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Discussion Starter #1
So I'm curious - I've been diving into clutch tuning theory and everything I can find online suggests that you need to tune for peak HP and there is never any mention of peak torque.

So using an N/A XP1000 as our example, the way I understand things at this point is that you want to jump up to approx 8250-8300rpm as soon as possible and hold it there. Why wouldn't you want to aim for peak torque, which I believe is about 7500rpm (someone correct me if I'm wrong), for the shift curve before hitting full shift out?

Once you hit shift out, you would then want to climb to peak HP and hold at that point. To me, that would seem to make sense, as you would be in the peak torque range if your load changes while climbing through your shift curve and then once you finally hit shift out, your peak HP will hold you there.

Can someone explain to me my the torque peak is never mentioned in the clutch tuning discussions?

Or let me know if I'm off base on my assumptions in any way. I'm looking to expand my knowledge on the technical aspects of this sport.

Cheers! :icon_thumleft:
 

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:popcorn:Good question ...I think I know the answer but I cant explain it .....so I will wait for someone more intelligent than me to respond
 

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I think the torque comes in when it back shifts under load. If you really want toque, get a turbo. Great torque at lower speed. The non turbo needs the rpm for power. We have a 17 non turbo and a 18 turbo. With the turbo one needs a lot less throttle to climb the same hill the 17 does with foot to floor. One needs to get the rpm's up on the 17 and hold them. With the turbo, power on tap any time. Start a long climb and if you need more power just tap and away you go.
 

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These have plenty of low end torque. Torque gets ya out of the hole. HP gets you across the finish line. Need a balance. HP is a by product of Torque.
 

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I am with Paxx on torque concerns..
Have been clutching for way way to may years.
From the CVT system in snowmobiles in the early 70's to the now RZR's
( same concept)

I always clutch for torque- just not a lot of people understand the helix in the secondary as it loads the motor - Depending on what you looking for -
I never ever use the lazy helix in the stock machines- especially in the xp 1000's so so much torque left on the table with that flat helix.

Get the torque load with the helix-correct- weights in the primary (placement) to carry the added load but not so much enough so you can't achieve top rpm AND maintain-it.
You have to have the springs to complement the changes and ALL SPRINGS are not the same.. as an example... A 60/150 spring from EPI is not the same as a 60/150 from team as they all measure initial compression at different heights.

Most don't want to mess with it, and just buy a clutch kit- but how many clutch kits do you see with weights springs AND a helix for elevation!!!!

I have my helix's made at Venom and they cut what I need/want...

Sorry been so long winded- but there are clutching improvements instead of just adding HP and just head for the turbo line up-
BTW that clutch system in stock form is way lazy..IMHO
 

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Discussion Starter #6
I think the torque comes in when it back shifts under load.
This is an interesting thought - So you are suggesting the machine is tuned for peak HP because when you get hit with a load, ie. a steep hill, etc. the backshift will place the RPM into the torque peak and then pull you hard back into the HP peak?
 

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Discussion Starter #7 (Edited)
I am with Paxx on torque concerns..
Have been clutching for way way to may years.
From the CVT system in snowmobiles in the early 70's to the now RZR's
( same concept)

I always clutch for torque- just not a lot of people understand the helix in the secondary as it loads the motor - Depending on what you looking for -
I never ever use the lazy helix in the stock machines- especially in the xp 1000's so so much torque left on the table with that flat helix.

Get the torque load with the helix-correct- weights in the primary (placement) to carry the added load but not so much enough so you can't achieve top rpm AND maintain-it.
You have to have the springs to complement the changes and ALL SPRINGS are not the same.. as an example... A 60/150 spring from EPI is not the same as a 60/150 from team as they all measure initial compression at different heights.

Most don't want to mess with it, and just buy a clutch kit- but how many clutch kits do you see with weights springs AND a helix for elevation!!!!

I have my helix's made at Venom and they cut what I need/want...

Sorry been so long winded- but there are clutching improvements instead of just adding HP and just head for the turbo line up-
BTW that clutch system in stock form is way lazy..IMHO
So in saying all that, do you aim for Peak Torque (7500rpm) on the holeshot with climbing RPM up to Peak HP (8300rpm), or do you aim for a straight shift at 7500rpm, straight shift at 8300rpm, or something in-between?
 

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Torque is an interesting subject. Couple of ways to make HP, torque or RPM's. Ford is making new engine based on old school, single cam, push rods, cast-iron block, heavy lower end. A long stoke engine will produce lots of torque at low RPM. The Ford engine max torque is at 2000 RPM. Diesel engines are long stoke and make lots of torque at low RPM's. Most modern car engine are small and use RPM to produce HP. Racing engines use lots of RPM's to make HP. Our RZR engine idle just below 2000 RPM. Small engine needs lots of RPM to make power, unless they are turbo'ed. Then more fuel/air in forced making a bigger bang on top of piston = more power at lower RPM.

Have worked on the 17 XP1000 a lot with clutching. When it was not working at the 8400 to 8600 RPM it was flat on power. A big noticeable lack of power. One had to keep the power on hard to make some dunes. With things right, it has so much more power. Needs less throttle to safely climb the same dunes easy.

One other issue with torque. A torque engine needs more cooling as the heat of combustion is held in the cylinder longer, transferring more heat to block, etc.. As the RZR turbo did not have enough cooling the first year, as an example. Also a torque engine needs it's oil cooled because of the more pressure on lower end. Oil is a lube and coolant.

To clutch an XP engine to work in it's max torque area, I believe one would be very disappointed. Of course a lot depends on where and how one rides. The XP1000 engine is a great engine with lots of power. The turbo is a big step above mainly do to the torque it can produce. It was the biggest surprise I had with the turbo as had not seen anyone talking about how much torque it has. Just not possible to get lots of torque out of a very small engine without forced induction. Torque needs long stroke or forced induction.

Some things to think on.
 

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So in saying all that, do you aim for Peak Torque (7500rpm) on the holeshot with climbing RPM up to Peak HP (8300rpm), or do you aim for a straight shift at 7500rpm, straight shift at 8300rpm, or something in-between?
What I aim for is what the motor likes.
Good holeshot-hard pulling all the way through but still achieving max rpm, top speed and maintaining it.
Coming up on a incline, rpm should hold, not be lazy falling ever so lightly and wait for the backshift. It should be instant!

If the helix is to steep or to shallow it (the motor) tends hits that invisible wall.
Most don't even recognize this, and think since they are hitting 8300 -8350 they are ok and that all she has got... till one goes past you generally mid way ( because torque) you cant catch it, you have run out of legs.
Sandblster is correct 8400- 8550 is where it's at.

A lazy backshift to hold rpm is annoying and that what most of these have from factory- They run ok that most don't mess with it- until they ride in a completely stock machine or comparable machine that has been clutched properly.

Most might not agree with the above comments- and that is OK... but I have to clutch RZR's for over 9,000' elevation where we live and ride- and since the air is so thin up here- clutching is paramount- we have lost the HP#'s( 110hp from the XP1000) that the lower elevation guys still maintain.
Even the RZR turbo's benefit from a properly set-up machine,and we haven't even got into spring combinations yet.
 

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Discussion Starter #10
This is a good conversation, thanks for the input from everyone so far.

As I've been playing around with my tuning, I've been reducing flyweight and seeing increased performance as a result of each reduction in weight. I've now hit a point where all the weight has been removed from the arms and the pull is amazing compared to stock but I am borderline slipping belt under mid to high load and this is at the lowest elevation that I ride at, 2200' +/-.

It's currently a climbing RPM tune, hits 8000rpm by 35kph and then slowly climbs to 8400rpm by 80kph.

I live in a valley and on my local rides, I will go from 2500' up to 6000'+. The machine is great at the 2000-2500' (other than the minor slipping) but obviously didn't perform nearly as well on my trip up into the mountains.

I've been looking into it and chatted with a few pros and I've now ordered 2 new springs to try, one for the primary and one for the secondary. Both of my current primary and secondary springs had a finishing force of 260. I've ordered a replacement primary with a force of 295 and a secondary with a force of 300 so that I can weight up the arms for reduced slippage, and have adjustment again in the higher elevations.

I'll try each one out and see if I prefer the added backshift of the increased force in the secondary or if it responds better with just the increased force in the primary. I'll also check to see if my sheave temps stay balanced or not.

My understanding is that having more weight on the arms will make you a little less susceptible to elevation change. If that holds true I will likely try and find a (rare) straight stretch at around 4000' and tune for that elevation.

So getting back to the discussion on torque, when I start dialling my setup back in for the higher elevation, don't worry so much about where the stated torque peak is on paper? Just tune for the feel of the machine and a snappy backshift?

Haha, a little bit of a long-winded approach to ask a simple question! Just helps my thought process to write things out I suppose.
 

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One thing you need to REALLY do is check the clutch alignment before you do all the tuning. If that is wrong noting else works as it should. All my clutching problems went away once the clutch alignment was set correctly. Very critical that is done first.
 

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Discussion Starter #12
Good point - I did buy the tools from Boondocker to align the belt and the shafts but I haven't checked them yet.
 

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Paxx-
Just remember if your trying to achieve backshift with a heavier secondary spring rate, keep in mind your facing in creating more heat, as the secondary is working harder to compress the spring. So baby steps

People don't believe the light spring rates I run, but it's in the helix that will allow lighter rates with zero heat and snappy backshifts.
It's an art- and doesn't come cheap, as I have a shelf full of trials and errors...LOL
 

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Discussion Starter #14
Paxx-
Just remember if your trying to achieve backshift with a heavier secondary spring rate, keep in mind your facing in creating more heat, as the secondary is working harder to compress the spring. So baby steps

People don't believe the light spring rates I run, but it's in the helix that will allow lighter rates with zero heat and snappy backshifts.
It's an art- and doesn't come cheap, as I have a shelf full of trials and errors...LOL
Haha, I believe that! with the shipping rate to get these springs up to Canada, I'm paying about $75/spring, not to mention all the other clutch parts!

My clutch is a bit of an unusual set-up with the Boondocker and the primary has an extremely low engagement force of 45. That is the initial reason I bought the secondary spring, I needed the extra spring force for the increased weights, and I was told that there wasn't a spring for the primary with a low enough engagement force and a 300 finish force. With that said I ordered the 180/300 secondary spring.

I started getting worried about too much backshift with that increased secondary force so I started hunting around again for a primary spring and managed to find a venom vintage snow series of springs. Ordered up a 65/295. I have a 1/4" spacer under the primary spring I can pull out to keep my engagement in check.

The secondary spring had already shipped by the time I found the primary so I figured I would toss it in and see what happens for my own knowledge. I have an infrared heat gun that I can use to check the sheave temps after a good pull so I can try and find the right combo with balanced heat.

The goal isn't really to achieve more backshift, it is to allow more flyweight. I do have a two-track helix that I can play with as well. Track 1 is a 64-60 and track 2 is a 57-53. I think it is set from Boondocker on track 1 but I will have to check when I pull it to start playing with the springs.

Now that I'm typing this, I guess I could have simply tried the shallower helix to bring up my RPM and then add more weight, couldn't I? Would essentially achieve a similar effect to the stiffer secondary spring, correct?
 

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Paxx -Just remember mixing spring MFG's have different inital compression rates as they are measured differently but sold as a constant.. as mentioned in my earlier post... but you seem to be pretty savvy...

In theory what you have asked is true to a point. Placement of your adjustable weights within your weights have an effect on running RPM but don't be to scared to add tip weight so your pulling through to the top instead of just getting there.

Have you done the old snowmobilers trick and mark your primary & secondary to ensure your getting a full shift out?
 

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Discussion Starter #16
That's actually ended up being how I found the vintage snow springs - I searched until I figured out where Boondocker sourced the original primary spring and it turns out it was from the vintage line and they had others available that were equally rare forces. So both are Venom and both measured the same! :icon_thumleft:

And no, I haven't tried the marker trick yet. To be honest, to this point I have only ever adjusted weights on a CVT. (and read a ton of theory! lol) I'll definitely make sure to give that a try when I open it back up to start playing with the springs!

Thanks again for all the input, it helps a lot talking through this stuff with people who understand it.
 

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Thanks again for all the input, it helps a lot talking through this stuff with people who understand it.
Even this may seem old- The author is well respected in the CVT tuning.
There is a TON of supportive information in this book to provide excellent understanding-That is still used today- The CVT theory has not changed- we just tweak the concept a bit.

Good reading though- Just thought I would this pass the info along.

s-l640.jpg
 

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Discussion Starter #18
Thanks for sharing - I have definitely heard reference to the book several times while researching but have yet to read it. I managed to find a PDF copy of it that I am going to dive into soon!
 

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Discussion Starter #20
So I ended up down at the Moses Lake sand dunes this weekend, all excited to dial in my clutch with my new knowledge and ended up with an issue that I couldn't solve. Hoping you guys might have some insight.

Everything was running great on the machine up to about 7300rpm and then it would just stop producing power. Almost felt like it was hitting a rev limiter. You could put the pedal right to the floor but nothing more would happen.

I tried changing to the shallower helix, I tried the stiffer secondary spring, I tried reducing weight - nothing. I could feel the effect of all the changes up to the 7300rpm but as soon as I hit that point, same thing - no power. I also did the marker trick on the primary and wasn't hitting the top half inch of the sheaves.

So at this point I decided to pull the secondary completely apart and I noticed that the sheaves didn't slide very freely. It seemed that there was some bind coming from the shaft somehow.

1. The sheaves didn't slide open and closed very easily - very jerky
2. If spinning the secondary, even a slight bit of side load caused the secondary to bind and stop spinning.

Is there a bushing or a bearing in there that could have failed? The primary is brand new, just recently replaced after a failure, so my assumption is that there is an issue in the secondary.

I'll try and upload a video of the binding and maybe someone could let me know if this is normal or not?
 
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