Metallicat
TY 4 Stroke God
I finally purchased a subscription to DynoTech today and saw their 2005 Vector pulled over 117 hp all the way from 7800 rpm to 9100 rpm.
So given that fact, would the best clutching for top speed be up at the higher rpm limit, or are the clutches simply slipping the belt too much if set to turn at 9100 rpm's? I had mine turning 9100 rpm's a couple of years ago, adjusted down to 8800-8900 a couple of weeks ago, and added even more tip weight yesterday which should make it turn closer to 8600.
The carbed Nytro from the 2006 shoot-out shows a bit different result with peak hp over 118 from 8200-8900, which is probably more realistic I would imagine. But at 9100 rpm it is still pulling over 116 hp. Peak torque at 9100 down almost 6.5 ft-lbs from peak hp rpm @ 8500.
So given that fact, would the best clutching for top speed be up at the higher rpm limit, or are the clutches simply slipping the belt too much if set to turn at 9100 rpm's? I had mine turning 9100 rpm's a couple of years ago, adjusted down to 8800-8900 a couple of weeks ago, and added even more tip weight yesterday which should make it turn closer to 8600.
The carbed Nytro from the 2006 shoot-out shows a bit different result with peak hp over 118 from 8200-8900, which is probably more realistic I would imagine. But at 9100 rpm it is still pulling over 116 hp. Peak torque at 9100 down almost 6.5 ft-lbs from peak hp rpm @ 8500.
Turk
Tech Advisor
lower rpm,s will give much better acceleration.
Higher rpm,s will give better top end
Usually99% true in theory & in the real world in perfect conditions.
Higher rpm,s will give better top end
Usually99% true in theory & in the real world in perfect conditions.
RJH
TY 4 Stroke Junkie
Thats a big power band...run it at 9100.
Our old race sleds had a 300 rpm power band...never lugged it at the bottom
Our old race sleds had a 300 rpm power band...never lugged it at the bottom
Metallicat
TY 4 Stroke God
Turk said:
So Ideally the clutch should pull for a while at say 8400 rpm's and then slowly build up to 9100 on a long run. But that seems almost impossible to accomplish in the real world. Unless some other clutch technologies exist that exceed the STM Supertips capabilities that I am using.
Turk
Tech Advisor
It,s easy to acheive. I set up every sled I own like that. it can be done with any weight that uses replaceable rivets/screws/bolts...any hardware. I would clutch your sled to run from 8k rpm & run it up to 8700 rpm for best results if you want the best all around performance. Backshift & throttle response suffers tho.
Metallicat
TY 4 Stroke God
RJH said:
Torque curve on this engine is pretty flat from 5000 rpm up through 8800 rpm or even more. 74 ft-lbs at 5000 rpm, peaking at 81 ft-lbs @ 6900, still over 70 ft-lbs at 8800. On most of my 2 strokes, if I was a mere 200 rpm's past peak I was dead in the water and the torque curve usually crested just about 300 rpm's below peak hp rpm's so clutching had to be spot on. I could clutch my Vec anywhere from 8000-9000 and still pull nearly the same hp and torque. I think I'll load this baby heavily with weight and see what it does compared to lighter clutching pulling higher rpm's.
Metallicat
TY 4 Stroke God
Turk said:
Ok, so I'm using weights with 3 possible adjustment locations (heel, center, tip). Maybe I should put a bit more weight in the center and leave some out on the tip?
Original clutch kit setup had the tip lightly loaded (1g washer), none in the center, and a fair amount (9g of washers) in the heel, and I pulled 9100 rpm's with very little time in the meaty 8000+ rpm portion of the powerband. With 2g on the tip, 10g in the heel and none in the center I pull 8500 then peak at 8900. Thinking about keeping 10g in the heel, adding 1g to the center, and adding 1g to the tip for a total of 3g on the tip. Does that sound reasonable?
But I am noticing that the more weight I add to the tip, the crappier the backshift / on-off throttle response seems.
Turk
Tech Advisor
I have posted this a gazzilion times. If you want better acceleration you lose backshift & throttle response. clutching is a compromise. You can not have both. Last time I post this info cus I have done this to death!!!
Metallicat
TY 4 Stroke God
Turk said:
Ok, thanks. I don't read all of your posts.
I just get excited because these are the first weights I can adjust on the fly by myself without having to shave down weight from the the tips or sides, like when I was running 10 series Poo weights in my older 2s sleds. Adjustments then were made by a gram scale and properly shaving off portions of the weights to achieve the desired rpm levels. The adjustable weights are really nice but I just don't know when to add weight to the center, as opposed to the tip, heel, etc. as engagement rpm is also affected by weight placement. I added a bunch of weight to the center post and heel and my engagement dropped to 2500 rpm (full choke rpm levels) so I knew that wasn't the answer. Seems like the tip weight keeps the engagement rpm levels in check. I guess it is a balance like you said.
