Clutching help

[kviper]

That varies depending on the spring and cam angle. May be 150-200 RPM?

 

[Studroes144]

I need some help with general tuning questions....looking at brown grass.

What is the expected RPM change up or down from the stock secondary/stock belt going to the machined secondary/ulmer red spring in 6-2 position using stock belt?

What is the shift RPM change for each 1 mm thick shim added into the primary spring?

How much RPM difference is there between 6-1 and 6-2 wrap?

I experimented with this a bit just last week. 6-2 on the secondary would pull 8950-9000 which is where it's clutched for, switched to 6-1 without making any other adjustments and it pulled 8750-8800. So I'd agree that it changed it roughly 200 rpm, again that's not the proper way to do it, engine rpm needs to be adjusted in the primary, however if you're in a pinch and need to you can adjust your secondary, however just be advised it's very possible you'll lose acceleration and top speed

 

[stingray719]

I experimented with this a bit just last week. 6-2 on the secondary would pull 8950-9000 which is where it's clutched for, switched to 6-1 without making any other adjustments and it pulled 8750-8800. So I'd agree that it changed it roughly 200 rpm, again that's not the proper way to do it, engine rpm needs to be adjusted in the primary, however if you're in a pinch and need to you can adjust your secondary, however just be advised it's very possible you'll lose acceleration and top speed

Yep, Barry is right.

 

[PAvector]

With Ulmer machined secondary with pink spring in 6-2 location, stock helix, 8jp belt and 3mm shims in stock primary.....will I be bouncing off the rev limiter or be under?
LTX model.

 

[Stubbs]

Don't own a Viper, don't want to at this point.
I wish Turk was still around. People would listen to him.
Has anyone done side by side, in equal state of tune, one sled coming out low and building RPM, vs one sled coming out very close to peak and letting it "wail" all the way?
It didn't matter if it was an RX, Vector, Apex or Nytro. Boosted or NA. He ALWAYS clutched to come out close to peak torque and run the RPM up as the sled accelerated.
Side by side, both tuned, he said lugging was faster in a drag race. Period. If your sled revs to peek RPM in an instant it will "feel" very quick, but you will likely be leaving some acceleration on the table.
As for being more fun to trail ride, yep, it's fun. I get it.

 

[Studroes144]

Don't own a Viper, don't want to at this point.
I wish Turk was still around. People would listen to him.
Has anyone done side by side, in equal state of tune, one sled coming out low and building RPM, vs one sled coming out very close to peak and letting it "wail" all the way?
It didn't matter if it was an RX, Vector, Apex or Nytro. Boosted or NA. He ALWAYS clutched to come out close to peak torque and run the RPM up as the sled accelerated.
Side by side, both tuned, he said lugging was faster in a drag race. Period. If your sled revs to peek RPM in an instant it will "feel" very quick, but you will likely be leaving some acceleration on the table.
As for being more fun to trail ride, yep, it's fun. I get it.

Last year we did 100% of our clutch testing with two vipers side by side, both ltx models, mine was always set to rev up as fast as possible to 9000 rpm range. No matter what we changed the other guy always lugged his to 8600 and then build to 8900-9000 rpm, his viper no matter what style race was ALWAYS slower. From a dig, doing slow roll ons, fast roll ons and top speed, my viper revving up as quick as possible was always faster. Both sleds totally stock, same exact clutch kit, he just loaded his weights differently than I did but everything on the sleds was the same except for the fact that I weigh 30 pounds more than the other guy. If it was the other way around believe me, that's how I'd have mine setup but I've seen it, and did it first hand, in order to run at it's peak in the real world the viper needs to really rev, anything less and you're leaving easy performance on the table.

 

[titanrcr]

Don't own a Viper, don't want to at this point.
I wish Turk was still around. People would listen to him.
Has anyone done side by side, in equal state of tune, one sled coming out low and building RPM, vs one sled coming out very close to peak and letting it "wail" all the way?
It didn't matter if it was an RX, Vector, Apex or Nytro. Boosted or NA. He ALWAYS clutched to come out close to peak torque and run the RPM up as the sled accelerated.
Side by side, both tuned, he said lugging was faster in a drag race. Period. If your sled revs to peek RPM in an instant it will "feel" very quick, but you will likely be leaving some acceleration on the table.
As for being more fun to trail ride, yep, it's fun. I get it.

You won't get many people buying that theory. Everyone is so programmed to think that the RPM should shoot right to the peak HP RPM and stay there whenever the throttle is wide open. That is true for the most part with a two stroke because the torque and HP peaks are very close to each other, not true of the four stroke engine.

 

[Studroes144]

Peak torque on the viper is at 8000 rpm. Just checked the dyno sheet from last year with my viper, I couldn't imagine clutching for 8000 rpm or even slightly higher than that and letting it build, yes I've tried it, sled is less torquey, not as quick or as fast and has no fun factor. That's one great advantage of having 3 good friends with the same exact sled so u can test and compare.

 

[titanrcr]

Last year we did 100% of our clutch testing with two vipers side by side, both ltx models, mine was always set to rev up as fast as possible to 9000 rpm range. No matter what we changed the other guy always lugged his to 8600 and then build to 8900-9000 rpm, his viper no matter what style race was ALWAYS slower. From a dig, doing slow roll ons, fast roll ons and top speed, my viper revving up as quick as possible was always faster. Both sleds totally stock, same exact clutch kit, he just loaded his weights differently than I did but everything on the sleds was the same except for the fact that I weigh 30 pounds more than the other guy. If it was the other way around believe me, that's how I'd have mine setup but I've seen it, and did it first hand, in order to run at it's peak in the real world the viper needs to really rev, anything less and you're leaving easy performance on the table.

That would seem to be a good side by side test but you have not changed the clutching, you only changed the operating RPM in the primary by loading the weights. To utilize the engines torque and unleash the acceleration you need to work on the secondary, steeper helix and somewhat stiffer spring. The RPM should build during acceleration and eventually get to 9000. Primary clutch controls RPM and secondary controls rate of acceleration or backshift (torque sensing).

 

[kviper]

I'll just say this for now. Every clutch kit out there is hinged around a more agressive profile weight with the ability to load the heel very heavy generating as much centrifugal force as possible when the belt in the primary clutch is wrapped around the smallest diameter pulley, giving the least contact to the belt. Every kit I have seen has the heel loaded very heavy for this reason! This whole cenareo (more agressive profile lighter total weight) allows for less total weight allowing the driven clutch to over come the primary quicker for a quicker back shift when compared to the heavy flater profile OEM weight's. Yet being more agressive down low.
I would be willing to bet the sled's with heel weight were spinning a lot more! So do we detune our sleds so they hook up or do we add traction and use the gained track HP?
Heavy tip weight is good for top MPH! Most clutch kit's are doing good it they maintain top end and very few gain top end unless there is a problem as with the Viper.
Cam angles and driven clutch spring's control belt side force. You need enough side force to stop belt slip as much as possible (remember the belt has to slip to shift) less cam angle generates more side force (resists up shift) the reason you have less cam angle on the last half of the shift curve is for two reasons, as the belt drops deeper in the driven clutch it is on a smaller diameter pulley equaling less torque censing and it applys more side force on the smaller pulley where it has less belt contact.

 

[skidooslayer687]

I'm curious the outcome of this thread as well, I have the hurricane power kit installed on my sled with the clutch kit Dave has supplied. It runs the supertips as well and I had he exact same issue with the sled hitting the rev limiter on take off. A few emails back and forth with Dave and I've went from 7 washers in the heel up which is basically 7 grams up to 11 grams of weight. Now with the lack of snow currently here it's hard to test and see what the wot Rpms are. The only thing that I know for sure is that as I was adding more weight to the heel it wasn't hitting the limiter as bad as the original setup was, also the original setup there seemed to be a lot of belt dust created just from quick tests around the yard

 

[newtron]

I'm curious the outcome of this thread as well, I have the hurricane power kit installed on my sled with the clutch kit Dave has supplied. It runs the supertips as well and I had he exact same issue with the sled hitting the rev limiter on take off. A few emails back and forth with Dave and I've went from 7 washers in the heel up which is basically 7 grams up to 11 grams of weight. Now with the lack of snow currently here it's hard to test and see what the wot Rpms are. The only thing that I know for sure is that as I was adding more weight to the heel it wasn't hitting the limiter as bad as the original setup was, also the original setup there seemed to be a lot of belt dust created just from quick tests around the yard

I had daves setup when I got the turbo as well. He has an aggressive setup but not what everyone one is looking for . The STM weights supplied are just not heavy enough in the heal to stop the initial over rev . I switched to Dalton dtya-1 weights and cured the initial over rev but these weights are not as adjustable as the STM weights

I look for a little lower initial rpm around 8700 then climb to 9000 so had to change the secondary setup as well. I do a lot of trail riding but enjoy the top end pull so my setup is not for the ditch bangers

 

[skidooslayer687]

So no matter how much weight you add in the heel you weren't able to overcome that initial over rev? I know I've made it better, not cured yet... And I also don't know what wot Rpms are going to be because of the lack of testing so far, just no snow and nowhere long enough to open it up safely and look down

 

[kviper]

I used the same 50y STM weights on my 12 Apex Turbo that I used in Allens stock kit for that sled, just more cam and weight. I was in semi hard snow, leaving on stutter and spinning enough to blow a 12" hole in the snow and never hit the limiter! If you can't load enough weight on the STM's to stay off the limiter you either need the 60's or more cam.

 

[skidooslayer687]

I can put more on, there's room, I'm just wondering what the effects of me loading up the heel of the weight are going to be... Right now there's 11 grams in the heel and I believe 2 grmas in the tip, stock primary spring