Why J. Costa works so well

x

Am I correct in interpreting then that any variator/clutch mod that would rapidly get you to 5500 RPMs would get similar results as the J Costa? Like maybe lightweight Variator Rollers or Sliders combined with upgraded (say Malossi red or yellow) clutch springs?

Tim

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Oops!, My mistake. I meant "interpreting". Oh well, it is the start of a holiday weekend.

My J Costa seems to work different from bigbird's.

If I am at a standstill and go WOT, it will hit 6900 or 7000 rpms. It will hold it until about 60 mph at which point it will start to drop a bit as speed continues to increase. It really is close to 7000 rpm, not 5500 rpm, on my scoot. Believe me, I have witnessed it many, many times since installing the J Costa!

I had read an article somewhere that stated that the engine has two horsepower peaks - 5500 and 7000, with 7000 having just a bit more hp.

Not sure why mine would be different - it is the only engine or transmission mod that I have done. Stock size tires (first IRC's then Diablos). Factory clutch.

x

[quote="bigbird]
The J. Costa not only gets to 5500 rpm, but it stays there under the acceleration conditions. That is as much a function of the sliding pins as the shape of the drive sheave face.

... it's the shape of the sheave that maintains the 5500 rpm spot. This is done by varying the ratio of the front of the belt to hold the 5500 rpm no matter what the road speed of the Swing.[/quote]

So is it the shape (profile) of Ramp Plate and the variator Roller (Slider) Weight tracks --as in the OEM variator assy-- which effects the performance? Or is it the face angle of the belt pulley section of the variator which is changed?

Tim

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bigbird wrote:

Tim: I'm no engineer. I believe from my snowmobile experience, which use a similar CVT, that the profile of the ramp plate in conjunction with the slider weights governs the rpm rise and the face angle ultimately determines the gear ratio. These three variables work together. I'm sure the J. Costa engineers did lots of tinkering with the ramp profile against which the sliders push and the face angle which grabs the belt between the sheaves for forward motion.

If that is so, then it may be the 'odd' shape of the Dr Pulley variator Sliders which effectively alter the profile angle(s) of both the ramp plate as well as variator's roller tracks and seem to deliver the significant difference in performance over variator Roller weights.

Maybe that 'odd' shape Slider weight serves to infinitely (non-linearly) alter the ramp profile, as the the Slider's rounded as well as angled faces both come into play as the weight advances up the ramp to change ratios.

Sheesh, talk about a lot of out-of-the-box ramp profile engineering...

Tim