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When tuning for elevation and deep snow.....

byeatts

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Are you guys tuning for the peak torque or peak horse power when you ride above 8000 feet and the snow is deep.

DPG

I and SRC did can/pipe pressure testing at elevation, Very interesting results , Your stock settup will not be tuned at elevation..in fact any settup will be out of perfect tune with 4K change of elevation.This is for the truely Anal[like SRC] pipe pressure will drop Aprox .2 every 1k feet. That perfect pipe pressure is what charges the cylinder from the pipe.
 
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D
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I and SRC did can/pipe pressure testing at elevation, Very interesting results , Your stock settup will not be tuned at elevation..in fact any settup will be out of perfect tune with 4K change of elevation.This is for the truely Anal[like SRC] pipe pressure will drop Aprox .2 every 1k feet. That perfect pipe pressure is what charges the cylinder from the pipe.

Peak Hp I agree what about peak torque....You can clutch cashed for both Peak Hp or Peak Torque

DPG
 
O
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Most 2 strokes need to be tuned for clutching to run at peak hp rpm. They do not make enough torque to move the sled, it requires the inertia of the rpm/hp to make track speed.

Now my buddies 200 hp M1000 LOVES to crawl through the trees at about 5500 rpm, right around its peak torque. It is quite the tractor on a 162 track. The clutching allows this and the sled works well in the trees. It is still to heavy but impressive, and the torque makes a BIG difference over the 800s.

When you crack it open on the hill it climbs like nothing short of a turbo. Climbing starts around treeline 11,000 + and on up to the tops around 13k.
 

kanedog

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No one has a dyno within 10 hrs of me so I don't know where my peak hp and torque are. I shoot for 8300 on the oem tach which I think is 150rpm high.
2013 Turbo Polarii 800.
 

kiliki

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set for target rpm for the pipe at alt. no peters are measured on the trail (in the west). i even set for 100 rpm higher as heat will take this back on long climbs and back to back pulls.
 

Dartos

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So if I understand this right, the peak horsepower will change as you change altitude because of pipe pressure?

Assuming that is correct how much RPM are we looking at per 1000 feet of change? 2? 25? 100? 500?
 

Dam Dave

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So if I understand this right, the peak horsepower will change as you change altitude because of pipe pressure?

Assuming that is correct how much RPM are we looking at per 1000 feet of change? 2? 25? 100? 500?

the horse power changes because the engine runs out of air just like you do, less air = less HP = less RPM = must remove weight from Pri clutch to get RPM back
 

Coldfinger

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How much rpm is lost per xx of elevation gain? I'm not 100% (haven't owned a Ski-doo since 2005) sure but I believe the Ski-doo TRA clutches with the adjustment bolts would change the rpm in 200 rpm increments. The numbers went up to 6 but I don't recall if there is a 0 setting. Assuming there is a 0/no mark for sea level, this gives 7 settings x 200rpm, so 1400 rpm worth of adjustments to take you from sea level up to 13,000 ft or so.??
 

Dartos

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I and SRC did can/pipe pressure testing at elevation, ?.............. pipe pressure will drop Aprox .2 every 1k feet. That perfect pipe pressure is what charges the cylinder from the pipe.

So if I understand this right, the peak horsepower will change as you change altitude because of pipe pressure?

Assuming that is correct how much RPM are we looking at per 1000 feet of change? 2? 25? 100? 500?

the horse power changes because the engine runs out of air just like you do, less air = less HP = less RPM = must remove weight from Pri clutch to get RPM back


I understand that the horsepower changes with elevation.

In byeatts post I was trying to discern if the change in pipe pressure he refers to - 2 tenths of 1 psi per 1,000 feet of elevation - actually causes a change in the RPM where peak horsepower is produced. And if so, how much?

So as an example if I produce peak horsepower at sea level on a 20 degree day @ 8,000 RPM and then at 10,000 feet on the same 20 degree day is my peak still 8,000 RPM?

NOTE: I choose 20 degrees at both elevations to remove temperature as a variable.
 
D
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Since hp at high elevation gets depleted from 150 hp @ sea level to approx. 115 hp @ 9000 ft. ( 3% per 1000 rule ). It alway a good idea to clutch for the quick and snappy torque of your motor regardless of brand.

DPG
 
D
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All CVT's have an overdrive and at high elevation deep snow riding you never hit overdrive...Before you hit the steep & deep next time take a Black EL Marco and draw vertical lines on you primary sheave to visually see how far your sled is shifting. You'll be surprised to see that your sled at high altitude aka deep powder snow doesn't achieve full shift out aka overdrive.....Which is OK you want to be in the meat of the clutch which is where the torque is.

DPG
 
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geo

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The peak HP and torque rpm of a particular engine-pipe combo doesn't change very much with elevation.

Total HP-torque is lost with elevation (for reasons everyone knows) and for the same reasons pipe pressure is lost. Restricting the outlet on the pipe to get back that pressure is a bandaid that can bring back some noticeable peak but usually with a slight loss at midrange due to the restriction acting like a restriction at low flow.
Best results is a pipe built at your elevation but we all get pipes for Alaska lol stock.

Of course less HP-torque needs clutching changes which is why we have that sticker near the clutches.

More important info to know (when picking a shift rpm) is your pipe temp. Not pyro point (like where you mount for gauges) but belly point (like where they all mount a prob now).
Pipes are tuned for the speed of sound but speed of sound is very different at different temps. So, warm pipe compared to hot pipe can change pipes tuned peak by 300 to 600rpm. (the better mountain pipe is the one that only changes it's peak by 300 rpm.).
This 'putor input (belly temp senor) was added to help the pipe get to the temp that it was designed for in the dyno room. Usually with timing retard. So with most modern sleds it is easier to pick a shift rpm than in the past.
Remember clutching twin and triple piped sleds without this help from the 'putor in the past. How you rode it was just as important as the weights you picked lol.

Torque or HP? You have to remember that both move up and down in rpm with pipe temp and really your powerband is more important in the mountains (why we all love big bores lol).
Pipe temp changes a lot on a mountain sled. Brap brapping through the trees can cool your pipe as much as warm it if your a bit rich or advanced no matter how much wrap or coating it has. Cooler pipe needs less rpm to be at peak.
So the same engine-pipe-sled, ridden at the same elevation may run better clutched for 200 rpm less with a brap brapper on it compared to a high-marker. That`s not because one is clutched for torque and one for HP but because they are clutched for average pipe temp peak.

Powerband. The best NA 800 mountain sled out there today (lol) has the least HP-torque, yet still wins everything gate to gate on a hill or tree to tree in the real mountain world cause it`s snappy. It`s snappy because the torque peak goes from 7600 to 8300 so pipe temp changes moving peak around are not as noticeable to the governor (primary clutch) and it keeps trying to push the belt up the sheaves.

One thing I`d like to add about clutching a mountain sled (I`m a brap brappin torque guy), if you err a gram or so towards the HP side there can be some advantages.
One, a bit more rpm can be mile or 2 more full bury trackspeed just from rpm. Two, lighter backshifts faster than heavier. Three, the best days are low pressure storm days lol with snow piled over everything so the little motor is a bit more breathless and haulìn' more. Four, if you join the high markers you'll be closer to peak that pipe temp dictates.

All the info you want on the pipe temp and peak changes can be found on DTR. Worth the 30 loonies if your interested.
 
D
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Pipe temp definitely factors into the equation even with pyro's 6" from the "Y" my temps were always steady at 1200 to 1250 @ 9000 feet. The issue at the altitude is "Air" and changing "Barometric Pressure" which will rob peak horsepower...There's a cure for everything it's called Turbo.

DPG
 
L

LRD

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I and SRC did can/pipe pressure testing at elevation, Very interesting results , Your stock settup will not be tuned at elevation..in fact any settup will be out of perfect tune with 4K change of elevation.This is for the truely Anal[like SRC] pipe pressure will drop Aprox .2 every 1k feet. That perfect pipe pressure is what charges the cylinder from the pipe.

Pipe pressure drops like a stone as you go from flatland MN (1000 ft) to ride in mtns at 9000 to 11000 or more ft.

Here is the thread on Snowest that has a great deal of info on pipe pressure.
http://www.snowest.com/forum/showthread.php?t=299780

Last winter I found pressure sensor that I hooked to my digital touch screen dash gauge. I was able to monitor my egt's on cylinders plus a third egt center of pipe plus the pressure sensor.

As the pipe temp at the belly goes up to full operating temp the pressure goes up to, so they are interrelated.

I picked up considerable performance by getting pipe pressure from just under 2 psi to close to 3 psi, 300 to 400 rpm increase at 9000 feet by just raising the pressure with pipe restriction, no clutching changes.

Its free HP almost!! Just need a gauge to find it. Appears over 3.5 psi is pushing the limits and pushes to much heat back k into cylinder causing possible detonation etc.

In the early 90's I took my Land & Sea Dyno to Cooke and Rick at Exon let me do some dyno test on my sled, Big bored 617 in a Phazer to see what was happening with the power curve. I knew about pipe pressure back then as I had designed the pipe and can and made them myself but didn't have the third EGT in the belly of the pipe or anyway of measuring Pipe Pressure.

Still alot to be learned about two strokes!!

Good Luck
 

byeatts

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Nov 29, 2007
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Pipe pressure drops like a stone as you go from flatland MN (1000 ft) to ride in mtns at 9000 to 11000 or more ft.

Here is the thread on Snowest that has a great deal of info on pipe pressure.
http://www.snowest.com/forum/showthread.php?t=299780

Last winter I found pressure sensor that I hooked to my digital touch screen dash gauge. I was able to monitor my egt's on cylinders plus a third egt center of pipe plus the pressure sensor.

As the pipe temp at the belly goes up to full operating temp the pressure goes up to, so they are interrelated.

I picked up considerable performance by getting pipe pressure from just under 2 psi to close to 3 psi, 300 to 400 rpm increase at 9000 feet by just raising the pressure with pipe restriction, no clutching changes.

Its free HP almost!! Just need a gauge to find it. Appears over 3.5 psi is pushing the limits and pushes to much heat back k into cylinder causing possible detonation etc.

In the early 90's I took my Land & Sea Dyno to Cooke and Rick at Exon let me do some dyno test on my sled, Big bored 617 in a Phazer to see what was happening with the power curve. I knew about pipe pressure back then as I had designed the pipe and can and made them myself but didn't have the third EGT in the belly of the pipe or anyway of measuring Pipe Pressure.

Still alot to be learned about two strokes!!

Good Luck
Ewe nailed it! I ran one can @ 3.55lbs @ 7500 feet on flat trail @ 8300, Then switched to custom built can for my 880 and instantly over reved 200 rpm,@ 8500, I clicked down one to settle back to 8300, pressure was 3.3 lbs and is spot on 3 lbs at 10K. All the mods people do and they are giving up the free HP by tuning pipe pressure.A can will NOT give max.performance at all elevations. I have the full pressure kit if anyone wants to test. rent or sale . I also learned this from lancelot and Turbo AL, very valuable info, A can is really only in the zone for about 4k feet and this means every stock can that will run at sea level will be giving up HP due to a loose can at elevation.too tight and HP drops as well and retains heat.
 
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byeatts

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So I have often wondered why someone hasnt made an adjustable stinger on the can. Is it not possible or is it just not been experimented with yet. Is it still future technology?

adjustable stingers have been around 40 years. I have one as well on the sled for testing, Its best to create the correct pressure by creating with the correct can flow., I have the pressure gauge installed in the dash, interesting stuff! others just put the gauge in coat pocket for testing and changing cans Easy.
 
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