elevation changes and reason for varied clutch setup is bottom end performance. The change in pre boost performance is wild. The sleds rev way faster t lower elevations and the turbo spool is quicker as well. This presents an issue. The oem clutching is meant to handle this fast upshift at low elevations but as you go up in elevation bottom end gets lazier and lazier. After some substantial playing with clutching I've got a high elevation clutching setup that allows the motor to free rev more easily down low and make the bottom end performance much more enjoyable in the 7-10k elevation range. Unfortunately if I run this setup down low I will actually get a bog. I'm not sure if it's just a mapping error or a legitimate rate of rpm change saftey thst polaris programs in. I have to add more heel weight and softer primary start rate to load the motor out of the hole or its virtually unridable due to this bog. And consequently, if I run my low elevation configuration at high elevation it absolutely sucks on the bottom end and j want tk dell the sled for a 9r.
So bottom line is peak power is very close to thr same 0-12k BUT. Power curve is vastly different and there are some gains to be made for specific riding elevations in regards to maximizing throttle response.
Peak power is almost the same high to low. There does seem to be a little bit of variance in polaris' altitude correction tables. Seems like they target an absolute pressure only and not an air density. Higher elevations mean more boost less atmospheric so inherently higher intake air Temps = less actual oxygen in combustion chamber. Regardless the change is fairly small amd does not warrant clutching changes unless your very picky.
The much bigger issue when making large elevation changes and reason for varied clutch setup is bottom end performance. The change in pre boost performance is wild. The sleds rev way faster t lower elevations and the turbo spool is quicker as well. This presents an issue. The oem clutching is meant to handle this fast upshift at low elevations but as you go up in elevation bottom end gets lazier and lazier. After some substantial playing with clutching I've got a high elevation clutching setup that allows the motor to free rev more easily down low and make the bottom end performance much more enjoyable in the 7-10k elevation range. Unfortunately if I run this setup down low I will actually get a bog. I'm not sure if it's just a mapping error or a legitimate rate of rpm change saftey thst polaris programs in. I have to add more heel weight and softer primary start rate to load the motor out of the hole or its virtually unridable due to this bog. And consequently, if I run my low elevation configuration at high elevation it absolutely sucks on the bottom end and j want tk dell the sled for a 9r.
So bottom line is peak power is very close to thr same 0-12k BUT. Power curve is vastly different and there are some gains to be made for specific riding elevations in regards to maximizing throttle response.
So leave it clutched for 6k+, and ride a 9r below 6k. Best of both worlds.
I notice the Polaris parts fiche doesn't even offer alternative weights for the Boost as it does for the 850 and 9R. My 23 Pro 165 was holding 8550rpm on climbs, right from new. I went with the Ibexx clutch kit. Unfortunately won't get to test it until next season...
Maybe just change to a softer primary spring finish rate?
I had heard the Ibexx was a major improvement all around and is a pretty big hit with a lot of locals in my riding areas, so I just went that route.
