825i Clutching Drop RPM's

[jordantractor]

Recently bought a new 825i S4 and have the same opinion as many, that the clutching lets the engine rev higher than it needs to at cruising speeds. Knowing a thing or two about CVT systems from snowmobiling I dug into the primary clutch. There are two ways to drop the shift out rpm. Both involve changes to the primary clutch. You generally don't want to mess with the secondary clutch as long as there is no belt slippage and the system backshifts well under load (ie... lets the revs come up when there is increasing load like going up hill). In the primary clutch there are fly weights and a spring. The rate at which the clutch closes in and raises the belt in it's sheaves is determined by the difference between the force applied by the flyweights and the resistance of the spring. Generally the spring rate gets you in the territory you want to be and then changing the weight to fine tune the rpm curve you want either by changing the weight of the flyweight or the profile. There are whole books on this subject so I wont go any further here. What I found with the calibration in our gators is they have a stock primary spring from TEAM (makers of the CVT system and famous in the snowmobile world for their TIED Secondary clutches which our Gators have, funny that my Gator has a more high tech secondary clutch on it than my brand new Ski Doo sled) is a Black/(I think tan stripe) spring which is good for 42lbs at the low end and 205lbs (or so) at the high end. It's a little more technical than that but if you look up springs on TEAM's website you'll get the drift. They are all rated in a Low/High fashion. Low end force gives you a reference point for the engagement RPM and high end force the full shift out RPM. TEAM has a Red/Sliver/Purple spring that is 43/180 something and they only being about $22 it's cheap R&D. Pop in the red silver purple spring (about a 1hr job maybe more for a novice, less if you have the right tools) and what you get is a lot closer to what people have been asking for. The cruising speed (20 - 30 mph) RPM's drop by about 500rpm, maybe more at times. It still revs up if you stomp it, which is what you want. And it still limits the speed to 45mph. I'm baffled as to how some are claiming that clutching gets them 50mph when it seems like there is an electronic speed limiter that cuts out the ignition at 45mph no matter what the rpms are???? Like to know the secret on this one. But anyway for about $30 and a little time with the wrenches if you have the know how will get you a more civilized 825i. I think they should have gone with this calibration from the get go and offered the stock spring as an accessory high elevation kit. It works well, and since I didn't mess with the secondary there's no fear of belt slip. And it seems like it accelerates a little harder. And I'm sure one could keep on fiddling with springs and weights to do more but like I said, for $30 it's a pretty simple option.

[GATORDONE]

Very interesting! I might have to check into this. :Thmup: Oh, and welcome aboard!!

[Suthern1]

I've got one of the Team Clutches installed on my 825i gator. (By the way, they are the manufacturer of the original CV transmission on the gators, so I don't really consider them "after market"). It in fact does lower the RPM's a bit, but not significantly - around 500-600 rpms as best as I can tell.

You are correct in your evaluation about the CV transmission and wondering how you can achieve more speed. I had the same doubts as the limiting factor is the RPM limiter on the machine. However, my gator will top out with the new clutch at 52 mph according to my GPS, and I can tell you why as I spend some time on the phone with the engineers at Team because I had the same doubts that you have.

The new clutch is almost identical to the original clutch with one significant difference. The positive stops on the primary clutch have been machined allowing the belt to settle deeper in the primary clutch, which in turn allows the belt to get further out on the secondary therefore resulting in a higher ratio than the stock clutch. I know this, because the first clutch I received from Team blew up my brand new belt because it bottomed out on the primary clutch in the "wide open" condition. I called Team and explained what happened and they sent me a new clutch with a .030" spacer already installed to keep the primary from opening up quite as much. This should have reduced the top speed by about 1 mph, but that doesn't seem to be the result.

The clutch does reduce the low end just a tad. I have a buddy that has an identical gator to mine, which also has the 27" Bighorn tires. We lined them up for a drag race before and after the installation of the new clutch. They were pretty much dead even before. After the new clutch install, he pulled away from me off the line about one gator length, then I caught him and walked away from him.

I have to say the guys at Team are very good to work with, and they stand behind their product. I had the issue with the belt blowing up, and they were all over it.

[jordantractor]

Suthern 1 Thanks for the info, that's good to know. As far as it changing the acceleration, there must be some different weights in there and probably a different spring. As far as TEAM goes I didn't have as good of an experience, the guy I talked to blew me off and quit responding to my e-mails. The difference I guess is that I didn't spend any money with them. I'm pretty happy with my setup. I think if I pulled the motor down any more I'd run out of torque and I still want this thing to do some work.

So could you explain a little further? Not to be critical or anything but in the info you give above there are a few contradictions. You say the different clutch allows the belt to settle deeper in the primary and get further out on the secondary. I think you meant the opposite. Top speed is achieved by the primary closing in and pushing the belt out and thus pulling the belt down into the secondary. I'm guessing the machine work done in the new primary lets it close in further? Or does it have a larger OD? Is the new clutch a new primary or a new secondary or both? I have seen somewhere that TEAM sells this for $299? But I could not get them to answer this. And finally at 52MPH what RPM is the engine turning in yours?

[wieserjoe]

Hello Suthern1!
can you please tell me which parts (part numbers) you have installed from Team? THANK YOU!