elevation and clutching?

mkhoskins · Aug 28, 2010

I know this is a little elementary, but why do you set the clutch up according to elevation? What the difference if a clutch is set up for 5-7k feet or 8-10k feet, I dont understand....if someone could explain I would greatly appreciate it. :face-icon-small-con

philsummers21 · Aug 28, 2010

Higher altitude you lose hp.

mkhoskins · Aug 29, 2010

philsummers21 said:
Higher altitude you lose hp.

On a boosted sled why would that matter if you can just turn your boost up when you lose power? I am just wondering because so many guys are saying that there clutching is set up perfect for 7k-9k feet and I wonder if that means it will run like **** when you are not at that altitude?

MTN_VIPER · Aug 29, 2010

mkhoskins

What that means is it would probably over-rev slightly at lower elevations and under-rev slightly above 7-9k feet.

I may run ok, however the shift rpms may not be in the ideal range at wide open throttle.

Boosted sleds will usually have a nice broad power peak curve. Possibly as wide as a thousand rpms! While a high strung small displacement 2 stroke can have a very narrow power peak band. Sometimes as narrow as a couple hunderd rpms.

Because of the adjustable boost levels and the broad power band, your boosted four stroke will be less sensitive to elevation changes. This is because it is much easier for the engine stay at it's peak power output. It may not care if it's turning 9200 or 8600! While a 600 rpm change is huge for a N/A two stroke.

I would set it up, so that the rpms are at they're peak power output for the most common areas that you ride. If you happen to go up or down a couple thousand feet in elevation, your still going to have plenty of power to bring a smile to your face!

Motleyone · Aug 29, 2010

Somebody correct me if this does not sound right. To answer your question about a turbo sled you would want to change clutching (especially primary) at a higher elevation at some point because you can only turn the boost up so high. In terms of a NA sled you lose hp as you go up in elevation. Because of this your sled does not have the abililty to throw the heavier weights around like it did at a lower elevation. Since your motor is robbed of power at higher elevation you need to make it easier for the clutch to close to reach your peak rpm. You do this by decreasing your primary clutch weights. Notice I said spring rate and not preload. This is why there is such a wide variety of spring preload/spring rate combinations out there. The preload determines at what rpm your belt will engaged and the sled starts to move. The spring rate determines how much the spring will compress under load, usually measured in kg/mm. If you leave the same spring in the primary and just decrease the weights there is less resistance for the motor to spin those weights out on the arms to compress the spring and fully close your primary clutch and reach peak rpms. At higher elevation you would want to reduce your preload on your primary spring if it is a deep powder day. This will allow for lower rpm engagement. This will stop you from banging into engagement which will cause you to trench.

mkhoskins · Aug 29, 2010

Motleyone said:
Somebody correct me if this does not sound right. To answer your question about a turbo sled you would want to change clutching (especially primary) at a higher elevation at some point because you can only turn the boost up so high. In terms of a NA sled you lose hp as you go up in elevation. Because of this your sled does not have the abililty to throw the heavier weights around like it did at a lower elevation. Since your motor is robbed of power at higher elevation you need to make it easier for the clutch to close to reach your peak rpm. You do this by decreasing your primary clutch weights. Notice I said spring rate and not preload. This is why there is such a wide variety of spring preload/spring rate combinations out there. The preload determines at what rpm your belt will engaged and the sled starts to move. The spring rate determines how much the spring will compress under load, usually measured in kg/mm. If you leave the same spring in the primary and just decrease the weights there is less resistance for the motor to spin those weights out on the arms to compress the spring and fully close your primary clutch and reach peak rpms. At higher elevation you would want to reduce your preload on your primary spring if it is a deep powder day. This will allow for lower rpm engagement. This will stop you from banging into engagement which will cause you to trench.

always what I am looking for, motleyone, You're the best. That makes a lot more sense, I have my clutch setup for my sled perfectly right now(done by someone else) And just wanted to know what that truly means. Thank you guys for the post it has been helpful.

Motleyone · Aug 29, 2010

No problemo, hope you get her dialed this winter.

Bigbragg · Jan 27, 2014

So what would be the ideal RPM for a 2013 nytro with the MCX 270 kit at 5000 - 7000 feet ?

up-high · Jan 28, 2014

8600 whatever the altitude. That seems to be the rpm that motor likes. Unless you ride over 10,000 feet, I don't think clutching is an issue. The turbo just spins faster to maintain the set boost. Never changed the clutching on 2 Apexes and 2 Nytros. Course I rarely rode over 10,000 feet either.

Bigbragg · Feb 8, 2014

Clutching

I took my nytro in for service and dealer put in a purple Epi spring. Now I rev at 9100 and only get 13 or 14 lbs of boost

BCBOOST · Feb 8, 2014

Bigbragg said:
I took my nytro in for service and dealer put in a purple Epi spring. Now I rev at 9100 and only get 13 or 14 lbs of boost

But is that spring not in the Secondary?? Put a little weight in the primary clutch to load engine and build more boost.
BC.

Bigbragg · Feb 14, 2014

BCBOOST said:
But is that spring not in the Secondary?? Put a little weight in the primary clutch to load engine and build more boost.
BC.

I bought the sled new off the showroom floor with MCX 270 all ready installed. Pretty sure the clutches are stock except for the secendary purple epi spring that a different dealer had just installed.
What weights and what weight would u recommend. I live at 1600 feet and drive 11 hrs to Mcbride where I ride at a max of 8000. So trial and error not really much of an option.
I never ride it here at home.
Thanks for all your help

BCBOOST · Feb 14, 2014

You really do have to take it apart and confirm what is in there!! But you would really like a 47 degree helix with the purple spring set at 0-1, and in the primary a Blue white Blue spring and the 8BU yamaha weights fully loaded with steel rivets or the Dalton DTYA-2 adjustable weights!!
BC.

julio · Mar 14, 2014

clutching

Bigbragg said:
So what would be the ideal RPM for a 2013 nytro with the MCX 270 kit at 5000 - 7000 feet ?

the mcx automatically adjusts boost for you, I have ran my nytro from 2000 to 12000 and have barely seen a rpm change, a little more sluggish up high but the same when throttled up. bc boost gave you a great set up for your clutching, however there are other ways to get there check what you have in the clutches and compare to advised.. if you have the set up you should be able to gas it and run it anywhere you want.. julio

Search

elevation and clutching?

mkhoskins

Free Member

philsummers21

Well-known member

mkhoskins

Free Member

MTN_VIPER

Well-known member

Motleyone

Well-known member

mkhoskins

Free Member

Motleyone

Well-known member

Bigbragg

Free Member

up-high

Well-known member

Bigbragg

Free Member

BCBOOST

Free Member

Bigbragg

Free Member

BCBOOST

Free Member

julio

Free Member

Similar threads