Originally posted by: OT
As i said there not for everyone. LOL
The real debat should be if weather or not these kits reduce heat. In my experiance with the older TRA's is they do reduce heat.
2 sleds one with HC one without.
Both sleds make 5 long vertical pulls. After the 3rd pull the sled without HC can not pull the same highmark due to a very hot primary.
To confirm that its a heat issue go out and make 5 hard pulls and than try to put your hands on your older style TRA. With the HC i could touch the primary at any time........can anyone comfirm if the new TRA still get as hot as the older TRA ? I here there not s hot.
The debate imo is real simple and there are many kits that address the issue. "Clutch Heat Caused By friction Is Your Belts Worst Nightmare"......than thars the belt debate.....which one is best. LOL
ot]...Both sleds make 5 long vertical pulls. After the 3rd pull the sled without HC can not pull the same highmark due to a very hot primary.
Joe]...One thing you have to analyze is "why" did the primary get hot?
A primary clutch reveals excessive heat because:
Drifting rpms; 1]drifting from a low rpm to correct rpms 2]Drifting from high rpms to low rpms
You make a straight shot run to peak track mph and hold it under load for about 10 seconds. With any of the 3 causes mentioned, the primary will reveal heat - the secondary won't. The secondary will eventually reveal heat upon repeated loads or extended wot throttle run. A good portion of the temperature a secondary reveals is due to "convection" - Heat transfer thru the belt to the secondary.
Now have to know why the engine groans under repeated loads or extended wot throttle run.
What Freddie mentions about racing a sled in heat after heat is same in expression as you mention of [ot writes; 5 hard pulls]
Quoting Freddie SUPERTUNER klies:
You need to know what to do in a drag race environment where we make heat after heat, you cool the engine between heats and because your pipes are thermally efficient in that they have been heated once and subsequently heat easier the next time, when the pipe heats up it creates a loss in how much time it takes to accelerate (low end torque). There is almost always a trade off of low-end torque for top end HP RPM. When you know this, you could operate the sled properly and gain some of the best of both of these worlds back.
People learn to take advantage of that torque in the hole shot and then change the clutch tune-up at the top end to allow the clutch to keep the engine in the RPM range that occurs and changes as you go down the racetrack while adding heat into your pipes. This is where progressive helix's come into play. Load heavy at the beginning, and then drop a few degrees in angle as the shift plays out.
Now of course this varies from sled to sled...in an open modified with no hood or with a sled having lots of vents in front of the pipes. O.M. sleds, the pipes run cooler due to the wind hitting them and assisting with their cooling as you run down the track.
In a case where you have a full-bodied sled with a heavily shrouded and concealed pipe, you don't get the wind and the under hood temperatures become "sauna like" resulting in a scenario where you need to clutch for a low-end torque loss and a top end RPM gain. The deal here is doing exactly the same thing every time between rounds, heat the sled the same amount on the jack stand, stage for the same amount of time and get the same repeating results every time."
ot]...To confirm that it's a heat issue go out and make 5 hard pulls and than try to put your hands on your older style TRA. With the HC I could touch the primary at any time........can anyone confirm if the new TRA still get as hot as the older TRA ? I hear they're not as hot.
Joe]...Because of repeated pulls and/or extended w.o.t. run, the torque falls off and as the track speed increase, the load gets heavier, any extra resistance, softer snow, deeper snow, hump, dip, pulling back on the handlebars, sled skis coming back to the snow...all those change the loads.
Any time the load becomes lighter, because the clutch is torque sensitive, it thinks you let off the throttle for a moment, however you did not let off the throttle...the ground load changed and causes rpms to fall off slightly because of torque loss.
ot]...The debate imo is real simple and there are many kits that address the issue. "Clutch Heat Caused By friction Is Your Belts Worst Nightmare".
Joe]...I agree 100 % ("Clutch Heat Caused By friction Is Your Belts Worst Nightmare")
Friction from excessive slippage due to engine rpms that are not running at rated rpms.
What I am explaining is something happens to the torque when the pipe gets hot.
The torque reduces in value from 6300 to 7700 rpms when the exh pipe gets hot.
You let off the throttle with a hot pipe;
Your engine is at 8400, you let off the throttle, the engine decelerates...
8400, 8300......74,73....6000..you get on the throttle again. How long did this take? Measure the time - A second and a half?
Instead of the engine flashing back to 8400 quickly; It labors to peak slowly climbing from 6000, 6500......8000....Maybe the rpms will hang at 8000 for several seconds unless you slow down or the snow load gets lighter giving the engine a chance to recover.
Why was there a slow recovery? Hot pipe and large helix angle value at that point on the shift curve.
How do you compensate for this? In the case talking above I would play with the pretension and try to tune it for best "average" results in the conditions you drive in. If using a compression spring secondary I would increase the secondary spring force. If only wanting to adjust helix angles then I would lower the final angle to help compensate for the torque loss. All increased values at that point where the engine starts to get soggy - all increase values will help the engine be quick to rev again, getting back on the pipe.
I say "average" because if you have too many forces resisting the push of the primary, you will lose top speed and rpms will increase. So be happy with your happy medium and expect a good average that will perform average in loaded conditions.
...Rpms drop or are difficult to recover because of torque loss in midrange rpms - the pipe is hot and wants to provide peak hp.
I have example:
I run a 440 on the dyno. BRP rates this engine 105hp at 8400 rpms.
With a cold pipe dyno pull, the torque is 66 lbs 99hp @ 7950 rpms. torque 21 lbs 34hp @ 8300 rpms
With a hot pipe dyno pull, the torque 60 lbs, 91 hp @ 7950 rpms. torque 64 lbs, 103hp
Cool pipe the torque is at 66 lbs and hot pipe hp is 103.
So how do you take advantage of this "feature" of the power changing? Secondary spring forces and/or Progressive helix.
Use spring final forces that increase towards full shift, increase more than previous spring. Example; You had a 200/300 now can try a 200/320.
Use large angle to capture the cool pipe torque and progressive reduce the helix angle as the shift increase. Example: Previous you had a 47/44, can go to a 49/42.
My experience if you are getting hot clutches after successive pulls then start to increase the belt clamp in the secondary to help the engine maintain rpms at higher shift ratios. Like Aaen says, correct and tune rpms by the primary clutch flyweight.
Hot clutches work the same as a cold clutch, they don't bind, they dont get loose..they have a personality for their fitness.
If you are getting heat, it is because the engine rpms are not operating at rated good enough.
A primary clutch reveals excessive heat because:
Drifting rpms; 1]drifting from a low rpm to correct rpms 2]Drifting from high rpms to low rpms.